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

[Click map to enlarge]

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

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!


3 Answers

Should I get spray foam insulation applied to the outside of my flat roof?

A spray foam insulation company recommended that I have spray foam insulation applied to the outside of my roof (which is totally flat) and then coat that with a reflective material. (I can't have it sprayed in my attic because I don't really have an attic, just a 2-3 foot crawl space.) However, a roofer said that he would not recommend doing that because it would cause trouble down the line if something happened to the roof, such as a tree falling on it. I have no idea what I should do. Advice?

In GBA Pro help | Asked By Beth Dillmann | Jun 19 12
5 Answers

Anyone know of a good article on how to spray foam the attic "floor" to create a vented, unconditioned attic?

I have been looking for a how-to guide on the ins and outs of spray foaming the floor of an unconditioned. Attic. I have found a great article from fine homebuilding 2009 by Michael Chandler, but it only covers how to create a conditioned (unvented) attic. I want my attic to have foam between/over the joists w/ baffles at the edges connecting to the soffit (a vented attic), but I haven't been able to find a decent, detailed resource on how to do this. Anyone have any ideas?

In Energy efficiency and durability | Asked By Thomas Sweets | Jun 18 12
0 Answers

Should we always ask what's for Hot Water with Htg and Cooling?

When is it appropriate to ask for Hot Water Heating , or HW as in getting quotes on HVAC altogether?
I believe whenever a GeoThermal is being compared to any heat pump, GT, Air, Air-Mini...

How could we be explaining bundled HW+ HVAC as A SINGLE SYSTEM?
and how without having more than 1 unit for all, without extra heat exchangers, etc.?

Sometimes an additional water:water can fit best in a 25-30 year application. True.

2) Have you heard of-
GT systems of one unit that also has a shared DX-Coil , after the internal fan-coil, for HOT and CHILLED fluids?

In Energy efficiency and durability | Asked By JP Jon Pierce | Jun 19 12
7 Answers

Do My External Insulated Walls Even Need Sheathing?

I am building a heated garage to be built in Minnesota - climate zone 6. I have designed the walls as follows (in to out): gypsum wallboard -> 2x6 stud wall 16" o.c. w/ cellulose insulated wall cavities -> 7/16" OSB sheathing -> WRB -> 1 1/2" XPS foam panels (R7.5) -> 3/8" strapping to create rain screen (w/ venting above & below) -> cement fiberboard cladding above & stone veneer cladding below.

In Energy efficiency and durability | Asked By Kent Jeffery | Jun 18 12
8 Answers

Floor over insulated concrete slab, Zone 3

I am trying to decide what to do with our ground level floors - we have let the new slab with 1 inch XPS underneath dry out adequately (thanks to advice gained here) , and our floor guy is suggesting oak over plywood and 10mm plastic.
We are sensitive to eating up the room height, but are thinking of putting rigid foam under the plywood. Does XPS come in 1/2 inch or 3/4 inch? Is a floating floor with insulation possible?
Might the insulation under the concrete be adequate?
Thanks in advance,
Donovan

In Energy efficiency and durability | Asked By Donovan Corliss | Jun 5 12
11 Answers

Insulation under basement concrete slab.

I am building an energy efficient home in Southern Maine. I am planning on using ICF's and a spray foam insulation in the wooden frame stick built structure. Would it be cost effective to install styrofoam insulation under the basement slab, and if so how thick?

In Energy efficiency and durability | Asked By Dana St.Ours | Feb 21 12
1 Answer

Insulating ceiling fixtures

Would you suggest the best way to insulate ceiling fixtures exposed to an unconditioned attic is to set an insulated box (rigid foam) over the fixture? Then seal the box to the drywall ceiling. Fixtures such as ceiling fans, recessed lights, and speakers.
Do you have any other suggestions to seal & insulate these fixtures?

In Energy efficiency and durability | Asked By Mark Lancaster | Jun 19 12
1 Answer

Can I use Platon as a cedar breather behind cedar wall shingles?

I'm in zone 5A -- SE Iowa -- sheathing is OSB -- Platon is a foundation moisture prevention product by CertainTeed -- http://www.certainteed.com/products/foundations/waterproofing/311508 thanks, John

In GBA Pro help | Asked By Redstone Group LLC | Jun 18 12
18 Answers

Exterior wall "headers"

I'm planning to build a one story 'green' energy efficient, net zero with PV panels, house in northern Michigan. I plan on using 'advanced framing' 24" OC for my exterior double stud walls. I would like to use trusses specifically made to "replace" one stud or two studs (this may require some slight 'repositioning' of openings). The trusses bottom chord would be the top of the rough opening and it's top chord would sit directly under the single top plate. In my situation, only two truss lengths would be needed , 46 1/2" and 70 1/2"..

In Green building techniques | Asked By Jerry Liebler | Jun 12 12
4 Answers

Moisture question with rigid Insulation on interior of poured concrete basement walls.

Hello,

I know this question may have been beaten to death, but I haven't been able to find this specific details in any of the posts on here yet.

I have a basement with poured concrete walls that have a slight moisture issue (they weep very slightly in spring and fall when it rains excessively). So I know that I'm supposed to insulate them using EPS, PolyISO or closed-cell spray polyurethane foam and then build my walls on top of the insulation. I also understand that I should NOT use any vapor barrier so that the moisture doesn't get locked in.

In Green building techniques | Asked By George Heinrich | Jun 18 12
Register for a free account and join the conversation


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