Vented Attic Insulation? Here’s a trick We Stole From European Builders
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- čas přidán 21. 03. 2024
- A genius ceiling air sealing technique not as well known in the US! Matt and Steve explore the concept of maintaining continuity in the air barrier across the ceiling by utilizing a wind and rain proof facade membrane , along with a double-sided tape and finished off with some strategic framing techniques.
They explain the purpose of incorporating these techniques in a vented roof system to prevent air permeability issues and optimize insulation performance and the importance of these techniques in achieving superior energy efficiency and minimizing heat loss.
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What's the R value of that mustache?
Based on the thermal differential between upper and lower lip. Assuming no anomalous thermal bridging by way of soup or milk stuck in the stash. We are seeing estimates around an R 1.4 - R 1.6. Which is pretty good considering it is a fully vented stash. I believe they were first popularized in Europe, but many people are saying they are making a big resurgence in the US as well.
Lol best description of a vented mustash ever 😂
😂😂😂
Probably the hardest I've ever laughed at a comment 😂
LMAOOO
Kyle from RR Builders has been showing of the Majrex in his latests buildings. He was inspired by The Build show to not just build sturdy buildings, but dramatically improve efficiency by "sweating the details." He has shown that you don't have to use spay insulation as the only way to get get great blower door scores. The Majrex is kind of like Gortex for a house. It's makeup (chemistry and weaving) makes it so moisture can more out at a much higher rate than moisture can move in. So it lets a building dry, while not allowing much if any outside moisture back in. The Swiss are doing some amazing things with Building Science. The materials aren't cheap, but the long term benefits to a property are fantastic. Low energy loss through air movement, moisture can migrate outward. Interesting that in this video as well, they show they are using a little bit of spray insulation in key spots, but can then switch over to cheaper blown in insulation, while still creating a super insulated house.
Just recently finished re doing my vented attic. Blew all the loose fiberglass to different corners and worked on air sealing penetrations and top plates then adding 2 layers of R15 rockwool, then clear a different section snd repeat. Then doubled the length of vent baffles to they'd actually be above the insulation layer unlike before where they were clogged with fiberglass. At the end i have an R30 rockwool layer and somewhere between R30-45 loose fiberglass on top.
Also, anybody that has issues with insects like bees nesting in their attic, i suggest putting in a finer stainless steel mesh for the vents. I had tons of paper wasp nests in the vent baffles (palm sized range), so i put in a .22mm mesh, about what a window screen is, and sealed any non vent openings to the outside. No more bees should be getting inside, nor spiders, stinkbugs, or most things.
Good info!!
Another option is to get a pump hand sprayer and spray your eaves, soffits, and vents every 2-3 months in the spring & summer with something like Tempo SC Ultra. I do that along with spraying around the house foundation and do not have any issues with insects inside the attic or the house itself.
I’m about to do something very similar including doing t & g soffit under the eaves so I can seal up and re-screen the vented blocks.
I'm about to do this type of work in a bungalow with a south facing half of the roof which gets sun all day. A bungalow with a finished upstairs goes from 1 big attic to 3 small attics when you finish the upstairs. The two lower ones need to be vented, and they're not on most bungalows, causing the upstairs to really cook in the summer. When the lower ones are vented, the vents serve as cold air intakes for the air to travel up the inside of the roof rafters and exit the gable vents at the top that was already there before.
It was a bummer finding out in this video that loose fill gets blows around when you vent an attic because I have loose fill and the south facing lower attic needs to be vented so badly. I'll probably do what you do with two layers of rockwool underneath and then loose fill back on top, and do it in sections like you did. The gable vents that I bought from home depot already have a mesh on the back which looks like the holes are small enough.
@@readtherealanthonyfaucibyr6444 consider solar powered intake and exhaust fans to compliment the gable vents. Also, for the vented eave blocks, there are spacers that maintain the air gap creating a duct/chase for the convection path. The loose fill doesn’t blow around much at all once it is installed by “blowing it in”, the air exchange doesn’t move any appreciable amount of the loose fill around
Just yesterday, I saw a commercial property (an old auto repair shop) fully resheathed with ZIP System. This would have been a pleasant surprise, except for... They didn't use any tape and/or liquid flashing. Yeah, they paid the extra money for ZIP system sheets, but skimped out on the tape and liquid flashing.
Matthew.... I mustache you a question, but I'll shave it for later.
You're blowing up my gable
Matt you have inspired a generation of future owner-builders to take pride and enthusiasm in their construction.
Agreed
Steve's projects are often above the level that the energy codes require, and can be very expensive to build as you chase down heat and air loss. I doubt that the majority of builds in these areas are anything like this. I applaud Steve's creativity in finding new ways to seal and insulate homes.
Appreciate the comment - sometimes your comment may be true, but here we need to hit .30 ach 50 (clients wants sub 1.0) and the code requires R-60. Ok take out 5" of blown in insulation (that would pay for itself in as many years) - how would you detail the ceiling / roof to hit 3.0 ach 50? You have to do something? So, what would you do? How do you design this detail?
@@stevenbaczekarchitect9431 I personally would just do spray foam. That seals the house and seems like a lot less labor and issues for lighting and penetrations. Also makes for a very clean and accessible attic space.
I heard about that wrapping technique before. Cool to see it up close in practice. Great way to merge a couple of approaches.
Agreed
Love these videos. Plan is to (eventually) self build a house similar to some of the techniques Matt brings us.
Can't go wrong
Great video! Explains the continuous air sealing and sequencing very well. 👍
Thanks!!
I was beginning to have Steve withdraw! Always a pleasure to see what he's up to!
Always lurking in the building corner's coming up with new ideas to old problems - I do appreciate the concern...
Steve has a youtube channel that he uploads to several times a week
I’ve been building houses for quite some time now in Washington state. I’m assuming because of moisture conditions, our codes require more air flow throughout the building. I get that, and some climates, having things, sealed and airtight is necessary. But I’ll tell you one thing. I’d hate to be the person paying for all these extra details. All these companies trying to come up with new systems to sell more material for higher costs. I try and look out for my customers and only do things overkill if they’re 100% necessary. These look like some great systems but are they all necessary? How do you change out lighting if it’s sealed in the ceiling? And we use baffles in the attic all the time, but why run them so close to the peak? One baffle will keep your insulation from blowing away from the bird block. Again we have to deal with high humidity’s and lots of mold and mildew so it could just be the climate. But I’m curious?
You cannot create a tight home without also adding in energy capturing ventilation systems. These have to be active. Building a tight house is like putting on a wind breaker over a sweat shirt. On a windy day a sweat shirt won't keep you warm. Add the wind breaker and you are comfy again. Start to move a bit and now you need to shed internal moisture. By controlling the ventilation, filtering it as it enters and then capturing heat and controlling moisture, you keep a house comfortable. Extra air "make-up" has to be added for high speed air extraction like big kitchen vents. That's been shown in other builds. The energy consumed with the active energy recovery systems is more than offset by energy losses you have in older style homes. This is at the core of good passive house design. Get this wrong and you have no end of trouble later. In high humidity climates, you may need to add central dehumidification, especially if your building is so efficient that the AC doesn't have to run much. Dehumidifying uses energy, but it's less than full AC cooling.
Sounds about right. I live in Washington State - King County Area. I've been working on my house bit by bit, including 2x R15 layers of rockwool added as a base layer, with about R45 average depth of existing blown fiberglass on top. I extended the vent baffles by about double to get them well above the loose insulation rather than right at or a bit below the insulation level like before. I also went through and air sealed all penetrations from plumbing, electrical, lights, and wall top plates, no matter how difficult it was to reach. Tight areas of the attic are straight R60 rockwool like one side of the vaulted ceiling above the master bedroom where the down slope of the ceiling also has the downslope of the roof and comes to a tight point at the end.
Moisture shouldn't be a problem in the attic now, but in the house during the fall it can get humid inside and before the attic project I had needed a dehumidifier to run. However that humidity primarily comes from outside when it's 60F average and 80-99% humidity all the time. So having a tighter home and controlling fresh air intake, and eventually something like an ERV would reduce the amount of humidity management required theoretically. In the winter its cold enough that humidity is not a problem, and summer usually isn't too bad but we'll see.
Next project probably next summer will be replacing the rat feces/pee laced fiberglass in the crawlspace with new R30 rockwool and air sealing wall bottom plates and penetrations. I probably won't do encapsulation even though HVAC ducting is in there, but I'll have to do more research for my situation. @@andrelam9898
FYI there are homes and small apartments/condos built this tight in the Seattle area
@@andrelam9898 With just doing the typical sealing like zip wall and being thorough on details, it is often necessary to mechanically add fresh air because the house is already too air tight. I can' t imagine we need this product. Or that it wouldn't be more effective to just do spray foam and a conditioned attic.
I'm definitely curious how we'll look back at this period of time in building technology development in a few decades. I try to stay very open minded to new technologies and innovation - it's how we get better. But, my skeptic hackles spike when I see all this stuff. For now, I'm sticking with tried and true methods, and letting other builders experiment with the new tech. As time goes on, the best products will reveal themselves and I'll start incorporating them as well.
Just inspected a 6 year old house with big snow drifts of loose fill insulation near the porch overhangs, and big patches of uninsulated drywall, of course. Builders get annoyed with inspectors for "overthinking" but I'd say our building practices have a long way to go.
Great info as usual - nice video!
Thanks for the comment
I also agree on the Building Practices.....
😂 I literally decided to do this last week on our next build. Thought I will be the first. Awesome! Matt want some pictures of the build in a couple of months?
Hey guys, 1st comment! just got out of my insulated attic. Been working on it for a few months. Need to vent it.
In 1992, we did something similar with 6mil poly vapour barrier: continuous from basement to attic, wrapping around and completely enclosing both the first and second floor platforms, in zone 5 (which required vapour barrier towards the interior and the bulk of the insulation outboard).
The danger is poly is not vapor open, Mayrex is...
@@stevenbaczekarchitect9431 Thanks for the reply. In Canada zone 5, 3000 square feet, with HRV. It used some techniques that were not common at the time, was affordable, and could be heated in winter by inviting a few people over. 🙂We did not know about Majrex in 1992. Was it commonly available in Canada then?
@@gregh99 im a younger tin basher, I was born in 1990! No it was not common in fact its a newer technology. Im in zone 6 in canada and it also wasnt necessary in 92. Its only with the onset of much warmer, more humid summers and an increased use of central AC that its needed. Instead of only worrying about water vapour condensing in the winter we essentially have a summer situation that is similar to a southern set up like texas. Hot humid air travels inwards through the wall from outside and hits the cold air on the interior of the house and condenses on the back side of that poly. Mayrex is the solution to this. Poly should be banned in Canada and smart vapour retarders should be the new code. But back in 92? Id say you where being forward thinking. Its so easy to make these decisions with the level of building science education now adays thanks to youtube but 92 was a different beast, I dont even understand who you guys managed a business without widespread cell phone usage haha
In my new home we used 1/2" OSB as the air barrier on the ceiling, sealed with wet flashing to periphery and joints. Then ripped 2x6s in half and installed on edge for a service cavity for plumbing and electrical. Blower door tests out at .58 ACH.
That' good air tightness, but the permeability of OSB is only around 2-3 perms......
You totally sold me on conditioned attics. There is no way I would ever want a vented attic in my house now. The way you did it in your own house is just the right way to do it.
That one was really expensive.
Btw in cold climates you have to vent to prevent roof rot and ice daming.
And of course it's a LOT cheaper.
European here :) at 2:23 he probably meant that moisture definitely cannot pass through SIGA membrane, it's not air barier but rather moisture barier membrane. Foam as roof corner air barier is one of the options, but not greatly used here, given most of the time insulation is EPS foam, which runs through the outside wall up to the roof. Piece on roof beam can be blocked off by simple osb or plywood to prevent wind from passing through the usually "blown insulation", but also as a way to be able to blow and stack more of that insulation towards the corners of the roof. One item that I missed, on 2x4, didn't he miss to add nail sealing tape? It usually gets added on top of the roof, but given this is moisture membrane you need to seal off those gaps here as well. Also, wouldn't just rely on tape, membrane glue should be a must, which can be used around nails/screws as well.
Siga says Majrex is vapor open.
Majrex allows vapor to move well in one direction, but not the other. You will see it clearly stamped with direction. If installed backwards, it would be bad. It's like Gortex for a house. You can let moisture out, but almost no moisture can come back in.
@@andrelam9898 nope. Check the website and read the PFF.
It’s all dependant on RH and absolute humidity.
It can move outwards, jjst not as well as what it lets inwards.
Most smart VB let it go both ways, still dependant on RH and absolute humidity.
Siga separates themselves by controlling it one way, but not totally stopping it still lets some out from the warm side to the cold.
Your welcome 😘😘
For the OP, this is why I love cardboard rafter vents. They are easily manipulated at the heel, and can pass moisture through if needed if siga or poly lets sow through.
If you have raised truss heels, run your exterior foam boards up to the roof leaving your inch or two for venting. That’s for new builds or Siding and attic coupled Reno’s with raised heels.
If not the cardboard in old roofs with no raised heels allows best height of insulation. At edge wall, without stuffing batts below the stryo rafters as many do, as that takes in soffit cold air and your top plates aren’t really insulated.
Are you saying majrex isn't considered an air barrier? If that's the case that is absolutely false and is marketed specifically as a smart vapor and air barrier.
Ah puberty and growing facial hair. Also the voice cracking high...which you clearly hear at the end of his videos when he says, "oooooon the build show". Matt's growing up so fast! *sniff* *sniff*. ;)
Comedians among us - love it!!
As someone who has fiberglass cavity wall insulation, as well as exterior cladding Styrofoam insulation, as well a vented R50 attic that originally had R15 batting then topped up with blown in. The weak points are definitely these edges where the air is vented in the drywall at these ceiling lines sometimes gets down to 9 or 10 C in the winter when the rest of the room is 22 C, using a thermal camera you can see pockets where additional air sealing under the insulation is required.
I am not guessing when I speak - thanks for the supporting comment
I don't understand how it can be air tight but not water tight. Got any good reads on it?
As an insulation contractor, there are a few more points on spray foaming in vent chutes.
First, it seal the air flow from coming into the small amount of fiberglass on the edges and dropping cold air down the wall. It keep all the air going up and over the blown in like states.
Second though is it gives full insulation value down at the top plate and heal ends. We primarily work in zone 6 and 7. R49 min but really like r60 of fiberglass which is 20 inches. Well down in the ends of most trusses you get 6 to 8 inches max. Add a baffle/chute in there and you are even less. By spraying closed cell foam there, you give those ends up acceptable performance values vs if not you only have around an r15 of blow in at the rafter heels in most new construction.
We do it on every build and regularly have to talk customers through why the added cost is needed
So on your project homes are there ridge vents, gable vents, or other venting system? I have a bare bungalow that I am trying to decide how I will insulate it.
@@maddierosemusicno gable for sure. I’m R60 min cold climate R29-31 for walls now it’s insane.
Ridge vents are good if it’s steep or you don’t have snow.
They are more continuous, just snow blockage creates an issue.
Maximum makes a ‘cathedral’ custom vent look it up real cool shit. But that’s for old school cathedral where you have to vent every bay because it’s rafters.
Cathedral ceiling with truss, and normal open attics stack vents are the best. (Again my climate lots of snow regular ridge vents get buried) but If roof is steep enough or not a lot of snow ridge vents are great.
Gables suck. Air pressure from temp difference draws cool from lower (soffits) evacuates hot from higher (roof vents).
Another thkng to add here, soprema cardboard rafter vents are far better than the styro ones, and yes spray foaming top plate to rafter vent connection is awesome.
To the OP, again soprema cardboard vents are king, reason being is they install to the top plate, rise vertically before you then bend them up the roof pitch.
Blocks wind from going through the batts most people stuff below styro.
I know that’s not in this vid, it’s just common practice.
This roof is steeper and doesn’t appear to have as much as the heel but I could be wrong.
We’re vaulting heels 1ft or more now to have higher R value at the wall also. Have seen some really tall vertical rise at the heel.
I go cardboard, and if the customer wants to pay I’ll spray foam.
Only reason I say it that way is I’m retrofitting attics not building, and I still go to this extent.
Also I’m seeing new/different values.
Some say 18 inches for R60 but what I’m used to is 21-1/2 or so.
I’ll go high to be safe, but wondering the difference if anyone knows.
My packaging still shows 21-22 so I’ll stick with it just curious as OC didn’t have an answer for me.
Thank you, I am getting a new roof and will go with the roof vent, and foam at the base of my rafters. I do not have gable vents currently. The whole 2nd floor is open to do as I wish. Thanks!@@justinstevenson2061
The chase ways are convenient but also use a considerable amount of extra lumber taxing our lumber supplies and the wallet of the final customer. As a contractor I have known for some time now that there are way more materials for housing construction on the market than the average homeowner would ever need. The trick is knowing just what is necessary for each house. Building suppliers will always come up with more and more materials for you to use. Well, for them to sell anyway.
There are nails/connections going from the rafters to the top plate that break that air seal, right? Do you do anything to seal those?
Just a truss screw sealed in the wood - not really contributing to Air leakage.....
Its kinda like using tyvek in place of poly, something i’ve thought about before, i think the product could be pretty effective in some horizontal applications if it was made easier to handle for those areas
Kinda- except this is a better than Tyvek at managing moisture
Specifically, what are the baffles used at the soffit?
Please do a video on ProClima Intello for the same application.
It would look the same
Good 2 man team! 👍
AGREED!!
Agreed. It’s just that he only shows siga. It would be helpful for people to know about other products. I missed it he said the episode was sponsored by them.
It isn't and a few companies have smart vapor retarders, just need to google it......
Aren’t all his videos these days basically infomercials?
Why didn't you do a raised heel truss to get more insulation thickness above the ceiling under those baffles? You say r 80, but no way your getting r 80 under those baffles.
Yeah it’s amazing how far behind the states are in some departments
There is a 10” raised heel. There has to be a balance between heel height, roof pitch, height of the building and overhang relationship to the top of the windows on that floor. This was the best overall balance given all those factors.
Also understand, using a 10" heel with a flash of a couple inches of CCSF, you get R-65 at the plate
RRbuildings has been doing that for a while, looks like a great alternative to condition attics and or spray foam.
He has, but we did this in the late 90's at Building Science Corp
Do you have any information to which is more cost effective Between this air barrier method and closed cell foam on the roof deck?
Great question. This has to be at least 1/2 to 1/3rd the cost but it would be good to get actuals for a future video.
It really is build science ! What type of blown insulation and any proof of longevity? Thanks
Cellulose, Nu - Wool to be specific.......and of course this will last
What recessed lights do you use with flat 2x?
I love the attention to detail and all of the energy you put into building science, but all of these videos need a quick explanation at the beginning of the location/climate zone. I’m a builder in MN and most of the insulation and air sealing methods on your channel would not be best practice here. People who are not experienced (my customer base) need to know why certain methods are best in certain climates. The scary thing is that there are likely a lot of DIY guys that are creating future mold disasters based off of CZcams advice for a different climate.
There would be no issue with this detail in your climate zone
Why would this not be best practice in your climate zone? This type of assembly could be used in your zone and colder. I would not expect any mold issues specifically due to the use of the smart vapor barrier.
can someone post the eli5 of the trick in comments? i couldn't catch it in the description/in video
We recently went through this and documented it, but our architect wanted the sheathing to tie the trusses into the building. That meant that the top of the sheet did not fall exactly on the top plate, so we couldn't wrap the tape / membrane through to the outside of the building like this. We ended up doing the same idea, but had to seal the membrane to the backside of the sheathing. Curious if anyone feels that the structural tie in of the trusses down to the wall with sheathing is necessary?
Assuming I understand your comment correctly, It's a good detail imo, especially with high wind loads. Personally, I like the idea of a raised heel truss with the sheathing running all the way up the heel of the truss. It ties the truss to the wall and serves as a baffle for blown insulation.
@@noneyabidness7226 Yeah that's exactly how I did it. Raised heel truss, sheathing goes all of the way up. Before setting trusses I placed a strip of intello down on the top plate and, depending on the spot, did my best to air seal to the sheathing with tape, air dam, and gaskets.
Couldn't find a "proper" way to air seal this. Felt a bit makeshift.
@@bellrisefarm If you had used zip sheathing would you really need anything else? Aside from airtight drywall.
@@noneyabidness7226 In my current house, that is the weak spot. I'm trying to get ACH50 below .6, so I was hoping for a continuous air barrier around the entire house. Airtight drywall works, but requires attention to detail. Conservation technologies has gaskets made for that top plate connection behind the drywall. I can go that route. The easy way would be just some sort of tape/membrane that laps over the sheathing onto the top plate as shown in this video, but that doesn't work well with raised heel trusses.
ok - i have solved for that too, put a couple beads of Tremco acoustical sealant on top of the plate run the Majvest across the plate smooshed into the plate and into the room to connect to the Mayrex. As for the sheathing all the way up - simply run a bead of tremco along the face of the top plate - now you air barrier connections are Zip sheathing to plate to majvest to Mayrex......
why do they put the vent through the roof vs through the wall? it seems like over time the vent boots always end up causing leaks when going through the roof
Couple of things I’m curious about.
And I absolutely love this style of full envelope, and love what these guys are doing not trying to knock I’m genuinely curious.
Wondering first how is the blown insulation supported? Because the drywal is going onto the horizontal 2x4, so what about that 1.5 inch space?
Typically the drywall holds the insulation weight, how is the weight bearing down to the drywall in this scenario?
Insulation is light of you grab a handful, but R60 let alone R80-90 etc is a lot of weight, how does that sit on that smart vapour barrier?
Also another thing I’ve always noted, is that (with standard 6 mil poly) when it’s drywall - poly - strapping - insulation the poly is flush on the drywall.
But when they do drywall - strapping - poly stapled to truss - then insulation over found the strapping gets mouldy a bit due to that 3/4 gap between the poly VB and the drywall.
While moisture forms in that cavity, on the warm side of the poly VB, it’s forming on the wood strapping and then not drying out as easily as opposed to poly behind drywall where it’s forced to dry onward to drywall and conditioned home.
How is that dealt with? I know it’s a smart VB but still moisture forming where the 2x4 is would be an issue here wouldn’t it?
The siga majrex is taped to the bottom chord of the truss with a tenacious siga tape, then the 2x4 strapping is nailed over that to the bottom chord of the trusses. The 2x4 strapping provide more than enough support for the blown in insulation that is to come. We’ve successfully used this approach before.
The one directional nature of the majrex allows any potential vapor from the warm side to pass through into the vented attic. The blown in cellulose is vapor open as well.
@@brettpelletier1219two things;
First the 2x4 of course strong enough to hold, more thinking of the span between 2x4 strapping. The insulation will weigh on the VB causing it to stretch or pull off staples or tape holding it in place etc.
Also two things with the vapour drying I think possibly problematic.
First you don’t want and moisture passing into the attic insulation, that’s the point of VB.
Also the main of my original point is that when there is a cavity there between drywall and VB, the strapping will take some moisture which regardless if the drywall breathes or this new VB breathes it’s the point that the wood will not dry as quick.
So standard 6 mil poly when done flush on drywall the strapping, moisture form warm side of poly directly on the drywalls back. Moisture has no other choice but to go into drywall and dry to inside.
But everytime (not exaggerating every single time) I’ve seen the VB on the truss, and then strapping the cavity created has moisture forming. Yes it will dry through the drywall, but it’s now wetting the strapping somewhat. And that strapping is slower at releasing moisture.
My understanding of the smart VB is that it can function both way.
As in when it’s warm inside and cold outside it should act as a normal VB.
But in the summer and it’s warm outside, and cool inside with typical poly VB now the moisture forming on the warm side which is the insulation contact side.
That’s bad because with dual climate -30C to +30C poly VB only works in one season properly.
That’s what the smart VB works with isn’t it? But regardless if it lets moisture breathe to the insulation that’s a problem isn’t it? literally the reason we use poly VB in the first place is to not let the moisture form in the insulation.
Cellulose or fibreglass regardless they’ll all be open breathing, the issue is when that reaches the top of the insulation depth and hits the cold attic air it rapidly condenses causing mould.
Not trying to call anyone out, jjst trying to see if there’s a missing link here.
@@justinstevenson2061 my mistake, I see what you’re getting at. The 2x4 strapping is spaced 16” oc. I agree with your line of thinking here in regards to the science and your experience with how moisture moves, I just don’t think the real world application will be an issue here. We have dedicated dehumidification and this assembly isn’t trailblazing. This approach has been used successfully in many high performance homes and we’ve had success with it ourselves.
@@brettpelletier1219 oh yes absolutely. I’m just the retro fit insulator. Main trade roofing, naturally moved to siding, and then natural to insulation.
Have to do siding to swap wall/step flashings effectively.
And have to understand insulation and venting to do roofing/siding so they all fell together.
I’m always baffled these idiot mass builders don’t for example put poly over the interior partition walls to connect each rolls VB continuous. Literally have said this for many years now.
Also as to why when they lay tyvek strips on top exterior plates is it only for the exterior tyvek to join, and never hung over the inside to join to poly.
Yes both different uses, but can at least air seal and still not trap as tyvek to VB not creating any double VB scenario.
And literally 9 days ago o jjst started leaning about smart VB, so when I saw this video I was crapping myself.
Like everything I’ve seen as failures and wanted to address (just haven’t made the jump to build yet, want to but nervous lmao even if I know more than most custom builders I’ve seen hacking it up on 2 mil builds) but all of those failure are addresed in this vid.
So two fold I pat myself on the back to say “it’s not what we’re taught but what we can come up with” but also to show this system in full use by these two in the vid, and it being in practice more in Europe so tried and results noted.
But also then even with perfect poly VB (before learning of smart VB) over partition walls you still have penetrations, and that’s another mass failure.
So this method of 2x4 strapping to me is incredible.
But then started thinking of strapping dead air space downfall.
Wondering if siga on bottom chord and then drywall or plywood etc (whatever has higher vapour permeance) then strapping and interior finish drywall.
Only strictly for weight of insulation. But to run electrical and some horizontal plumbing etc is brilliant.
But then still the same air space problem I’m bothering myself with. Between the two layers of drywall the strapping is still where vapour can be.
But at least my way I’m thinking the vapours not forming on the strapping at the siga, more it’s forming on the ply/drywall at the siga, and then drying to the cavity and then drying to the home.
I overthink things ridiculously.
My metal roofs are double strapped and ridge vented.
Not many do it but some do. But they also cut the ridge wood and use that ridge vent to vent attic and under metal panels.
I don’t cut the ridge wood, and the ridge vent is only for under panel venting.
I then use a stack vent like a Maximum to vent the attic.
Yes the detail to vent the attic through stack vent through double strapping and make stack vent watertight while using hidden fastener metal panels is a pain, I custom make drip edge with drilled holes on a horizontal 1/2 bump out from fascia as an intake for under panel venting.
But all in all that house won’t suck heat, metal will expand/contract far less backing screws (even with plastic washers) but I just am as mentioned self admittedly way over the top.
But that how innovation happens right?
Im just wondering how 20 years later the strapping and moisture diffusion will go.
Not saying you or these guys are causing failure in any way, I’m just killing my self thinking as I always do.
This system is still far far better than what’s out there for sure, just wondering what the next step will be.
R&D takes us so far, trial and error is where we inevitably learn.
I love the soprema cardboard vents, as opposed to the stryo.
The cardboard is better manipulated to fit the truss heel, and if there is any issue (Reno’s down the road and some mook makes holes and doesn’t seal them) and hot air rises it then condenses on the styro rafters where cardboard will breathe outside.
I’ve had people ask, well cardboard isn’t as water resistant as styro, I tell them then you should make sure your roofs kept in good shape 😅. Ideally if I do your roof and attic you’ve got not damn worries anyways.
@@brettpelletier1219 I appreciate your responses, and no I’m not going to seek help for my overactive thoughts, I enjoy stressing myself it seems.
Doesn't the weight of the insulation strain the membrane at the fasteners? I see the membrane supported by the trusses on 2' centers then the 2x4's at 90 degrees to the trusses. Any possibility of breaking the membrane from insulation weight?
The 2X4's are 16"OC
Just make sure that no mouse will bite through the vapour retarder or air barrier.
Dam mices
Ok, you're going to get me in trouble with my wife, because now I want to tear out the ceilings and Siga wrap it.😂😂😂
Who's the boss lol?
I see someone has informed Matt of Air Force tradition.
Around 3:35, they say going to use drywall for aesthetic reasons. What about for fire blocking? Is Majrex fire blocking, and if so, then in theory Majrex could be used in a freestanding garage ceiling (without living space above) in a vented roof construction, correct?
What are your thoughts about having a vented attic but spraying the backside of the sheet rock with Spray Foam?… not the roof line???
This is an interesting idea. Dunno if I like it considering electrical in the ceiling but... non flammable/ flame resistant foam....
I've seen people do it only at the drywall joints where air is likely to make it's way through. Also a lot cheaper than spraying the whole thing.
Open or closed cell?
It's going to cook the shingles, I've had this setup for 35 years, I have reason to believe it's taking at least 7 years off my asphalt shingles.
It's a VENTED ROOF
At least in Northern Europe we have our air and vapour barrier on the inside of the wall assembly. This means you don't have to go over the top plate to maintain an air barrier.
Yeah, they could have continued the majrex down to the walls and air sealed from the inside. That does require a service cavity or extra detailing to keep the airtight seal going. This seems like a somewhat budget conscious build given the vented attic which Matt typically avoids so maybe they didnt want to pay for the additional labor for that detailing.
I am fully aware of how you all do it - I appreciate it, but I do not agree with it for a wood framed building. For your Masonry buildings yes - wood frame here, NO
Many consumers demand can lights. Might be good to cover all there is involved with that. ... I've gotten where I hate the glare from can lights and prefer task lighting, torch floor lamps, etc.
“Can lights” in the era of LED lighting should really amount to the low profile units that can easily fit below that vapor barrier. If your customer tells you they want old-school cans, show them how much better the new options are.
@@shawnbrennan7526 The "wafer" or "pancake" lights that you mention are more suitable for tract homes or the DIY'er. I'd compare these type of fixtures to using traditional OSB and house wrap for the wrb. If your customer desires can lights, then do them a favor and get regressed cans at a minimum. This will greatly reduce glare. Good can lights, which typically require a housing, also provide the option for different trim/flange color options. Good can lights will also provide more consistent CCT between fixtures, dim more consistently, and provide a greater dimming range.
The best option would be tape and channel, which would work great for this detail, but budget is a factor just like every other decision. Most of these videos are geared towards a higher end client and I can't think of an application where I'd provide a $25 wafer can light for a house I was building for myself or specifying for others.
Owners interact with their lighting every day. Remember that they can actually see their lighting whereas they cannot see their air barrier. Both can greatly contribute to occupant comfort.
Pretty much what has been code in Ontario Canada for 10 years !!
Appreciate this - people talking about how this is overkill......it's an Air Barrier and some additional insulation
Nice furring strip Matt!
Awesome video, but wont it still need to be sealed correctly after penetrating for pipes, electrical boxes, etc. Just like old school vapour barrier? As for now HVAC, thats only in the US it seems. Canada its inside the structure. So without soffit ventilation, how is the roof being vented?
I think they said it is vented through the soffit at about 5:20.
Yes, we use gaskets and tape to seal the plumbing vents and conduit for future solar. We treat it the same as penetrations in our exterior walls.
I must achyou .... Are you gonna apprentice as a cop on your next trades show you're doing?
You should get one of those monocles, with that stache, so you can finish the look of the Monopoly guy at a younger age. Change is good.
Kool, very kool.
If you are still installing drywall, taping, and mudding, why is this SIGA Majrex of use? Seems like extra labor/materials cost... Does it help with air-tightness since wiring and other drywall penetrations can use the raceway instead of actually breaching the attic? Seems like you could still just air-seal before you blow in your attic insulation with just drywall...
I've been asking the same question. They say the majrex allows moisture to come out of the wall but if the interior wall is covering it how does it pass through that?
How is this different from Tyvek?
It's smarter......the truth
@@stevenbaczekarchitect9431 OK, but I was hoping for some details?
Couldn't we place a second layer of majrex on top of the insolution to hold it in place. I know Matt likes to use the example of putting a coat on the outside of the living space, but don't most insulated coats place the insulation between a sandwich of fabric to protect it and keep it in place.
The cost isn't worth the result
@@stevenbaczekarchitect9431 They used spray foam to achieve the same thing.
Matt went a little belt and suspenders with that 'stache.
cant you use a house wrap, on the ceiling and be just as good. Just keep the eves and sofets closed off from the main part of the attic...
Plus wouldnt a heat tower/cooling tower built into the gable of the house, serve well?
I've been trying to figure out what the difference is between Majrex and a traditional plastic-sheet vapor barrier. Most of my searches have turned up no useful info (they say "smart vapor control" but never explain what that means). But just now I looked again, and a site says that it's directional, in that it lets vapor move from the wall to the interior to dry out the wall, but not the other way. That seems good for the heating season, but not so good for the cooling season where it sounds like it'll let exterior moisture into the conditioned space, perhaps condensing on the back of the drywall. I think what Steve said in this video (2:19, "it's a smart vapor retarder, so moisture can pass through it, very easily") is probably wrong. I suspect he was pointing/motioning in the wrong direction.
moisture majrex venting it out of the living space I guess is best way to think of it. giving moisture a way to leave the house without letting any back into it in general.
@@Tenspound If that's what it does (e.g. the way Steve pointed), it'd definitely be a bad product to use in regions that have any kind of significant heating season, where people are using humidifiers to try to bring the indoor humidity up to normal. The moisture would then condense as it migrates through the insulation, going into the colder part of the wall/roof.
@@kc9scottNo it allows for moisture to move BOTH ways based on the given RH. This would allow it to dry to the warm side OR cold side depending on the current conditions.
@@Deluxe754 So then it’s kind of like not having a vapor barrier? How does it decide which way to let the moisture flow? In the winter, people have normal humidity in the house interior and (if everything’s working properly) low humidity in the wall cavities, and the goal is to keep it like that, as much as possible.
@@kc9scott The material allows transfer from low RH to high RH but does at different rates based on the side. Its all based on RH and each side has a different perm rating range.
Is Matt growing a stache? Go goatee, Matt! LOL...
feel bad for the next guy having to do work in that attic !
Really cool, over engineered though, doubt anyone will use it on production housing. More likely spec homes or custom homes
I don't know about production housing being the standard???
Wait ... what is up with the huge section of black on the wall over the porch? It looks like a $1000 worth of zip tape!
It's an adhered membrane
Ted Lasso is now hosting?
Just a SIGA ADD. With all that work must, be cheaper to just spray few inches of closed cell on flat ceiling and top it off with some open cell, if you dont need unvented attic, No settling no adding stuff later, no extra 2x4 on a ceiling. Probably would.cost almost same or cheaper.
It would be more expensive here
Is the attic now removed as a storage area?
In the northeast, that's what basements are for.
It's trussed and only 22' wide, you need less stuff, not more storage
Aah Matt, that's a big NO on the mustache. You look like you should be a member of the Gestapo.
This house is crazy complicated for a wood framed house which probably wont last long enough to make it worthwhile. Like a contractor friend said, "High codes, low quality".
I wouldn't listen to that friend very much - what's Crazy Complicated? Putting up a membrane is complicated?
That stache is giving me vibes of some old comedian 😆
Smothers brothers
this idea in the video suggests , use Additional attic insulation baffles between All roof trusses to extend from the soffits Higher up the roof slope ... (we use 6 mil poly vapour barrier in Canada, 🥱 your welcome
basically you don't need that "product " you need extra baffles
OK good to know somebody is out there doing things I wouldn't. Enjoy
As if air can migrate through taped and muddled drywall.
It can't and I never said it could, you just need to be very diligent about any holes........as if!
What a mammoth house.
It's 2000 sq ft.....mammoth?
Rockin the 'stache 🥸
R84... w/blown insulation... 😂. Maybe in a test tube. The electrician and plumber will tear it up installing cans and vents.
IMO in North Texas the best attic is sealed and conditioned to keep the humidity near 40-50% with a properly installed Zip roof deck and open cell foam.
Nobody installs cans anymore. Led pucks sit in that 2x4 cavity. Hvac comes from below
All the electrical will be below the majrex (besides 1 conduit for future solar) the only plumbing penetrations are the vents which are installed well before the blown in insulation is installed.
But is that really a ventilated attic? It really seems like you’re air sealing the air baffles to just allow air to run in a narrow stretch up and against the roof, which is fine, but the attic itself just seems to have become this dead space, no?
It looked like in the pictures you are spray foaming all the baffles all the way up, and the seams, and just hadn’t finished the ones on the right 5:37. I imagine you’re then spray foaming the ridge to seal where the two sides of the baffles come together?
It just seems like an odd combination versus just having a well insulated and sealed hot roof with extra usable attic space within the conditioned envelope (if desired). Maybe this method just allows for cheaper bulk insulation like you mentioned about the blown in?
The baffles only run up far enough to extend past the 24” of blown in cellulose. In the roof section you see in that part of the video it’s a lower gable roof. The spray foam is mostly to lock in those baffles and prevent wind washing of the loose fill cellulose that is to come. My personal preference is the vent the attic until you’re forced not to.
@@brettpelletier1219 fair enough, and that’s what I would have normally assumed, but the angle in that shot looked like they were basically just trying to make a mini/thin vented airspace.
@@brettpelletier1219So you will have 10" of blown-in between the top plate and baffle?
@@D2O2 yes, minus 1 1/2” where the vent channels are in the baffles. So there’s 2-3” of ccsf that starts at the top plate and goes about 2’ up the baffles, then blown in cellulose.
Side note: the neighbors had a great natural view from a very nice house until that new house went up right in front of it.
So the millions of builders who installed poly were wrong? Why would you want a permeable membrane allowing moisture to migrate into the attic anyway?
In areas of Canada that can get very cold I would worry where that moisture would start to freeze and depending on what insulation is in the attic when would problems show up. I'll stick with my poly. Like the strapping on the ceiling chase idea though, to help protect the vapor barrier.
@@kerrryschultz2904I like the blue material over the top plate too..
They mention at around 7:30 that for colder climate zones you would use a vapour retarder (like poly).
😀
When detailing is too complicated, the majority of builders will get some of the detailing wrong. When small mistakes in detailing result in critical problems with a building, the design itself is bad.
Good designs are robust when construction details aren't absolutely perfect.
I have a lot of respect for Matt and Steve, but 95% of houses should not be built with very complex details that could result in a critical failure if those details aren't followed precisely.
I think simple, low-tech vented roof designs are OK. Otherwise, I think continuous-insulation designs with non-vented roofs would actually be easier for builders to complete without errors than vented roofs that require large amounts of specific flashing details.
I would argue exactly the opposite, but it is a free country, fell free to go roll the dice
No raised heel trusses? That seriously reduces the R-Value around the entire perimeter of your attic. It might be R84 in the middle but the average will be way less, maybe R20 at the top plates.
There is a 10” raised heel.
@@brettpelletier1219 my idea of a raised heel is to allow a uniform insulation thickness all the way out to the edge of the wall. Otherwise any truss that keeps the truss top chord from touching the wall plate would be considered a “raised” heel.
A true raised heel also makes for larger overhangs, a good thing from a durability perspective. I guess something is better than nothing.
Also, a 10” raised heel needs attic vents installed, so that takes away from the thickness of the insulation as well. I see they also needed to spray foam this area to seal it. Using a true raised heel truss you can fasten strips of OSB to the trusses and seal with acoustic caulk or canned foam.
Were small overhangs a styling decision or wind load requirement?
@@superspeeder I agree with you that the larger the heel the better and in an ideal world it would match the depth of the insulation. We have 2’ overhangs which I would consider fairly large. We had to balance the height of the building, pitch of the roof, overhang relation to the top of the windows on that floor, etc. Overall, with all these factors we arrived at what you see. There are always things that could be done better from a building science perspective, we’re just trying to do our best to strike a good balance.
@@brettpelletier1219 thanks for clarifying! Agreed, there are often compromises made that aren’t always obvious.
I’m in the process of building my own home and these are all things I considered. I have 3’ and larger overhangs with an 8:12 pitch, so lots of room for raised heels and simplified attic venting details. In my area, maximum building height per zoning regulations was not an issue so I had lots of design freedom.
Cheers, and good luck with the build! Looking great so far!
@@superspeeder that sounds like a recipe for success! Thank you very much and best of luck with your build as well.
Soffit vent still works the best in my opinion
Agreed
You are still going to have hardly any insulation at the edges due to the room pitch.
10" Raised heel with R-65 CCSF......I think that is good enough
@@stevenbaczekarchitect9431OK, I must have missed that in the video. So if you are filling from the top plate to the underside of the baffle with CCSF, how far in are you coming before transitioning to blown in? Seems you are still going to have a dramatic step change in R-value at some point. Like 65 down to 38 before climbing back up to the center at full thickness of blown-in?
I mustache you a question !!?
Raises more questions than answers imho , this is a builder on the cheap to pass local building codes , I wouldn't want to live in that house , you can buy a shredded steel insulation that is both fire proof and sound proof , foam sprayed in sucks , there are no firestops in those walls aside from the fact they are 2/4 which means 2/3 covered in foam instead of sheathing , a kid playing while your building could run right out of that house an fall to his death , inside walls support or not should have a double plate , that vented attic is a gimmick a roof is vented anyway insulated or not , an guess what if you charge a customer to foam the entire outside of the house then cut out the openings what happens ? then look at the window framing , those window openings aren't framed , could go on a on about how cheap and crappy that house is but have said enough pretty sure anyone reading this knows it disgusts me as someone who has built homes that last are comfortable in Canada and use little energy
LOL have you watched this video? Cause you make no sense.....
@@stevenbaczekarchitect9431 Did watch it an feel your engineering as cheap as possible by the lowest bidder an trying to pass it off as well made which it isn't but i'm sure the new home owner will be charged well made , I probably designed super insulated homes before you were born , I know bullshit when I see it , but believe what you want I won't change my opinion
@@stevenbaczekarchitect9431 Your advocating homes built to last until the builders warrenty expires after about ten years and passing them off as something they are not and you know it , so yes I have issues with that , I have no problem with making money on youtube , be upfront about what you can expect from that build and I will shut up , we both know the difference between well built and O look what we can get away with now with lax codes
They're trying to sell me a can of beans for 3 dollars now
It is little overkill
What part - love this discussion. We need to hit .30 ach by code here (client wants 1.0 ach) and the insualtion required is R-60. We have added a little insulation per client wishes. How would you achieve these metrics? Less expensively?
Siga products are not cheap. Not sure why you're so concerned about air penetration at the gables when you've clearly got large gaps at the top of your roof trusses where your plastic vents terminate to let air pulled from the soffits out through the ridge vent. Why not go with something simple like LP TechShield as a radiant barrier and then put R13-19 batt insulation all the way from the eaves to the ridge with at least a 2" gap for max radiant barrier efficiency? A lot of Matt's stuff is not transferable to anything below custom homes, including most Siga products. Builders just aren't going to put that kind of money in things. I live in NW Atlanta, and I've never seen a builder even use Zip tape and Zip sheathing is once in a blue moon.
Not a ventilated attic. It is a ventilated roof deck. Very interesting.
From Europe, a hut is a hut is a hut, no matter how hard you try to fake a house
California found that tightening the envelope causes indoor air population so in idiotic fashion they now required a 24/7 ventilation fan. Might as well keep the front door open.
I can't say I see as California as a leader for what I should do......
Some of the energy recovery air handling systems use very little power in contrast to a leaky home that requires much more energy to heat or cool because of the excess air exchanges per hour.
You might want to look into how an Energy Recovery Ventilator (ERV) actually works instead of comparing it to an open door.
@@LooseNut - I think that is where the code is going but the cost of regulations has become so high there is beginning to push back . Panasonic makes a reasonably priced one but I question the longevity.
@@LooseNut It was @markmarcinik that was talking about tightening the envelope causing indoor air pollution requiring a fan running 24/7. He said might as well keep the front door open. I know exactly how an ERV or HRV work because I have researched them since the 1980's. Ill informed people that think a drafty house with all the energy loss associated with poorly built houses probably have never lived in a building approaching super insulated standards with adequate ventilation through out the house to remove excess humidity and stale air or damp and odour that a proper house should provide.
Some simple COB or Hemp built structures eliminate all the increased steps and constant solutions to the constant problems from this inferior, industry/guvment led building method.
The mustache adds 20 years 😮
Reinventing the wheel again !
Dorks
Well not really.....but you can sling mud, "first one thru the wall gets bloody"
Did Matt lose a bet?
Yup, he bought me lunch
Grocery stores are trying to sell me potatoes for 2 dollars a pound
Even more jokes!!!
@1:32 you can see daylight.
The zip tape isn’t opaque and lets light pass through. I promise that seam in the window opening is taped. We werent concerned with the panels butting up super tight in the window openings when they are going to be cut out for the windows to go in.
This is just adding cost, paranoid overkill. There is nothing wrong with long tried and tested traditional 6 mil poly vapour barrier and insulated, vented attics.
I would never put poly in a code built home today - metrics are different, but you go roll the dice.