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!

7 Answers

Controlling humidity levels in unvented attic space

We have three attic spaces that are sealed with open cell spray foam. There are HVAC systems in all three spaces. We live in Herndon, VA. I checked temperature and humidity levels the other day and found the attic spaces to be running about the same temperature ( 76 degrees) but 10% to 12% higher in humidity (54% first floor vs. 65% attic space). Is there a need for us to be concerned about this differential and if so how would we reduce the attic space moisture levels? We do use the attic spaces for storage. Thank you.

In Energy efficiency and durability | Asked By Woody McMahon | Jul 8 15
11 Answers

Foam in the middle - Will it stand the test of time?

I've done a lot of looking/reading and I must not be searching with the right key words. I can't find anyone else that has built this style of wall/roof (layer of foam in the middle) but I'm sure someone has.

In Energy efficiency and durability | Asked By Carl U | Jul 17 15
9 Answers

Best strategy for waterproofing and insulating a half block/half brick basement?

I live in a 1920's home in Central Ohio (Climate Zone 5A). The basement has an exposed French drain (ie, the weeping holes, trench, gravel and tile are there, but have not been covered with concrete) with sump pump. The basement is 2/3rds below ground, with the walls made up of half cement block (bottom portion) and half brick and mortar (top portion). The brick and mortar is partially above ground and is covered on the exterior with a stone and mortar veneer.

In Plans Review | Asked By Matt Bierlein | Jul 13 15
1 Answer

Grading/slope around house and using gravel

I am in the process of re sloping around the foundation of my house. Can anyone recommend what slope I need?

Also, I have been thinking of using crusher run and tamp it to the proper slope around the foundation. Then installing black 6 mil plastic. On top of this my land scape river gravel. At the end of the slope would be a French drain.

Does anyone see any problems with using the crusher run to slope or using the plastic the way I am talking about?

In General questions | Asked By don gilbert | Jul 20 15
10 Answers

Adding rigid insulation?

Hi, I've been reading through information for a few days now, and am honestly more confused now than when I started. I'm sure this question has been asked before but I couldn't find anything specific to my area(zone). Here is my situation... Thanks in advance for all replies.

In Energy efficiency and durability | Asked By Mike Watts | Jul 16 15
6 Answers

Moisture concerns with double stud in 4a?

Hi all,

First off, this is a great website! I have been reading all that I can on super-insulated homes and this site has been a huge help.

In Energy efficiency and durability | Asked By Clay Whitenack | Jul 17 15
3 Answers

Flashing 120-year-old windows to new ZIP R-sheathing

I am slowly retrofitting an 120 y/o home in climate zone 1. As typical with homes of this vintage it was very leaky, both of air and occasionally wind blown water during hurricanes. We had to remove most of the siding on one of the walls and are building it back with ZIP R-sheathing and rainscreen siding.

In Green building techniques | Asked By MIke Truxillo | Jul 17 15
25 Answers

What's the range of window air leakage values for good-quality US windows vs. garden-variety vs. Passive House-quality?

It's very hard to find published window air leakage rates (in cfm/ft2), harder still to get independent test reports with this information. So far I've found the following data points:
* a maximum of 0.3 for all of one US mfr's product line (in an internal manual);
* .02 for a tilt-turn unit by same mfr (from independent test report);
* .003 for a Canadian mfr's tilt-turn unit (from website literature).

I've also been told that the test apparatus doesn't yield a result smaller than .01.

In Green products and materials | Asked By Ann Edminster | Sep 19 09
2 Answers

Looking for a ductless air conditioning unit with a low indoor temperature setting

Looking for a ductless air conditioning unit with a low indoor temperature setting. Just had a Mitsubishi guy out, and their lowest setting is 67 degrees, which isn't low enough for sleeping. My window unit goes to 60 and I usually set it at 62 but my room is still a few degrees warmer.

I've been in hotels where the air goes only to 67 and it's uncomfortable.


In General questions | Asked By Liz Cullen | Jul 16 15
21 Answers

Community insights for a straw & steel green build?

We are building a straw-bale house with steel bones in Sacramento, CA in spring 2015 and I'd love to get some insights from the community! We are pretty far along into the design process, but with nothing purchased as of yet I'd love to get some input before we put our money where our mouths are.

Our goal is to have a (mostly) passively heated and cooled home in (relativity) temperate Sacramento, CA. Passivhaus would be nice but it's an aspiration rather than a goal. Our lot has a number of trees for shade that we plan to utilize, especially in the western aspect.

In Plans Review | Asked By Nick Campbell | Aug 26 14
Register for a free account and join the conversation

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