Q&A: A Forum for Green Building Experts and Beginners

Q & A Instructions

[Click map to enlarge]

The GBAGreenBuildingAdvisor.com web site has a wealth of articles on a wide variety of construction topics. Before posting your question, you may want to check out the articles on this page: How To Do Everything. You just might discover an article there that provides the information you seek.

Please register for a free account or sign in to ask and answer green building questions.

If you want to post a question, the usual rules of courtesy apply:
1. Be nice.
2. If you can't be nice, be polite.
3. If you can't be nice or polite — well, please be brief.

To attach a photo or illustration: Under the box labeled “More explanation,” look for the words “File attachments.” Click that, and you should be able to attach a photo.

Thanks for joining the conversation!


9 Answers

Double stud walls - vapour retarders

Good day folks. I am in a cold climate (Halifax, NS, Canada) climate zone 5 or 6 I think???

I am constructing my house in the spring and will be using some variation of the DBL stud wall; either the Riversong DBL bearing wall, or constructing the house conventionally then stand up walls from the inside. I will be going for 10-12" thick. My main question is about air leakage control, and vapour control. On the inside I am going to likely do ADA, and on the outside is it overkill to use adhesive on every stud and plate before I attach my 1/2" PLY and then tape all the seams?

In Energy efficiency and durability | Asked By Mark Pennell | Mar 15 13
2 Answers

Climate Zone 7 Colorado

I'm struggling to understand the use of Rigid foam on exterior of a home, new construction. I understand the benefits and want to use it. I would like to use from the interior wall out, 5/8" drywall, smart vapor retarder, blown in BIBS, Zip System sheathing, polyisocyanurate per the code R-15, for a 2X6 wall all seams taped. Apply wood siding over foam.

Questions: Should my wall cavity be filled with insualtion to meet current code 2012 R-20 or can I use a portion of my R-15 Rigid to makeup the required R-20 cavity and R-5 continuois sheathing?

In GBA Pro help | Asked By Forrest Watson | Mar 22 13
7 Answers

Selecting an HVAC and hot water systems

We are building a new house. I need to select the guts for the heating/cooling. Solar and geothermal are not feasible. How does one whittle down the options/brands/models for a high efficiency (.95+) gas furnace? My builder is recommending a Trane furnace and cooling units. For hot water, he is suggesting tankless Navien units (NR-240A). I'm just not sure how to consider other brands and/or options. Any suggestions are greatly appreciated.

In Mechanicals | Asked By scott sch | Mar 19 13
1 Answer

What needs to go behind a shower surround on an exterior wall with 2" of exterior foam sheathing?

I have a client doing a whole house remodel. They've already wrapped the entire exterior with 2" of EPS and are insulating the interior with blown in fiberglass. What insulation / air sealing is needed behind the fiberglass shower surround on an exterior wall to achieve a dry, air-sealed envelope? Can they get away with just fiberglass batts there or is a rigid air barrier needed on the interior?

In Green building techniques | Asked By Elizabeth Coe | Mar 22 13
1 Answer

How can I turn my root cellar into good foundation insulation?

We're in detail design phase of our new house in northeast CT. The frame will be a 2,000sq ft Saltbox, set into a slope. General scheme is superinsulated & airtight shell, and decision tree is in progress - on the HP window, active solar, and back-up choices.

In General questions | Asked By Joe Pandolfo | Mar 22 13
6 Answers

Can insulating concrete be used for footings?

One of the tough questions about 'super-insulated' building is what to do about footings? Some say don't mess with them, too risky just take the heat loss hit. Some have used foam under footings. Those opposed to foam point out it's propensity to 'creep' under long term stress and that it'll deform substantially under rated stress conditions. An alternative, that I've seen little discussion of, is lightweight concrete mixed with perlite as the aggregate. www.perlite.com/concretemixdesigns.PDF

In Energy efficiency and durability | Asked By Jerry Liebler | Mar 20 13
2 Answers

Basement insulation and air sealing question

I am insulating an existing basement. Assuming that the exterior drainage issues are taken care of, here's what I would like to do.

Floor
1. Lay 1"EPS foam on the slab, tape the seams.
2. Place 1/2 inch plywood subflooring, screw down with concrete screws.
3. Place cork flooring.

Walls
1. Attach by adhesive, 3.5" of EPS foam on the CMU walls, tape the seams.
2. Frame a wall to attach drywall by using 2x lumber
3. Drywall.

In Green products and materials | Asked By Roger Lin | Mar 21 13
4 Answers

Long-term effects of spray foam?

Hi all,

I have a client who's "not sure of the long-term....20 years from now effects of open or closed cell foam on his family." Right now his house is leaking like a sieve, and is balloon framed and back plastered. Of course he's just finished painting all the interior walls.

A bit of history:

In GBA Pro help | Asked By Steve Greenberg | Mar 21 13
12 Answers

Best Way for Homeowner to Air Seal?

After getting some really helpful advice on here (will link below) for our new construction, we've decided to insulate with Roxul batts that we'll install ourselves. Now that we're looking in to how to properly air seal, it seems like to do it right takes a professional and proper equipment. Is that the case? Should we just be hiring a contractor to do it all (air seal and insulate)? None of the quotes we received for insulation included air-sealing, except for one, which added over 2k to the price. Is this a high, hidden cost of insulation that we're just discovering now?

In GBA Pro help | Asked By Cathy O | Mar 15 13
9 Answers

A basement for my double wall dream house, second try

I've now pretty well settled that a poured concrete basement with exterior insulation and aligned under the inner main floor wall which carry s the roof load is the simplest and most " buildable" if the floor framing is simply extended (cantilevered) beyond the basement .

In Energy efficiency and durability | Asked By Jerry Liebler | Mar 20 13
Register for a free account and join the conversation


Get a free account and join the conversation!
Become a GBA PRO!