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!


6 Answers

Should I insulate around the edges of a basement slab if it has in-floor radiant?

I'm building a house in zone 6a. Local codes require 2" of rigid foam on the outside of the foundation wall, so that's what we did. We plan to insulate under the basement slab (1.5 or 2 inches of rigid). We also plan to install radiant heat in the basement slab. Should I insulate around the edges of the basement slab to prevent continuous thermal bridging and heat loss from the heated slab into the foundation wall and eventually down to the footing and into the ground?

In Energy efficiency and durability | Asked By Mike McKernan | May 8 13
5 Answers

Managing overheating in a 1.5-story home

I’ve purchased a small 1950’s 1.5 story (or Cape style) house, where the second floor has knee walls and sloped ceilings. We’re in Nova Scotia, Canada which is a cold climate but spring/summers can get hot. We plan to super insulate the house using the PERSIST/REMOTE approach when we can afford to, but in the meantime the house has no mechanical ventilation and minimal insulation. The second floor bedrooms are already getting uncomfortably warm on sunny days. I’m curious what methods can be used to manage the overheating in this type of building.

In General questions | Asked By Mark Fredericks | May 8 13
3 Answers

Problems with configuring minisplit system as ONLY heat source

I am having trouble finding the best possible configuration for a mini-split system. I'm building a small house in NW Ohio, a story-and-a-half with full basement). Total calculated heat load is 16,000 Btu/hr.

In Mechanicals | Asked By Andy Chappell-Dick | May 9 13
3 Answers

Shock absorbing system for exterior dance floor?

I'm building an exterior wood framed, 8 by 8, 1/2" marine grade plywood dance floor, (1 layer only) so a typical floating floor method won't work. Is there a way to put , maybe, bridge rubber or springs, or some polycarbonite foam in between the pier block and the bottom of the floor joists, or in between the top of the joist and the plywood for some flex in the floor for the dancers legs?

In General questions | Asked By Roger Aiton | May 7 13
51 Answers

Open-cell foam on roof deck

My house is spray foamed with open-cell Icynene on the roof deck as well as all walls. I have an HRVv for fresh air.

Everything's been good but I'm noticing now that the humidity in the attic starts out around 36% in the a.m. but gets up to 60-70% during the day then back down to 40-50% at night. The temp is always within 5% of the house temp. I'm not sure what to do.

There isn't any moisture sources in the attic. To make it more confusing is, there are two separate attics and both are doing the same thing.

Any help would be greatly appreciated. I don't know what to do.

In General questions | Asked By mark hanson | May 1 13
1 Answer

What to do about undersized Marvin double-hung windows installed without spray foam, with sloppy exterior caulking?

After reading all of the FH and GBA articles I could, I elected to order Marvin Ultimate custom-sized insert double-hung windows for my 1910 brick row house with a flat roof since I had limited options to improve the energy efficiency and comfort without disturbing the plaster or reroofing. My storms didn't help much and I vowed not to put up plastic another year.

In General questions | Asked By sharon slovenec | May 7 13
9 Answers

Sealing blocking in floor framing?

My dream house will use double stud walls over a full basement. The basement will be poured concrete with exterior insulation. It is a one floor above basement plan. The inner main floor wall will be over the concrete while the outer will be over insulation. The simplest way to support the outer wall is to 'cantilever' the floor framing over the concrete. Yes this creates a wood "thermal bridge" at each floor framing member but the heat loss is modest and tolerable.

In Energy efficiency and durability | Asked By Jerry Liebler | May 5 13
7 Answers

Cathedral ceiling exterior insulation retrofit

Climate zone 5A . I need to replace my roof and want to add exterior insulation over a cathedral ceiling.

I am pretty sure there is poly in the ceiling and am worried about trapped moisture. How should a person handle a retrofit when there is drywall, poly, fiberglass batt insulation, roof deck and shingles.

In General questions | Asked By Robert Hronek | May 5 13
4 Answers

Rim joist air-sealing options

We are using 2" of exterior polyiso foam with air-barrier established at the Zip sheathing. Our first choice in regards to the basement rim joist was to use closed-cell spray foam. Now I understand that we should avoid this "foam sandwich" but open-cell is an option due to its vapor permeability properties. Then I read more about foam and am a bit afraid of spray foam in general.

In Green building techniques | Asked By Troy Stevenson | May 4 13
7 Answers

What climate zone am I in?

http://energycode.pnl.gov/EnergyCodeReqs/?state=Massachusetts
My house will be located in bristol county, zip code 02717. Am I climate zone 5 or 4 marine?
I ask because I'm trying to determine what thickness of exterior rigid foam insulation to use.
I'm thinking of using 2x6 walls fiilled with dense packed cellulose, covered with plywood, then tyvek, then 1 inch of xps foam.

Going off this http://www.greenbuildingadvisor.com/blogs/dept/musings/calculating-minim...

I'm either ok or under what I need to avoid the dew point issues.

In Energy efficiency and durability | Asked By Jason carreiro | May 5 13
Register for a free account and join the conversation


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