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2 Answers

Framed floor over concrete slab

I'm working on building a new home near Seattle (4C) that will be, for the most, a concrete slab on grade finish floor. In the bedrooms, though, I'd like to install carpet and I'm trying to come up with the best assembly to do so.

The slab will have 2-4" of rigid insulation (depending on budget) and a vapor barrier under the slab.

I was thinking of laying (non-pt) 2x4s on edge @ 24" o.c. with a layer of 3/4" plywood over that, then installing the carpet on the plywood.

Asked By Daniel Stewart | Mar 18 18
7 Answers

No need to tape outdoor sheathing if walls are all spray foamed?

Hi. I asked my GC about if he was planning to tape the gaps between the outdoor plywood panels for air sealing. He said there was no need to do that because he'll be spray foaming (open cell) all the walls on the inside.

Note that he's using Tyvek Drainwrap on the outside, and then a 2 ply layer of asphalt felt paper on top of that, with cedar shingles as the exterior cladding.

What do you think? Taping the sheathing doesn't sound like that much work, but if it doesn't buy you anything no point in doing that.


Asked By mike myers | Mar 16 18
8 Answers

Greatest (new) thing in air sealing?

The importance of air sealing is emphasized at every point by GBA and other organizations that use building science for designing (!) and retrofitting residential housing. It is a cornerstone for energy efficiency and for controlling air quality, and also for comfort in buildings. Good air sealing is a prerequisite for using increased amounts of insulation that may reduce energy flow and drying potential in walls and ceilings.

Asked By andrew c | Mar 16 18
5 Answers

Is it Safe to Sandwich Rim Joist Between Rigid Foam and Vapor-Impermeable Flashing?

The contractor on my renovation project has put a thick, flexible, black plastic or rubbery flashing material (York Vascoseal) around the bottom of the wall where it meets the CMU crawlspace. It is roughly the same width as the rim joist and covers it completely. He said the it pleases the inspectors, is required behind deck ledger boards, and helps protect the bottom of the house from splashes and whatnot, so they just run it around the entire house for good measure. I assume it is vapor impermeable just by inspecting it, due to its thickness.

Asked By Gordon Franke | Mar 15 18
9 Answers

Air seal the ceiling or the attic?

I live in the East Bay part of the San Francisco Bay Area. Maps show me in Climate Zone 3B, but I'd say I'm a good deal cooler than that suggests. I'm on the east side of the Coastal Range/Berkeley HIlls, but still in the hills, not the hotter flat area further east. I'm also at the bottom of a valley near a creek with some tall trees and a big hill to the west and the house gets very little direct sunshine on all but one of its windows during the warmer months. We heat a lot in the winter and cool very little in the summer.

Asked By Domenico Perrella | Mar 13 18
8 Answers

Vented over roof on parallel chord truss

I'm about to commence a project and I've got all the details dialed in up to the roof and I'm leaning towards the following.

Asked By Will Schebaum | Sep 19 16
10 Answers

Raised-heel trusses can be annoying

We installed raised-heel trusses with bottom chord overhangs on our house. The top of the top chord is 20" above our top plate. According to the 2012 International Residential Code for seismic zones or zones designated for winds of 100 mph, raised heel trusses more than 15.25" have to be blocked and braced.

Asked By Jimmy Nguyen | Feb 6 16
5 Answers

Can a rainscreen become a chimney for fire?

I have a client who is concerned about fire in a rain screen I recently put up to go under siding.
This is a wall of rough cut 1 inch board sheathing covered in typar and taped at all penetrations and seams. The typar is the primary air barrier. The rain screen is 1X3 (3/4 thick) strapping running vertically every 16" oc. The bottom is open and covered with fiberglass mosquito netting and the top is open to the soffit. The soffit is not vented into the attic. I am planning to insulate with dense packed cellulose. The siding will be vertical grain unpainted cedar.

Asked By Josh Engle | Oct 5 16
3 Answers

How should I redo my Zone 5 crawl space, please?

I recently purchased a weekend home (soon to be a weekday vacation rental) in the foothills of Colorado’s Front Range. It’s in region 5. It has a crawlspace with uninsulated concrete block walls that are an average height of five feet. One end is about six feet and the other is four, if that matters. There are a few cracks in the mortar that I can see daylight through. The floor joists are insulated with fiberglass batts and have been a home to mice for years I believe. There’s a bit of an odor, to say the least. The propane furnace is down there, too, and the ducts are not insulated.

Asked By Chris Bata | Mar 9 18
2 Answers

Anyone familiar with Terra Firma foundation system?

We don't have expansive soils in my area, but I was reading about a project in Austin that uses the Terra Firma foundation system.

[Editor's note: Steve Knapp later wrote a clarifying comment. He meant to write Tella Firma, not Terra Firma.]

I understand it to be a type of post-tension slab that can be elevated above the grade. It looks like an interesting idea, but I wonder if the air gap under the slab makes it less energy efficient.

Asked By Steve Knapp CZ 3A Georgia | Mar 6 18
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