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

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
1 Answer

Attached garage ventilation

I am looking for some guidance for venting an attached garage of exhaust fumes when coming and going. I have AirCycler's Garage Vent module. Now, all I need is to pair it with a fan of some sort. The garage is roughly 24x24x10. Any recommendations on brand, CFM, location?

I am considering a simple Broan through the wall exhaust fan that will do around 300 CFM at 6 sones, but that is designed for interior use. While the garage is protected from the elements, there are the issues of temperature, humidity and critters.


Asked By Norman Bunn | May 26 18
1 Answer

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
17 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
2 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
2 Answers

Grab bars in universal design energy pretty good house


We are building a pretty good house in Colorado zone 6b. The master shower is 4x5 curbless, we a built in bench. We had planned for a full glass wall between the shower and the commode. But I am thinking a half wall instead with glass extending from the half wall. And install grab bars on the shower and commode sides.

Our GC says that since it is a slab on grade with infloor radiant heat it is going to be hard to do the half wall sturdy enough for the grab bars.

He says I can have grab bars on the glass shower wall, but somehow that doesn’t seem right.

Asked By Lydia Segal | May 26 18
3 Answers

Where can I find a green building contractor?


It's difficult to find who in my area is familiar with green building techniques. For example, we will redo the siding to cement board, put in new windows and reroof, and contractors I speak to are inexperienced with putting a layer of rigid foam underneath this.

Where is there a database of green contractors for my area?
The Delaware valley green building association doesn't have any info like this.
thanks very much!

Asked By sarah clarke | May 26 18
1 Answer

Vent or Not Vent

I was recently struggling with this question for the house we are building and found this article particularly helpful. I had decided to go with a non-vented roof assembly until I started to compare the costs. I then ran into the standard trade-offs that I'm sure most people find. I finally settled on using a vented roof assembly with batt insulation from below on my scissor trusses (gable and hip). I only have a couple of ducts that will be in the attic space and will use rigid duct.

Asked By Kevin Camfield | May 26 18
2 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
0 Answers

ICON siding from CertainTeed

1.) Does anyone have experience with this product. It is new from CertainTeed, and has the look and feel of Hardie plank(cement) siding, but is lighter weight. I hate to be a guinea pig (at least the first one), but its lighter weight seems that it would be easier to install, avoid some cracking, etc problems that I have heard from my supplier.
2,) Any idea of the price compared to Hardie plank? I have a feeling the distributor is pushing us toward Hardie.

Asked By user-6870177 | May 26 18
Register for a free account and join the conversation

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