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

Duct heater required with an HRV in a cold climate??

I'm in the beginning stages of building a super-insulated house near Ottawa, Canada. The foundation is completed and we're about to start framing. One of the last details / sub-contractsI need to tie up is the HRV system. One of the firms providing a quote insists a 1500-2000w duct heater is required.

I recognize that the fresh air is likely to be somewhat cooler than the temperature of the house. However, this suggestions a little over-the-top given that the house will have R50 walls, R80 attic, tripled-glazed fibreglass windows and will be tight at less than 1.0 ACH50.

In Mechanicals | Asked By John Scime | Jan 16 12
10 Answers

Powered direct-vent gas water heater recommendations?

My water heater is on the last legs (just started to leak). The current unit is an atmospheric vented unit that is located in the basement. Based on Martin's article (www.finehomebuilding.com/design/articles/the-water-heater-payoff.aspx) it appears that a power direct vent (sealed) or gas condensing is the best way to go for a basement location. Besides minimizing drafting and makeup air issues, I like that I can eliminate the vent to the roof.

In Mechanicals | Asked By Brad Stoppenhagen | Nov 4 14
3 Answers

Air sealing windows

I am building a Passive House with double stud walls and all OSB seams sealed with Prosoco Joint and Seam filler. I have plywood window bucks and triple pane windows with nailing flanges installed on the exterior of the rough opening. I need to air seal the inside of the window frame to the plywood window bucks. I would like to fill the space between the window frame and the plywood with foam and then air seal.

In PassivHaus | Asked By Gerald Blycker | Nov 6 14
6 Answers

Efflorescence / spalling in brick basement


I think I have an efflorescence/spalling problem in my basement foundation walls. This will be a bit of a long post as I want to include any details that may be relevant.

I'm not sure of a few things about it:
A) How much of a problem it is (cosmetic or structural?)
B) If the paint on the basement walls is a contributor
C) What the source of the moisture is (although I have suspicions)

Photos posted here: http://imgur.com/a/7TtkL

A bit of background:

In General questions | Asked By Jon Haque | Nov 6 14
4 Answers

Where does the water vapor go?

This is a question more of curiosity and needing an education rather than a specific request for advice or guidance on a building issue.

In General questions | Asked By Ted In New Hampshire | Nov 4 14
4 Answers

Radon Gas Piping - number of holes or pattern required?

Is there a standard or code for the number and pattern of holes required for a new radon system?

In General questions | Asked By RUSS CROUCH | Nov 6 14
4 Answers

HVAC question: tiny DC fans

Hi, all,

You may remember me from my 120sf outbuilding threads. About that outbuilding:

I've been looking at low CFM quiet DC fans such as the Panasonic Whisper series, the Broan ones, etc. What I've learned over the past couple of years is that there are very few that run down to 10CFM (basically, the Panasonic ERV does) which is the correct size for the space in question.

In General questions | Asked By Minneapolis Disaster, 6B | Nov 6 14
11 Answers

Metal roof & underlayment (AquaGuard - DryTech)

Curious to see if anyone has used or seen the product called "AquaGuard Dry-Tech"?

It's designed to allow airflow underneath a metal roof to drain any condensation that can form under the metal roof and it also provides an acoustical reduction in metal roof noise.

The bottom of the underlayment is NOT breathable/non-permeable and this attaches via peel & stick to the roof sheathing (OSB SIPs).

In General questions | Asked By Peter L | Nov 3 14
12 Answers

Drywall directly on stem wall

I've got a 1' tall stem wall in my current design for a house, the outside of the stem wall is insulated with 6" of XPS and will have a moisture barrier on the stem wall. The slab has 3" XPS underneath.

I'm wondering if I should build the walls flush with the inside edge of the stem wall, and then run the drywall all the way down over the stem wall- attaching with glue?

Or is it better to make the drywall end at the stem wall and paint that last 1' of concrete, in case of moisture?



In General questions | Asked By Tom Frisch | Oct 30 14
2 Answers

Longevity of valves on PEX manifolds

I am planning on a home run installation in a new house. I never had much luck with the PVC valves currently used in residential plumbing actually working when you need them to.. They either are stuck open or will not shut off. I would try exercising them to keep them loose but they would end up leaking past the stem.

I am concerned with the poly valves used on the manifolds not doing there job 10-15 years down the road. Some manifolds offer the optional copper or brass valves, but our water has a high content of limestone and is tough on copper pipes and fittings.

In General questions | Asked By John H. Stehman | Nov 5 14
Register for a free account and join the conversation

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