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!


1 Answer

Spray foam my ridge vents and soffits closed?

Okay so I am investigating spray foam insulation for my garage. The most recent company I spoke with gave me a quote but also asked if I had a ridge vent. I said yes. They said they would also spray the vent closed because spray foam creates another atmosphere and we would not need it. Another atmosphere??

I don't understand why you would want to get rid of the ridge vent. Can someone shed some light on this topic, I am in the dark.

Asked By Joe Overhaulin | Aug 17 16
62 Answers

Questioning my logic...GSHP, ASHP, radiant?

I'm in the planning/almost ready to break ground stage of a new home and I'm beginning to question my sanity when it comes to figuring out the right approach for heating & cooling.

The home is:
North end of Climate Zone 5
Main Floor: 1700 sq ft + 1000 sq ft garage, vaulted ceilings through much of it
2nd Floor: 1100 sq ft (2 bedrooms, 2 baths, living room) primarily over the garage
Basement: 1700 sq ft, partial walkout + 1000 sq ft shop under the garage (separated from the rest of the basement)

Walls: R30+ (2x6, 2" XPS outside, 2lb SPF for sealing + 1/2lb SPF for cavity fill)

Asked By Dave De C | Jul 16 16
1 Answer

Can you use Blueskin without a drain plane?

The architect for my client's home has specified Blueskin WRB under untreated Alaskan Yellow Cedar with no drain plane. The house is facing the ocean just 200 feet away from the water on the central coast of California. In our mild climate we can often get away with building assemblies that other climates can't, but the ocean is relentless on building materials.

Asked By Steven Jungerberg | Aug 17 16
3 Answers

Venting a combined basement bathroom / laundry room into existing 4" vent / drain stack

I've had a few quotes for installing a new 4 piece combined basement bathroom / laundry room (dryer, shower sink toilet) as apart of getting our basement finished.

Currently the main 4" stack serves as a combined vent / drain for a 3 piece washroom (2nd story), and as a drain for a (1st story water closet - 2 piece, that is separately vented with a 2" vent through the roof)

Asked By Mike Tew | Aug 16 16
3 Answers

"Flash and batt" question: can I re-use existing batts?

We had a tree fall on our house and damage a section of roof that includes a cathedral ceiling/roof. It was previously insulated with R30 batts (faced) under the rafters followed by drywall (this is in part of our bedroom). We are planning to spray 3" of closed cell foam under the rafters and fill the remaining 6.5" with fiberglass batts. I realize that the R30 batts are designed to fill an 8-9" rafter depth but was wondering if re-using them would significantly compromise their insulation properties vs using new R-19 batts.

Asked By Rob Moore | Aug 17 16
19 Answers

How should I address the lack of plywood boxes for my double stud wall rough openings?

Blame it on lack of clarity on my part, but when my framer built my double stud walls he didn't oversize the window rough openings to account for 1/2" plywood sheathing connecting the inner to the outer walls. He figured that this gap could be covered solely with drywall.

What is the disadvantage of not having plywood in this location?

Asked By Adam Peterson | Aug 12 16
5 Answers

Provia Entry Doors

Found the Provia entry doors online. They claim a U-Value of 0.10 on the fiberglass polyurethane core doors.

Anyone use these doors?

What about cost for a 36" x 84" door?

Asked By Peter L | Aug 12 16
10 Answers

Fiber-faced rigid foam as basement insulation?

I have some extra fiber faced rigid foam sheets that I have left over from our build. Would this be OK to use as wall/floor insulation for a small crawlspace? The fiberglass facing has me wondering if it will be a problem.

Asked By Clay Whitenack | Aug 11 16
6 Answers

High humidity in new construction - Mitsubishi Multi System playing a role?

Hi Everyone - Longtime lurker and looking forward to being a member of GBA. Thank you in advance for advice.

Question/concern I have is high humidity in new home I've built for my family. Highest levels in upper level bedrooms. Project location is Western Maryland (Zone 5A I believe). Here are a few details about construction that might help:

Main Level - 1,223 sq.ft. - ( Dense packed cellulose)
Upper Level - 586 sq.ft - (Dense packed cellulose)
Basement - 1,179 sq.ft - (2 inch EPS Foam followed by 2x4 wall with unfaced fiberglass)
Attic - blown cellulose - R44

Asked By Ben Thrush | Aug 15 16
11 Answers

Looking for design software recommendations

Hi -

I'm a new member and I'm looking for recommendations for relatively easy-to-use design software (I did try searching the site but didn't find anything discussing that). My first task will be a simple floor plan so I can ask the good folks here for advice on placing mini-splits. Further down the road, I'd like to be able to draw out details for roof and wall assemblies for the retrofits I hope to do. Any then maybe a tiny house (or at least a tiny shed) in the future.

Asked By Nickolas Van Kleeck | Jul 23 16
Register for a free account and join the conversation


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