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!

0 Answers

Insulating Garage Ceiling below bedrooms

Hi everyone, I have a split ranch with a 2-car garage under the bedrooms. The back wall of the garage is completely below grade, the left wall is half below grade (slope), the right wall connects to the 1st floor and the front wall has two 8x7 insulated doors. There are no windows, the joists are 9" tall, and I am in Massachusetts.

The ceiling is currently drywalled and i could see some R-9 batts through a gap.

The bedroom floors, particularly at the front of the house, get quite cold in the winter.

Asked By mike93lx | May 27 18
8 Answers

1 1/2 story farmhouse in British Columbia

Hi, I'm looking for some thoughts on our current design for our 2000 sqft home.

Asked By Michael Blake | May 22 18
3 Answers

Best Value Mini-Split for Cooling, Some Heating?

Climate Zone 6A, Toronto Ontario

I was at my Mom's place over the weekend and we were discussing windows and air conditioners for her small house. Her house is a small 1970's backsplit layout, about 1500 sqft including the rear basement living area, all 2x4 construction. Right now all she has is a window mounted air conditioner that she places in the master bedroom which is on the upper level a the rear of the house. It does a poor job of cooling the house but does give her relief at night for sleeping.

Asked By Lance Peters | May 26 18
2 Answers

Roof design

This rear roof includes a shed dormer, two large walkout dormers, and various roofing materials including a flat EPDM roof over a large addition as well as garage bonus room. There was formerly a wooden deck over the large addition, which was not replaced following a major storm 10+ years ago (previous owner regretted not replacing the deck).

Asked By Emerson | May 27 18
5 Answers

Mitsubishi hyperheat multi-splits and modulation

I'm thinking about having an MXZ-4C36NAHZ installed. The indoor units would be one (1) MVZ-A18AA7 ducted air handler and and two (2) MSZ-FH09NA wall units.

The 4C36NAHZ submittals say it can modulate down to 6,000 btu cooling and 7,200 btu heating.

I cannot find the minimum operating capacity of the MVZ-A18AA7, but the similar PVA-A18AA7 can modulate down to 7,000 btu cooling. The MSZ-FH09NA units can modulate down to 1,600 btu cooling.

Asked By Aun Safe | May 25 18
3 Answers

Insuation in a non-vented roof assembly

I am building a flat roof home that we are using TPO roof on that the roofer will need a minimum of 1" polyiso for an underlayment. I plan to spray the underside of the roof sheathing and up the vertical side of the raised heel truss with closed cell foam for air seal. So my question is, to protect the roof sheathing from condensation is it better to use the 1" of Polyiso and 2" of closed cell or 2 of poly and 1 of closed cell?
I am in climate zone 5.

Asked By Kelly Coons | May 27 18
3 Answers

Faced direction in kneewall

Hi, I'm installing the faced pink stuff in my knee wall. Which direction do I point the face? I know generally its on the heated side, however, im in NY and the crawl space gets super hot in the summer and i might be putting an AC in, so technically the knee wall would be the heated side, no? And the humidity in the house hits can hot 60 at times, averaging 50 on the first floor (which shouldn't be an issue once the a.c. is in). But then what about the winter?


Asked By Champak | May 6 18
4 Answers

Do generous overhangs need venting or insulation?

Building a 1900 sf house, Berkshires, ma - zone 6. We have an unvented roof assembly - flat roof 2 x12s. Interior to be spray foam, but what about the exterior and carport area? I have attached a some perspective elevations for reference
Lukas Schwartz, Great Barrington MA

Asked By Lukas Schwartz | May 26 18
7 Answers

Fasteners for concrete, brick, and CMUs

For an upcoming article on fastening various materials to concrete walls, brick walls, and CMU walls, I'd like to hear about your favorite fasteners.

I'm looking at fastening three types of materials:
1. 1x4 furring strips directly to a concrete wall, brick wall, or CMU wall.
2. 2x4 furring strips directly to a concrete wall, brick wall, or CMU wall.
3. Continuous rigid foam (2 inches thick or more) directly to a concrete wall, brick wall, or CMU wall.

I will also look at a fourth situation:

Asked By Martin Holladay | May 23 18
20 Answers

High-R Wall Design in a Wildfire Zone?

I am in the process of designing a high-R wall for my future home build in Nederland, Colorado. The property is located at 8600 ft. in climate zone 6/7 and in a high wildfire danger zone. My priorities are a tight building envelope with high-R walls and more environmentally friendly materials that also resist fire, but I'm also trying to get the most bang for the buck on those materials. I’ve read various articles on this site and others, and they’ve been very helpful, but I’d love some input on my design. Here’s what I’ve come up with:

Asked By Will Welch | May 25 18
Register for a free account and join the conversation

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