5 Biggest MYTHS About Unvented Roofs | What You Need To Know

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  • Опубликовано: 30 окт 2024

Комментарии • 66

  • @ASIRIDesigns
    @ASIRIDesigns  7 месяцев назад +7

    0:29 Myth 1 Unvented Roofs Will Rot
    2:49 Myth 2 You Must Use Spray Foam
    5:34 Myth 3 Unvented Roofs Cause Ice Dams
    7:40 Myth 4 Unvented Roofs Make Shingles Blow Off
    8:20 Myth 5 Unvented Roofs Are Hotter

    • @LuminairPrime
      @LuminairPrime 7 месяцев назад

      Are there calculations done on preventing the need for a vented over-roof by using more roof insulation and a colder attic space? How much fiberglass insulation and vapor barrier can you buy with the cost of an over-roof...

  • @roundhill4
    @roundhill4 7 месяцев назад +25

    Great information. I had a tree fall on a home in 2020. The roof needed significant repair, and had zero insulation (in a cold climate where 3-4 feet of snow in the winter is normal). I could not find anyone willing to rebuild as you describe in option 1, so I did it myself, with a staggered 6" layer of polyiso (3"x2). I've had zero issues with moisture or ice dams since then and the house stays warm and comfortable. Everyone I talked to thought I was crazy... Thanks for spreading the word and hopefully more will begin to understand the science around this method.

    • @ASIRIDesigns
      @ASIRIDesigns  7 месяцев назад +1

      So sorry to hear that! Glad the new roof assembly turned out well though. Thanks so much for watching!

    • @Supercharged111
      @Supercharged111 7 месяцев назад +1

      Only thing I'd say about that is polyiso R values drop in the cold whereas EPS and XPS go up when the temps drop. But if it works, it works.

    • @markmartin7384
      @markmartin7384 Месяц назад

      Did you put all the iso boards on the out side?

    • @roundhill4
      @roundhill4 Месяц назад

      @@markmartin7384 Roof sandwich from inside to outside: 2x6 T&G pine (original roof, cathedral ceiling with no inside insulation)-->GAF Peel and stick membrane-->3" PolyIso layer 1-->3" Polyiso layer 2 (staggered joints)-->5/8" OSB attached with 8" screws-->Peel and stick membrane on edges and synthetic underlayment in field of roof-->Asphalt shingles.

  • @ericjacobs7795
    @ericjacobs7795 7 месяцев назад +4

    Wow. Great content. Please continue with this. It’s exactly what I’d been hunting around for. Bravo.

  • @asilvestre1108
    @asilvestre1108 Месяц назад +1

    Bro this is what I've been looking for for a long time. I thought I was crazy, asking myself, "Why the heck hasn't anyone figured out a better way to build roofs?" Great video man

  • @latitude48design
    @latitude48design 7 месяцев назад +2

    Great video, as always! Coming from the PNW and cold climate design further up north, we exclusively use a vented roof assembly as per the BCBC. You can spray foam with closed cell, however, as you mentioned, it can introduce condensation risk through cracking over time. We'd prefer to avoid that. Generally, we only use spray foam for joist ends, if required.
    Our go to system is a vented roof assembly which is trussed or hand framed with I-joist and 2X4 cross purlin, with a smart vapor barrier such as Siga Majrex. In marine environments we also spray the framing with a natural anti-mold agent. There's actually a good argument in those situations to go with an unvented roof assembly, however, it's not commonly practiced in our market and the cost would certainly exceed the anti-mold spray.

  • @dr.coole.
    @dr.coole. 7 месяцев назад +8

    Unsurpassed !! Great video presentation. Great graphics, narration, nice quick pace, thorough discussion of the topics.

    • @ASIRIDesigns
      @ASIRIDesigns  7 месяцев назад

      Thank you so much! Cheers!

  • @mjf1036
    @mjf1036 7 месяцев назад +3

    Great video and pleased to see someone take on this topic.

  • @guytech7310
    @guytech7310 7 месяцев назад +7

    For Roof with exterior insulation, your better off just install SIP panels, since you basically hand building one. For SIPS use a high perm roofing membrane so there is a path for moisture to escape. Better would be a vented metal roof, which the metal roof panels are installed on perlings that have air channels from the eaves up to the ridge cap. This will also help reduce heat load during the summer months as it will create passive convevtion air flow as the hot air escapes from the ridge vent & pull in cooler air from the eaves. Also recommend have a 2 foot roof over hang which will protect the walls from weather, & reduce summer sun radiant heat from the walls and windows directly above the roof.

  • @LuminairPrime
    @LuminairPrime 7 месяцев назад +3

    Great video topic. While the geometry of a roof peak means it requires more insulation and other construction materials than an attic floor, it's not THAT much more when you consider the total cost of the home and the extra clean space provided. It only SEEMS inefficient on paper. In reality, how much would it cost to ADD that much extra space to a home after it's built? Exactly.
    If you want to save money, save it somewhere else. Don't put a rat's nest on top of a new home if you can help it.

  • @nothingmuch2023
    @nothingmuch2023 Месяц назад

    Good content, thanks!
    I've built, demolished, and rebuilt a number of roofs now, and I love that you've quit the spray foam insulation, that stuff is nasty. I also build tiny houses, and SO many people use spray foam insulation - with minimal space for off-gassing to go.
    My favorite insulation material is hempcrete, I've been a certified hempcrete builder since 2018 and can't say enough good stuff about it. Hygroscopic, no condensation barriers as it is a monolithic material, and it can be used for floors, walls and ceilings.
    Also, construction materials are tested individually and in laboratory settings rather than IRL, not accounting for how they work together, and how they deteriorate over time. Where for instance rock wool diminishes in insulation capacity over time, hempcrete lasts. Just sayin'.

  • @charliewheeler725
    @charliewheeler725 5 месяцев назад

    Great explanation on assembly s, on your condition attic with the sheathing separated and vented for cold climates. I think for air intake at eaves either vented drip edge or continuous soffit vent. For exhaust air continuous ridge vent. Important to have air flow under roof sheathing. No matter what type of assembly. As a carpenter who has first hand experience.

  • @JMgmkh
    @JMgmkh 7 месяцев назад

    I built a non vented 2 story 2010 , using spray foam in the attic and batt insulation in the walls below in north central Fl.
    I added a couple A/C outlet ducts and tapped into a return in the attic(easy) to condition it. Never had a problem.

  • @eliinthewolverinestate6729
    @eliinthewolverinestate6729 6 месяцев назад +1

    I am going with exposed rafters and roof board. Gonna insulate the outside of the roof. Doing a sealed shell with eaves on outside of shell. Going with mineral wool board on roof. Have a 6/12 pitch to help with snow sliding off.

  • @FrankReif
    @FrankReif 7 месяцев назад +2

    Great videos.
    You could add that the ratio of exterior rigid to cavity insulation can change depending on climate zone. The ideal being that the sheathing remains warm over the whole year - this covers cold climates and hot humid climates. Building Science Co has tables for a general rule of thumb.
    The other aspect you could talk about is having a vapour open ridge detail, allowing buoyant vapour to migrate up to the ridge over a diurnal cycle, of heating/vaporization and cooling and condensing, before venting out to the environment.
    Cedar breather under metal roofing helps with redistributing localized water accumulation, but still requires vapour drive into the condition space to dry. I think a vapour oven ridge and an interior vapour throttle is the most general assembly.
    Finally, unvented roofs are excellent where wildfires are a risk. There is no vent for the embers to get into the roof assembly.

    • @ASIRIDesigns
      @ASIRIDesigns  7 месяцев назад +2

      Thank you so much for watching, great points. I actually put up an image of the required climate zone ratios at 1:23 per BSC. The vapor diffusion port is a great option for those warmer humid climates, but we just aren't sure how to get them to work in colder climates without a smart vapor retarder. Might need to make a separate video on these too.

    • @FrankReif
      @FrankReif 7 месяцев назад +1

      @@ASIRIDesigns Nice, I missed that at 1:23.
      In cold climates you either vent, or tend towards a vapour barrier right?
      The diffusion vent would be a redundancy for any accidental moisture accumulation - being cheaper that vented over-roof.
      If you're taking request: I think suspended ground floor assemblies need much more attention.

    • @matthewruckle1965
      @matthewruckle1965 2 месяца назад

      ⁠@@FrankReifwhat is a suspended ground floor assembly?

    • @FrankReif
      @FrankReif 2 месяца назад +1

      @@matthewruckle1965 timber floor over a crawl space. Not using a concrete slab.

    • @matthewruckle1965
      @matthewruckle1965 2 месяца назад +1

      @@FrankReifthank you!

  • @SteveThompson-li2fc
    @SteveThompson-li2fc 7 месяцев назад +1

    I’m a roofer in south Louisiana. Heat and humidity are the overwhelming factors to consider when building a home, with hurricane resilience a close runner-up. It’s so frustrating trying to explain to a homeowner that the spray foam in their attic is what is causing their asphalt shingles to peel right off the roof. “But I’m saving $$$ on my electric bill….”
    Question: what is a “vapor permeable peel & stick underlayment”? All of the peel & stick underlayment I am familiar with act as a vapor barrier.

    • @stucorbett7905
      @stucorbett7905 7 месяцев назад +2

      Hes probably referring to a product like Henrys Blue skin. Cheers from Montana

    • @ASIRIDesigns
      @ASIRIDesigns  7 месяцев назад +4

      Adhero 3000 is one example of a self-adhered vapor permeable membrane that can be used as a roofing underlayment as well as a WRB. In Louisiana it makes sense to have a vapor impermeable underlayment in most cases due to all that warm humid outside air.

  • @CharlieZenenour
    @CharlieZenenour 7 месяцев назад

    for the ice dams issue you can just build the roof tiles or metal roof with a vented space between the underside of the roofing material and the counter battens on top of the roof membrane or sarking board.
    Specially in a gable roof, it has the perfect airflow for ventilation between the roofing materials and insulated structure it self.
    of course before thinking about any of this you also have to make sure your structure is insulated up to standards, so make sure you have air exchange of less than 0.60 and a U value of less than 0.20 at the very least.

  • @perfectchaos27
    @perfectchaos27 20 дней назад

    ***PLEASE HELP!!!!
    Hey man, I watch a lot of your videos and really appreciate them. I just bought a house with a metal roof that resembles Spanish tile. I’m confident there's enough airflow under the roof, but I’m unsure if the soffit and gable vents are sufficient to cool the attic.
    The contractor installed pink fiberglass insulation (not spray foam) between the attic and roof, using staggered wavy plastic pieces between the attic beams with insulation laid on top. I’m not sure if there's enough ventilation behind it. He also raised part of the ceiling in the dining, kitchen, and living room, leaving a smaller attic space there.
    Is this a problem? I’m under contract and can still have him remove it. I was thinking of adding a fan for better airflow, but after watching your videos, I’m concerned. My home inspector mentioned the insulation shouldn't be there, but your metal roof videos suggest insulation is okay if not better. I know you use spray foam, and this is fiberglass, but I don't want to make a big mistake in our first home. Any advice would be appreciated. Thanks!
    Also I'm in New Jersey if that helps and I'm open to anyone else in the comments opinions thanks very much

  • @CaseyEwald
    @CaseyEwald 7 месяцев назад

    Could you provide a suggestion for myth #4 - open cell scenario? Is it as simple as inhibiting the moisture diffusion through the open cell, so adding the "taped smart vapor retarder" membrane on the face of the rafters under the strapping?

  • @timbrown9305
    @timbrown9305 3 дня назад

    Love the content, needed something like this 35 years ago but please don't talk to my customers 🤣Easy fix??? Furring strips AND another layer of sheathing $$$. Gotta love engineers. I built homes for several engineers. My favorite was using pressurized concrete for a basement. Uhh even in a state with no seismic activity, cost was unbelievable.

  • @lilsabin
    @lilsabin 2 месяца назад +1

    @6:50, I live in Canada , can you please explain how letting cold air getting in (aired soffites) a -20 celcius , help with melting ice dam at the eaves ? 🙂

    • @ASIRIDesigns
      @ASIRIDesigns  2 месяца назад +4

      Great question and good timing (we're going to have a whole video on ice dam prevention in a couple weeks) but to summarize, ice dams form when there is snow melt over the portions of the roof where heat loss from the interior is coupled to the sheathing and the build up of snow above, in which it refreezes at the cold unconditioned roof eaves. The idea behind a vented overroof is that we prevent that initial snow melt that causes the ice dams to form in the first place.

  • @kukaro
    @kukaro 4 месяца назад

    Great video thanks!

  • @MrTenkara
    @MrTenkara 8 дней назад

    I've seen vapor ports cut in the roof sheathing and covered with a vapor open membrane near the ridge. A place to allow the "ping pong water" to escape. What are your thoughts on that?

  • @disqusrubbish5467
    @disqusrubbish5467 7 месяцев назад

    At about 4 minutes in - the smart vapor retarder - is that sort of a "one way" barrier? If so which way do you want the vapor to go? Or it doesn't matter? Thanks.

  • @Foodman824
    @Foodman824 7 месяцев назад

    My house is from 1920s and i noticed under the aluminum soffit covers there isnt any openings the roof comes flush to the plate…and theres no ridge vent

  • @CharlieZenenour
    @CharlieZenenour 7 месяцев назад +2

    this is a American thing.
    In Germany we have been building unvented roofs for many generations already and never had such problems in mass.
    We build living spaces in the roof, so for us is quite normal not to leave it as a open space in contact with the outside, but rather as just another part of the house insulated just like any wall but with roofing membranes and sarking boards but sheathing boards as well depending on the design.

    • @SteveThompson-li2fc
      @SteveThompson-li2fc 7 месяцев назад

      You have a different climate and different building materials. A lot of your building code is written in stone and has not changed for 50 years. In America, cheap is king when it comes to the majority of our new construction.

    • @CharlieZenenour
      @CharlieZenenour 7 месяцев назад +5

      @@SteveThompson-li2fc
      I live around Munich in the south of Germany and my climate is much of the same as your's in the US.
      In winter I get -5 to -10 Celsius degrees and in summer I consistently get 30 to 33 Celsius degrees.
      Not sure about "writing in stone" and "not changed in 50 years", it has changed a lot in the last decade alone, especially in regards to energy efficiency, but the building practices themselves truly don't change much.
      a lot the detailing around houses has been an evolution of old practices to fit new building products and standards, however most buildings still adhere to the basics of vapour permeability, health living without hazardous materials and use of traditional styles and materials such as bricks, klinkers (lime bricks or paver bricks), plaster and use Walmdach and Krüppelwalmdach roofs that you know as hip and jerkinhead roofs.
      nobody builds houses anymore out of bricks, instead most buildings are made out of single leaf solid clay block walls made out of concrete columns/beams with clay blocks in-between or just clay blocks if its a small structure.
      The exterior is usually finished with continuous insulation in the exterior or with bricks for the facade finished look.
      If if has bricks of the outside or not depends if the clay blocks have enough insulation within than.
      And as I said on my fist comment, the common practice is to construct a unvented steeply pitched roof to server as a additional living space in what you would call a attic.

    • @SteveThompson-li2fc
      @SteveThompson-li2fc 7 месяцев назад

      Your climate is not the same as south Louisiana. @@CharlieZenenour

  • @cxsey8587
    @cxsey8587 7 месяцев назад

    Is it possible to design a perfect wall/air tight house that can work without the need of mechanical ventilation? Or would you always run into moisture problems without active ventilation and dehumidification?

    • @ASIRIDesigns
      @ASIRIDesigns  7 месяцев назад +1

      Why wouldn't you want ventilation or a fresh air system?

    • @cxsey8587
      @cxsey8587 7 месяцев назад +1

      @@ASIRIDesigns For a structure that is air tight but won’t be occupied full time, i.e. a shed or a vacation cabin.

  • @JeremeyHowlett
    @JeremeyHowlett 7 месяцев назад

    Unvented roofs are basically the same as walls. The only issues that arise from unvented roofs is that the roofing and waterproofing degrades faster because of the heat not having a way to escape.

  • @brandonswafford861
    @brandonswafford861 7 месяцев назад

    What is an example of the "taped smart vapor retarder?" Is this just housewrap that allows moisture out, but not in?

    • @ASIRIDesigns
      @ASIRIDesigns  7 месяцев назад +1

      Intello and SIGA Majrex are the two big brands.

    • @swaffstudios
      @swaffstudios 7 месяцев назад

      @@ASIRIDesignsthank you! I opted for r30 mineral wool in my attic because I didn’t like the idea of spray foam concealing a roof leak for a long time if one occurred. If I wrap the inside of the cathedral ceiling with either one of these products you mentioned, will they let water through if I get a leak?

  • @almaxie342
    @almaxie342 7 месяцев назад +2

    Technically great presentation. However finding a competent contractor to do the work is a big challenge. Also an inspector should be checking on the contractor to make sure they are following the specifications as the project moves forward.

  • @BronxRebel
    @BronxRebel 7 месяцев назад

    @Incredibletinyhomes Is there a better alternative to spray foam???

    • @ASIRIDesigns
      @ASIRIDesigns  7 месяцев назад +3

      Yes! Rigid insulation installed outboard with an air barrier membrane is significantly better.

  • @jackjmaheriii
    @jackjmaheriii 7 месяцев назад +2

    Great video, I’m not hating, but… It completely skips non-spray foam options for trussed roofs. Dense pack will settle and you’ll be left a pocket at the ridge in which humidity will collect. If you use blown fiberglass the pocket will be even bigger. No one is doing blown mineral wool right now, and mineral wool bats create a ton of cold spots. That only leaves a vented over roof assembly, which is hilariously expensive in terms of labor and materials. You can do LVL rafters but that is also super expensive. BCI is better but mineral wool leaves a lot of voids with that too. Now we’re back to foam. I like Zip-R 9 🤫, with two inches of closed cell sprayed over the truss members and plussed up with open cell, then covered by a clay based fire retardant paint I’m not trying to pretend I’m a building science expert, but I have a JLC subscription and I think about this problem ALL the time.

    • @TroyWarr1980
      @TroyWarr1980 7 месяцев назад

      Properly installed dense-pack cellulose does not settle. It's blown in at twice its settled density, so there's simply no room for it to settle. You might be thinking of standard blown cellulose used in attics, which does settle because it's just loosely blown. There's also damp-spray cellulose, though, which I have in the walls and under the floor of my house. it adheres to the substrate and builds up into a spongy mass. I haven't seen it used in roof assemblies, but I'm not aware of any reason it couldn't be blown that way just like it is for walls. I have 6+ inches of the stuff between my floor joists directly exposed to humid central TX outside air, and after 15 years, it's still adhered just as well as the day it was applied.

    • @jackjmaheriii
      @jackjmaheriii 7 месяцев назад

      I’ve never remodeled a house with damp blown, but I worked in San Antonio for 4 years and dense packed definitely settled in areas above showers, and other places with high moisture exposure.

  • @rodfreess6019
    @rodfreess6019 7 месяцев назад +1

    Myth #3, just fix your unvented roof by making it a vented roof, myth busted? Worst ice dams I've ever seen were in Washington DC, not just a cold climate issue if you don't want water running into your house.
    9:06 "negative pressure", as far as I understand, the code requires at least half the venting to be soffit vents, ridge vent is optional, soffit vent is required, for this very reason. The outdoor air will be warmer, more humid and less dense than the indoor air to lessen the amount of air being pulled through the ceiling by ridge vents.

  • @theonewoo
    @theonewoo 7 месяцев назад

    Myth 3 Unvented Roofs Cause Ice Dams. Solution: build a vented roof over top of the unvented roof. Ooof!

  • @murraysheppard1153
    @murraysheppard1153 7 месяцев назад +2

    Who has the money for that?..sure you can do it...but...

  • @jasonbeisiegel5550
    @jasonbeisiegel5550 7 месяцев назад +1

    Number 3, by your own admission, is not a myth. You solved the problem by venting the roof.

    • @ASIRIDesigns
      @ASIRIDesigns  7 месяцев назад +1

      You're venting the sheathing/roofing finish, not the actual roof itself.

    • @jasonbeisiegel5550
      @jasonbeisiegel5550 7 месяцев назад +2

      @@ASIRIDesigns, that's not a real distinction. You're making the distinction because it fits your argument, but it's not a distinction that is made in the real world. If you were making the argument that the roof structure doesn't need to be vented, then sure, but you aren't.
      You've offered a presentation that gets all the details right, and then makes an overbroad conclusion. You're sacrificing accuracy and confusing people to make yourself sound like some sort of revolutionary. The reality is you are saying the same thing that anyone who has a basic understanding of building science would say: You can get away with an unvented roof in many scenarios, in an area with high snow loads, you need a vented roof.

  • @JohnDoe-kp3sw
    @JohnDoe-kp3sw 7 месяцев назад

    WHAT ???

  • @tar170
    @tar170 7 месяцев назад

    $100k roof defeated by mice.

  • @CarlAyers-x8h
    @CarlAyers-x8h 7 месяцев назад

    So you're venting about venting. Ok.
    It's like I always said....idk.
    I said a lot of stuff. Age 67.