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!

5 Answers

A new low for radiant barrier misstatements

Don't you love radiant barrier websites? They are a constant source of amusement. My latest favorite stupidity comes from the EnergyFoil website, which helpfully defines R-value. Are you ready?

"An example would be a product with an R-Value of R-19 which means that it will take about 19 hours for the temperature on the inside to become the same as the temperature outside. R-38 = 38 hours, R-11 = 11 hours, etc."

And all these years, I mistakenly thought that R-value was 1/U.

In Green products and materials | Asked By Martin Holladay | Apr 24 14
2 Answers

Foaming a low-pitched roof

I have a 4/12 roof that is being converted to an unvented attic. The foam subcontractor assured me that he could get foam, being sprayed on the underside of the roof, to the plate line. He finished the job assuring me that they had been successful.

I drilled holes and used a scope to see the void that extends out to 6 -10" from the exterior wall plates. How much of an issue is this?

In Energy efficiency and durability | Asked By Hugh Stearns | Apr 24 14
0 Answers

Who has a green/high-performance building innovation that successfully pushed the permitting envelope? I want to study it!

My organization, the Northwest EcoBuilding Guild, Olympia, WA, just launched a new website, the Code Innovations Database, Its a new resource with one simple goal in mind: “making it easier to build green.” www.CodeInnovations.org.

In Building Code Questions | Asked By Chris van Daalen | Apr 23 14
7 Answers

Wall section? Attic insulation? Energy / Moisture / Storm


I'm a licensed GC designing an addition to my personal residence which we built in the late 80s. The original house was built with 2x6 studs and might very well have been the first house built in NC with a sealed crawl space. (I gave my building inspector a copy of a sealed crawl space article by the TVA, and he OK'd the sealed crawl space.)

I would greatly appreciate some input on a couple aspects of the design.



Project synopsis:

In Energy efficiency and durability | Asked By Bill Daugherty | Apr 20 14
4 Answers

Retrofitting an uninsulated slab for radiant

We are planning a major renovation of our 1970s ranch and would like in-floor radiant heat. The house is on an uninsulated slab in climate zone 5A. Our current plan is to insulate with 1.5" XPS over the slab, lay Schluter Bekotec over the insulation, place the the PEX in the Bekotec, screed then tile thoughout the house.

In Plans Review | Asked By Jessica Marchesi | Apr 6 14
1 Answer

Martin Holladay will be speaking this week in Montreal

Martin will be speaking on "Affordable Green Homes for Cold Climates" in Montreal, Quebec, at 7:00 p.m. on Friday April 25, 2014. The event will be held in Room 3110 at the School of Architecture at the University of Montreal. He will be speaking in French.

For more information on the event, visit the Maison Saine website.

In General questions | Asked By Martin Holladay | Apr 21 14
12 Answers

REMOTE vs. PERSIST approach for a flat roof?

I'm not sure I fully understand, but the REMOTE system states an advantage over PERSIST by allowing more insulation in the roof and not building a second roof structure.

Does this advantage apply for a flat roof?

I'm also trying to understand whether a vapour permeable barrier is needed for the roof and walls on the outside of the sheathing, before the exterior insulation is installed. REMOTE promotes vapour permeable, and PERSIST uses impermeable.

In Green building techniques | Asked By Jerry Chwang | Feb 11 14
2 Answers

Roof insulation

I am rehabbing a house located in zone 5, Pennsylvania. The room I am working is a kitchen with a cathedral ceiling. The room is completely gutted. The rafters are 2 x 10 on 24 o.c. The roof pitch is about 15 degrees.

In General questions | Asked By Anthony Jackson | Apr 21 14
2 Answers

We need some advice on a solar envelope house

My husband and I are considering a home on a huge lot we love, but we found out it is a solar envelope home built in 1983. I've read mixed reviews on this type of home and we have some concerns. We'd appreciate any help!

1. If we wanted to ever convert it to a normal home, is that possible?

2. Have people really experienced health issues stemming from mold and modes growing in the walls and under the house from the moisture in the air? How common is that? Fires seem to be a concern too.

3. This home is in southwestern Illinois. Will it really make a big difference in our bills?

In Energy efficiency and durability | Asked By Erin Litteken | Mar 22 14
2 Answers

What is the best angle for a skylight on a low-slope roof in Chicago?

I am replacing a 30 year old plastic bubble skylight as part of a major remodel. The skylight is located a flat (low slope) roof in a typical Chicago small residential building and serves a third floor bathroom. The skylight will not be openable.

I have searched this site, the web, and the manufacturer's installation information, but am still unsure how to orient the skylight to maximize its benefits, while reducing drawbacks, like unwanted heat in Summer. It appears that the only requirement is that the skylight be installed at a slope greater than 15 degrees.

In Energy efficiency and durability | Asked By Dan Nehm | Apr 19 14
Register for a free account and join the conversation

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