Another reason I appreciate Belindas' video is that they present the information in a short, concise manner. They are bite-size and not full of filler. And that is fine for me. There is another RUclipsr (the name I can not recall now) who often talks about older technology in his videos. While I found the subject matters interesting, I often felt the videos were at least twice as long as they need to be. And no, it is not that I have a short attention span. But I can tell when something is mostly filler.
Technology Connections perhaps? I enjoy both types of content but I do agree sometimes youtubers tend to make things more complicated than they need to be. Belinda does an amazing job focusing on the most important stuff.
@@makte9616 I just checked, and you are correct. While his videos are well done, I think they are almost always twice as long as needed. And this is not necessarily a bad thing. But sometimes I do not have twenty to forty minutes to spare.
Great subject, this is such an important thing to get right. Its highly related to climate and so location. In colder climates its important to have the best vapor barrier possible on the inside of insulation and an air barrier only on the outside, tight osb sheating on the outside can act as a vapor barrier and create problems within a year of construction. Basically the thing to avoid is having isulation trapped between two vapor barriers. There should be only one and it should be on the right side of insulation depending on climate. This definitely needs a follow up as i cant think of a more important aspect of building science to understand. Great introductory video on the subject Belinda, keep up the good work :)
I work in residential construction in a colder (zone 5/6) climate and don't know of any modern builders still using vapor barriers (class 1 vapor retarders) in walls; everyone I work with has moved to class 2 vapor retarders on the interior and class 3 on the exterior. The core concept is to reduce air flow through the wall to only the bare minimum required for the drying of incidental moisture while preventing condensation buildup inside the wall regardless of temperature difference between the outside and the inside of the building. This is further complicated by the increasing prevalence of air conditioning in my area, meaning we can't just focus on preventing cold-weather condensation anymore. It's also important to remember that the exterior sheathing (and continuous insulation) itself is often vapor retarding, like you mentioned - from up to 10 perms for some plywood, down to 1 perm for some OSB. A low perm exterior sheathing may be fine with an interior class 2 vapor retarder, since it can dry (albeit slowly) in both directions simultaneously, but that same sheathing with an interior class 1 vapor barrier may be a potential problem as it may not be able to dry outward quickly enough should any incidental moisture be introduced. The construction industry has been moving away from extreme absolutes in favor of balanced approaches, so there's no one right answer to most things anymore. I personally like the balance of ZIP System sheathing (class 3) under Comfortboard (class 4) continuous insulation, with a more dynamic class 2/3 interior vapor retarder (which changes permeability as needed) like MemBrain or Intello.
@@paulslevinsky580 The extra coatings would probably lower the vapor permeability of the sheathing, and that could cause worse drying performance within the wall assembly if there isn't enough vapor permeability in the other direction. If the wall retains a lot of moisture from condensation or incidental exposure, I suppose even PT plywood would eventually start to rot.
@@JamesCusano Yeah I'm worried about the potential for added barriers trapping moisture and causing more harm than good. It goes without saying that I'll add a barrier coating on the outside (that is near the waterline) but the inside of the box would also look much better if the pt wood were painted grey.
Have a question, I live in zone 3 and I building a Conex that'll be used for grow op. I had it spray foamed with an average of about 1.5 inches of closed cell was supposed to be 2" inches average. So was trying to determine if I should install fiberglass insulation between the studs that would be installed over the foam I'm kind of leery of doing this I'm worried about causing moisture problems you can get up to 100 degrees but that metal on the outside exterior could probably be I'm guessing 130 degrees in the summer and the inside is going to stay at a round 75° do any of y'all have an opinion of what I should do in that instance
Another great one Belinda. Still mystifies me that we have roofing materials that allow water vapor to pass through but won’t allow water to penetrate! I had my own deep dive into vapor barriers when building an almost-passive pool-house! Suggestion: Do one on MERV standards. After two years (and counting) of pandemic people may be interested to learn how AC filters can passively clean air
Thank you, Belinda! I am a 45 year veteran builder, and this topic, Vapor Transfer thru an assembly, has been one of the most challenging to comprehend, must less determining a feasible and cost effective way to address the issue, and how an assembly performs. Understanding that vapor travels from high pressure to low pressure is a game changer in comprehending the issue and is foundational to start to address the problem. I build in Climate Zones 1 & 2, mostly concrete slab and wood frame wall assemblies. To illustrate, approx. 40 years ago, I built a custom home in Jacksonville, FL. Even back then, I was pushing the envelope in an attempt to give my customer more for their investment. I made the mistake of putting .06 mil Visqueen on the interior of the walls and ceiling. I only did this on one house, but seeing your video brought clarify to the multiple issues that decesion created! The people were good friends and I shutter to think what they must have gone thru because of my bad decision. I so regret that mistake, even today! I have come to believe that a sealed attic is the most energy efficient decision that can be made. With that decision though, comes some challenges, such as Vapor accumulation in the attic envelope, which if non-permeable materials are used, can lead to condensation issues, mold, wood rot, etc... To combat this issue, it's my understanding that the attic needs to be included in the heated and cooled space, allowing air changes to occur or using a dehumidifier to eleminate moisture. This might be a topic for you to present. Coupled with that may be a discussion on roof assemblies, types of Vapor Barriers or Retarders, that would be preferable. I have believed for some time that a thermal break, in both wall and roof assemblies was key in creating an energy efficient structure. We are about to sell our home and build new. With that decision, I am contemplating the design of the home to have a double wall exterior with a 2" space between the walls. Because of cost, I am leaning toward and sprayed cellulose insulation which will be me approx. an R-31 wall, it will accomplish a thermal break and give the exterior cladding something solid to be adhered to. I am stopping the foor system at the exterior of the interior wall, which allow for the insulation to be continuous thru to the roof framing. With the above in mind, I am also in the process of determining how to insulate the roof system, a long with water resistive Barriers. My concern here is not to create a condensation plane within the assembly. My thought process is to allow the rafters to terminate at the wall exterior edge. This will allow the wall sheathing to right all the way to the roof decking. That joint can then be tape to seal it and make it air tight. Once that is done, my thoughts are to screw rafter tails and barge/gable look outs that are cut to a two inch thickness up to the edge of the sheathing. This will allow two layers of 2" rock wool to be installed in opposing integration to each other. Then I plan to use 1x4 battens under metal roofing. A few questions existing here:: I net and blow 5 1/2" of Cellulose between the 2x6 rafters for $1.24 per SF. In my area, this is what 1" of closed cell foam costs, installed. This application gives me an R-17 cavity without figuring the thermal transfer thru the rafters, thus the need for a thermal break on the exterior and boosting the overall assembly R-value. Off the top of my head, I don't recall the R-value per inch of Comfort Boad, but I would think it to be R-3.5 per inch, giving me an overall R-30. To my question, What underlayment would you recomend of the roof sheathing? My plan is to use 5/8" OSB for sheathing for screw retention capacity. From both a cost and function perspective, What would you recommend for an exterior wall sheathing, and a vapor retarder? Zip, OSB and a Vapor Retarder, or...? I am also so planning on installing battens on the exterior walls, that create a rain screed continuous on the wall, leading up to and including the roof with the metal roof battens. Any suggestions there? Thanks again! I think you're really great! My very best to you and your family!
I knew instinctively that vapor barriers behind the drywall was going to be a big problem. I always used a vapor barrier primer, which also met code, and moisture gets stopped at the wall and evaporates back into the heated envelope where it gets dispelled by heating or air conditioning. If I'm not mistaken, in cold climates vapor barriers are no longer required, and I think she says that, but I still see a lot of people saying it is required.
Now if we could only get roofers in western Oregon and Washington (zone 4 marine) on board. Everyone wants to use synthetic underlayment which has a perm rating of < 0.05. I've been insisting on a permeable underlayment, and the contractors seem to think I'm nuts. I'm standing pat.
Belinda, I read only a few of the comments added here by many a varying range of expert. Many answer difficult questions, many ask difficult questions. Absolutely there is need (a deep need!) to further discuss this most mist.. ifying phenomenon of moisture control. Back through history, a home breathed nearly as many cubic feet of air as was big the house, hourly. But heat was cheaper, without care and maintenance eventually even these old houses wood.. rot. Locking moisture in a wall can devastate a house in less than one year. Clearly I'm not a professional builder, and my knowledge lacking. If I without the proper information attempt even a "simple" basement renovation could severely damage my most precious expense, my house! Keep the good information flowing, enjoy your channel very much.
This is the best video explanation I have watched! I am not in construction, but I have a small 1972 home in central Florida. A screened in patio was converted to a walk in closet with a flat roof. There was a temperature and humidity difference in the closet. After removing the walls we could see it wasn't constructed or insulated properly and the 2x4s weren't spaced properly. Given all the issues I have discovered in this home, I'm sure that even if we fix the gaps that a proper vapor/air barrier wasn't done on the exterior. It is constructed of thin concrete block with stucco on the outside. I don't believe they used plywood or tyvek. So I have been considering how to stop the humidity from coming in without causing a mold problem. I considered using drylock masonry water proofer on the interior of the block then using foil faced R5.9 board insulation (max I can do with space) before adding the dry wall. But was concerned about mold forming on the blocks. Would it make sense to use a vapor barrier paint on the stucco or would you recommend vapor retarder paint? Do you have any other suggestions? What brand of paint would you recommend? Sorry I know that was a lot. Thank you!
For the layman like me, this was valuable! And now I know the mistakes I've made in the past. Not getting bent out of shape over vapor saves money too!
We are moving from NE Illinois (zone 5) to Tulsa (zone 3) the house we’re looking at is a 50’s build that is a complete gut job. The information you have provided is greatly appreciated, this and other videos.
Great start! I think a deeper conversation about wall assemblies would really help... I'm up in Seattle in Marine 4, and you see everything from Zip around Rockwool to Tyvek around craft-faced fiberglass to closed cell foam behind metal siding. Presumably they are all doing the same job, but it's unclear when/how a mold-sensitive insulation product (like fiberglass) needs vapor protection vs. when it's not (Roxul can be used outside the vapor barrier on exterior insulation as well as on interior).
I agree and would appreciate a deeper conversation as well. I recently downsized from a stand alone house to an ICF (insulated concrete form) condo building built in 2013. Nice and tight I assumed! I thought this was a great move from my old 50's built wood frame, stucco exterior, blown in cellulose wall cavity insulation but I am missing that old breathable house! I'm also in the Marine 4 area and the humidity levels inside my new home range in the 50 to over 60% many months of the year even with constant ventilation. I'm considering installing a dehumidifier but would like to learn more about solutions in multi-tenant buildings so I can decide if we should move or just deal with what we have purchased.
@@user-vp1sc7tt4m a dehumidifier is always a great choice. I would be happy if my house stayed around 50% humidity all the time. Here in Florida if I don't have dehumidification going or hbac running more than I really want it to it would easily get about 70 or 75% humidity inside the house. My house was built in 1937 though so it does not have any moisture barrier or vapor barrier that's all! Because the exterior cladding has been stuck over I am left with the best practice of being just air sealing it well whenever I decide to remodel. ICF homes are great but you can still get condensation in the structure so if it is sealed on the outside a dehumidifier would greatly help.
This is very clear as all your videos are. I finally have subscribed after watching I do not know how many of your videos. I will have to watch this again to take in all the information. It's very relevant for me right now as I'm doing some renovating to an approximately 45 year old log cabin "kit built" home. Thanks Belinda.
If you haven't already, you might want to look into blower door tests which provide evidence on how airtight the construction is. Really useful process and with the help of "smoke" can see where the air leaks are (around windows/doors/ceilings etc).
As usual, another great video Belinda. Your presentation style and delivery is spot on. In the UK, Vapor Retarder is called Vapour Check, and is green, typically 125mu thick. Where I am, the latitude similar to the southern quarter of Hudson Bay and the humidity of Seattle, fibreglass insulation is a bad choice where a lot of condensation is expected, and polystyrene fares little better. Rockwool is my insulator of choice (walls and loft), so I did enjoy your video on that subject too (plus the hilarious follow up complaint letter video).
Belinda, great video. Perhaps this has already been commented on: At the end you state that Rockwool stops air infiltration and stops the thermal bridging. The effects from thermal bridging from the studs or other structural members is definitely helped by the layer of Rockwool. Regarding the air infiltration, I think you simply misspoke. The Rockwool in that example building is keeping the sheathing warm, this helps prevent condensation on that sheathing. The Blueskin is stopping the air infiltration and does the bulk of the water management. All this is, is a reminder to put up my own videos. Thanks for being a rockstar!
Great video. I am currently in the process of removing the 6 mil plastic vapor barrier that I installed last year in my walk-up attic space that will generally remain unfinished in this 100 year old home. The roof is not vented and has a fair number of hips and valleys as well as a flat section at the top. The roof joists are 2 x 6 and 2 x 8 (actual size, not the modern reduced sizes). I put Rockwool insulation in between all of the joists and it made a significant difference in reducing heat loss over this past winter. However, last summer I noticed that I had condensation on the plastic against the insulation on hot days after it rained. We just had a few warm (70F) days here the other week and the condensation was pretty significant. I decided to pull down all of that plastic to let the assembly breathe. I checked the underside of the roofing boards and the insulation up against them and they were dry, the condensation was all on the plastic and the underside of the insulation. I know that the "proper" assembly would be ridge and soffit vents and an airspace between the insulation and the underside of the roof deck, but -- a. I don't have any venting due to the construction of the roof and b. I don't have the space for an air gap anyway unless I build out the roof joists and even then the insulation isn't even up to current code for zone 5. During the summer their is an attic vent fan, so I don't anticipate any issues, but I'm hoping that there isn't condensation this winter on the underside of the roof deck. That was a long set-up, but my question -- should I get a vapor retarder for the inside face of the roof assembly if the space will remain unfinished? What about if I were to add sheetrock of beadboard to the underside of the joists to create a semi-finished space? Note that the space is not heated except that heat rises through the uninsulated ceiling below and keeps that attic space at 50F or above even when the outside temperature is close to 0F.
Steven you may not have a vented attic as in the traditional sense but you are definitely getting outside air in there and that is where the moisture is coming from that condenses against your cold surface beneath the insulation. Is there no way to put in vents at the soffit? You can always use insulation board there are special types made to screw up against the bottom of the Rafters so that the space between the rafters still allows air to vent the roof but you keep the heat from building up inside the Attic. You mentioned a vent fan that runs in there and if it is blowing air out of the attic the air has to come from somewhere so if you seal off the attic with a vapor retarder you will just be focusing that make up air from fewer areas. This may cause a increase in moisture in those areas which probably isn't desirable. If you could do something to vent the roof itself via air movement between the rafters and insulate beneath them then whatever moisture condenses at that margin between the two spaces would also be removed because of the ventilation of air moving through. As far as the attic and drywall if you do that, or even if you don't, I think I would probably install a dehumidifier to maintain the humidity at a desirable level.
Thanks for the reply, Daniel. The house was built in 1920 and the construction is some sort of masonry block with stucco exterior and an air space between the masonry and lath and plaster walls -- no insulation. The attic floor (2nd floor ceiling) is also uninsulated. The roof joists overhang the walls and have blocking between the joists at the wall line. The soffits are closed in with beadboard below and what is probably a 1x6 and a trim molding as fascia. So, technically, yes, there is air flow through the gaps. The only time there was a condensation problem after I insulated and added the vapor barrier was for a day or two after it rained, so I am assuming that it was vapor passing inwards towards the attic when the sun heated the roof. I've now removed all of the plastic vapor barrier, which should solve the problem for this summer and I'll check the underside of the roof deck (above the insulation) next winter to see if I have a problem with moisture condensing and freezing on the cold underside of the roof. That will help me decide what steps to take to mitigate it. At this point I don't plan on adding drywall at this point. The main purpose of the insulation was to eliminate the heat loss through the roof in the colder months and prevent excessive heat build-up in the hotter months. The attic vent fan draws air from the entire house during the summer. With the insulation in place, the attic temperature is typically close to the outside temperature in the warmer months.
@@stephenboots that sounds like a pretty good strategy. Checking on it to make sure it is okay and not building up condensation is probably the best first step. If time and budget were not a concern a ridge vent and some soffit vents would help keep the roof assembly dry and moisture build-up from happening on the other side of the insulation but it may not be necessary. Good luck!
Great information. On roofs, synthetic underlayment has become all the rage. It has a typical perm rating of < 0.05 and is definitely a vapor barrier. It is used extensively for roofs in western Oregon and Washington which is a zone 4 marine area, which never made sense to me. I'm having a new roof installed and have been insisting on a permeable underlayment. This video confirms my choice and reasoning.
Today is the first time I came across your informative you tube videos And I am very impressed with all the knowledge you have on the products you're sharing in your videos. Keep up the excellent work. Thank you for taking the time to do this.
I’ve watched a video of yours before on LVPs and just came across this now that I’m looking at underpayment requirements for my LVP. Just discovered that you live in Dallas! Subscribed because of your great informational videos!
In Canada, It's still code to use a vapour barrier on the "hot" side of the wall (the inside). We use 6 mm poly. We then use a vapour retarder, like Tyvek, on the outside of the heating, with an air gap for the brick or siding. I've worked on many older homes built this way and there has been no mold, except where there were air leaks. You could do a follow up specifically for cold, moderate and hot climates. Great info. I appreciate all of your content.
Poly in the wall is still allowed by building codes in most of the US, too, it's just no longer considered best practice - you kind of answered the question as to why: one little leak somewhere and you have mold. Use a class 2 retarder to let the surfaces breathe slightly and the chance of mold from small moisture intrusions is greatly reduced, with almost no loss of energy efficiency.
I live on the Canadian prairies and just built a new house last year. Using a vapour barrier on the warm side and a vapour retarder (like Tyvek) on the outside is a code requirement if using batt insulation. The problem in extremely cold climates is that any warm, moist air that leaks into the wall cavity freezes at the zero line (the area in the wall were the temperature is below freezing). Ice builds up during the winter and then melts in the spring resulting in very wet wall cavities and possibly mold. It is even worse in attics. Ceilings have been brought down by the weight of the melting ice in the spring. (this happened a lot when I was a kid in the 1970's as the rapid increase in energy costs back then caused people to insulate previously uninsulated attics without installing a vapour barrier on the warm side. The following spring people discovered water dripping from their ceilings and in some cases the ceiling collapsing). I have always believed the vapour barrier was one of the most important features of a house (in my area) yet it was usually poorly installed and never inspected. I was pleasantly surprised last year when I found out that the vapour barrier had to pass an inspection by the building inspector. I was also fortunate in that the contractor that installed the vapour barrier was as fanatical as me that it be done right and he did an excellent job. I looked it over for hours and could not find a hole anywhere. If you live in a cold climate you have to take some of the advice given on RUclips with a grain of salt as it is usually geared toward warmer climate areas.
@@hmw-ms3tx perfect answer and confirms my thinking. My inspector was very strict as well and demanded a good acoustic sealant to seal the vapour barrier.👍
@@hmw-ms3tx Thank you for confirming what I've seen in practice (I'm an electrician) but never received a clear explanation of the rationale. Easy to understand how an entire winter of damp air gathering and coming back at once causes a bad situation! Unfortunately, in my newer house (2017, YEG) the builder was not as ... attentive. There were huge gaps in some spots where the acoustical sealant was dragged too fast, and holes were left un-taped after nails or screws were pulled through (not to mention none of the staples were taped over). I will have to go through my basement now with a sharp eye to ensure everything is fully sealed up, as I did have a moisture issue last spring - luckily, I caught it and was able to pull out the batting and dry everything out with fans.
Idea for a video, I think you'd do some justice: Tiny homes and safety. Fire safety and prevention, personal safety in small spaces, EMS access, security all that sort of thing. Perhaps, cover things like concerns people often over-look and what are measures tiny home builder are taking.
Really interested in insulation of basement concrete walls. Seems like lots of conflicting information out there regarding vapor barriers, foam board, plastic sheeting on exterior side of studs, etc.
Thank you for this video! I loved the list of products in each category! I've been trying to understand Tyvek more thoroughly. They're giant in the industry, and yet no one seems to be able to satisfy my curiosity about how so many holes in its installation and then how many more holes it gains with siding can measure up to its vapor qualities. It seems like too much water can get in and then not escape.
iirc there is a layering process to meet code requirements, a price and performance comparison of different combinations as well as describing the pros and cons in terms of what to expect as a builder or homeowner
I love your informative videos, really really helpful. I'd like to see more deep in some examples of cold/warmer climates and what could work better. Sending love from South America!! 🤠
Building Science, Interstitial Condensation 101. The water vapour carrying capacity of air is proportional to its temperature. As temperature falls the relative humidity of air increases until it reaches 100% saturation and then excess water vapour starts to condense out. The colder it gets the more condensation takes place and if it drops below zero the condensate of course freezes. If you know the relative humidity and temperature of the air then a psychrometric chart will tell you the dew point temperature. Where there is a difference in temperature across a building element (i.e. wall, roof, floor etc) there will be an internal temperature gradient. When an element is vapour permeable and there is warm humid air one one side and it is colder than the dew point of that air on the other side then as that warm humid air permeates into the element it will progressively cool along the temperature gradient and start to condense out water at the precise place where its temperature reaches its dewpoint. This is known as interstitial condensation. It is prevented with a carefully installed vapour barrier placed on the warm side of elements to stop vapor laden air from permeating to a dew point position on the internal temperature gradient within. Thermal insulation is usually installed in concert to keep help the vapour barrier warm. For example, in cold climates we have warm moist indoor air and cold outside air so the vapour barrier goes on the inside of the thermal insulation. Positioning the barrier on the warm side of the insulation helps to keeps it warmer than inside air dew point and that vapour laden air is prevented from getting past it into the colder parts of the element where it would cool to the point where it starts to condense water. In the humid tropics the vapour barrier position is reversed. Where we have air conditioned buildings the warm vapour laden air is outside and colder air is on the inside so the vapour barrier is placed on the outside of the thermal insulation. In milder climates with less extreme temperatures and relative humidities ventilation is an effective way to expel vapour laden air from indoor spaces bathrooms and kitchens and with well ventilated buildings this usually suffices. Interstitial condensation mitigation measures should be based on relevant local climate and building use and construction data.
Love your channel! Thank you for this video but also help!! Plz go into this topic in more detail! A first principles explanation would be great. What is the dew point? How can you use building materials to control where the dew point is in a wall assembly? Most climate zones in the US have four seasons, how do these “cold climate” building envelopes perform in the summer? It seems like an air tight home is desirable but a water tight home is not? Thank you!!❤
commenting to help the algorithm, nothing of note here.... Thank you for helping to, "bridge," some of my gaps. This information dovetails with what I'm learning from Matt Rissinger's channel (I'm in zone 6-7 though where the perm rating should be 1.0 and extend below grade). I had to stop & rewind several moments many times, because I have A.D.D. (but, I know I'm learning when I have to rewind -- hehe). I am PROBABLY overthinking how to extend the life of my Sister's 20 yr old shed. (Her girls & their friends re-painted it regularly, but prolly should've included under the over-hangs.)
Thank you for having both US Customary and metric units. Quarts and cups still confuse the hell out of me. I'm surprised you didn't touch on Water Vapour Resistance Factor (μ [unitless]) and Equivalent Air Thickness (sd [m]) when talking about Perms. Both of these are common in Europe, whereas a Perm is new to me.
I need your opinion on the following: I have stairs that go up into an attic which is not finished except for flooring. The stairs has a ceiling and walls which need to be insulated inside the attic. There's drywall on the living space of the stairs which descend into the first floor. Previous owner was using a spun insulation encapsulated in plastic which has deteriorated because he never finished the project. I want to use the materials that I have on hand and the way I understand your explanation, I would paint the attic side of the drywall with a latex. Then I can use the insulation (without a craft or encapsulated plastic covering) my sealing the attic side of the walls with vapor retarder and drywall or just drywall. Or second, perhaps just seal the cracks to stop air movement The warm interior air goes to the attic when it's cool in winter and in summer hot attic air goes to the cool interior air in the stair well side of those walls.
Great resume. It’s like a little but powerful seminar. Can you say something for liquid air barriers. Like Stogoldfill or Stogoldcoat. From STO. In advance Tks .!!!!
EDIT: i found a 1h+ podcast video talking exactly about this topic, in particular about zoning building codes vs climate change and the specifics of when and why humidity related problems happens. i understand your goal audience and you probably know about them podcast but in case you dont and for anybody interested in the subject here's the link ruclips.net/video/XfiRYQBU4_M/видео.html Hi Belinda, quick comment from a true OG fan of yours since the beginning. I was just looking to answer a very geographic specific question about wall assembly in zone 6 considering that climate is changing and we are starting to have problems with condensation. i know we just have to migrate towards building codes of zone 5 but id be nice to have this topic discussed in more details in a future video on this channel. again im a huge fan of your channel and building science in general, i guess im just hungry for more 😊
I understand now why no plastic on interior walls behind the drywall! Simple elec outlet's will permieate the plastic sheeting allowing moisture into the insulated wall cavity.
She said continuous insulation like Rockwool Comfortboard "can" stop air infiltration, which is accurate depending on installation detailing. One common approach is to apply the insulation in two layers, with the seams staggered. It does not qualify as an air barrier on its own (which she didn't say that it did), but it reduces air infiltration to such a degree that you're no longer completely reliant on only the integrity of a vapor-permeable air barrier membrane.
You had mentioned in region 4 marine you also need an interior vapor retarder. I this because in the 4 marine, you have some much moisture in the air? By putting exterior insulation like 2" of rockwool on the exterior of the sheathing will that solve the problem and not need the interior vapor retarder?
During my winter reno, I forgot to turn on my heater. So when the morning sun came up I thought there were a serious leak in the envelope. But everything went away as soon as I remembered to turn the heater on at night and kept the interior temperature higher than the outside during day time. The moisture quickly went away. I was quite surprised at how much moisture can collect on the barrier on a South facing wall. Unfortunately our code requires them. So practically? I would never use them in the Pacific Southwest (as far Canada's south west lol).
Thank you for the video. In New Zealand it is typical to have long run corrugated steel roofing on a tar paper or vapour barrier nailed to trusses. Insulation is either below this with gaps in skillion roof insulation or insulation resting on the ceiling joists of the building. Many vapour barriers last a shorter period than the roof itself and tear or fall apart - which vapour barriers last the longest?
Yes I have an all steel building and I am going to add an interior stud wall And fiberglass insulation. There will be an air space between the metal exterior clading and the fiberglass insulation. I live in a Denver like climate. High and dry. Very cold in the winter. Very little rain....more snow then rain... Need help with the "correct " insulation schedule....!! Thanks Jim
My question is about van conversion insullation... As mentioned, it is a very confusing subject... does it need vapor barrier, what kind and where does it need to be placed?... And generally, what is the best Insulation for the walls, floor and ceiling? Thank you for sharing 🙏😌
Nice!! Love 2 Learn!! What effect does cutting sheetrock for electrical outlets have on air infiltration measurements an how to minimize air leakage around these wall fixtures (outlets, light switches)? Thanks for the videos!!
Electrical boxes that come through the drywall is the reason she talked about the difference between a solid sheet of drywall with latex paint and one with a 1 inch hole. So if you want to control vapor you need to make those electrical boxes airtight. There is a couple different ways you can do that. I plan on taking the plug covers off and using fireblock spray foam in and around the boxes.
I'm now worried; I just have been renovating my 125 year old house with a vapor barrier (6mil plastic sheet). The house is in climate zone 7; the sheeting is on the inside of the exterior walls, and the insulation is not paper faced (i.e. unfaced R13 in the walls). Based on your info, for the remaining 1/4 of 1 floor, I will likely aim for non-barrier (i.e. retarder instead), but I worry for the remainder of what I've already done. If I were to make sure the electrical outlets were all sealed via spray foam around/behind the boxes, do you think it's likely I can avoid pulling the walls off of the 7 rooms I already completed last year? The house is 125 years old now. I won't own it for more than another 6 or so years by current plan, but I'd like this old beauty to last for another 125. Given that I was pulling off original horse-hair-laden plaster/lath, I'm not expecting the walls to come back down for a long time to come. Thoughts are appreciated. Thank you.
As a builder and renovator of old houses, I imagine you’ve inadvertently created an unfortunate condition. Don’t be too hard on yourself. We can all look back and see errors made with the best of intention. Sealing around electrical devices will slow or eliminate the passage of air into the cavity. But controlling for water vapor isn’t the same as controlling for air-tightness. Before thinking about tearing out what you’ve already completed, consider a testing regimen done a couple of times a year where you test for mold and moisture. Perhaps sections of baseboard on outside walls could become removable to facilitate the testing regimen.
Its still standard to use 6mil poly under drywall in 6,7 & 8 in Canada. I would be a little concerned if you haven't sealed the poly around one outlets but you could look at other options before tearing walls out but one thing that is important is sealing your base plates on old houses, Ive seen amazing amounts of moisture and mold build up due to lack of sil. gasket or air sealing. If you are redoing the siding one thing to look at would be to do a rain screen to help the water that does migrate through the wall to not get trapped. Old houses lasted a long time because they didn't hold moisture at any point... or heat!
Given the comments of differences between Canadian outlook and American, it’s prolly worth mentioning when I went to college in this town 25+ years ago, the neatest Taco Bell was further than the border with Canada (crow flies). Houghton, MI is a good stretch from Texas. Thanks for the advice everyone. I’ll check in on the new outlet sealing this coming summer (Great Stuff FTW if needed?) and consider how to handle the walls I’ll be dealing with this year. I’m thinking I’ll NOT be tearing up 70 sheets of drywall to redo everything… :)
Yes please more articles!! I need advice about the correct insulation schedule for a zone 5 Denver like climate. Cold snowey winters, mild(4800 feet elevation) very dry summers. Metal clad building. Concrete floor(wood shop) no interior plumbing. Will erect interior wood stud wall with 12" fiberglass insulation with kraft paper on inside face. Air space between insulation and exterior metal cladding. Stud Walls sheeted with 3/4" plywood painted. Ceiling sheet rock with blowen in insulation. Continuous ridge venting. Do I need a air barrier? And if so where? Between the fiberglass and the plywood...?? I need advise, thank you!! just jim
I live in Winnipeg, Manitoba, Canada and our code here is to use a vapor barrier on the warm side. I recently had a new garage built so plan on using 6 mil poly for that as the vapor barrier. But in my basement I used 2" XPS on the walls so I would classify that as a vapor barrier so I feel that I shouldn't need to use poly down there. But I'm sure the inspectors here would disagree and say that I need to use the poly vapor barrier. To me, this is then having 2 vapor barriers which wouldn't allow any water to escape. What are your thoughts on this?
The code in your area likely calls for a class 1 or class 2 vapor retarder, which 1"+ thick continuous XPS foam sheathing qualifies as. Your 2" XPS would need to be either continuous on the outside of your foundation or continuous on the inside of your foundation to qualify, though, you couldn't just place it between studs. Class 1 vapor retarders (like poly sheeting) are no longer considered best practice for moisture management in walls, but are still allowed by most codes.
@@JamesCusano The 2" XPS is glued (PL 300) to the foundation so I would consider it continuous. I then built a 2x4 wall in front of that and then used Roxul insulation (R14) to insulate that. The only thing is the floor joists were put into the foundation when it got poured back when the house was built. So I didn't put the XPS in the spaces between the floor joists as I read that could cause the ends of the floor joists to rot.
Great video, was wondering what would be best insulation in Chicago zone 5 concrete basement built in 1976. 2" XPS foam board against concrete wall with 2x4 wall with roxul r15 and no vapor barrier or 1" Xps foam against the concrete wall 2x4 wall with roxul r15 and with a smart vapor barrier.
Thanks, a bit confused ! How about an attached, unheated garage in Canada. The portion attached to the home was insulated, dry walled, vapour barrier under drywall. To insulate the rest of the garage and dry wall…..continue with Fiberglass insulation, vapour barrier and then drywall ? Exterior walls are 6” studs, OSB, vinyl siding. Any advice ?
Hi Belinda. We live in a cold climate, Alberta. We plan on building this summer. The wall assembly will be metal cladding, strapping, zip r6, 2x6 walls, rock wool r24, strapping and drywall. Should we use Siga Majrex taped all seams ceiling and walls as well?
I live South East of Chicago in zone 5. We get cold winters and hot humid summers. I'm planning to remove my siding and exterior sheathing, paint a vapor retarder on the exterior side of my drywall and studs, then fill the cavities completely with rapid set mortar/portland with a strong mixture of packing pea styrofoam rather than stone in the mixture. I believe this will let interior moisture escape to the outside. I doubt I will need an exterior vapor barrier as that would trap condensation in the walls. I'm seeking a consistent insulation in the walls working from the inside out, a fill for the concrete blocks below that allow insects and creatures into my walls. I would strengthen the structure with exterior sheathing, half inch plywood. I would like to install a quarter inch gap between the exterior plywood and the new siding. I'm hoping to install fake brick for the exterior siding. I may not need any gap for these products. Right now my house is susceptible to birds pecking holes in the wood exterior, and mice somehow getting under my siding into my attic. I hope to get better insulation and seal up the exterior to prevent critter invasion. My house is built on a 2 foot crawl space. I want to start with the South wall to see how this works and if satisfactory, move on to the other 3 walls, most likely doing the East wall next. That wall has been attacked by chipmunks entering the vents and around the vents built into the crawl space. I suspect the blocks on the wall in the crawl space has never been filled with any cementious materials. This is a long way of saying I don't think I know any sufficient scientific facts about materials to help me make a decision. My attic is also not properly vented. When I talk to architects they don't listen. They just want to build new cheaper and smaller structures with their own concepts and their own visions. I don't want an ugly box for a house.
Hopefully someone can help me. I just bought a cabin in the mountains. Temp here gets as low as 28 in winter and as high as 90 in summer. The house has been built this way, T&G wood exterior sidding, thin black paper, 2x6 lumber. The garage has no insulation and I want to add some and cover it with Knoty pine T&G. Should I add MemBrain in between the pine and the unfaced insulation? BTW: Garage is heated but is not cooled since I don't have AC here. Also in the future I would like to add tyvek to the exterior over the existing exterior sidding and add James Hardie Hardie Plank Fiber Cement Lap Siding to cover the old T&G exterior sidding. Any educated info will be appreciated.
Hi Belinda👋🏻I have a tiny house project that I would love some advice on. I bought a garden shed with a tin roof and plywood siding sealed with water based paint. I have cut windows in it, insulated using Kraft faced fiberglass insulation for the ceiling and mineral wool for every thing else in the single room. I have been leaning towards using real wood for floors and walls/ceiling, but I’m wondering if I can seal the wood? Would this cause a vapor/air barrier sandwich between my water based paint exterior walls and the sealed wood interior? I’m constantly worried about causing mold to grow. Is there a sealant that can still let vapor diffuse? Or is that contradicting their definitions? Help please 🙏🏻
We have a Bathroom in our basement that we are renovating, and our house is brick on the outside and cinderblock on the inside. We are wanting to put up 2x4 studs and finish the basement bathroom with drywall. My question is should I use a vapor barrier in between the cinderblock and 2x4 studs in the basement bathroom? Also, can I put insulation in between the 2x4s? I live in the very southern part of Indiana if that helps for the climate zone. Any feedback would be greatly appreciated!
It is a confusing subject. Now, I’m not as confused as I was. Thanks.
In other words, you are still confused.
My thoughts exactly
This!😂
Another reason I appreciate Belindas' video is that they present the information in a short, concise manner. They are bite-size and not full of filler. And that is fine for me.
There is another RUclipsr (the name I can not recall now) who often talks about older technology in his videos. While I found the subject matters interesting, I often felt the videos were at least twice as long as they need to be. And no, it is not that I have a short attention span. But I can tell when something is mostly filler.
Technology Connections perhaps? I enjoy both types of content but I do agree sometimes youtubers tend to make things more complicated than they need to be. Belinda does an amazing job focusing on the most important stuff.
@@makte9616 I just checked, and you are correct. While his videos are well done, I think they are almost always twice as long as needed. And this is not necessarily a bad thing. But sometimes I do not have twenty to forty minutes to spare.
Belinda is so awesome. I love her informed delivery.
Great subject, this is such an important thing to get right. Its highly related to climate and so location. In colder climates its important to have the best vapor barrier possible on the inside of insulation and an air barrier only on the outside, tight osb sheating on the outside can act as a vapor barrier and create problems within a year of construction. Basically the thing to avoid is having isulation trapped between two vapor barriers. There should be only one and it should be on the right side of insulation depending on climate.
This definitely needs a follow up as i cant think of a more important aspect of building science to understand. Great introductory video on the subject Belinda, keep up the good work :)
I work in residential construction in a colder (zone 5/6) climate and don't know of any modern builders still using vapor barriers (class 1 vapor retarders) in walls; everyone I work with has moved to class 2 vapor retarders on the interior and class 3 on the exterior. The core concept is to reduce air flow through the wall to only the bare minimum required for the drying of incidental moisture while preventing condensation buildup inside the wall regardless of temperature difference between the outside and the inside of the building. This is further complicated by the increasing prevalence of air conditioning in my area, meaning we can't just focus on preventing cold-weather condensation anymore. It's also important to remember that the exterior sheathing (and continuous insulation) itself is often vapor retarding, like you mentioned - from up to 10 perms for some plywood, down to 1 perm for some OSB. A low perm exterior sheathing may be fine with an interior class 2 vapor retarder, since it can dry (albeit slowly) in both directions simultaneously, but that same sheathing with an interior class 1 vapor barrier may be a potential problem as it may not be able to dry outward quickly enough should any incidental moisture be introduced. The construction industry has been moving away from extreme absolutes in favor of balanced approaches, so there's no one right answer to most things anymore. I personally like the balance of ZIP System sheathing (class 3) under Comfortboard (class 4) continuous insulation, with a more dynamic class 2/3 interior vapor retarder (which changes permeability as needed) like MemBrain or Intello.
@@JamesCusano What about painting both sides of pressure treated plywood? Will it extend the lifespan or hinder it?
@@paulslevinsky580 The extra coatings would probably lower the vapor permeability of the sheathing, and that could cause worse drying performance within the wall assembly if there isn't enough vapor permeability in the other direction. If the wall retains a lot of moisture from condensation or incidental exposure, I suppose even PT plywood would eventually start to rot.
@@JamesCusano Yeah I'm worried about the potential for added barriers trapping moisture and causing more harm than good. It goes without saying that I'll add a barrier coating on the outside (that is near the waterline) but the inside of the box would also look much better if the pt wood were painted grey.
Have a question, I live in zone 3 and I building a Conex that'll be used for grow op. I had it spray foamed with an average of about 1.5 inches of closed cell was supposed to be 2" inches average. So was trying to determine if I should install fiberglass insulation between the studs that would be installed over the foam I'm kind of leery of doing this I'm worried about causing moisture problems you can get up to 100 degrees but that metal on the outside exterior could probably be I'm guessing 130 degrees in the summer and the inside is going to stay at a round 75° do any of y'all have an opinion of what I should do in that instance
Another great one Belinda. Still mystifies me that we have roofing materials that allow water vapor to pass through but won’t allow water to penetrate! I had my own deep dive into vapor barriers when building an almost-passive pool-house! Suggestion: Do one on MERV standards. After two years (and counting) of pandemic people may be interested to learn how AC filters can passively clean air
Brilliant job of tackling a topic that seems to confuse just about everyone! Thank you.
You should do audiobooks. You have a great delivery. I personally could listen to you for hours.
Thank you, Belinda! I am a 45 year veteran builder, and this topic, Vapor Transfer thru an assembly, has been one of the most challenging to comprehend, must less determining a feasible and cost effective way to address the issue, and how an assembly performs. Understanding that vapor travels from high pressure to low pressure is a game changer in comprehending the issue and is foundational to start to address the problem. I build in Climate Zones 1 & 2, mostly concrete slab and wood frame wall assemblies. To illustrate, approx. 40 years ago, I built a custom home in Jacksonville, FL. Even back then, I was pushing the envelope in an attempt to give my customer more for their investment. I made the mistake of putting .06 mil Visqueen on the interior of the walls and ceiling. I only did this on one house, but seeing your video brought clarify to the multiple issues that decesion created! The people were good friends and I shutter to think what they must have gone thru because of my bad decision. I so regret that mistake, even today!
I have come to believe that a sealed attic is the most energy efficient decision that can be made. With that decision though, comes some challenges, such as Vapor accumulation in the attic envelope, which if non-permeable materials are used, can lead to condensation issues, mold, wood rot, etc... To combat this issue, it's my understanding that the attic needs to be included in the heated and cooled space, allowing air changes to occur or using a dehumidifier to eleminate moisture. This might be a topic for you to present. Coupled with that may be a discussion on roof assemblies, types of Vapor Barriers or Retarders, that would be preferable.
I have believed for some time that a thermal break, in both wall and roof assemblies was key in creating an energy efficient structure. We are about to sell our home and build new. With that decision, I am contemplating the design of the home to have a double wall exterior with a 2" space between the walls. Because of cost, I am leaning toward and sprayed cellulose insulation which will be me approx. an R-31 wall, it will accomplish a thermal break and give the exterior cladding something solid to be adhered to. I am stopping the foor system at the exterior of the interior wall, which allow for the insulation to be continuous thru to the roof framing.
With the above in mind, I am also in the process of determining how to insulate the roof system, a long with water resistive Barriers. My concern here is not to create a condensation plane within the assembly. My thought process is to allow the rafters to terminate at the wall exterior edge. This will allow the wall sheathing to right all the way to the roof decking. That joint can then be tape to seal it and make it air tight. Once that is done, my thoughts are to screw rafter tails and barge/gable look outs that are cut to a two inch thickness up to the edge of the sheathing. This will allow two layers of 2" rock wool to be installed in opposing integration to each other. Then I plan to use 1x4 battens under metal roofing.
A few questions existing here::
I net and blow 5 1/2" of Cellulose between the 2x6 rafters for $1.24 per SF. In my area, this is what 1" of closed cell foam costs, installed. This application gives me an R-17 cavity without figuring the thermal transfer thru the rafters, thus the need for a thermal break on the exterior and boosting the overall assembly R-value. Off the top of my head, I don't recall the R-value per inch of Comfort Boad, but I would think it to be R-3.5 per inch, giving me an overall R-30. To my question, What underlayment would you recomend of the roof sheathing? My plan is to use 5/8" OSB for sheathing for screw retention capacity.
From both a cost and function perspective, What would you recommend for an exterior wall sheathing, and a vapor retarder? Zip, OSB and a Vapor Retarder, or...?
I am also so planning on installing battens on the exterior walls, that create a rain screed continuous on the wall, leading up to and including the roof with the metal roof battens. Any suggestions there?
Thanks again! I think you're really great! My very best to you and your family!
I knew instinctively that vapor barriers behind the drywall was going to be a big problem. I always used a vapor barrier primer, which also met code, and moisture gets stopped at the wall and evaporates back into the heated envelope where it gets dispelled by heating or air conditioning. If I'm not mistaken, in cold climates vapor barriers are no longer required, and I think she says that, but I still see a lot of people saying it is required.
Now if we could only get roofers in western Oregon and Washington (zone 4 marine) on board. Everyone wants to use synthetic underlayment which has a perm rating of < 0.05. I've been insisting on a permeable underlayment, and the contractors seem to think I'm nuts. I'm standing pat.
Belinda, I read only a few of the comments added here by many a varying range of expert. Many answer difficult questions, many ask difficult questions. Absolutely there is need (a deep need!) to further discuss this most mist.. ifying phenomenon of moisture control. Back through history, a home breathed nearly as many cubic feet of air as was big the house, hourly. But heat was cheaper, without care and maintenance eventually even these old houses wood.. rot.
Locking moisture in a wall can devastate a house in less than one year. Clearly I'm not a professional builder, and my knowledge lacking. If I without the proper information attempt even a "simple" basement renovation could severely damage my most precious expense, my house!
Keep the good information flowing, enjoy your channel very much.
This is the best video explanation I have watched! I am not in construction, but I have a small 1972 home in central Florida. A screened in patio was converted to a walk in closet with a flat roof. There was a temperature and humidity difference in the closet. After removing the walls we could see it wasn't constructed or insulated properly and the 2x4s weren't spaced properly. Given all the issues I have discovered in this home, I'm sure that even if we fix the gaps that a proper vapor/air barrier wasn't done on the exterior. It is constructed of thin concrete block with stucco on the outside. I don't believe they used plywood or tyvek. So I have been considering how to stop the humidity from coming in without causing a mold problem. I considered using drylock masonry water proofer on the interior of the block then using foil faced R5.9 board insulation (max I can do with space) before adding the dry wall. But was concerned about mold forming on the blocks. Would it make sense to use a vapor barrier paint on the stucco or would you recommend vapor retarder paint? Do you have any other suggestions? What brand of paint would you recommend? Sorry I know that was a lot. Thank you!
For the layman like me, this was valuable! And now I know the mistakes I've made in the past. Not getting bent out of shape over vapor saves money too!
We are moving from NE Illinois (zone 5) to Tulsa (zone 3) the house we’re looking at is a 50’s build that is a complete gut job. The information you have provided is greatly appreciated, this and other videos.
Great start! I think a deeper conversation about wall assemblies would really help... I'm up in Seattle in Marine 4, and you see everything from Zip around Rockwool to Tyvek around craft-faced fiberglass to closed cell foam behind metal siding. Presumably they are all doing the same job, but it's unclear when/how a mold-sensitive insulation product (like fiberglass) needs vapor protection vs. when it's not (Roxul can be used outside the vapor barrier on exterior insulation as well as on interior).
I agree and would appreciate a deeper conversation as well. I recently downsized from a stand alone house to an ICF (insulated concrete form) condo building built in 2013. Nice and tight I assumed! I thought this was a great move from my old 50's built wood frame, stucco exterior, blown in cellulose wall cavity insulation but I am missing that old breathable house!
I'm also in the Marine 4 area and the humidity levels inside my new home range in the 50 to over 60% many months of the year even with constant ventilation. I'm considering installing a dehumidifier but would like to learn more about solutions in multi-tenant buildings so I can decide if we should move or just deal with what we have purchased.
@@user-vp1sc7tt4m a dehumidifier is always a great choice. I would be happy if my house stayed around 50% humidity all the time. Here in Florida if I don't have dehumidification going or hbac running more than I really want it to it would easily get about 70 or 75% humidity inside the house. My house was built in 1937 though so it does not have any moisture barrier or vapor barrier that's all! Because the exterior cladding has been stuck over I am left with the best practice of being just air sealing it well whenever I decide to remodel. ICF homes are great but you can still get condensation in the structure so if it is sealed on the outside a dehumidifier would greatly help.
This is very clear as all your videos are. I finally have subscribed after watching I do not know how many of your videos. I will have to watch this again to take in all the information. It's very relevant for me right now as I'm doing some renovating to an approximately 45 year old log cabin "kit built" home. Thanks Belinda.
If you haven't already, you might want to look into blower door tests which provide evidence on how airtight the construction is. Really useful process and with the help of "smoke" can see where the air leaks are (around windows/doors/ceilings etc).
This explained so many of my questions I have had around Vapor Barriers. Thank you for breaking it down so well.
THANKS BELINDA, FOR HELPING US OUT 🤗👍💚💚💚
Carr explained that best practice depends on climate zone, and it's good to see the comments qualified by country at least.
As usual, another great video Belinda. Your presentation style and delivery is spot on. In the UK, Vapor Retarder is called Vapour Check, and is green, typically 125mu thick. Where I am, the latitude similar to the southern quarter of Hudson Bay and the humidity of Seattle, fibreglass insulation is a bad choice where a lot of condensation is expected, and polystyrene fares little better. Rockwool is my insulator of choice (walls and loft), so I did enjoy your video on that subject too (plus the hilarious follow up complaint letter video).
Great job on explaining types of vapor permiability!
Belinda, great video. Perhaps this has already been commented on:
At the end you state that Rockwool stops air infiltration and stops the thermal bridging. The effects from thermal bridging from the studs or other structural members is definitely helped by the layer of Rockwool.
Regarding the air infiltration, I think you simply misspoke. The Rockwool in that example building is keeping the sheathing warm, this helps prevent condensation on that sheathing.
The Blueskin is stopping the air infiltration and does the bulk of the water management.
All this is, is a reminder to put up my own videos. Thanks for being a rockstar!
Great video. I am currently in the process of removing the 6 mil plastic vapor barrier that I installed last year in my walk-up attic space that will generally remain unfinished in this 100 year old home. The roof is not vented and has a fair number of hips and valleys as well as a flat section at the top. The roof joists are 2 x 6 and 2 x 8 (actual size, not the modern reduced sizes). I put Rockwool insulation in between all of the joists and it made a significant difference in reducing heat loss over this past winter. However, last summer I noticed that I had condensation on the plastic against the insulation on hot days after it rained. We just had a few warm (70F) days here the other week and the condensation was pretty significant. I decided to pull down all of that plastic to let the assembly breathe. I checked the underside of the roofing boards and the insulation up against them and they were dry, the condensation was all on the plastic and the underside of the insulation. I know that the "proper" assembly would be ridge and soffit vents and an airspace between the insulation and the underside of the roof deck, but -- a. I don't have any venting due to the construction of the roof and b. I don't have the space for an air gap anyway unless I build out the roof joists and even then the insulation isn't even up to current code for zone 5. During the summer their is an attic vent fan, so I don't anticipate any issues, but I'm hoping that there isn't condensation this winter on the underside of the roof deck.
That was a long set-up, but my question -- should I get a vapor retarder for the inside face of the roof assembly if the space will remain unfinished? What about if I were to add sheetrock of beadboard to the underside of the joists to create a semi-finished space? Note that the space is not heated except that heat rises through the uninsulated ceiling below and keeps that attic space at 50F or above even when the outside temperature is close to 0F.
Steven you may not have a vented attic as in the traditional sense but you are definitely getting outside air in there and that is where the moisture is coming from that condenses against your cold surface beneath the insulation. Is there no way to put in vents at the soffit? You can always use insulation board there are special types made to screw up against the bottom of the Rafters so that the space between the rafters still allows air to vent the roof but you keep the heat from building up inside the Attic. You mentioned a vent fan that runs in there and if it is blowing air out of the attic the air has to come from somewhere so if you seal off the attic with a vapor retarder you will just be focusing that make up air from fewer areas. This may cause a increase in moisture in those areas which probably isn't desirable. If you could do something to vent the roof itself via air movement between the rafters and insulate beneath them then whatever moisture condenses at that margin between the two spaces would also be removed because of the ventilation of air moving through. As far as the attic and drywall if you do that, or even if you don't, I think I would probably install a dehumidifier to maintain the humidity at a desirable level.
Thanks for the reply, Daniel. The house was built in 1920 and the construction is some sort of masonry block with stucco exterior and an air space between the masonry and lath and plaster walls -- no insulation. The attic floor (2nd floor ceiling) is also uninsulated. The roof joists overhang the walls and have blocking between the joists at the wall line. The soffits are closed in with beadboard below and what is probably a 1x6 and a trim molding as fascia. So, technically, yes, there is air flow through the gaps. The only time there was a condensation problem after I insulated and added the vapor barrier was for a day or two after it rained, so I am assuming that it was vapor passing inwards towards the attic when the sun heated the roof. I've now removed all of the plastic vapor barrier, which should solve the problem for this summer and I'll check the underside of the roof deck (above the insulation) next winter to see if I have a problem with moisture condensing and freezing on the cold underside of the roof. That will help me decide what steps to take to mitigate it. At this point I don't plan on adding drywall at this point. The main purpose of the insulation was to eliminate the heat loss through the roof in the colder months and prevent excessive heat build-up in the hotter months. The attic vent fan draws air from the entire house during the summer. With the insulation in place, the attic temperature is typically close to the outside temperature in the warmer months.
@@stephenboots that sounds like a pretty good strategy. Checking on it to make sure it is okay and not building up condensation is probably the best first step. If time and budget were not a concern a ridge vent and some soffit vents would help keep the roof assembly dry and moisture build-up from happening on the other side of the insulation but it may not be necessary. Good luck!
Great information. On roofs, synthetic underlayment has become all the rage. It has a typical perm rating of < 0.05 and is definitely a vapor barrier. It is used extensively for roofs in western Oregon and Washington which is a zone 4 marine area, which never made sense to me. I'm having a new roof installed and have been insisting on a permeable underlayment. This video confirms my choice and reasoning.
Today is the first time I came across your informative you tube videos And I am very impressed with all the knowledge you have on the products you're sharing in your videos. Keep up the excellent work. Thank you for taking the time to do this.
I’ve watched a video of yours before on LVPs and just came across this now that I’m looking at underpayment requirements for my LVP. Just discovered that you live in Dallas! Subscribed because of your great informational videos!
In Canada, It's still code to use a vapour barrier on the "hot" side of the wall (the inside). We use 6 mm poly. We then use a vapour retarder, like Tyvek, on the outside of the heating, with an air gap for the brick or siding. I've worked on many older homes built this way and there has been no mold, except where there were air leaks. You could do a follow up specifically for cold, moderate and hot climates. Great info. I appreciate all of your content.
Poly in the wall is still allowed by building codes in most of the US, too, it's just no longer considered best practice - you kind of answered the question as to why: one little leak somewhere and you have mold. Use a class 2 retarder to let the surfaces breathe slightly and the chance of mold from small moisture intrusions is greatly reduced, with almost no loss of energy efficiency.
I live on the Canadian prairies and just built a new house last year. Using a vapour barrier on the warm side and a vapour retarder (like Tyvek) on the outside is a code requirement if using batt insulation. The problem in extremely cold climates is that any warm, moist air that leaks into the wall cavity freezes at the zero line (the area in the wall were the temperature is below freezing). Ice builds up during the winter and then melts in the spring resulting in very wet wall cavities and possibly mold. It is even worse in attics. Ceilings have been brought down by the weight of the melting ice in the spring. (this happened a lot when I was a kid in the 1970's as the rapid increase in energy costs back then caused people to insulate previously uninsulated attics without installing a vapour barrier on the warm side. The following spring people discovered water dripping from their ceilings and in some cases the ceiling collapsing). I have always believed the vapour barrier was one of the most important features of a house (in my area) yet it was usually poorly installed and never inspected. I was pleasantly surprised last year when I found out that the vapour barrier had to pass an inspection by the building inspector. I was also fortunate in that the contractor that installed the vapour barrier was as fanatical as me that it be done right and he did an excellent job. I looked it over for hours and could not find a hole anywhere. If you live in a cold climate you have to take some of the advice given on RUclips with a grain of salt as it is usually geared toward warmer climate areas.
@@hmw-ms3tx perfect answer and confirms my thinking. My inspector was very strict as well and demanded a good acoustic sealant to seal the vapour barrier.👍
@@hmw-ms3tx Thank you for confirming what I've seen in practice (I'm an electrician) but never received a clear explanation of the rationale. Easy to understand how an entire winter of damp air gathering and coming back at once causes a bad situation! Unfortunately, in my newer house (2017, YEG) the builder was not as ... attentive. There were huge gaps in some spots where the acoustical sealant was dragged too fast, and holes were left un-taped after nails or screws were pulled through (not to mention none of the staples were taped over). I will have to go through my basement now with a sharp eye to ensure everything is fully sealed up, as I did have a moisture issue last spring - luckily, I caught it and was able to pull out the batting and dry everything out with fans.
From Johannesburg South Africa 👍💕
She make a very confusing thing easy to understand.
Thank you very much !!!
Idea for a video, I think you'd do some justice: Tiny homes and safety. Fire safety and prevention, personal safety in small spaces, EMS access, security all that sort of thing. Perhaps, cover things like concerns people often over-look and what are measures tiny home builder are taking.
an interesting topic of conversation would be your current take on residential wall assemblies for each zone, ranging from basic to advanced
Thank you! I have been worried about this issue in my own home!
I love cork and I am very surprises how good a vapour barrier it is I may use it in my bathroom outside the shower or bath area much easier work too.
Amazing job explaining. Thank you.
Really interested in insulation of basement concrete walls. Seems like lots of conflicting information out there regarding vapor barriers, foam board, plastic sheeting on exterior side of studs, etc.
Thank you for this video!
I loved the list of products in each category! I've been trying to understand Tyvek more thoroughly. They're giant in the industry, and yet no one seems to be able to satisfy my curiosity about how so many holes in its installation and then how many more holes it gains with siding can measure up to its vapor qualities. It seems like too much water can get in and then not escape.
iirc there is a layering process to meet code requirements, a price and performance comparison of different combinations as well as describing the pros and cons in terms of what to expect as a builder or homeowner
Thank you for making this video. So helpful!
Excellent Presentation!
Thankyou.
I love your informative videos, really really helpful. I'd like to see more deep in some examples of cold/warmer climates and what could work better. Sending love from South America!! 🤠
Building Science, Interstitial Condensation 101.
The water vapour carrying capacity of air is proportional to its temperature. As temperature falls the relative humidity of air increases until it reaches 100% saturation and then excess water vapour starts to condense out. The colder it gets the more condensation takes place and if it drops below zero the condensate of course freezes. If you know the relative humidity and temperature of the air then a psychrometric chart will tell you the dew point temperature.
Where there is a difference in temperature across a building element (i.e. wall, roof, floor etc) there will be an internal temperature gradient.
When an element is vapour permeable and there is warm humid air one one side and it is colder than the dew point of that air on the other side then as that warm humid air permeates into the element it will progressively cool along the temperature gradient and start to condense out water at the precise place where its temperature reaches its dewpoint.
This is known as interstitial condensation. It is prevented with a carefully installed vapour barrier placed on the warm side of elements to stop vapor laden air from permeating to a dew point position on the internal temperature gradient within. Thermal insulation is usually installed in concert to keep help the vapour barrier warm.
For example, in cold climates we have warm moist indoor air and cold outside air so the vapour barrier goes on the inside of the thermal insulation. Positioning the barrier on the warm side of the insulation helps to keeps it warmer than inside air dew point and that vapour laden air is prevented from getting past it into the colder parts of the element where it would cool to the point where it starts to condense water.
In the humid tropics the vapour barrier position is reversed. Where we have air conditioned buildings the warm vapour laden air is outside and colder air is on the inside so the vapour barrier is placed on the outside of the thermal insulation.
In milder climates with less extreme temperatures and relative humidities ventilation is an effective way to expel vapour laden air from indoor spaces bathrooms and kitchens and with well ventilated buildings this usually suffices.
Interstitial condensation mitigation measures should be based on relevant local climate and building use and construction data.
Thank you! Watching from Europe, I'd be definitely interested a follow-up video about application methods.
I would like you go much deeper into this topic!
This is a timely review. Thank you.
Love your channel! Thank you for this video but also help!! Plz go into this topic in more detail! A first principles explanation would be great. What is the dew point? How can you use building materials to control where the dew point is in a wall assembly? Most climate zones in the US have four seasons, how do these “cold climate” building envelopes perform in the summer? It seems like an air tight home is desirable but a water tight home is not? Thank you!!❤
I would love more information on this subject. Thank you!
Always love your videos, they’re spot on!
commenting to help the algorithm, nothing of note here....
Thank you for helping to, "bridge," some of my gaps. This information dovetails with what I'm learning from Matt Rissinger's channel (I'm in zone 6-7 though where the perm rating should be 1.0 and extend below grade).
I had to stop & rewind several moments many times, because I have A.D.D. (but, I know I'm learning when I have to rewind -- hehe).
I am PROBABLY overthinking how to extend the life of my Sister's 20 yr old shed. (Her girls & their friends re-painted it regularly, but prolly should've included under the over-hangs.)
Great video adds clarity, thanks
Thank you for having both US Customary and metric units. Quarts and cups still confuse the hell out of me.
I'm surprised you didn't touch on Water Vapour Resistance Factor (μ [unitless]) and Equivalent Air Thickness (sd [m]) when talking about Perms. Both of these are common in Europe, whereas a Perm is new to me.
I need your opinion on the following: I have stairs that go up into an attic which is not finished except for flooring. The stairs has a ceiling and walls which need to be insulated inside the attic. There's drywall on the living space of the stairs which descend into the first floor. Previous owner was using a spun insulation encapsulated in plastic which has deteriorated because he never finished the project.
I want to use the materials that I have on hand and the way I understand your explanation, I would paint the attic side of the drywall with a latex. Then I can use the insulation (without a craft or encapsulated plastic covering) my sealing the attic side of the walls with vapor retarder and drywall or just drywall.
Or second, perhaps just seal the cracks to stop air movement
The warm interior air goes to the attic when it's cool in winter and in summer hot attic air goes to the cool interior air in the stair well side of those walls.
Great resume. It’s like a little but powerful seminar. Can you say something for liquid air barriers. Like Stogoldfill or Stogoldcoat. From STO. In advance Tks .!!!!
Great video. Was actually trying to find that info few months back (wasn’t having great success). Anyway thank you :)
Thank you for your amazing explanations!
You really sound good with your microphone setup.
Great video, thank you, it is very clear!
I wiould love to see a follow up video on vapour retarders in the Australian climate!
Thank you! I have been wondering about this.
Great video on a tricky subject!
EDIT: i found a 1h+ podcast video talking exactly about this topic, in particular about zoning building codes vs climate change and the specifics of when and why humidity related problems happens. i understand your goal audience and you probably know about them podcast but in case you dont and for anybody interested in the subject here's the link ruclips.net/video/XfiRYQBU4_M/видео.html
Hi Belinda, quick comment from a true OG fan of yours since the beginning. I was just looking to answer a very geographic specific question about wall assembly in zone 6 considering that climate is changing and we are starting to have problems with condensation. i know we just have to migrate towards building codes of zone 5 but id be nice to have this topic discussed in more details in a future video on this channel. again im a huge fan of your channel and building science in general, i guess im just hungry for more 😊
I understand now why no plastic on interior walls behind the drywall! Simple elec outlet's will permieate the plastic sheeting allowing moisture into the insulated wall cavity.
I never thought of using aluminum foil as a vapor barrier, that's brilliant.
you're the best. but now we need to cover smart vapor barriers 😆
Man I love this lady
wonderful job as always
I’m sure you misspoke when you said “ROXUL Comfort Board can stop air infiltration.” It is an excellent choice for continuous insulation though.
She said continuous insulation like Rockwool Comfortboard "can" stop air infiltration, which is accurate depending on installation detailing. One common approach is to apply the insulation in two layers, with the seams staggered. It does not qualify as an air barrier on its own (which she didn't say that it did), but it reduces air infiltration to such a degree that you're no longer completely reliant on only the integrity of a vapor-permeable air barrier membrane.
You had mentioned in region 4 marine you also need an interior vapor retarder. I this because in the 4 marine, you have some much moisture in the air? By putting exterior insulation like 2" of rockwool on the exterior of the sheathing will that solve the problem and not need the interior vapor retarder?
During my winter reno, I forgot to turn on my heater. So when the morning sun came up I thought there were a serious leak in the envelope. But everything went away as soon as I remembered to turn the heater on at night and kept the interior temperature higher than the outside during day time. The moisture quickly went away. I was quite surprised at how much moisture can collect on the barrier on a South facing wall. Unfortunately our code requires them. So practically? I would never use them in the Pacific Southwest (as far Canada's south west lol).
Thank you for the video. In New Zealand it is typical to have long run corrugated steel roofing on a tar paper or vapour barrier nailed to trusses. Insulation is either below this with gaps in skillion roof insulation or insulation resting on the ceiling joists of the building. Many vapour barriers last a shorter period than the roof itself and tear or fall apart - which vapour barriers last the longest?
@Belinda Carr, Can you talk about how this topic intersects with steel buildings?
Yes I have an all steel building and I am going to add an interior stud wall And fiberglass insulation. There will be an air space between the metal exterior clading and the fiberglass insulation. I live in a Denver like climate. High and dry. Very cold in the winter. Very little rain....more snow then rain...
Need help with the "correct " insulation schedule....!!
Thanks Jim
Danko Belinda Danko...
My question is about van conversion insullation... As mentioned, it is a very confusing subject... does it need vapor barrier, what kind and where does it need to be placed?... And generally, what is the best Insulation for the walls, floor and ceiling? Thank you for sharing 🙏😌
Nice!! Love 2 Learn!! What effect does cutting sheetrock for electrical outlets have on air infiltration measurements an how to minimize air leakage around these wall fixtures (outlets, light switches)? Thanks for the videos!!
Electrical boxes that come through the drywall is the reason she talked about the difference between a solid sheet of drywall with latex paint and one with a 1 inch hole. So if you want to control vapor you need to make those electrical boxes airtight.
There is a couple different ways you can do that. I plan on taking the plug covers off and using fireblock spray foam in and around the boxes.
Very interesting, thanks !
Your educational are awesome. 👍 👍 👍
Well done.
Thank you very much
Te amo Belinda!
Great Video! Great Content!
I'm now worried; I just have been renovating my 125 year old house with a vapor barrier (6mil plastic sheet).
The house is in climate zone 7; the sheeting is on the inside of the exterior walls, and the insulation is not paper faced (i.e. unfaced R13 in the walls).
Based on your info, for the remaining 1/4 of 1 floor, I will likely aim for non-barrier (i.e. retarder instead), but I worry for the remainder of what I've already done.
If I were to make sure the electrical outlets were all sealed via spray foam around/behind the boxes, do you think it's likely I can avoid pulling the walls off of the 7 rooms I already completed last year?
The house is 125 years old now. I won't own it for more than another 6 or so years by current plan, but I'd like this old beauty to last for another 125. Given that I was pulling off original horse-hair-laden plaster/lath, I'm not expecting the walls to come back down for a long time to come.
Thoughts are appreciated. Thank you.
As a builder and renovator of old houses, I imagine you’ve inadvertently created an unfortunate condition. Don’t be too hard on yourself. We can all look back and see errors made with the best of intention. Sealing around electrical devices will slow or eliminate the passage of air into the cavity. But controlling for water vapor isn’t the same as controlling for air-tightness. Before thinking about tearing out what you’ve already completed, consider a testing regimen done a couple of times a year where you test for mold and moisture. Perhaps sections of baseboard on outside walls could become removable to facilitate the testing regimen.
Its still standard to use 6mil poly under drywall in 6,7 & 8 in Canada. I would be a little concerned if you haven't sealed the poly around one outlets but you could look at other options before tearing walls out but one thing that is important is sealing your base plates on old houses, Ive seen amazing amounts of moisture and mold build up due to lack of sil. gasket or air sealing.
If you are redoing the siding one thing to look at would be to do a rain screen to help the water that does migrate through the wall to not get trapped. Old houses lasted a long time because they didn't hold moisture at any point... or heat!
If your in zone 7 I would put 6 mil poly, all houses here in Canada have it and no problems if the exterior side can breathe,
Given the comments of differences between Canadian outlook and American, it’s prolly worth mentioning when I went to college in this town 25+ years ago, the neatest Taco Bell was further than the border with Canada (crow flies). Houghton, MI is a good stretch from Texas.
Thanks for the advice everyone. I’ll check in on the new outlet sealing this coming summer (Great Stuff FTW if needed?) and consider how to handle the walls I’ll be dealing with this year. I’m thinking I’ll NOT be tearing up 70 sheets of drywall to redo everything… :)
That was ver comprehensive!
Thank you !
great info, impressive
Thanks for video 👍
Yes please more articles!!
I need advice about the correct insulation schedule for a zone 5 Denver like climate. Cold snowey winters, mild(4800 feet elevation) very dry summers. Metal clad building. Concrete floor(wood shop) no interior plumbing. Will erect interior wood stud wall with 12" fiberglass insulation with kraft paper on inside face. Air space between insulation and exterior metal cladding. Stud Walls sheeted with 3/4" plywood painted. Ceiling sheet rock with blowen in insulation. Continuous ridge venting.
Do I need a air barrier? And if so where?
Between the fiberglass and the plywood...??
I need advise, thank you!!
just jim
I live in Winnipeg, Manitoba, Canada and our code here is to use a vapor barrier on the warm side. I recently had a new garage built so plan on using 6 mil poly for that as the vapor barrier. But in my basement I used 2" XPS on the walls so I would classify that as a vapor barrier so I feel that I shouldn't need to use poly down there. But I'm sure the inspectors here would disagree and say that I need to use the poly vapor barrier. To me, this is then having 2 vapor barriers which wouldn't allow any water to escape. What are your thoughts on this?
The code in your area likely calls for a class 1 or class 2 vapor retarder, which 1"+ thick continuous XPS foam sheathing qualifies as. Your 2" XPS would need to be either continuous on the outside of your foundation or continuous on the inside of your foundation to qualify, though, you couldn't just place it between studs. Class 1 vapor retarders (like poly sheeting) are no longer considered best practice for moisture management in walls, but are still allowed by most codes.
@@JamesCusano The 2" XPS is glued (PL 300) to the foundation so I would consider it continuous. I then built a 2x4 wall in front of that and then used Roxul insulation (R14) to insulate that.
The only thing is the floor joists were put into the foundation when it got poured back when the house was built. So I didn't put the XPS in the spaces between the floor joists as I read that could cause the ends of the floor joists to rot.
Did you come up with new zones? USDA zones with a smaller number are colder.
Very good video!
Hello from Cleveland, Ohio
Thank you
Great video, was wondering what would be best insulation in Chicago zone 5 concrete basement built in 1976. 2" XPS foam board against concrete wall with 2x4 wall with roxul r15 and no vapor barrier or 1" Xps foam against the concrete wall 2x4 wall with roxul r15 and with a smart vapor barrier.
Thanks, a bit confused ! How about an attached, unheated garage in Canada. The portion attached to the home was insulated, dry walled, vapour barrier under drywall. To insulate the rest of the garage and dry wall…..continue with Fiberglass insulation, vapour barrier and then drywall ? Exterior walls are 6” studs, OSB, vinyl siding. Any advice ?
Hi Belinda. We live in a cold climate, Alberta. We plan on building this summer. The wall assembly will be metal cladding, strapping, zip r6, 2x6 walls, rock wool r24, strapping and drywall. Should we use Siga Majrex taped all seams ceiling and walls as well?
Big fan from india 😍😍😍😍
I live South East of Chicago in zone 5. We get cold winters and hot humid summers. I'm planning to remove my siding and exterior sheathing, paint a vapor retarder on the exterior side of my drywall and studs, then fill the cavities completely with rapid set mortar/portland with a strong mixture of packing pea styrofoam rather than stone in the mixture. I believe this will let interior moisture escape to the outside. I doubt I will need an exterior vapor barrier as that would trap condensation in the walls. I'm seeking a consistent insulation in the walls working from the inside out, a fill for the concrete blocks below that allow insects and creatures into my walls. I would strengthen the structure with exterior sheathing, half inch plywood. I would like to install a quarter inch gap between the exterior plywood and the new siding. I'm hoping to install fake brick for the exterior siding. I may not need any gap for these products. Right now my house is susceptible to birds pecking holes in the wood exterior, and mice somehow getting under my siding into my attic. I hope to get better insulation and seal up the exterior to prevent critter invasion. My house is built on a 2 foot crawl space. I want to start with the South wall to see how this works and if satisfactory, move on to the other 3 walls, most likely doing the East wall next. That wall has been attacked by chipmunks entering the vents and around the vents built into the crawl space. I suspect the blocks on the wall in the crawl space has never been filled with any cementious materials.
This is a long way of saying I don't think I know any sufficient scientific facts about materials to help me make a decision. My attic is also not properly vented. When I talk to architects they don't listen. They just want to build new cheaper and smaller structures with their own concepts and their own visions. I don't want an ugly box for a house.
Great video
Hopefully someone can help me. I just bought a cabin in the mountains. Temp here gets as low as 28 in winter and as high as 90 in summer. The house has been built this way, T&G wood exterior sidding, thin black paper, 2x6 lumber. The garage has no insulation and I want to add some and cover it with Knoty pine T&G. Should I add MemBrain in between the pine and the unfaced insulation?
BTW: Garage is heated but is not cooled since I don't have AC here.
Also in the future I would like to add tyvek to the exterior over the existing exterior sidding and add James Hardie Hardie Plank Fiber Cement Lap Siding to cover the old T&G exterior sidding.
Any educated info will be appreciated.
Hi Belinda👋🏻I have a tiny house project that I would love some advice on. I bought a garden shed with a tin roof and plywood siding sealed with water based paint. I have cut windows in it, insulated using Kraft faced fiberglass insulation for the ceiling and mineral wool for every thing else in the single room. I have been leaning towards using real wood for floors and walls/ceiling, but I’m wondering if I can seal the wood? Would this cause a vapor/air barrier sandwich between my water based paint exterior walls and the sealed wood interior? I’m constantly worried about causing mold to grow. Is there a sealant that can still let vapor diffuse? Or is that contradicting their definitions? Help please 🙏🏻
Well, done
We have a Bathroom in our basement that we are renovating, and our house is brick on the outside and cinderblock on the inside. We are wanting to put up 2x4 studs and finish the basement bathroom with drywall. My question is should I use a vapor barrier in between the cinderblock and 2x4 studs in the basement bathroom? Also, can I put insulation in between the 2x4s? I live in the very southern part of Indiana if that helps for the climate zone. Any feedback would be greatly appreciated!
Hi, I enjoy your video. please extrapolate these findings to mobile residences such as vans, RVs, and mobile homes.