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

Fiberglass batts in a cathedral ceiling — Round 2

Thanks, Martin and Dana, for your timely responses and comments [in a previous Q&A thread called “Fiberglass batts in a cathedral ceiling?”].

My wife and I read the articles, "How to build an Insulated Cathedral Ceiling" and "Site-Built Ventilation Baffles for Roofs." The air-sealing of the site-built baffles sounded formidable and the mention of no known failures from the use of impermeable baffle materials was enough for us to consider using them.

In GBA Pro help | Asked By Michael Watson | Jul 27 16
3 Answers

Abandoned brick chimney: is it hurting energy efficiency?

Brick single-story house, brick chimney protrudes from the exterior wall from ground level, basement.

Furnace & water heater used to exhaust - clay liner.

Water heater was then orphaned, smaller metal liner inside the clay liner.

Water heater was then removed. Metal liner capped from the bottom.

At this point the chimney is unused. It's still open from the top, has a cap, but has a couple "tin-can" caps at the bottom where the furnace & water heater flues would connect.

In General questions | Asked By J Pritzen | Jul 23 16
9 Answers

Zone 6 dew point

Would a 2x6 wall with:
R-23 Roxul Batts in the cavity,

Exterior layers of:
OSB sheeting,
1" R-6 R Max rigid insulation (taped),
R-6 Insultex House Wrap (taped)
And finished with stucco,
eliminate the dew point problem in a Zone-6?

I called Insultex and they recommended their product be installed over the rigid insulation


In General questions | Asked By David Dunn | Jul 27 16
16 Answers

Banging noise from thermal expansion/contraction

My dwelling has cathedral ceilings and we have a problem with thermal expansion/contraction causing a "banging" noise after sunrise and at sunset. I have a high moisture reading in the morning and but the attic temperature is close to the outside temperature and by mid-day, the spread between the attic and outside increases to around 20 degrees and the moisture reading will goes from wet to dry. At the recommendation of 3 roofers, I had ridge vents added. The overhang is only about 10 inches but has vinyl venting all the way across. There is no venting on the side eves.

In General questions | Asked By David Burns | Jul 27 16
9 Answers

1903 home, first time with central air, lots of questions about insulating, ductwork, etc

Hello! Grab a cup of coffee and hopefully you will have a little insight on this! Thank you!!!!!!!!!!!!!!

I have an early 1900s 2 story victorian home 2200 sq ft, currently getting a new roof next month, and had to remove the old insulation on the attic floor that was outdated in roof preparation (in april). Blown in insulation was added to all exterior walls, as well as a thin sheet of foam fiberglass insulation, prior to installing vinyl siding over the wood siding about 25 years ago. Also storm windows to cover the old windows.

In Energy efficiency and durability | Asked By John Friend | Jul 25 16
13 Answers

Insulating a raised floor over an old concrete slab

Hi, I have a house in Seattle. The back portion of the house has a 60 year old 600 square foot slab with approximately 2' deep footers. The ground slopes gently away from the foundation, and the roof overhangs each side by about 2-3'. Let's assume there is no gravel, sand, plastic, or insulation underneath the slab. There is no plastic or insulation on the exterior perimeter of the foundation either. The foundation perimeter vertically extends approximately 1/2"-1" above the slab. While the perimeter is level, the concrete slab is uneven, hence the 1/2"-1" inch variance.

In General questions | Asked By Jo Lee | Jul 8 16
15 Answers

Exterior walls to meet code without gypsum?


Maybe this has been discussed here. Feel free to link me to other threads that I haven't seen if this is fully covered elsewhere.

I'm not a fan of drywall. A quick rundown with no real surprises: it used to be cheaper; now it's not. It also takes plenty of work and more money to make it look nice. It's heavy but also very breakable. Even when you don't break it, it's messy. Etc, etc. I *am* a fan of 3/4 plywood, which is less breakable, more durable, and looks nice.

In General questions | Asked By Minneapolis Disaster, 6B | Jul 22 16
2 Answers

Closed-cell spray foam insulation under a sunporch

We installed 2 inches of spray foam closed cell insulation on the underside of a sun porch which is open on a sides underneath. My husband wants to store his riding lawn mower underneath which means he will have to drive it under the porch and start it up under the porch. I understand that this foam is highly flammable. Please advise if this is safe or what we can do to ensure safety of the storage of the riding mower. Thank you.

Denise P

In Building Code Questions | Asked By Denise Phelps | Jul 27 16
7 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.

In General questions | Asked By Nickolas Van Kleeck | Jul 23 16
6 Answers

Polyurethane foam vs. Icynene foam: What's best for subfloor insulation?

I have a house that is brick veneer and the front section has the polished timber floors.
The sub floor area was not properly ventilated and we had some mould issues. Since then we have had vent’s installed and a sub floor fan under one of the rooms.
However it is a clay soil that the house is suspended on, there are still a some mould spurs on the soil. The air under one room is always quiet damp.

I was wondering if product is more suitable for this type of application ….does notabsorb the moisture in the air and will mould grow on it ??

In Energy efficiency and durability | Asked By Rheems I | Jul 25 16
Register for a free account and join the conversation

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