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8 Answers

Polyethylene as an air barrier in very cold wall assembly

My question pertains to the use of a polyethylene air barrier (6 mil) within a double wall assembly (and ceiling) in a very cold climate. My concerns when we came up with this wall were obviously wall performance, related to moisture buildup and drying, as well as keeping the build relatively inexpensive both in materials/labor while at the same time providing me with a system provides high R-value while decreasing air leakage.

In GBA Pro help | Asked By Matthew Michaud | Nov 13 13
3 Answers

Extremely humid interior atmosphere

We are currently working on a project in the Chicagoland area at a water reclamation district. We are re-roofing a building that enclosed the water filtration pools with extremely high levels of humidity.

We are installing a new roof membrane over the concrete topping slab on the roof and running vertical on the multi-wythe brick walls that serve as both parapets as well as extend up to a higher level than the adjacent roof. The roof membrane will be attached to an exterior grade plywood that is attached to the brick.

In General questions | Asked By Nathan Kipnis | Nov 12 13
4 Answers

Interior walls using rough cut lumber and insulation?

We are using a restored barn frame to build a home. Our thought was erect frame, then wrapping the frame with painted rough cut, then applying 15lb felt paper, then framing w/ 2x4 or 2x6. We would then insulate w/ fiberglass, apply OSB sheathing, house wrap and then the necessary R value of foil faced poly iso to conform w/ code, being careful to seal all joints. Is this a proper wall build up or is there a better way to do this?

Thank you for your time GBA pros have been very knowledgeable.


In GBA Pro help | Asked By matt bowman | Nov 12 13
1 Answer

Wall venting

I posted this yesterday but I think it got caught up in the spam.

I am having a disagreement with my siding/trim subcontractor and my immediate superior about the need for a rain screen/venting space between PVC panels and the sheathing. I believe installing an impermeable sheet of plastic over an otherwise permeable wall is a bad idea leaving no way for the wall to dry to the exterior and potential of trapping water between the PVC and wall sheathing

The make up of the walls is as follows (inside to out)

Board and plaster
2x6 wall with OC spray foam
3/4” CDX sheating

In Energy efficiency and durability | Asked By Bruce Friedman | Nov 12 13
15 Answers

Damp beam in the middle of the house

Hi, I've got an old house (probably in excess of 200 years) through the middle there is a beam sitting on a couple of courses of bricks. I've noticed that the bottom of the beam is wet and starting to crumble (although it could have been like this a very long time) The wooden floor was replaced with concrete about 35 years ago. I am assuming that the water is coming up through capillary action. I was wondering if there was a substance to stop the rot and seal the beam?
Many Thanks

In General questions | Asked By Roger Watling | Nov 10 13
1 Answer

Steel siding vs. fiber-cement siding

I was planning to use fiber cement lap board (Hardie Board), but am wondering whether residential seamless steel siding might be a better choice (lap style like this: http://www.usseamless.com/Platinum/index.htm).

Steel siding seems to be used a lot in the Midwest, but I haven't heard of anyone using it here in California.
It seems as weatherproof, as fireproof, lower maintenance, and lower priced. Ecologically, it seems like a slightly better choice due to its recyclability.

In Green products and materials | Asked By Nathan Kurz | Nov 11 13
3 Answers

What type of roofing material is best above a SIP roof with PV modules on top?

I am a home owner in the final design stage for a net-zero house. The house will be located in update New York near Albany at an elevation of 1360 feet and is probably closer to Zone 6 than Zone 5. The area can have heavy snowfalls and also ice storms.

The house will have SIP walls and an 8.25 inch R50 SIP roof. I plan to add 2 inches of polyiso insulation either to the outside or the inside of the SIP roof in order to increase the R-value to R62. The ceiling below the SIP roof will be a cathedral ceiling.

In Green products and materials | Asked By Robert Walker | Nov 9 13
5 Answers

Flashing finless (European) aluminum-clad windows

I have finless, wood-frame, aluminum-clad windows to flash, and have attached a detail of what I'm planning so far. I'm looking to address water that makes it behind the aluminum cladding and comes down along the outside of the wooden frame, at the bottom of the window. I want to move it outside of the wall assembly rather than leaving it to run down behind the clapboards.

In General questions | Asked By Bill L | Nov 6 13
6 Answers

Do I need a vapor barrier in an unvented roof assembly?

I am building a roof assembly with 2x10 rough hemlock rafters exposed on the inside with cathedral type ceilings and no interior insulation. Rafters are covered with 3/4" pine shiplap decking, then 5 1/2" of polyiso insulation (2 layers of 2 3/4", joints sealed and overlapped), then 1x3 strapping, then metal roofing panels. I'm wondering if I need to include a vapor barrier anywhere in this assembly, and if I should put tar paper on top of the polyiso and underneath the strapping? The polyiso is paper faced. I am in upstate ny.. thanks for any advice!

In Energy efficiency and durability | Asked By walter button | Nov 8 13
9 Answers

Failed wall assembly

I had some questions with regard to some pictures of a “failed” wall assembly that was shown to me. I included (attached) a few pictures.

The “back story” on this wall assembly.., a 20-25 year old wall assembly in Northeast Massachusetts which consists of:
From the outside of the building to the interior…
• Cedar vertical siding
• Tyvek house wrap
• ½” or 5/8” CDX plywood
• white mold (on interior sided) of ½” or 5/8” CDX plywood
• 2”x6” kd wall studs
• R19 unfaced fiberglass insulation

In Energy efficiency and durability | Asked By JP Palm | Nov 8 13
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