# Airtight Drywall Asemblies



## SlimPickins (Aug 10, 2010)

I've now worked on three of these, one gasketed house, and two sealed using acoustic sealant. Is anyone else running across these assemblies? They are definitely more time consuming and I'm starting to be able to find a way to price them out....but there's definitely a learning curve involved.

The science makes sense, but without knowing what's gone on during the preceding phases I wonder how effective it really is.

Wouldn't it be nice if builders would meet with drywall contractors _before_ show time to see if there were ways we could work on this stuff _together_ rather than showing up to a sh!t-show with multiple areas of possible assembly failure? I've already given one of my builders at least 3 ideas that he says would have saved time and money on the current project, and made his assembly a lot more fool-proof.


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## chris (Apr 13, 2011)

I had to do po last project on top floors (near roof). Cold roof is what they called it. That way the snow piles up nice and tall


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## SlimPickins (Aug 10, 2010)

chris said:


> I had to do po last project on top floors (near roof). Cold roof is what they called it. That way the snow piles up nice and tall


Was that that big custom monster?

A cold roof is a little bit different, but the idea of isolating it is the same. Did you rock over gaskets applied by a high-tech insulation outfit or did you guys use caulk?


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## D's (Jan 15, 2009)

I'm definitely interested in this building technique and I think it bodes well for drywall contractors to assume the responsibility of delivering the interior components of an airtight envelop. I went to a green building conference last winter and their was much discussion of this becoming part of the BC building code in the the near future. It would likely elimimate the plastic vapor barrier(allowing drywall adhesive to be used), and replacing it with gasketing and a vapor retardant primer - all things the drywall contractor could provide.

Do you think the extra effort on the drywallers side outweighs the savings of not installing the vapor barrier plastic?


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## SlimPickins (Aug 10, 2010)

D's said:


> I'm definitely interested in this building technique and I think it bodes well for drywall contractors to assume the responsibility of delivering the interior components of an airtight envelop. I went to a green building conference last winter and their was much discussion of this becoming part of the BC building code in the the near future. It would likely elimimate the plastic vapor barrier(allowing drywall adhesive to be used), and replacing it with gasketing and a vapor retardant primer - all things the drywall contractor could provide.
> 
> Do you think the extra effort on the drywallers side outweighs the savings of not installing the vapor barrier plastic?


I dunno, I'm not sure of the cost of visqueen, but the labor on the insulators end to install it is minimal, especially when those guys can insulate a rambler in a day. It takes me nearly twice as long to hang an airtight sheet as a regular one, at least on the exteriors. You DO NOT want to be running your tape, or anything else for that matter into the sealant...it's nasty stuff. Plus, the sealant itself is $150+ for 12 tubes. The latest house doesn't have a vapor barrier, they decided to maintain permeability in the wall system, so I was caulking over cellulose net.

If nothing else, I've been doing a lot of reading on building envelopes, permeability vs. breathability, condensation, HRVs, ventilation, etc. It's all very fascinating.


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## moore (Dec 2, 2010)

A house needs to breath..don't jump down my throat!! JMO! 
location . climate . depends on where you are.but I say It's not good for home to be too tight..It' best for a home to breath through the roof .JMO!!


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## D's (Jan 15, 2009)

I think that's the goal - have walls at the optimal permeability, keeping moisture from getting in but allowing it out, and keeping indoor heated and humid air from moving out throught the walls & ceiling.


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## SlimPickins (Aug 10, 2010)

moore said:


> A house needs to breath..don't jump down my throat!! JMO!
> location . climate . depends on where you are.but I say It's not good for home to be too tight..It' best for a home to breath through the roof .JMO!!


Totally not gonna jump down your throat!

Every house/location has a different solution to how it should be built. Everything has an impact on how the house will manage moisture (well, _almost_ everything)...interior paint finish, insulation type, vapor barrier, exterior cladding/siding. D' is right, you want to keep moisture from going into the wall, but you also need to allow it to get out.

I'm going to parrot the book I was reading last night when I say this, but Breathability is misleading. People think that if their house "breathes" then they will have good air circulation. That's not the case...interior air needs to be managed to have good quality....even if that means opening a window for 15 minutes every morning.

Airtight assemblies serve multiple purposes, two of which are heat/energy conservation and moisture management. I'm still trying to figure out how a wall can be "airtight" and allow water vapor to escape A lot of these new super-insulated homes are skipping the vapor barrier, but interior paint qualifies as a barrier.....there's a lot to learn:blink:


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## chris (Apr 13, 2011)

SlimPickins said:


> Was that that big custom monster?
> 
> A cold roof is a little bit different, but the idea of isolating it is the same. Did you rock over gaskets applied by a high-tech insulation outfit or did you guys use caulk?


 yes it was the Beast, sounds like a different assembly tho. Every penetration on ceiling was taped tight and sealed. The sub responsible for sealing wasnt me,we just had to hang and tape sparky,sprinklers ,hvac,etc. had to do final seal


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## SlimPickins (Aug 10, 2010)

chris said:


> yes it was the Beast, sounds like a different assembly tho. Every penetration on ceiling was taped tight and sealed. The sub responsible for sealing wasnt me,we just had to hang and tape sparky,sprinklers ,hvac,etc. had to do final seal


You lucky dog!

I'd imagine you're going to start seeing more of these assemblies, if your area is anything like mine, which I'm guessing it is.

Where in Idaho are you? Near Sun Valley?


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## chris (Apr 13, 2011)

SlimPickins said:


> You lucky dog!
> 
> I'd imagine you're going to start seeing more of these assemblies, if your area is anything like mine, which I'm guessing it is.
> 
> Where in Idaho are you? Near Sun Valley?


 That is where the Beast lives. Im about 2 hrs south. Just started another little addition up there today.


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## SlimPickins (Aug 10, 2010)

chris said:


> That is where the Beast lives. Im about 2 hrs south. Just started another little addition up there today.


I've heard about the houses that get built in that area.....crazy town. We get the same sort of opulence up north in Whitefish.


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## D's (Jan 15, 2009)

Do you work in Whitefish Slim? I'm only 100 miles North and the Mrs. and I head there often for getaways. Nice place with some equally nice estates!


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## Mudshark (Feb 8, 2009)

*Whats the big deal*

Whats the big deal boys? They have been building like this in Canada for a while now. What, you were not putting poly on before?

Some very minor things when boarding is not getting any of the vapour barrier or the insulation on your butts or bevels. Some insulators are bad for not leaving enough slack in ceiling corners to get the board all the way into corner but there is a bit of give to the poly. On exterior walls dont let the poly near the floor bunch up behind the board. Yes the acoustic seal is messy, try to avoid it and dont get any on the face of the board or the tapers will hate you.


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## SlimPickins (Aug 10, 2010)

D's said:


> Do you work in Whitefish Slim? I'm only 100 miles North and the Mrs. and I head there often for getaways. Nice place with some equally nice estates!


I live about 3 hours south, and rarely do any work up north. I had a good friend who lived in Whitefish for years and we would visit and hit Big Mountain or GNP while we were up. Now, with the wee ones, we're lucky to get up there every couple of years.

I hear you've got some nice snow hills up there.....:thumbsup:


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## SlimPickins (Aug 10, 2010)

Mudshark said:


> Whats the big deal boys? They have been building like this in Canada for a while now. What, you were not putting poly on before?
> 
> Some very minor things when boarding is not getting any of the vapour barrier or the insulation on your butts or bevels. Some insulators are bad for not leaving enough slack in ceiling corners to get the board all the way into corner but there is a bit of give to the poly. On exterior walls dont let the poly near the floor bunch up behind the board. Yes the acoustic seal is messy, try to avoid it and dont get any on the face of the board or the tapers will hate you.


Almost every house here has had vapor barrier for as long as I can remember, but the sealant is new (the gaskets too).

I decided to play around with smudged sealant and see what I can get away with....NOT MUCH. One small bit of angle had tape failure, but that looked like a spot where I had rubbed it trying to get it off and the petroleum had soaked into the paper.

I'm reading up on the assemblies so I can be the "expert"


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## chris (Apr 13, 2011)

Mudshark said:


> Whats the big deal boys? They have been building like this in Canada for a while now. What, you were not putting poly on before?
> 
> .


 boy... I hope you meant Roy.


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## 2buckcanuck (Jul 9, 2010)

chris said:


> boy... I hope you meant Roy.


It's not a big thing to say boy or boys in Canuck land. It has no racial implications or meaning, if that's what your referring to.

And until Mudshark posted, I had no idea what you guys were talking about


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## moore (Dec 2, 2010)

2buckcanuck said:


> It's not a big thing to say boy or boys in Canuck land. It has no racial implications or meaning, if that's what your referring to.
> 
> And until Mudshark posted, I had no idea what you guys were talking about


Down here It depends on the group of guys your talking with.:yes:


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## SlimPickins (Aug 10, 2010)

2buckcanuck said:


> It's not a big thing to say boy or boys in Canuck land. It has no racial implications or meaning, if that's what your referring to.
> 
> And until Mudshark posted, I had no idea what you guys were talking about


So now that Mudshark enlightened you, what's your experience with the acoustic sealant? Were you using it when you were hanging? It's more time consuming than just hanging the rock, that's for sure....although I bet it doesn't take as long as gluing board to framing.


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## 2buckcanuck (Jul 9, 2010)

SlimPickins said:


> So now that Mudshark enlightened you, what's your experience with the acoustic sealant? Were you using it when you were hanging? It's more time consuming than just hanging the rock, that's for sure....although I bet it doesn't take as long as gluing board to framing.


OK

Now I don't know what your talking aboot after reading D's post

A new system where you can seal the house without using poly ???????

Enlighten me,,,,, give links


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## D's (Jan 15, 2009)

http://www.finehomebuilding.com/how-to/departments/energy-smart-details/airtight-drywall.aspx

http://www.cmhc-schl.gc.ca/en/inpr/bude/himu/codemo/codemo_046.cfm


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## Mudshark (Feb 8, 2009)

OK Looks like I was confused as well. :surrender: 

Looking at D's link it looks like we are moving towards less poly and using board as the air barrier. Either way that is mostly the other trades concern. Boarders will continue to cover the walls and ceilings and tapers to cover the board and make it ready for the painters. It does look like those lightboxes could suffer damage from a wild boardman with a router though.


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## chris (Apr 13, 2011)

2buckcanuck said:


> It's not a big thing to say boy or boys in Canuck land. It has no racial implications or meaning, if that's what your referring to.
> 
> And until Mudshark posted, I had no idea what you guys were talking about


 Its all good. Just a phrase I use when I get called boy. :whistling2:


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## SlimPickins (Aug 10, 2010)

2buckcanuck said:


> OK
> 
> Now I don't know what your talking aboot after reading D's post
> 
> ...


I see D's already did that for me. Do I need to start paying him now?

Basically, you can do it with plastic sheeting and gaskets, or with acoustic sealant (or I believe, drywall adhesive). Your paint coat can be designed to either "breathe" or be air-tight as well. Some systems want to keep moisture from getting into the wall (in the form of vapor), and some want it to be able to _get out._ The house I'm working on right now is designed to keep moisture in the house, and allow it to escape through high-CFM air exchangers. Any moisture that makes it into the walls will be "encouraged" to go outside.

This link covers the basics on airtight drywall assembly:

http://www.buildingscience.com/documents/information-sheets/air-barriers-airtight-drywall-approach

And this one is a better overall view on airtight:

http://www.buildingscience.com/documents/insights/bsi-053-just-right-and-airtight/


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## SlimPickins (Aug 10, 2010)

Mudshark said:


> OK Looks like I was confused as well. :surrender:
> 
> Looking at D's link it looks like we are moving towards less poly and using board as the air barrier. Either way that is mostly the other trades concern. Boarders will continue to cover the walls and ceilings and tapers to cover the board and make it ready for the painters. It does look like those lightboxes could suffer damage from a wild boardman with a router though.


The gasketed outlets suck, and they hold the board way out from the wall. A conscientious trades-person would need to remove stud-face material to make them work properly.....or someone could just design a good one.


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## D's (Jan 15, 2009)

The gasketed fixtures can be a pain. Heres some tips...
Lay out the board to avoid joints near fixtures
Screw directly through the fixture flange rather than beside it
If one ends up close to a joint, shim the adjacent board to match the depth(I use my empty Hilti screw strips)

Maybe there will be an ADA(Airtight Drywall Assembly) certification contractors could obtain. $$$


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## SlimPickins (Aug 10, 2010)

D's said:


> The gasketed fixtures can be a pain. Heres some tips...
> Lay out the board to avoid joints near fixtures
> Screw directly through the fixture flange rather than beside it
> If one ends up close to a joint, shim the adjacent board to match the depth(I use my empty Hilti screw strips)
> ...


Unfortunately, you and I both know that switches are right near the seams, which is particularly troublesome in the kitchen No one wants to rip a 4' sheet in half to avoid the boxes at the seams... I screw into the flange too:thumbsup:


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## D's (Jan 15, 2009)

I'll rip it in the kitchen if I remember to- at least the two joints only need firetaping where covered by cabinets vs. having one deformed joint through all the fixtures. Barely worthwhile though.

Those metal tabs on potlights can wreak havoc too. Worth snipping if close to joints.


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