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!


8 Answers

Slab — thermal break at vehicle roll gate

as I mentioned in a previous post we are putting in a new floating slab on grade in a warehouse building.

the grade has been leveled and sewer drains in trenches and backfilled
then there is a 4-6" layer of compacted gravel and we plan on using a 15mil taped vapor barrier and 2" of taped 60psi XPS on top of that.

for a thermal break we are using 2" 25psi XPS that extends 10" below the slab

there will be radiant installed throughout the building and we are in

my main question is:

Asked By Big Ern | May 2 16
5 Answers

Sewer vent location

We have a cleanout and sewer vent pipes currently sticking straight up from the sewer lines to above grade level in the area about 5' from the front doors to the building (there are 4 of them, as the house is a duplex). Porch is about to be built, and the area is dug out. The original plan was to have these 4 pipes terminate in the area of a planter that divides the front porch. The porch is 4'10''x12' and has 4 steps on all 3 sides. I hear that these vents may cause unpleasant smell in the area of the front porch. Could this be some kind of substantial smell?

Asked By Lucyna de Barbaro | May 5 16
12 Answers

Can someone explain the science behind mid-wall vapor barrier on a double stud wall?

In order to save money, I've switched my wall assembly last minute from using exterior rock wool board to a double stud wall construction. I would like to speak with my county inspector about using this approach to make sure I don't have problems during construction. I'm struggling to understand how I'm going to explain how a vapor barrier on the back side of the inside wall is a good idea.

I'm in climate zone 5, and here is my intended wall assembly:

From inside-to-out:
GWB
Insulweb netting (affixed to stud to hold cellulose)

Asked By Adam Peterson | May 4 16
1 Answer

Insulating two crawl spaces

A friend is having some work done on his old house in upstate New York, Climate Zone 5/6. There are two crawlspace issues.

Asked By Chris Ermides | May 4 16
1 Answer

Townhouse common wall upgrades

I had a kitchen fire in my Gaithersburg, Maryland townhouse (about 20 miles north of Washington DC). The insurance is going to pay to have the walls on the first floor removed and have the insulation replaced. The townhouse was built as part of a quad in 1986, with the main wall facing south, and east and west walls connected to neighbors, and half of my northern wall is connected to my neighbor behind me (the other half faces the central atrium).

Asked By Carl Fosler | May 5 16
7 Answers

Preparing for future solar panels

Building a new home and want to install solar panels at some point in the future. They won't be in the budget initially, when the house is built, but I want to prepare for them and make sure I don't miss something during the construction process that I will have to redo.

The panels will not go on the roof, they will go out in the yard or on an outbuilding or pergola, so I don't have to worry about running wires from the roof to the basement. However, do I need a particular type of breaker panel? Do I need to spec certain equipment?

Asked By Clay Whitenack | Apr 25 16
6 Answers

Photovoltaics: String vs. Microinverters

CZ-4. Southern Indiana. New Construction Ranch. Garage Roof faces 30 deg west of south (210 deg). NO shading from trees now or in future. About 36 Grid-Tied Panels. No battery back-up. A purchase arrangement, not a lease type transaction. Three major installers in the metropolitan Louisville, KY market.

Two competing PV installers. One for Microinverters ; one for Strings with single inverter/optimizer.

Asked By Ted Cummings | Apr 30 16
13 Answers

Comfortboard pricing - Triple $ per R vs foamboard??

Hi all,

Asked By Keith H | Apr 21 16
4 Answers

Interior vs. exterior air barrier

Wondering what the consensus is on the interior vs. exterior air barrier issue is? I am considering this question in light of a double-stud, dense-pack cellulose wall.

Marc Rosenbaum has indicated that he prefers exterior air barriers, because they are so much simpler to execute (no zig-zagging around floor systems, etc).

Asked By Burke Stoller | May 4 16
24 Answers

New slab with radiant heat

As part of our remodel north of San Francisco (ZIP code 94941), we are converting about 700SF of our lower level into living space. The existing slab has been removed we excavated a few additional inches to increase our ceiling height, and we are getting ready to put back a new 5" slab, in which we will also add radiant heat tied to the rebar.

Asked By Torsten Budesheim | Apr 22 16
Register for a free account and join the conversation


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