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!

4 Answers

Air quality sensor / controller?

After much time spent thinking about an air exchange system retrofit for my home, I'm amazed at the installed cost, and am left questioning the necessity of it all. I reputable installer has quoted me $3,500 to $4,000 for a HRV-based air exchange system, so I'm wishing for a cheaper and/or more scientific way to determine my home's ventilation needs, other than something that just vents continuously regardless of conditions.

This article intrigued me:

In Green building techniques | Asked By Ryan Griffin | Nov 20 15
18 Answers

Do screws through exterior insulation reduce the wall R-value?

I was in a Net Zero Building class this weekend and there was mention that screws that are used to attached exterior insulation reduce the whole wall R-value by 39%.

The screws are attached from the outside thru the rainscreen, insulation, WRB, sheathing and into the framing.

This individual referred to an article from Energy Design Update (no issue was noted). I'd check but $600.00 for a subscription is too rich for my pockets.....

Any help here on the article or data at least, with other references?

In General questions | Asked By brad hardie | Mar 1 15
1 Answer

Insulating a 1949 cinder-block house

Currently the walls are covered by cheap wood panels. In between there seems to be some kind of wool like insulation, I see seeping on the floor where I removed the baseboards.

Plan to remove wood paneling and other to bare cinder block walls. Clean for black mold. Fill in cracks and joints between wall and foundation. Seal with Concrete Treat. Insulate.

Questions are:
* What to use to fill in cracks-spaces?
* I use Concrete Treat to seal the walls without it having a reaction with crack filler?

In Energy efficiency and durability | Asked By Marta | Nov 20 15
5 Answers

Global warming impact of HFCs in CCSPF vs. transportation emissions of rigid foam

The consensus about the global warming impact of HFCs in closed cell spray foam and XPS rigid foam makes it pretty clear that they should be avoided.

In Green products and materials | Asked By Nick Welch | Nov 20 15
10 Answers

Cellulose retrofit

I recently acquired a late 40's vintage brick veneer house located in southwestern Pennsylvania. The house is a two story 30' x 22' rectangle topped with a hip roof. Like virtually every other house in this area, it has no overhangs other than oversized half-round gutters. Having said that, the bricks all seem to be in very good condition, and there are no signs of water damage on the interior walls or ceilings. Additionally, there is no insulation in the exterior walls.

In Green products and materials | Asked By Garrick | Nov 19 15
6 Answers

Heat pump water heater in an unconditioned attic... any issues?

I'm working with a builder building some townhomes in Orlando. One option is for them to install heat pump water heaters in the unconditioned attic (R38 blown cellulose floor). There are a couple concerns I have:

1. Will it be too cold in the winter? The 97.5% heating design temp in Orlando is 38F. I expect this, plus the small temp buffer from being in an attic, should make freezing not a problem. Does anyone have experience with this?

In Green products and materials | Asked By Cy Kilbourn | Nov 19 15
5 Answers

Is thermal imaging accurate?

Customer had a thermal imaging co come out .images showed temperature deference so around wall outlets and switches.He thinks it is because of bad insulation install around them . ????Isn't there a building code not to pack or install too tightly ???

In General questions | Asked By Will | Nov 18 15
3 Answers

Tape AND caulk around windows?

I'm planning how we'll install the windows in our house build and recently read Brian Knight's very good article in Fine Homebuilding. If you haven't seen it, Brian has it on his website:


and FHB has videos based on the article:


In General questions | Asked By Nick Hall | Nov 19 15
1 Answer

We have had a dog kennel for several dogs which we plan to remodel

We have had a dog kennel for several dogs which we plan to remodel. It has had painted OSB as exterior siding for several years.

We want to add new plywood siding on top of the OSB. Do you think we should take OSB off and replace it or add paper and a rain screen or 3/9" spacers so it can dry out? This is in n. CA. with lots of rain.

In Energy efficiency and durability | Asked By John | Nov 20 15
5 Answers

External air barrier and batt insulation

If batt insulation is used along with an internal air barrier (drywall system) do I still need an external air barrier? I mean, if there were no good air barrier on the outside, wouldn't cold air from the outside blow into the fiberglass or rockwool and kill its insulation properties, regardless of how tight the drywall barrier was?

In Green building techniques | Asked By Jack | Nov 20 15
Register for a free account and join the conversation

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