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5 Answers

Vented & unvented in same roof plane?

Hopefully you can all see this attached glass-house view of my proposed roof.


The open attic at the bottom right of the photo allows plenty of room to super-insulate, same too with the open attic above the 2nd floor ceiling, up in the top left/center of the photo. The sloped roof though poses a problem for super-insulation levels, just not enough depth. What I'd like to minimize is a path of least thermal resistance which would circumvent the high insulation levels in the open attics and favor "Easy" migration through the sloped roof section.

Asked By Alex House | Mar 3 15
1 Answer

Insulated slab details for zone 7 walkout

My build is in Kenora Onrtario Canada (zone 7). The basement is a walkout; I need to incorporate a sewage lift station under the floor to pump (shower/toilet/sink and washing machine) water up to my septic
I need to know how to detail the insulation and poly layer under the concrete.
Do I insulate the sides and bottom of the hole the tank (110 gallon) goes into; if so do the joints have to be taped like building an foam box; I can't have the sewage freezing in the tank! Is that even a concern?

Asked By tim brown | Mar 5 15
3 Answers

Condensation in (conditioned space) attic, built to "environmental standards"

I am in need of a (seasoned) building consultant, familiar with New England climate, able to make an "on site" evaluation in Guilford, Ct. 06437, for an attic space that was built to environmental standards and is a conditioned space) -- air conditioning, HRVs, etc etc., for a client that has environmental allergies -- mold, fabric softener, petrochemical products etc.

There is condensation from the attic space, with leakage of water into and onto the first floor after one year. Thank you in advance. We need help.

Asked By herbert suesserman MD | Mar 5 15
8 Answers

Insulation around a center chimney -- cape?

How would one insulate around the chimney in the attached pics? Would I start at the ceiling and just put a bunch of Roxul around it? How could air sealing work? Fireblock foam?

Bonus question: Is it too late to double stud these walls?


Asked By stephen edge | Mar 4 15
4 Answers

Recommended taping of plywood and foam layers

I am building a small casita (500 sq. ft.) in Northern California in a mild climate with hot summers. My wall framing is 2x4 w/ 3/8 continuous plywood shear (also insulated w/ R-13 fiberglass batt insul.), which I will cover with two layers of 1/1/2" Polyiso (Firestone) insulation (has fiberglass reinforced face). I will cover everything with Tyvek housewrap and fasten 1x4 battens creating a rainscreen, and attach lath and plaster as an exterior finish to the battens.

Asked By Dan Burgoyne | Mar 5 15
1 Answer

Roxul board used in basement as insulation against concrete wall?

I just watched a mike Holmes episode. He was building out a basement for bar, home theater, gym, etc. against all the walls he used roxul board as an insulation barrier then the walls were framed. I've read where Martin Holliday advised against this practice. Who's right? It makes more sense to use foam or foam board as it won't hold water. Thanks for any clarification on this topic.

Asked By tim gabriel | Mar 5 15
1 Answer

Membrain in walls, poly in attic. OK or not?

I join hundreds of others in trying to wrap my head around the nuances of vapor retarders.

In this thread in comment #32 Martin notes that ceiling poly is unlikely to cause much trouble and then in comment #34 he observes that another person should use Membrain in their walls.

Is there ever a need for Membrain in the ceiling or can cheaper poly always be used?

One other question.

Poly in walls should be on the warm side, Martin quoted the following from the same article:

Asked By Alex House | Mar 6 15
2 Answers

Critique of cathedral ceiling and wall design - Swedish Style

Planning on building a 1-1/2 story, well insulated home using 14” I-joists as the rafters. Then running 2 x 4” horizontally. The I joist cavity will be air sealed. The 2 x 4” cavity will not. I will have an ERV. This idea is a mix of concepts seen on greenbuildingadvisor.com, buildingscience.com and the USA new wall info provided by Gregory La Vardera’s site on Swedish framing/insulation - www.lamidesign.com

Asked By Jeff Von Haden | Mar 5 15
7 Answers

24" o.c. rainscreen furring concerns

Getting ready to start a house for a customer, double 2x4 walls, etc. We left the exterior side 2x4 @ 16" oc due to rainscreen furring concerns.

I'm beginning to question whether we can move to 24" oc on the outside wall and use our rainscreen furring 24"oc...?? Furring will be 2x4 KD lumber, mainly because we can get 2x4 cheaper than 1x4 and it's not that much more effort.

So can the furring go to 24"oc and not have problem with the clapboard siding going crazy?


Asked By RMills Miller | Mar 4 15
11 Answers

I am overwhelmed with the wall cavity options and need advice

After researching for the last few months on this website, buildingscience.com, and PHIUS.org I am just overwhelmed...buy maybe under informed. I am an owner/builder (former construction project manager...mainly responsible for foundation and electric work then) and this will be my second house. Most of the case studies and articles I have read are about homes in climate zones far more extreme than what we typically have in TN.

Asked By Andrew Bennett | Mar 4 15
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