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!

4 Answers

Building modified Trombe wall -- How to stop heat from sinking into foundation?

Howdy planning a modified trombe wall but wondering how to stop the heat from migrating threw the 8 " stem wall an down into the foundation an soils of the crawl space. Is there a method of installing say a 2" isolation foam wedge to isolate the wall above the main floor ?

In Green building techniques | Asked By tim miller | Dec 14 12
2 Answers

What's a good way to detail an exterior corner with rigid foam?

I'm planning on improving an existing 2x4 wall by installing 2 layers of 2" polyiso or 4-1/2" nail-base panels. I've found good pointers on this site for most of the details, but am still unsure about how to handle the exterior corners so that the rain-screen strips and siding corner-boards have something solid to attach to. The corner-boards will likely only be a few inches wide, so not wide enough to catch any framing. I'm assuming a butt-corner with nail-base, so there would be OSB on only one side of the corner. How do you do this without creating a thermal bridge?

In Green building techniques | Asked By Andrew Thompson | Dec 12 12
5 Answers

MiniSpilt or PV

I am building a single story house in the Pacific NorthWest which is 1800sq ft. I am using Pretty Good House/PassivHaus principles. The house will be well sealed and insulated, it will use good quality glazing for some solar gain.

I had been planning on using a MiniSpilt to heat the house. Only electricity is avaiable.

In Energy efficiency and durability | Asked By Stephen Carlton | Dec 14 12
5 Answers

Can closed-cell foam insulation be used to entirely fill double-stud exterior-wall cavities?

Can closed-cell foam insulation be used to entirely fill double-stud exterior-wall cavities (i.e., about 7" deep) for an entire wall? Other than higher cost, does this plan suffer from technical drawbacks?


In Green building techniques | Asked By Martin Hughes | Dec 13 12
4 Answers

Cellulose vs. fiberglass batt cavity insulation with rigid foam exterior in zone 5 central NJ

I'm looking at cavity insulation options for a new 2200SF house that will have 1-1/2" polyiso on exterior walls and 3" on the roof. Cavity insulation prices are coming in at roughly $4500 for fiberglass batt (R21 walls/R38 roof) and about 3 times that for cellulose. While the benefits of cellulose have been well covered on this blog, I'm having trouble justifying the added cost for cellulose and wonder to what extent the short comings of fiberglass are mitigated by the addition of the foam on the exterior.

In Energy efficiency and durability | Asked By Scott Schaub | Dec 12 12
3 Answers

Not damp/waterproofing a foundation?

Would it be foolhardy to not damp/waterproof our foundation? We have a very sandy site and low water table. We will be putting 6 inches of foam on the foundation (the foam is ship lapped).

In General questions | Asked By jessie pratt | Dec 13 12
4 Answers

Design for upgrade: Where are the debates or standards? 100 year buildings.

The timber is old growth and thick, the structure sound, the outside and inside is beautiful. The building is 87 years old and nothing is wrong with it... except it's been hacked to bits through upgrades to plumbing, electrical, telephone and (now) wireless internet.

In Green building techniques | Asked By Bryce Nesbitt | Dec 13 12
9 Answers

Basement ceiling

I've put insulation between my joists, and just was told, I put them in upside down. Apparently, the paper should face the floor above.
Would just slicing the paper suffice or should it all be turned around.


In GBA Pro help | Asked By Deb Malloy | Nov 26 12
4 Answers

Why am I not getting hot water consistently from my new Marathon hot water heater?

I have a closed loop geothermal system with two 40 gallon hot water heaters. They were old and rusting so I replaced them both with just one 40 gallon Marathon hot water heater. I have not been able to get hot water when I need it all the time. Can someone please help me figure out why?

In Energy efficiency and durability | Asked By Vonnie Guy | Dec 12 12
5 Answers

Cooling Down A House With No Attic.

Hi guys, first time here, so I want to thank you in advance for all your help...
Here's my situation, I live in Fremont, CA and I'm planning to buy the house I'm currently renting, but there's a problem, the house is "extremely hot" during the summer. It is 95 degrees inside. The house doesn't have an attic, it's a flat roof. When looking up to the ceiling, one can see the beams,etc and my wife happens to like that about the house. So, how can I fix the heat problem? In the winter, of course, the house is very cold.

In Energy efficiency and durability | Asked By Jose Figueroa | Dec 11 12
Register for a free account and join the conversation

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