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!

16 Answers

Can a cottage built on a concrete piers ever be as warm in Canada as one with a full foundation?

I am trying to minimize the use of concrete in the design of a cottage on flat sandy-ish soil near Huntsville, Ontario. I have heard from contractors that a cottage on piers will always be drafty and that I should go for a full 4 ft insulated concrete perimeter foundation (crawl space).

My question is this - in reality (not theoretically) - can I insulate the floor of a building built on piers enough that it could match the full foundation? What would it take?

In Energy efficiency and durability | Asked By sarah okeefe | Jan 5 13
0 Answers

Vented cathedral ceiling with foam board below rafters for air seal & insulation.

Hi all, I am building a log kit type home in the hill country of Tx (west of SA). This is a dry area I believe designated zone 3. This is a small (600+sqft)home. I will have one section as a great room with vaulted ceilings. I intend to ventilate that ceiling w/ 1" air channel using foam board. I will then use fiberglass batts between the 10" rafters and ridged foam boards (edge taped) below the rafters to air seal the ceiling then have pine T&G as the finished ceiling. I believe I have read that you need a flame resistant layer over foam board.

In Energy efficiency and durability | Asked By RJ Stalzer | Jan 12 13
1 Answer

Air barrier with polyiso foam insulation

I am building a house with steel C roof joists (flat) and polyiso 9 inch (3 3" layers) foam underneath. ( all material is reclaimed and free)
Should I use an air or moisture barrier between foam and steel joists? House is in Lexington, Va.

In Energy efficiency and durability | Asked By John Waller | Jan 12 13
1 Answer

Has anyone tried this?

Another Robert Argue related question...I was wondering if anyone has tried/had success with framing exterior curtain walls and then dense-packing cellulose into them...then re-siding. I am considering stripping the clapboard siding off my 110 yr old house in the NEK of Vermont and using Argue's (Super insulated retrofit circa 1981) idea of framing exterior curtain walls, sans 6mil poly, dense-packing the cavities, framed 24" o.c., capping this with 1/2" cdx fir plywood and my wrb. Finally applying vinyl siding. Thank you for your thoughts and opinions.


In Green building techniques | Asked By Chris Bachand | Jan 12 13
10 Answers

Installing a Condensing Modulating Boiler with an Indirect Hot Water Tank; still efficient w/ old plumbing and cast iron radiators?

Is installing a condensing modulating boiler w/ indirect hot water in an old home with cast iron radiators in Minneapolis still efficient if the house has old 2”+ dia. cast iron piping and cast iron radiators? I’ve read that if the water returning to the boiler isn’t under a certain temperature the heat exchanger won’t function efficiently. Also need to add an additional zone for a previously unconditioned space where we would like to use a wall hung radiant panel.

In Mechanicals | Asked By j chesnut | May 17 10
13 Answers

Preventing wall rot - new construction

In PA I've undertaken a renovation project on a 110-year-old home. The original structure is stone/brick and stucco and the kitchen/bath addition (constructed 50-70 years ago?) was built from lumber.

The kitchen and bath existed on a rotting wood beam foundation and severe water and termite damage was present in the foundation and walls, which buckled. I demo'ed these two structures and the underlying foundation.

In GBA Pro help | Asked By Lisa Weissbord | Jan 8 13
5 Answers

Why thermally insulate a below-grade basement?

Please sheath your literary swords, put the pitch forks back in the barn, turn off those torches, I am well aware that every source I have reviewed recommends insulating a below grade basement, and doing it well. However, thinking out of the box, given my climate zone 7, where the below ground temp is like mid 50's all year round (my assumption), wouldn't it be welcome to have a basement in the low 60's while the outside temp is either 30 or conversely 85 degrees F? My current 1950's construction uninsulated basement feels great in the summer.

In General questions | Asked By Sal Lombardo | Jan 10 13
1 Answer

Why no "ridge vents" for walls?

I've been thinking about wall insulation vs. attic insulation. Why is it that ventilation is not needed in wall assemblies using fiberglass or cellulose insulation in the same way that it is needed for roof assemblies. I certainly know this is true, but discover I'm not clear on the science behind it. For old 2x4 walls, I think it might be because the insulation is thin enough so the dew point isn't reached within the assembly. But what about double stud walls and other higher insulation assemblies?

In Energy efficiency and durability | Asked By Hallie Bowie | Jan 10 13
29 Answers

Rigid foam attached to underside of rafters: Good idea?

I live in zone 5a Connecticut , lucky me. Have mechanicals in attic and would like to semi condition space while maintaining a vented roof. Thinking 4" board, foil on both sides with a value of r28ish. Would like to use attic for storage as well. This method I believe if air sealed and installed well may be a good solution. Am I nuts or on the correct path. Thankyou, Noah.

In General questions | Asked By noah sharon | Sep 19 12
10 Answers

Crawl space wall insulation

I am trying to get my new build R2000 certified. One of the things the R2000 consultant would like to see is more insulation in the crawlspace wall.

In General questions | Asked By erik olofsson | Jan 9 13
Register for a free account and join the conversation

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