Community: Green building techniques

Much of the value of this site is the pooled experience of members and their willingness to share it. This page offers a Community area formatted for Questions & Answers dedicated to Green building techniques. Other topics appear to the right.

Anyone may ask a question and anyone may answer. Sometimes one of our 15 Advisors may chime in; in other cases, you'll get the wisdom of some of our members who have some experience in this area. We encourage everyone to give us the benefit of both their questions and answers. The usual rules of courtesy apply.

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7 Answers
Flash and Batt and moisture issues...

I am 2/3 way through a major remodeling project and insulation time is fast approaching. I am looking hard at sprayed foam insulation and have prices closed cell. I Iive in the outskits of D.C. so the climate is zone 4 with 5 not too far off and humid.

I have four areas to insulate:
1. First floor -existing Brick outside wall, airspace, 4" block wall and treated 2x2 lathing. Proposed 1 1/2 pink foam board glued to block wall between lathing and then drywall over it. Q - is this a good plan and do I need to worry about a vapor barrier?

Asked By Scott Miller | Sep 1 10
10 Answers
Challenging Floor Details

I've seen a lot of discussion about wall and roof details with respect to air, vapor, and thermal transmission. What I haven't seen is discussion of the flooring and how this contributes to thermal and moisture problems. And I have a quite challenging situation that has me a bit stumped.

Asked By corn walker | Aug 30 10
39 Answers
Ducting in slabs & passive solar

I'm looking for research that examines the effects of using ducting in concrete slabs to circulate heat. Specifically, I'm interested if there is any added efficiency in passive solar applications where air is circulated through the slab. My impression is that this technique opens you up to a lot of potential moisture/mould scenarios. Does anyone know of any research that looks at the implications of this technique?
Thanks,
Jay

Asked By Jay | Jul 19 10
5 Answers
Adding insulation from the exterior

Climate Zone 5 / Western Massachusetts

I am working on a project that involves a cape style house with existing 2 x 6 rafters spaced at 24" o.c. Currently, the 48" high knee walls and unused portion of the floor from knee wall to eave are insulated with fiberglass batts. The roof slope to the peak has been dense packed with cellulose insulation - no venting - and 2" of XPS rigid insulation and strapping applied prior to drywall.

The house will need a new asphalt shingle roof next year.

Asked By Jon Wyman | Aug 25 10
9 Answers
Air barrier with foam insulation.

Just a quick question regarding technique. When building a wall using polyiso or closed cell polystyrene insulation on the exterior wall, where all joints will be taped, siding will be HardiPlank horizontal clapboard 4 inches to the weather: Am I incorrect in assuming that I will need an air barrier over the plywood sheathing before installing the foam sheathing?

After referring to the drawing in the details section, I do not see an air barrier indicated either under the foam insulation on the plywood sheathing, or at the exterior surface of the insulation.

Asked By Edward Palma | Aug 27 10
9 Answers
Does bathroom exhaust fan piping need to be insulated?

I am building a two story home (mixed-humid climate), and will be venting the bathrooms to the outside. The upstairs vent piping will run in the attic.

Is there any particular type of piping to be used through the attic (metal ductwork, PVC, etc.)? Any typed of insulation to go on or around the vent piping? And is it ok to have the vents discharge in the soffits?

Thanks for any advice.

Asked By Chris Johnston | Aug 26 10
19 Answers
Moisture Control in Double Stud Wall

Hi Folks: I’m in the final design and modeling stage for a passive solar net-zero energy home and have a question on moisture control.
Wall system is traditional stucco over building paper and OSB sheathing (vapor semi-impermeable between 0.1 and 1 perm), offset double-stud 2x4 walls 24”OC framing with 5” gap, cavity filled with Spider blown fiberglass, then 5/8” gypsum covered with either latex paint or American Clay system (46 perm). Inside cavity seams at the sheathing will be sealed with closed-cell spray foam. Whole-wall R-value of approx R-47.

Asked By James Riggins | Jul 16 10
8 Answers
Roof structure for passive solar home

I'm working on the roof structure details for our passive solar home. We plan to use the "Perfect Wall" concepts from Building Science Corp. for our frame walls (advanced framing, exterior rigid foam) and would like to make that continuous with our roof structure. However, I need help putting the layers together. Here are some details:

-Standing seam steel exterior
-Rigid foam exterior insulation (polyiso or EPS)
-Dense pack cellulose fill between framing members
-T&G decking for interior finish material

Asked By Michael Schonlau | Aug 21 10
9 Answers
Thoughts on the Bensonwood OBPlusWall?

I've been a big fan of Bensonwood's ideas and innovations for some time. They recently announced their new wall system, dubbed OBPlusWall. I'd love to hear some of the GBA community's thoughts on this wall system, with the following considerations:

-Not sure exactly where the air barrier is... the Huber ZIP sheathing? Any knowledge or experience how Huber ZIP performs as an air barrier?

Asked By Ben Wilson | Jul 15 10
44 Answers
Rigid exterior insulation with vertical siding

I am looking for the most cost-effective and energy-efficient way of installing exterior rigid insulation where vertical siding will be installed. I want to minimize thermal bridging of the wood stud framing. I have explored blocking, stripping, extra layer or OSB or plywood sheathing. Nothing is looking quite right yet. Any ideas?

Asked By Claire Remsberg | Oct 28 09