Vapor Barriers: Do we REALLY need them?
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- Опубликовано: 21 ноя 2024
- In this course we will look at the difference between a vapor barrier and air barriers. What climate zones do you need a vapor barrier, how to eliminate the need for a vapor barrier with still being air tight. We will discuss ratios of continuous insulation needed with the building science testing to back these assemblies up. We will discuss both cold climate and warm climate solutions and dive deep into designing and building for 4 seasons and not just 1.
Continuing Education Units (CEUS) 1 hour in
• Green Business Certification Inc. (GBCI)
• Building Performance Institute (BPI) NonWholeHouse
• American Institute of Architects - AIA (HSW) (PENDING)
• Certified Green Professional (NARI & CGP)
• Certified GreenHome Professional (CGHP)
• AIBD
• State Architect / Builder License may be applicable
Lessons Learned:
1. Learn the difference between an air barrier and a vapor barrier
2. Understand why we need vapor and air control
3. Learn when we need added interior vapor control due to exterior conditions or when none is needed at all
4. Designing an air tight and vapor open design with stone wool insulation
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Speakers: Dan Edelman and Randy Williams
Dan has been in the built environment for 20+ years. Beginning as a project manager of large commercial projects and now working primarily with residential designers, builders and contractors. Dan has been with ROCKWOOL for almost 10 years and works with builders, contractors and architects nationwide, offering solutions to common issues with the building envelope. Dan has been a part of many high performance homes and even just turning a code driven home into a more energy efficient build with proper installation of the components of the building envelope.
Today, Randy mostly works for other contractors and homeowners helping them design their projects with building science based assemblies and occasionally get the chance to install some of the products he specifies. For some reason Randy enjoys installing WRB's and interior air/vapor control layers. Randy still performs energy assessment and audits but has added code compliant blower door testing to the mix. Randy still works some in the field, mostly tiling, something he did on all the new homes he built was install the tile. A custom shower is the ultimate in bulk water management, plus it satisfies his need to work with his hands. Randy also writes articles dealing with cold climate construction, most are on his blog, www.northernbuilt.pro. Randy has several that have appeared on the Green Building Advisor. Randy also has an Instagram account of the same name as his blog, @northernbuiltpro.
Thanks for this discussion... I have been studying in circles, trying to do the right thing.
1976 Single wide Mobile Home, Mid Florida East Coast. Rat infested rot, total rehab.
Ripped out all the rot. Down to bare joists and 2x4 studs. Replaced all rotted joists/studs. Removed all the wet insulation, skirting, heating , A/C and duct work.
What I do next will be lost inside the assemblies forever, so I have one chance to get this right.
I am 74 and doing all the work myself on a tiny budget.
I will not have any central heating of cooling, it will be handled with Inverter Style Window A/C units (MrCool)
I am installing new vapor barrier in crawl and sealing the exterior crawl wall the best I can . Very dry soil, good elevation from water table. Super dry, clean and empty crawl now.
One side of the home is flat to the South with zero shade... the heat pumps off the interior wall like a blast furnace.
I really want to us a radiant barrier to reflect that heat back out.
That will mean an impermeable barrier inside the wall assembly. (or is there a permeable radiant barrier that I haven't discovered?)
I am considering continuous installation of 5 mm 2 sided foil Bubble over the studs, directly behind the wall board... draping the bubble foil in 2" between studs, leaving an air space on each side. No additional insulation.
Or: permeable radiant barrier cut into bays against outside aluminum panel -> fiberglass batts -> wall board.
I am 100% open to any solution that is inexpensive. Replace Bubble Foil with a Vapor open - air tight wrap?
Aluminum sheathing -> Rockwool -> continuous vapor open/air tight -> Wall Board????
Help!! I have to make a decision
Thank you!!!!!
Great to hear you are doing the work. You may wish to get your home certified.
Thank you for this very informative video on a confusing subject. I have a question I'm hoping you can provide guidance:
-Zone 4 (Seattle)
-1920s house with 2x4 walls without insulation
-removed old siding and putting on new WRB over sheathing.
-over the WRB we will be installing a 6mm rainscreen
-new siding over above
Question: we were going to blow in insulation into the stud space but I'm concerned about trapped condensation. If the stud cavity remains uninsulated, this would allow for better drying? Thanks!
This may help you before you get started ruclips.net/video/nFZJVNESf8M/видео.html
My whole problem with vapor barriers is that in most of the US the vapor barrier is always on the wrong side of the assembly half of the year.
Stay tuned for the 475 webinar.
Bingo!!!
That's why it's better to install air barriers that are vapor open but have some capillary action.
That capillary action will allow the material to dry at the other side fromwhere it became wet, i.e. due to condensation.
Good materials are: wood fibre boards like HB or MDF.
in a zone 4 with EIFS system and rock wool, what would be the best vapor barrier to use inside?
"I would recommend a class 3 vapor retarder for this application. "
"Latex paint, enamel paint or other approved materials applied in accordance with the manufacturer's installation instructions for a perm rating greater than 1.0 and less than or equal to 10.0."
Chris Jessen
Business Development Manager, Builders - North Central
Building Insulation, USA
M 1-952-658-9004
CS 1-855-876-3755
Chris.jessen@rockwool.com
ROCKWOOL
www.rockwool.com
Video starts at 5:11
There is good info before that. Thank you!
I wasn't going to install poly on my interior walls before drywall but now I will be. It's a mobile home renovation, complete gut job. It will have a mini-split for heating and cooling. I tie the poly on the walls and the ceiling together. My question is considering this, should I go with plywood and typar or go with zip system for the exterior?
Either of those options work well.
Either of them will work, they are the same application. It would depend on your budget and the price of what each assembly would cost. If you are doing the work yourself then the cost of labour is not part of the equation for your budget...a nice bonus when being a DIY'er👍 😊🇨🇦
I should have mentioned that I live in the Northeast. After doing more research I vapor barriered the inside and will go with Tyvek on the outside so it can breathe out but no water can get in.
so in canada how much foam board do we put on outside of 2x4 walls and how much on outside of 2x6 walls?
If you put up vapor barrier on inside walls your going to put wood or sheet rock on walls with nails or screws and make hole in the vapor barrier so why would it hold air back when it has the holes in it just like outside ...
The holes from nails and crews as you put the sheet rock on are partially sealed from the pressure of the sheet rock pushed against it as the screw pushes the sheet rock into the hard surface, the stud. Also, the holes are very small, so not like totally being "like the outside" where there is significantly more air exposure. ☺ 🇨🇦
I live in climate 6 and use rockwool for my exterior walls. I have the zip system plywood on the outside walls. I plan on using tongue and groove boards on the interior walls, will I need polyethylene vapor barrier in the inside?
It depends on many factors of the entire assembly. I would recommend an interior vapor control like Siga Majrex or Intello. Never poly.
Zip is a vapour permeable, rock wool is vapour permeable, are the tongue and groove boards vapour permeable? I they are then how much R is on your exterior to keep the zip plywood dew point in check so that the zip plywood is kept warm in the winter to prevent it from getting cold and so condensation occurs? The rule of thumb is if you have a vapour permeable assembly then the poly plastic air and vapour barrier is only one and placed where drying can take place either to the outside or inside. Climate 6, our issue is how to keep that wall sheathing warm enough so condensation does not happen. What is the R value of rockwool to your exterior begs the question. 🤔🇨🇦
Did you end up using poly?
We are building a house in Utah near Salt Lake City where temps fluctuate from 0 to 105 winter to summer. We are doing fiberglass interior insulation on 2x6 walls and wondering if we need a “membrain” (or other) vapor barrier on the inside of the exterior walls (before drywall) or not? Also wondering the same about basement walls that we have framed up and plan to insulate with fiberglass bats. We have only had the outside of the basement sprayed in a black material for water proofing. I’m trying to make the case for rock wool, but have had no success convincing the general it’s better. This question is primarily to understand what we should be doing with the vapor barrier though. I think we border on climate zones 5 & 6. Thanks!
We live in climate 6, in Canada. It was mentioned in the video that in climate 5 and above the more xps Exterior insulation you have the less of a vapour barrier on the inside. This is because the xps showed in their chart has a perm of almost 0, or on chart .1. So the xps is a air and vapour barrier in itself, so you do not need a 2nd vapour barrier which would be generally considered in the inside. So it appears that you wrote you will Not be placing any exterior insulation, so this means drying can take place to the outside so you need a poly plastic (vapour barrier) behind the drywall, or poly over the studs. This means the sheathing of the exterior wall can get cold due to a lack of exterior insulation, so you want to make sure you eliminate vapour to condense on the sheathing from the inside, so you need the poly on the inside.
Replying to your basement question, well, this would take a long reply, but if you google and research all will be explained about the building science. Basement walls are a different "beast" to understand with lots of conditions to consider pending what your soil moisture and slope of ground is about, to name but a few particulars. Cheers, 😊🇨🇦
Regarding a shed that was built in Minnesota a few years ago. It has steel siding attached directly to the exterior walls (typicality pole barn structure). I plan to heat the shed in the future. I was planning to put batt insulation in the walls with a 6 mill poly vapor barrier on the interior and then either steel or plywood interior walls. Will I get in trouble with no air barrier on the outside of the insulation? I just installed 6 mil poly, 2" XPS insulation (taped), pex tubing and 5-1/2" of concrete. What are my options to prevent the wall insulation from failing (from air intrusion??) and damaging the wood structure and growing mold, etc. Thanks.
You have a very typical insulation strategy for your post and frame or "pole barn" structure in a cold climate. Will you have trouble? Maybe, it depends on a few things that you did not include in your question. What is the building going to be used for? For instance, will you be storing snow and ice covered vehicles during the winter months that will be melting off and increasing the inside humidity level. Second question, what temperature are you planning on keeping the building? Keeping the structure at 40°F is less of a risk than at 70°F. Chances are, if you can control the moisture level inside the building, keep it around 30%, there won't be an issue. Natural air leaks will help keep the indoor humidity low, but depending on where the air is leaking to, this could be a problem. If the air has enough moisture and it finds a surface to condense on, this could lead to the mold and rot you are worried about. When you insulate and add the poly, make sure all the seams are taped, use a really good tape, and do a good job sealing where the poly meets the concrete floor. I'd use a product like Contega HF from 475 Supply for this connection to the slab. Also seal any penetrations that go through the poly, like a plumbing vent or electrical wiring. If possible, keep the attic as a vented space, make sure the eave vents, if they are installed, aren't plugged with insulation. As far as the not having an "air barrier" on the exterior, you're actually missing a water resistive barrier or WRB. It's rare that a WRB is installed on a traditional post and frame structure. My advice, install the poly as air tight as possible and control the interior humidity level.
@@northernbuiltpro7197 - I forgot my main question. Should I use vapor barrier on the ceiling as well?
I have two radiant in-floor heating zones. Zone 1 will be a 16’ x 20’ office. Temperature will be kept a good office working temperature 65-68 degrees Fahrenheit all the time. The remaining part of the building (zone 2) will be for snow removal equipment and attachments and will keep this at a good working on equipment temperature maybe around 55 degrees Fahrenheit, to melt the snow and be comfortable working on equipment. The shed size is 36’ x 56’ with 14’ ceilings. I have heard some people in Minnesota say I don’t need a vapor barrier in the ceiling. That concerns me. FYI, my ceiling will most likely be steel.
@@D-Allen I would use poly on the ceiling, in our climate anyways. The steel alone would be a poor air seal. Be sure to tape the seams and tie to the wall poly to make everything continuous. You will need a way to control humidity inside the building. What you could do is a wait and monitor approach. Monitor humidity levels for the first winter and control using a dehumidifier if needed. If you are experiencing a higher humidity level above 40%, you'll need a more cost effective way to control, like a heat recovery ventilator (HRV), commonly called an air exchanger. An HRV will use 20% the energy of a dehumidifier. The building will let you know if the humidity is too high, widows, garage doors and possibly the steel panels themselves could have moisture on them, but I would still use a hygrometer to measure humidity levels. You can buy one for under $20 on Amazon. I would monitor both in your office and shop areas. The poly is serving two purposes, as both an air and vapor control. Vapor diffusion isn't much of a concern, the air leaks are. If you were located outside a cold or very cold climate, I would not suggest this strategy.
i will have a poured concrete wall with wet attached natural stone from the outside. so no way to put any sort of barriers from outside.. however what product can i use from the inside to make sure i do not have vapor or condensation or moisture in the air conditioned space. This is for Florida
Sounds very cool. Make sure you get your project green certified. We can help!
What did you end up doing? What product ended up working for you?
I live in Climate Zone 2 in a residential facing south where only one of the walls (front side) is possible to insulate exterior. So this makes me only go for interior insulation, construction is using CMU concrete block 15cm wide with mortar. I would like to know if I insulate interior, where does the vapor barrier go? does it go directly to the concrete block or after the insulation?
No need for a vapor barrier but if you wanted to use a vapor control layer it would go on the exterior. Air barriers are much better and be a multitude of products for this and these can go on the interior or the exterior, or even in the middle.
Just have decent ventilation and dehumidification - barriers trap moisture which is never good , not required in most cases if the building is designed correctly
Are you saying keep it permeable?
“A vapor barrier [sic] blocks _air_ …” applies to sub-terrain applications?
does California not need vapor barrier because we are in zone 10 look like zone 7 is the highest
CA has many zones though not sure they go up to 10. Check with your local code official to determine this.
Mitsubishi "Dry" mode overcools the room. Always, every time! Everyone knows that. It is not usable, will need a separate dehumidifier.
I dont want my heating system to know whether i'm occupying the space. Some shady person can have a livestream of when i am where.
Did we discuss that? It is something we do talk about. Typically it is more about sensing CO2 increases not people.
@@GreenHomeInstitute Yes you did briefly. I see. Still, unless i lose both my hands or something, i dont need any 'smart sensors' in my home.
@@GreenHomeInstitute It would be easy to work out if someone is home based on CO2 levels
@GreenHomeInstitute in zone 5 chicago area, what is best practice to insulate a 1976 concrete basement. 2" XPS foam board with 2x4 wall rockwool r15 and no vapor barrier or 1" Xps foam board with 2x4 wall rockwool r15 with a smart vapor barrier? Thanks
Okay I already know the answer. But I was curious. Of this RUclips channel 5 minutes and 44 seconds into it I gave up.
Don't give up!
That you said "taping plywood or osb is an air barrier" is absolute bullshit..