Two questions re the air tightness of a building at the sheathing-frame interface. 1) Would using a few long screws, alongside the nails, to help pull the sheathing tighter to the studs improve resistance to air flow in the long run. Nails are certain to loosen somewhat over time, possibly allowing lateral air movement at that wall structure boundary. How well these structures stand up to shrink and swell conditions over time isn’t a topic I’ve ever seen covered. 2) Is there a hypothetical benefit to have a gasket like surface on the exterior of studs? Or, probably better, and serving both of the above functions, applying a long continuous bead of adhesive between the studs and the sheathing? Acoustic seal? There suggestions may sound over the top, but one can characterize them, as Einstein did, as Gedanken experiments. It’s a way of exploring ideas. Besides, it’s fun! Thanks Steve!
#2 first - the gasket idea would be pretty ex[pensive, and gaskets are ALWYS questionable at the joints.......#1 I have returned to a number of projects to do subsequent blower door tests...the numbers stand true every time
I like the idea of the double wall assembly, but why not stagger the studs for better thermal performance? Also, have you considered moving the Majrex interior air barrier to the inside edge of the 2x6 portion of the wall instead of the 2x4 portion? This would make ensuring a continuous air barrier easier since you wouldn't have to worry about detailing around electrical boxes, and would only have to worry about penetrations that needed to go to the outside of the wall. You also wouldn't have to worry about the home owners putting holes in the air barrier when using nails to hang pictures or screws to mount TVs. You could then fill the 2x6 stud bays with blown in insulation like you did here, while then either using some Rockwool bats in the 2x4 stud bays or make up the difference with continuous exterior insulation. This would also leave that 2 inch gap open for running wires or pipes which could be accessed more easily in the future for repairs than if they were behind the Majrex air barrier and buried in cellulose. Also, using two different densities of insulation would help attenuate sounds passing through the walls, making the home quieter. Just my 2 cents on how to improve on an already interesting wall assembly.
Love your videos. What would it take for you to help my 1900s stucco home in Minneapolis?? No insulation and lots of air gaps - very noisy with the traffic
Sorry if you already did and I missed it but, if not, could you please make a video about the connection between the Sigma Majvest and the concrete foundation wall?
Has any study been done to measure the diminishing returns on increasing insulation in walls? R-42 is double what is required in my area. I am wondering how much added benefit it gives. Also, would there be any issue with using batt insulation in the framed walls and filling the 2" gap in between them with foam board/rockwool? Just thinking of alternatives to blown in. Thanks Steve! Love these videos!
Yes there are diminishing returns on insulation, there's easy-to-read graphs, do a google image search for "insulation diminishing returns" and you'll see several chart examples. Once you get beyond approximately R50, the return-on-investment becomes impossible to justify.
I'm sure, but please understand the number of variables in that equation are many on the return on investment......this is a Passive House inspired design, typically PH is right at the part of the curve that flattens out
What is the decision tree for using the double-wall as shown here vs. std 2x6 wall w/2”foam ZipR vs. 2x6 wall with 4+” of exterior insulation (assuming all the appropriate membranes/barriers/retarders were used? This house is in at least climate zone 7 b/c in ME, where I am. Is cost /PH certification the decision point? Other? Very informative videos, keep ‘em coming please!
Just a heads up, the arrow from the "ENGINEERED BAND JOIST" is extending past the band and pointing to the web of the ENGINEERED FLOOR JOIST. I like this detail better than the zip with the OSB a full 1.5" away from the stud. It gives you a no bs shear wall instead of shear-moment wall. Nice!
As a PE designing in the coastal area of 140mph winds, ZIP certifies its R6 panels for shear panels for my area. I'll take their warranty. I do other measures to counter uplift, overturning, and shear.
How is the Marjex terminated at the top plate and at the baseplate on the 2nd floor. Also what is restraining the cellulose against the band joist? I would love to see the gaps exaggerated for clarity of lapping in your details. Great work.
Love this assembly! How does it handle cold climate winters? With over R40 in that wall, I'd think that any moisture that found a hole (maybe an electrical penetration that got missed) might reach a cold enough point in the cellulose to condense and then freeze. I suppose it would then dry out trough the Majvest when the warm weather comes? I'm wondering if a layer or two of Comfort-Board might be needed on the outside to control where that vapor would condense...
Outer insulation is better for this reason. The best construction method is a 2x4 house with thick outer insulation and a vapour barrier on the inside of the wall. Theoretically you can skip the wall cavity insulation if your outer insulation has a high enough R Value. A vapour barrier doesn't have to be an extra product. Some OSB is rated high Sd value, taped off with Siga and covered in Gypsum gives you a great barrier. Behind that, an insulated wall cavity, outer insulation and a wind/water barrier and finally furring strips and siding. Doesn't get better than that. It's really important to choose your materials so that the Sd value gets smaller towards the outside of the house, guaranteeing no moisture build up.
Would it make sense to apply the self-adhesive WRB to the plywood before hanging the plywood on the framing? It just seems like it would be easier than fighting gravity while wrapping vertical walls.
I would think not because you would have FAR more taped seams, including many horizontal seams, which would introduce unnecessary risk of water intrusion, compared to the standard installation method with only vertical seams.
what’s the advantage of going with the double wall versus zip R? I own a commercial building with a double wall. The one thing I noticed is soundproofing it does seem quieter.
Few reasons: - Zip R is limited to R12 - Long fasteners required for zip R are more expensive, and harder to install correctly - You are locked in to the zip system, this assembly uses 1/2" plywood for greater drying potential than OSB - marginal cost for more R value in this assembly is effectively the cost of cellulose
What do you consider a minimum width for a rainscreen? I don't want to mention any specific brand or product but I'm sure you are aware there are 10mm (0.4 inch) rainscreen products which can be applied with a staple hammer/tacker. Do you feel this is sufficient?
If 2” cellulose gets moist, it may dry out or expel water to a degree but does mold get established or does it damage the cellulose? Would Rockwood work better?
You really have 11" of cellulose most of the time. Cellulose is hygroscopic and will distribute moisture throughout the wall. You can use any blown in insulation with the double wall assembly. Insulating with batts would be a pain (i think), unless you design the gap to be 3.5" or 5.5"
That's a great point, they went to the trouble of making it stick well and taping the joints only to come along and make nail penetrations with the furring strips. I see the same issue with the Zip system, they set their nails just perfect, tape and roll the joints, only to come along and put hundreds if not thousands of siding nails into that same sheathing. This doesn't make sense unless there is some type of self healing/sealing membrane, and then one could ask how log does that membrane remain soft and sealing? 50 years? 100 years? I personally prefer an old leaky home that has lasted more than 250 years already, and will last another 200 years as long as the rain and termites are kept out. Sick building syndrome is a real issue in these overly tight new homes, and to pay money for special ventilation equipment to bring in fresh air constantly is kind of silly.
@@c.a.martin3029 as long as there is an air gap, and the holes are small enough its not a problem. The wall assembly can dry to both inside and outsife
@@bfelb yes, to some extent, a very very knowledgeable colleague states a 3/4" space provides great draining and great ventilation .....more than that isn't really buying you more...
@@bfelb that claim is from joe lstiburek, so you can take your objections up with him. My understanding is you just need enough of a gap to relieve hydrostatic pressure and let it drain. ~1/8". Of course its hard to maintain a 1/8" gap, so lets use something thats widely available and cheap like a 1x
Two questions re the air tightness of a building at the sheathing-frame interface. 1) Would using a few long screws, alongside the nails, to help pull the sheathing tighter to the studs improve resistance to air flow in the long run. Nails are certain to loosen somewhat over time, possibly allowing lateral air movement at that wall structure boundary. How well these structures stand up to shrink and swell conditions over time isn’t a topic I’ve ever seen covered. 2) Is there a hypothetical benefit to have a gasket like surface on the exterior of studs? Or, probably better, and serving both of the above functions, applying a long continuous bead of adhesive between the studs and the sheathing? Acoustic seal? There suggestions may sound over the top, but one can characterize them, as Einstein did, as Gedanken experiments. It’s a way of exploring ideas. Besides, it’s fun! Thanks Steve!
#2 first - the gasket idea would be pretty ex[pensive, and gaskets are ALWYS questionable at the joints.......#1 I have returned to a number of projects to do subsequent blower door tests...the numbers stand true every time
I like the idea of the double wall assembly, but why not stagger the studs for better thermal performance? Also, have you considered moving the Majrex interior air barrier to the inside edge of the 2x6 portion of the wall instead of the 2x4 portion? This would make ensuring a continuous air barrier easier since you wouldn't have to worry about detailing around electrical boxes, and would only have to worry about penetrations that needed to go to the outside of the wall. You also wouldn't have to worry about the home owners putting holes in the air barrier when using nails to hang pictures or screws to mount TVs. You could then fill the 2x6 stud bays with blown in insulation like you did here, while then either using some Rockwool bats in the 2x4 stud bays or make up the difference with continuous exterior insulation. This would also leave that 2 inch gap open for running wires or pipes which could be accessed more easily in the future for repairs than if they were behind the Majrex air barrier and buried in cellulose. Also, using two different densities of insulation would help attenuate sounds passing through the walls, making the home quieter. Just my 2 cents on how to improve on an already interesting wall assembly.
Love your videos. What would it take for you to help my 1900s stucco home in Minneapolis?? No insulation and lots of air gaps - very noisy with the traffic
Sorry if you already did and I missed it but, if not, could you please make a video about the connection between the Sigma Majvest and the concrete foundation wall?
Has any study been done to measure the diminishing returns on increasing insulation in walls? R-42 is double what is required in my area. I am wondering how much added benefit it gives. Also, would there be any issue with using batt insulation in the framed walls and filling the 2" gap in between them with foam board/rockwool? Just thinking of alternatives to blown in. Thanks Steve! Love these videos!
Yes there are diminishing returns on insulation, there's easy-to-read graphs, do a google image search for "insulation diminishing returns" and you'll see several chart examples. Once you get beyond approximately R50, the return-on-investment becomes impossible to justify.
I'm sure, but please understand the number of variables in that equation are many on the return on investment......this is a Passive House inspired design, typically PH is right at the part of the curve that flattens out
@@stevenbaczekarchitect9431 Gotcha, makes sense. Thanks for replying!
Cool, Thanks!
Welcome
What is the decision tree for using the double-wall as shown here vs. std 2x6 wall w/2”foam ZipR vs. 2x6 wall with 4+” of exterior insulation (assuming all the appropriate membranes/barriers/retarders were used? This house is in at least climate zone 7 b/c in ME, where I am. Is cost /PH certification the decision point? Other? Very informative videos, keep ‘em coming please!
Just a heads up, the arrow from the "ENGINEERED BAND JOIST" is extending past the band and pointing to the web of the ENGINEERED FLOOR JOIST.
I like this detail better than the zip with the OSB a full 1.5" away from the stud. It gives you a no bs shear wall instead of shear-moment wall. Nice!
As a PE designing in the coastal area of 140mph winds, ZIP certifies its R6 panels for shear panels for my area. I'll take their warranty. I do other measures to counter uplift, overturning, and shear.
@@coasttal123 THanks for joining in.....likewise I have done Zip R-6 and Zip R-9 on the coast
How is the Marjex terminated at the top plate and at the baseplate on the 2nd floor. Also what is restraining the cellulose against the band joist? I would love to see the gaps exaggerated for clarity of lapping in your details. Great work.
the second floor is tediously installed cellulose netting
Love this assembly! How does it handle cold climate winters? With over R40 in that wall, I'd think that any moisture that found a hole (maybe an electrical penetration that got missed) might reach a cold enough point in the cellulose to condense and then freeze. I suppose it would then dry out trough the Majvest when the warm weather comes? I'm wondering if a layer or two of Comfort-Board might be needed on the outside to control where that vapor would condense...
Outer insulation is better for this reason. The best construction method is a 2x4 house with thick outer insulation and a vapour barrier on the inside of the wall. Theoretically you can skip the wall cavity insulation if your outer insulation has a high enough R Value. A vapour barrier doesn't have to be an extra product. Some OSB is rated high Sd value, taped off with Siga and covered in Gypsum gives you a great barrier. Behind that, an insulated wall cavity, outer insulation and a wind/water barrier and finally furring strips and siding. Doesn't get better than that. It's really important to choose your materials so that the Sd value gets smaller towards the outside of the house, guaranteeing no moisture build up.
@@bfelb Unfortunately, high r-value externally insulated assemblies are cost prohibitive for most.
When would you choose a self adhesive membrane vs zip system?
Would it make sense to apply the self-adhesive WRB to the plywood before hanging the plywood on the framing? It just seems like it would be easier than fighting gravity while wrapping vertical walls.
I would think not because you would have FAR more taped seams, including many horizontal seams, which would introduce unnecessary risk of water intrusion, compared to the standard installation method with only vertical seams.
Noooooooooooo, very very tedious
what’s the advantage of going with the double wall versus zip R? I own a commercial building with a double wall. The one thing I noticed is soundproofing it does seem quieter.
Few reasons:
- Zip R is limited to R12
- Long fasteners required for zip R are more expensive, and harder to install correctly
- You are locked in to the zip system, this assembly uses 1/2" plywood for greater drying potential than OSB
- marginal cost for more R value in this assembly is effectively the cost of cellulose
What do you consider a minimum width for a rainscreen? I don't want to mention any specific brand or product but I'm sure you are aware there are 10mm (0.4 inch) rainscreen products which can be applied with a staple hammer/tacker. Do you feel this is sufficient?
Steve, im doing a steel frame infill and I wondered if that product needs a primer on concrete?
I'd have to see the detail
No need to run the wrb horizontally to shingle the majvest?
How does one keep the end users and electricians from piercing that inner VB though?
On complex & expensive systems that Steve designs the owners then need to hire the Architect to do site inspections at every step.
How does the majrex smart vapor retarder allow water to pass through it when it is blocked by drywall and then paint?
If 2” cellulose gets moist, it may dry out or expel water to a degree but does mold get established or does it damage the cellulose?
Would Rockwood work better?
You really have 11" of cellulose most of the time. Cellulose is hygroscopic and will distribute moisture throughout the wall. You can use any blown in insulation with the double wall assembly. Insulating with batts would be a pain (i think), unless you design the gap to be 3.5" or 5.5"
Use dense pack cellulose borate to mitigate mold growth.
does it seal around fasteners like blueskin, adhero and vapordry?
That's a great point, they went to the trouble of making it stick well and taping the joints only to come along and make nail penetrations with the furring strips. I see the same issue with the Zip system, they set their nails just perfect, tape and roll the joints, only to come along and put hundreds if not thousands of siding nails into that same sheathing. This doesn't make sense unless there is some type of self healing/sealing membrane, and then one could ask how log does that membrane remain soft and sealing? 50 years? 100 years? I personally prefer an old leaky home that has lasted more than 250 years already, and will last another 200 years as long as the rain and termites are kept out. Sick building syndrome is a real issue in these overly tight new homes, and to pay money for special ventilation equipment to bring in fresh air constantly is kind of silly.
@@c.a.martin3029 I want a super tight house thats why i want a self healing membrane
The nail/screw act as a plug. If removed, it should be sealed.
@@c.a.martin3029 as long as there is an air gap, and the holes are small enough its not a problem. The wall assembly can dry to both inside and outsife
Steven, is there any benefit of using a slightly thicker furring strip, to increase the space for its drying potential??
My name isn't Steven but yes using thicker furring or doubling up is better for the construction.
It doesnt increase the drying potential significantly. 3/4" is already way more than you need.
@@bfelb yes, to some extent, a very very knowledgeable colleague states a 3/4" space provides great draining and great ventilation .....more than that isn't really buying you more...
@@Austin-fc5gs way more? It’s actually the bare minimum. Please don‘t spread misinformation.
@@bfelb that claim is from joe lstiburek, so you can take your objections up with him. My understanding is you just need enough of a gap to relieve hydrostatic pressure and let it drain. ~1/8". Of course its hard to maintain a 1/8" gap, so lets use something thats widely available and cheap like a 1x
Where can i buy this in America?
Swiss product imported
"SIGA" on their website.... www.siga.swiss/us_en/
Liked#23 N Subscribed!!!
Nothing simple or cheap about this system. But install as designed it will work great.
"good things cost $$$"