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

Does one need to ventilate a small roof area when replacing old fiberglas insulation with closed cell polystyrene?

I have recently gutted a bathroom in my 53 year old house which had old fiberglas insulation in the shed roof and walls. The roof line is a low pitch (3/12)shed roof framed with existing fir 2x8 rafters, and ties into the main gable roof (7/12) at the eaves. I would like to insulate the walls and roof with closed cell polystyrene because it is a tub area extended out off the back wall of the house. The framed floor of the tub area is insulated with R-40 closed cell polystyrene, under 3/4 t&g plywood.

In GBA Pro help | Asked By Edward Palma | Apr 5 09
1 Answer

How do you know what the best set of systems are for the house?

Do you need to hire an engineer for possibly a lot of money? Do you rely on your subcontractors who may end of recommending what they make the most money on? Or do you join Green Building Adv. and try to figure it out yourself? I know every house, based on its climate, size, orientation and budget will be different...but when you take those things into consideration, what do you do?

In Mechanicals | Asked By David Cook | Apr 3 09
10 Answers

What tolerances are required on grade preparation for an insulated slab floor

We are building a super insulated shop(4000 sq ft) with a concrete slab floor with radiant floor heat. thermal calculations and recommendations from American Concrete Institute indicate we should put 3" of extruded polystyrene insulation and a vapor retarder topped by 8" of gravel under the 6" floor. What tolerances are really required on the grade flatness under the insulation? Our sub-contractor is is charging a lot for a very tight tolerance. also, would 3 layers of crossed 1" foam be better and more forgiving than 1 3" layer?

In GBA Pro help | Asked By Anna Johnson | Apr 1 09
0 Answers

Great green products for a Habitat for Humanity home

I am designing a home for Habitat for Humanity in a mixed-humid climate. I am trying to find great green products to use while keeping our construction cost to under $35,000. Specifically, I am trying to find some good windows and carpeting, but any other material recommendations would be welcome.

In General questions | Asked By David Quillin | Apr 2 09
2 Answers

Who Pays for Net-Zero?

Imagine a large home with a good envelope and enough PV or Wind Energy to "Sell the surplus".
Can or does "the Grid" really use the surplus?
Has the Zero Energy Home really "zeroed-out" its impact at the power plant?

In General questions | Asked By John Brooks | Mar 31 09
5 Answers

I am searching for a plastic shimming product for providing a drain plain behind vertical siding.

I know there is a least one product on the market that provides a rot proof material to use behind vertical siding. It should be rigid,(not Rain Slicker) and only about a quater of an inch thick with drain holes. Has anyone seen or heard of such a product?

In Green products and materials | Asked By Mason Lord | Mar 25 09
0 Answers

solar home for sale

Great website! I am putting my 100% solar home on the market soon and wondered if anyone has suggestions of places to post it so that a like minded person can find it. It is a real nature sanctuary on my 5 acres and I want someone with a small footprint to come and fill mine. Thanks for your ideas! cheryl@buildingmind.com

In General questions | Asked By Cheryl Nichols | Mar 29 09
17 Answers

rigid insulation on the exterior of a wall assembly?

Does anyone have experience detailing rigid insulation on the outside of an exterior wall assembly? If so, do you have a solution that locates the rigid outside of the sheathing? I see most of the details here (strategies and details) locate the rigid between the studs and the sheathing. This is a problem for our seismic zone and advanced framing.
Any advice or experience will help!

In Green building techniques | Asked By Jennifer Reilly | Feb 26 09
10 Answers

Flashing details

I understand the advantages of using "outsulation" (rigid insulation on the outside)
I am still having trouble finding satisfactory details.
Especially concerning Window head details used with siding.
I went for the pro account here at GBA and started looking at the details.
I still wonder if anyone has actually constructed these details to see what they will look like and how they fit together.
It looks to me like the head details show the water draining behind the window trim(casing) and somehow magically weeping out between the bottom of the casing and the flashing.

In Energy efficiency and durability | Asked By John Brooks | Mar 17 09
4 Answers

Problem with Not to scale Details

I have started looking at the CAD details concerning how the window interfaces with framing and weather barrier.
I downloaded the head sill and jamb details for windows used with siding.
I put them together in a composite drawing(head/jamb/sill) and noticed that the materials and components do not "line-up".
I understand that the drawings are "not to scale" probably in order to exagerate the flashing layers.
Maybe what is needed is one drawing that is to scale and another that illustrates an exploded view to illustrate the layering.

In GBA Pro help | Asked By John Brooks | Mar 18 09
Register for a free account and join the conversation

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