Building a Vaulted, High-Performance, and Foam-Free Roof Assembly
Josh Salinger shows us how to create more space, vent a roof, and do it all with a reduced environmental footprint.
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Пікірлер: 53
"We're using no plastics!" First product used is Tyvek wrap
@michaelvonfeldt9629
4 ай бұрын
Haha yep yep
So glad I saw your video on unvented vaulted ceiling and moisture mitigation. I was going to do Vapor diffusion Port but there is no room in my roof assembly to allow free air flow from soffit to the ridge. I thought I had to use closed-cell foam + mineral wool until I see this. Thank you!
Josh, very nice work! There was a brief comment below about a radiant barrier on the top-side membrane. The overall theory I've been contemplating is to add a reflective foil membrane on the top-side, which reflects radiant energy back into that 1 1/2" vent channel. Reflecting that radiant energy back into that vent channel should transfer that heat directly into the air that is moving up, because expanding air has a natural buoyancy which helps that heated air to rise up to the ridge vent. Simple physics, actually (cf. gas laws: PV/T is a constant). I also really like the addition of standard 2x4s to create that air channel on the top-side. Depending on the nailing schedule, it also results in adding much additional strength and stiffness to the rafters. As such, a similar assembly could be very easily adapted to jobs where old roofing is being replaced: pick up at the point where all old shingles are removed, with bare plywood remaining. A 1/2" rigid insulation with foil backing can be quickly ripped on a table saw and placed between those 2x4s, leaving a 1" vent channel. Alternatively, 2 layers of 2x4s create an air channel that is 3" deep, allowing room for rigid insulation that is thicker e.g. 1" or 1 1/2". I'm sure your capable carpenters can work up the soffit intake and ridge vent details: piece o' cake for capable professionals like yourself. KEEP UP THE GOOD WORK!
Are you using longer nails (16d instead of 8d or 10d) to attach your roof sheathing?
I also live in the Portland Oregon area and wonder if Josh would use this assembly for a very low slope roof?
The low-slope side of your roof may have more issues with venting (less stack effect) did you change the assembly on the low slope side or do you have a working minimum slope for the 1.5" vent cavity to work? Also be careful not to use pva primer on your drywall!
Interesting. I just purchased a house with vaulted ceilings.. is there anything I can do to better insulate it. Or would I basically need to tear it all apart and rebuild it?
was there any thoughts of using a radiant barrier on top instead or with the tyvek?
It seems that thermal bridging is not considered in any way with this strategy though?? Also, is the water control layer going to be on the roof decking? Will it be taped at the joints to also become another air control layer effectively having 2 air control layers?
@JaredCzaia
3 жыл бұрын
I'm not aware of a way to break a thermal bridge to the exterior without foam. Thermacork perhaps.
@kenmarcou
3 жыл бұрын
@@JaredCzaia well, I mean you just need insulation. A non-foam vapor open option is mineral wool/rock wool on the exterior of the roof. Seems as though at least something breaking the bridge is like, really important no?
@JaredCzaia
3 жыл бұрын
@@kenmarcou True, comfortboard on the exterior would be about perfect for this scenario. I had to google to find it as I assumed mineral wool only came as a cavity filler and not as a sheet good.
@timothydillon6421
3 жыл бұрын
@@kenmarcou dont forget the drywall and paint add another layer of vapor and air on the inside.
@worganyos
3 жыл бұрын
@@JaredCzaia Low density fiberboard insulation is also an option.
I’m confused as to why the interior membrane “closes down” with high humidity going from interior to exterior, yet “open up” to let humidity escape going from exterior to interior to dry the insulation cavity. How can you have it both ways?
@DeadRedRider
Ай бұрын
Majrex membrane was designed based on the natural moisture balance of a cactus. SIGA brand name for this tech is: Hygrobrid. A cactus allows moisture into the plant at night to trap the moisture inside during the day, preventing the plant from drying out in the hot/dry desert climate. Similar to the cactus, Majrex allows the moisture to move from within the wall to the inside of the building but doesn’t allow interior moisture into the wall. It's “one direction vapor transportation”, as moisture only moves to the interior. Seems like magic but it's just fancy layering of different products to mimic something found in nature.
curious could you not just use 1X strapping instead of the 2x4??
@timothydillon6421
3 жыл бұрын
That makes adding electrical boxes and etc really tight.
@cognitive-carpenter
2 жыл бұрын
I think he meant on top of the rafters, not the horizontal underside of rafters
How many of these have you built to date?
@jdaz5462
4 ай бұрын
This is the only one because it has serious issues with its design. A roof with foam has decking first for strength, then foam and furring strips before more decking. It's not even air tight with Tyvek. He's installing decking over the sketchy 2x4's. This roof will have much less shear strength. It needs 2 layers of decking in order for this to work properly. Let's hope there's no big wind storm or tornado nearby.
Nice, but this system still has thermal bridging through the joists. That could be minimized with TJIs or with a rigid foam on the interior under your nailers, but I understand you are trying to avoid foam.
You now have a thermal bridge every 16 or 24 inch's. Could be done better
$399 for one roll? Siga must be very proud of this product. Finehomebuilding should also highlight less expensive alternatives to solve problems like this. With my build I'd have to purchase three rolls for around $1200 bucks. That ain't in my budget. I guess "Finehomebuilding" means expensive, uppercrust homebuilding instead of middle-class budget minded homebuilding. Thanks for the vid, though, because it has given me an idea on how to insulate my attic space.
@multidinero
3 жыл бұрын
The expense of the material may cause you to balk, but in most cases you get what you pay for. Also, take into account how long the assembly will last, its overall performance and how well it will handle as a conditioned space (As that’s what this whole thing is for). If the whole assembly costs upwards of $15k for the roof, for example, and lasts you 20 years, then the roof cost you $750 per year before any deductions you make for energy savings. For a high performance assembly like this one appears to be, it’s more than the upfront costs. Try to see the bigger picture of how your home’s performance can be improved.
@DavidWood-qw8rq
3 жыл бұрын
If anything about the phrase “fine home building” leads you to think budget friendly or middle class. You’re not understanding the term.
@JaredCzaia
3 жыл бұрын
To be fair to FHB, at least the expensive building materials they feature are typically for performance and longevity as opposed to luxury and appearance.
@willbass2869
3 жыл бұрын
@@multidinero 'the bigger picture' is that vast majority of Americans will not stay in one house for 20+ years. Sorry, not sorry, but I'm not taking on a 20+ year expensive system to benefit people who come 10 years after I sell. Really wish people would clear their minds of that fantasy.
@multidinero
3 жыл бұрын
@@willbass2869 from your statement, I’d recommend you not touch your roof at all. Being cheap always goes wrong when it comes to houses. The video is about energy efficiency and ultimately lowering your bills. If that’s too expensive for you, then you must like high energy bills. Small money, like bills, make those who think like you do, feel that the price of energy is cheaper than the upgrade to lower the bill. In actuality it’s a compounded effect. By installing high performance upgrades to the home you increase the home’s value and save money of the time you’re in the home. But, if you’re planning to move in two years because your house is too small, I’d disabuse yourself of that fantasy. You’re going nowhere! Between the Wall Street companies and the Oligarchs from foreign countries investing in American real estate, if 15k in upgrades makes you cry, you’ll be stuck for the next decade. Unless you’re building from scratch, then maybe you have a chance...but again, building doesn’t sound like your speed. But, I’m doing a lot of assuming. Suffice it to say that it’s no fantasy to live in a home for 10+ years. A lot can happen in a decade.
Origami?!!! Lol. I laughed. Cellulose compacts down I have read. So???? Blown out n loose fibreglass or rock wool is expensive. Maybe I could do this for my house next year. Post frame q 8’ 60’x40, maybe use floor trusses instead of roof trusses. Somehow make a vaulted ceilings out of them then use your idea mirpex bottom insulation then tyvek then maybe 2x4 on end with 5” Perlins screws for the air space and steel panels
Hold on. There is nothing rigid against the membrane?? I think you just made the world’s biggest harmonica. Every time there is a wind storm, the homeowner is going to hear that flapping around, no?
@HaploBartow
11 ай бұрын
It's stapled to underside of the rafters, and the lateral 2x4s every 24" up the length are also fastened through it to the rafters as well.
@reldred79
5 ай бұрын
No, the dense pack will hold it in tension
Why not just use regular vapor-impermeable membrane (0.2mm polyethylene sheet, for example) on the inside? The "smart pores" cost a lot of money for zero actual benefit.
@worganyos
3 жыл бұрын
Polyethylene generally results in moldy walls because it traps moisture in the cavity as it moves inwards from the outdoors. It's better to have no vapor barrier at all than it is to have polyethylene.
@AdityaMehendale
3 жыл бұрын
@@worganyos I generally know what I am talking about - it is difficult to judge if you do. Do you have knowledge in this, or is it "just a hunch"? In the former case, we can discuss further. In the latter case, let's just move on.
@worganyos
3 жыл бұрын
@@AdityaMehendale that's a pretty pointless response, isn't it?
@AdityaMehendale
3 жыл бұрын
@@worganyos On YT, it's difficult to determine who is trolling, who has a case of the Dunning-Kruger effect, and who is actually knowledgeable, and trying to make a point. My response isn't pointless - I am trying to discern which category you fall into. No conclusions thus far.
@worganyos
3 жыл бұрын
@@AdityaMehendale what are your thoughts?