Perfect summary! Yes

😂

Bear with me on this one. So if yo insulate your attic with closed cell spray foam, you still need a dehumidifier, right? I bought a new build in New Orleans and the house is tight, but could be tighter... Thanks y'all!

@@buildshow q11+1¹1¹1

70 pints a hour, a day, I see its a 70H but what do you mean?

Just insulate at the roof instead of the ceiling.

Lol my thoughts too. That is like my "weekend beard" 😆

I second that ... along with cross-section on his walls., eaves/overhang etc etc etc

I third that. This is to much for me, an up and coming builder.

How thick is the roof at this point?

@@ZNotFound I believe it to be over 1' lets see 4 inches of foam, I'm guessing a 10" rafter? then the thin layers of water proofing, and those stickers to raise the metal panel.

@@jayutley8748 yeah I studied architecture and i've lost track haha.

Joe balances scientific rigor against real-world experience. He's competent working with formulas, algorithms, and models, but he's not doctrinaire about them (unlike many in the climate space). His approach is a lot more conducive to serendipitous discoveries. And he has a sense of humor. We need more real people like him in decision-making roles, and fewer of the autism-spectrum, narrow-minded technocrats who have risen to the top, like scum in a pond.

Don’t be so high on him. He’s much more confident and in love with himself than he is a person that is, you know, actually correct! He’s been blasting off in-your-face talks for two decades and wrong half the time. That’s why this interview is awkward - Matt built his very own house off of Joe’s N-1 advice, and you can see he feels silly

Easiest way to ensure you are safe is to install a dehumidifier in your attic and set it to 40%rh and just let it run.

Agreed. I love matt, but i’m in CS4 and trying to learn what will work here in Missouri.

The problem is closed cell is a full 5x the price of open cell per inch. So 5 inches of open cell foam is the same price as one inch of closed cell

@@jl9678 yes, but, you don't need 5 inches if doing CCSPF🤷‍♂️

@@DigitalBenny you'd need at least three inches which is the same as the price for 15 inches of open cell foam.

So do a mix to get the r value you want 2 in of closed and 3 or so of open. Which he also said in the video.

@@shannabolser9428 that's still 3x the cost of open cell foam. If you've got the money do it

Any update on this? I'm curious about your experiment!

@@Shkrelic he died

you could buy a wireless temp/humidity sensor with logging. you'll be able to see just how humid it is up there.

I actually made a video about that: kzfaq.info/get/bejne/nKdgfc533bjco58.html I'd be interested to get your take on what I did verses what your team did. It was definitely a difficult process and if I hadn't built a second story I don't know how I would have fixed the rafters, which had bowed and sunk as well as the ridge.

Thank you, I've been trying to figure out a vented solution for an upcoming build. What do you think of a couple solar powered roof vent fans to pull air through the soffit? I live in the South so it gets HOT in a vented roof during the summers

@@LincolnLog yea i guess, i'm no expert but solar vents are good but can clutter your roof. soffit and ridge vents are built in and work well enough. My home heats and cools well in Louisiana.

@@ClearWaterPumpWell Thank you. Do you mind sharing with me the brand radiant barrier you used? And I'm assuming they were stapled against 24" oc roof trusses?

@@LincolnLog My roof is not a were wide span only 28' at most over living. So my rafters are 2x6 with 2x4 ridge cross boards. I stapled it to the underside of 2x6 stretched across entire attic. From wall top I had to split 2x2 sheets to fill the gap in ceiling joists are 2x12. I left the ridge more open by stapling the foil to the cross boards rather than all the way to the point. It almost makes like a crawl space but saved me time and more foam. The foil was one sided and I faced the radiant foil side towards roof to reflect heat. It works as so much better than spraying foam directly on the roof. The roof will not heat the foam due to conducting but only from rafters. Then soffets can vent normally to ridge vents. In the corners on the hips I had to put a spacer block on the rafter bottom so air can flow in corner to reach the ridge. The hip roof normally ties in on corner rafter so not much room if you staple it tight. It helps to more less bend or curve around the hip corners, easier to staple. The site I got my Radiant barrier from was : atticfoil.com/ Hope this helps! Thanks

@@ClearWaterPumpWell Thank you for the clear and detailed explanation. I copied it down and will apply the same principles to our home 🤠

Yeah I got lost right at that bit as well. It’s literally like having a soffit to allow moist air back in. That part didn’t make sense.

Just walk over there with some beer and a Rockwool t-shirt. He'll let ya in 🙂

that is Matt in a nutshell; always using the newest gadget to try to wring out the last bit of on-paper efficiency while not considering either design changes (like no ducts in the attic at all), or time for return on investment. I can't blame him too much; people tune in to see the new gadgets and trends.

I’d say the small dehumidifier, dedicated to the attic, is the easiest solution.

I have so many questions

It's all in the details, diffusion vent gives way for vapor to escape... Just don't block the vent...

Good question. IIRC he has two layers of Zip and ISO foam board in between. If you cut a port through all of those layers (and I don’t know if that’s the case)... it sure seems counter productive.

@@OHSCrifle Agreed. Matt's motto has been tight, tight, tight buildings and then he creates a breathable (not tight!) opening in his roof. I would think dehumidification and perhaps an attic vent/return would have been the answer.

19:21 “I also cut some slits...”

I assumed the problem with the vapor drive from the conditioned attic space is when it condenses on the underside of the sheathing. You guys (in cold climates) will have most of the insulation on the outside of the roof deck/structural sheathing, but you'll still need sheathing to support your cladding system above this exterior continuous insulation. OSB also has low perm ratings so vapor will find it difficult to migrate across this, or even plywood. This will limit the drying potential due to the reduced heat flow across the enclosure, and you therefore need to maximize the ventilation and drying potential from above.

@@FrankReif images.app.goo.gl/PMSVJ6aAzGjEqnW6A this is really usual roofing system here if the picture opens from this link

Spray foam, but Matt is the guy to listen to.

He mentioned cutting slits in the roof decking which would include cutting through the zip system. I would imagine this would allow the vapor to escape to the permeable membrane

Although it's not immediately apparent, and even seems a bit illogical or counter-intuitive at first glance, digging deeper into the details and peeling back the layers of the onion (namely, the roofing layers), as it were, reveals that Risinger's vapor diffusion port should actually work as designed and intended. By the way, it's clear, from 19:23 to 19:30 in the video, that Risinger cut the vapor diffusion slit *only* in the top Zip sheathing layer, and *not* through to any of the layers beneath that; namely, he did *not* cut the vapor diffusion slit in the two polyiso board layers underneath nor in the first Zip sheathing layer underneath the two polyiso board layers. But ... furthermore ... it's also evident that Risinger did *NOT* need to cut any slit at all! He did *NOT* need to cut that slit in the top Zip sheathing layer, which was totally unneccesary, and I think somewhat ill-advised and not such a good idea, IMHO. Here is the roofing layer assembly (from the ridge to 2 feet down from the ridge), starting from the bottom/inside and working up to the top/outside ... Layer #1: Rockwool R30 batts sandwiched between 2'x8' LVL rafters on 24" centers. The Rockwool batts are vapor permeable. Layer #2: Zip sheathing. This first Zip sheathing layer is taped and sealed to the house's exterior wall Zip sheathing that comes up from the foundation, for a continuous air-tight and water-tight weather-resistant barrier sealing of the entire house, without any breaks, in Risinger's "monopoly framing"/Lstiburek's "perfect wall" concept. The Zip sheathing is an air-tight and water-tight weather barrier, but it is vapor permeable. Risinger states this in another one of his videos, and Huber states this on their website ("the integrated protective overlay of a ZIP System wall sheathing panel is permeable to allow for drying to the outside"). Layers #3 and #4: Two layers of Atlas EnergyShield CGF (Coated Glass Facers) 2" polyiso insulation 4'x8' boards, oriented perpendicular to each other with offset seams. Atlas states on their website that these EnergyShield CGF polyiso boards are vapor permeable. Layer #5: A second Zip sheathing layer. Layer #6: Delta Foxx vapor permeable roof underlayment. Layer #7: 1"x4" battens/furring strips, to create a 1" air gap, for venting the roof. Layer #8: Standing seam metal roof panels. Layers 1 through 6 are all vapor permeable, all the way up to the 1" air gap roof venting system at Layer #7. That's exactly what's needed, and all that's needed, for the vapor diffusion port. Risinger didn't need to cut that slit in the top Zip sheathing layer (Layer #5), because it's already vapor permeable.

@@charleswhalen7332 I’m not sure how foil-faced polyiso could possibly be vapor permeable. Further, while I know that zip sheathing has some permeability, it has a pretty low perm rating. It seems that the concept of vapor diffusion ports, if I understand the video primarily concerned SIPS houses, where the needed permeability could be achieved. SIPS being constructed ordinarily with OSB and EPS foam. Comparatively, I don’t think Matt’s system names any sense due to the lower permeability of his construction materials. Further, he has his own dehumidifier in his attic. For whatever benefit he achieved with this, I think the vapor diffusion port was a total waste of time and money.

@@charleswhalen7332 I agree with my added conclusion that the stacking of all the various "perm" layers will be limited by the least permeable one. Like a 1/4" gas line in your car feeding a .1mm gas jet. Not sure what the least permeable layer here is however, maybe the polyiso. "Good thing Matt is covered by Dr Joes statement "I am the the man I am today because of all my mistakes"🤣

@@charleswhalen7332 Further research on analyzing this 8 layer sandwich reveals a 2010 article by Peter Yost on green building advisor "Vapor Profiles Help Predict Whether a Wall Can Dry" To avoid moisture problems in walls, think about the permeability of ALL the wall’s components - not just the “designated” vapor retarder. Also the BSC Info-500: Building Materials Property Table April 24, 2015; as well as Info-312: Vapor Permeance of Some Building Materials April 15, 2013.

it just lets water out.

@@zhugeliang777 correct, however my question is not about moisture/vapor, apologies. I wonder if having a large, open-to-the-exterior, vapor diffusion membrane creates a large *thermal* problem -- seems the AC/heat units in the attic would be working around the clock to compensate.

Personally, I think putting a hot water heater at the highest point of the house would be a risky proposition... A leak would be pretty bad.

Although it's not immediately apparent, and even seems a bit illogical or counter-intuitive at first glance, digging deeper into the details and peeling back the layers of the onion (namely, the roofing layers), as it were, reveals that Risinger's vapor diffusion port should actually work as designed and intended. By the way, it's clear, from 19:23 to 19:30 in the video, that Risinger cut the vapor diffusion slit *only* in the top Zip sheathing layer, and *not* through to any of the layers beneath that; namely, he did *not* cut the vapor diffusion slit in the two polyiso board layers underneath nor in the first Zip sheathing layer underneath the two polyiso board layers. But ... furthermore ... it's also evident that Risinger did *NOT* need to cut any slit at all! He did *NOT* need to cut that slit in the top Zip sheathing layer, which was totally unneccesary, and I think somewhat ill-advised and not such a good idea, IMHO. Here is the roofing layer assembly (from the ridge to 2 feet down from the ridge), starting from the bottom/inside and working up to the top/outside ... Layer #1: Rockwool R30 batts sandwiched between 2'x8' LVL rafters on 24" centers. The Rockwool batts are vapor permeable. Layer #2: Zip sheathing. This first Zip sheathing layer is taped and sealed to the house's exterior wall Zip sheathing that comes up from the foundation, for a continuous air-tight and water-tight weather-resistant barrier sealing of the entire house, without any breaks, in Risinger's "monopoly framing"/Lstiburek's "perfect wall" concept. The Zip sheathing is an air-tight and water-tight weather barrier, but it is vapor permeable. Risinger states this in another one of his videos, and Huber states this on their website ("the integrated protective overlay of a ZIP System wall sheathing panel is permeable to allow for drying to the outside"). Layers #3 and #4: Two layers of Atlas EnergyShield CGF (Coated Glass Facers) 2" polyiso insulation 4'x8' boards, oriented perpendicular to each other with offset seams. Atlas states on their website that these EnergyShield CGF polyiso boards are vapor permeable. Layer #5: A second Zip sheathing layer. Layer #6: Delta Foxx vapor permeable roof underlayment. Layer #7: 1"x4" battens/furring strips, to create a 1" air gap, for venting the roof. Layer #8: Standing seam metal roof panels. Layers 1 through 6 are all vapor permeable, all the way up to the 1" air gap roof venting system at Layer #7. That's exactly what's needed, and all that's needed, for the vapor diffusion port. Risinger didn't need to cut that slit in the top Zip sheathing layer (Layer #5), because it's already vapor permeable.

@@charleswhalen7332 thanks for the reply. I am guessing that it'll also depend on the weather zone that the house is built in. For really cold weather environment, there will be more vapour to manage. Cutting slots at the top seem to go against the thermal bridging he was trying the achieve. Awesome house though.

@@lozza2272 Lozza - Very important point and distinction regarding the relevancy of and dependency on the particular climate. In watching these many “Build Show” videos, I’ve noticed a big difference in that regard between Matt Risinger on the one hand and Steve Baczek on the other hand. Although Risinger apparently did build in colder climates earlier in his career (Portland Oregon and the Washington DC area, I believe he’s mentioned), it seems that in the last 20 or so years he has only built in Texas, a hot climate. Although Baczek apparently has designed some houses in Arizona, all of the videos I’ve seen of his houses have been in climates with colder winters, mostly in Massachusetts and one in Columbia, Missouri. Now to the point of the difference between the two of them. For all of Risinger’s houses he builds, he always does closed, sealed, conditioned attics. For every one of Baczek’s houses that I’ve seen on video, he always does open, vented attics. I gather that the salient reason for this difference is the serious problem of ice dams that come with closed, sealed, conditioned attics in places where there is a substantial amount of snow in the winter. I have also heard Dr. Joe Lstiburek discuss this problem. So apparently, for that reason (namely, ice dams), I gather that it’s not advisable to do closed, sealed, conditioned attics in cold climates, and really just isn’t done. Having a vented attic alleviates the problem of vapor build-up in the attic and associated ridge rot, as vapor can easily escape through the attic’s ridge and/or gable vents. So it would seem that this is really more just a problem associated with closed, sealed, conditioned attics in hot climates.