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!

3 Answers

ComfortTherm plastic-enclosed batting above radon retarder sheathing in crawlspace?

I have encapsulated my crawlspace (5-7' tall walls) with proper poly I got from radon mitigation specialist. Everything all the way to band joist is encapsulated. I also have good above code level ventilation going between crawlspace and basement. Basement walls I was able to cover in polyiso, but I don't have large enough access hole to the crawlspace to get even 1/4 size sheets of polysio.

Would attaching ComfortTherm plastic-enclosed batting work in that kind of situation? I am in Zone 5.

Asked By Apollo S | Nov 30 15
3 Answers

Insulating unvented roof assemblies

I had read the article here.... http://www.finehomebuilding.com/how-to/departments/energy-smart-details/...

and since 1 and 2 require foam above the roof sheathing which I can't do without redoing the roof which is high expense it leaves 3 and 4. The comment seems to be under the "how much insulation" that "code requires the [closed cell] foam layer to meet specific minimum R-values" in the table. I assume the closed cell based on the air-permeable comment.

Asked By Michael | Dec 1 15
3 Answers

Smart MemBrain in Zone 5

As some of you may have followed my other Q&A posts, you may know I have installed the Certainteed brand Smart MemBrain on the interior side of my walls.

I live in Zone 5. My walls are 2x6. Exterior to interior is vinyl siding - Green guard Raindrop 3D wrap - 7/16" OSB - 2x6 studs w/ R-23 mineral wool insulation - smart MemBrain - future 1/2" rock - latex paints.

Asked By Nicholas | Dec 1 15
3 Answers

Rescued lumber from 1930s roof trusses: It is treated?

I'm adding a second story to my 1930's bungalow. As far as I can tell it's the original roof trusses -- looks like 2x6s. I'm planning to save the lumber from the roof trusses to use in some other projects. Does anyone know if that wood was treated with any chemicals back in the '30s?

Thank you in advance for any thoughts/ideas/comments.

Asked By Michael | Nov 30 15
22 Answers

Two backdrafting appliances and dust — Do I need an HRV?

Hello, I have a problem with my house.

1) My house is probably air-tight

2) My water heater backdrafts whenever the bathroom fan is on. It's probably backdrafted every single morning (windows fog up & I feel the warm air at the flue when it kicks on....it only stops once turning off the bathroom fan).

3) Opening specific windows in the basement relieve the backdrafting of the water heater.

4) There was a lot of dust on a return-air duct that was right above the water heater. Another supply duct near the water heater had rust.

Asked By J Pritzen | Nov 26 15
3 Answers

Unvented attic and wall?

Zone 3, 12/12 pitch roof, Galvalume color roof.
Talked to insulation contractor and discussed options.

2x6 walls = Hardie lap siding, 3/8" rainscreen, Tyvek, OSB, air sealing, BIB insulation (R-23), 5/8" sheetrock.

2x8 cathedrial roof, unvented, with total elect units and ducting in kneewall area and spare room in the center = standing seam, membrane?, 7/16" OSB, 2 inch polyiso, membrane or taped joints?, 7/16" OSB, 7 inch open-cell or BIB insulation.
No venting.

Are we getting closer?

Asked By Quinton | Nov 29 15
2 Answers

New house question

After a lifetime in the Southwest, we are building our first home in a Zone 6 area (Northwest Montana near the Canadian Border). I stumbled across this website accidentally, and have read everything I can regarding insulation/ barrier techniques, but was hoping for some clarification.

Asked By Bill C | Nov 30 15
2 Answers

Saving beetle-damaged reclaimed framing lumber

Is there a practical way to make safe beetle damaged framing lumber?

In this case it's 1930's era old growth douglas fir 2x4 rafters, which were removed then stored outdoors. Pretty much all of them have beetle exit (or entry) holes (see representative picture). The wood is plenty strong, but clearly the beetles can (and did) spread.

In theory killing methods include: heat/kiln cooking, chemical saturation, microwave energy like that used for termites, freezing. But in practice, in the San Francisco Bay Area, is this wood compost or fixable? What's the green thing to do?

Asked By Bryce | Dec 1 15
7 Answers

Can I leave the fiberglass insulation in place and add 1/2-inch Rmax polyiso to the interior?

I am starting a renovation in a home with T-111 exterior siding, 2x4 walls, 3 1/2" fiberglass batts for insulation. Can I add 1/2" foil faced Rmax on the interior wall and then sheetrock? Is there a better way to increase the insulation/air sealing then what I 'm describing?

Asked By James | Nov 30 15
11 Answers

Pros and cons of Grace Ice and Water compared to Tyvek Drainwrap

If applying a WRB under rigid foam insulation, what are the pros and cons of using Grace Ice and Water Shield compared to Tyvek Drainwrap, in terms of protecting the sheathing, serving as an air barrier, difficulty of installation, flashing details, and any other reason you might prefer one product over the other to serve as a WRB? Assuming that the Grace product is more expensive, do you believe that it is worth the additional cost on a 2,000 square foot home in Zone 5?

As always, any advice or opinions are greatly appreciated.

Asked By James Timmerberg | Nov 29 15
Register for a free account and join the conversation

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