Smart membrain and 3/4 eps
zachm
| Posted in Energy Efficiency and Durability on
More ideas on insulating my shop walls will be sealed with certanteed smart membrane. And then 1×4 strapping ran horizontal over that to hang Sheetrock. Is there any reason I couldn’t install 3/4 eps to help with some thermal bridging in between the furring strips? Does it have enough perms to help dry out if needed and work with the smart membrain. I know thicker would be ideal but already have outlets and everything set up for this reveal and rough electrical. Insulating from the outside isn’t an option at the moment. In sw Minnesota climate zone 5a
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Replies
Hi Zachary,
The 3/4" EPS foam will only add about R-3 to the assembly. And, you are correct, the EPS will change the permeability of the wall. The Membrane can be more than 10 perms when it needs to be, the EPS will be well under that.
Randy
I think I read that the eps is 5 perms. Would that have a negative effect if it needed to dry inward could this trap “condensation or moisture? Maybe just apply to the stud face to give a thermal break?
Zach,
I you are adding the EPS, why not use that as an interior vapour-retarder and forgo the variable-perm membrane?
That could definitely be an option just didn’t know which way would work better. Since it’s an older building built in the 50s concrete slab isn’t insulated. But have a ducted mini split and dehumidifier in the shop. Have been wondering if the unisuoated slab is going to effect my moisture when heated and cooled.
The EPS would work as a vapor retarder, can it also be detailed as an air barrier?
Yes it could my wall assembly is wood siding felt paper then 1x6 tng. 2x6 studs I’m planning on installing 3/4 inch furring strips then 2 inch eps foam to make a “rain screen” then r13 batt was planning on smart vapor retarder. Then 1x4 furring strips for Sheetrock. Was just thinking the 3/4 eps between the strips would help give a little more r value and somewhat of a thermal break.
zach,
Your description is quite confusing. Is this the wall stack-up you are suggesting?
- Siding
- Rain-screen furring
- 2" EPS exterior insulation
- Building paper
- Existing board sheathing
- Existing studs with batt insulation
- Membrane
- 3/4" continuous EPS on interior face of studs
- Strapping
- Drywall
This is being done from the interior since I’m not re siding at the momentI the underlaykent is tng and some 3/4 boards so figured the interior “rain screen” space between eps and sheathing from the interior in stud cavity would mitigate any issues with the siding and sheathing to breath. So it would be wood siding , felt paper, tng and 3/4 board sheathing. A 3/4 inch air gap in stud bay 2 inch eps foam r13 unfaced batt. Smart vapor retarder, 1x4 during strips 2 foot on center. Then possibly the 3/4 eps inbetween furring strips if benificiap. then 1/2 Sheetrock with latex paint.
Zach,
Thanks, got it now. Adding 3/4" foam between the furring strips doesn't add much to the assembly, and isn't a thermal break. The interior horizontal furring does that. I'd stick with the variable-perm membrane and be done.
Zach,
Thanks, got it now. Adding 3/4" foam between the furring strips doesn't add much to the assembly, and isn't a thermal break. The interior horizontal furring does that. I'd stick with the variable-perm membrane and be done.
Awesome thanks for the info I’ll do that! I feel like the rest of my wall assembly seems the best I can do with working with what I have as a structure currently. Anything you would change? Have tried to find rockwool here but is hard for me to find from suppliers
Zach,
Others may have some suggestions, but what you propose sounds good to me.