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

Steel siding vs. fiber-cement siding

I was planning to use fiber cement lap board (Hardie Board), but am wondering whether residential seamless steel siding might be a better choice (lap style like this: http://www.usseamless.com/Platinum/index.htm).

Steel siding seems to be used a lot in the Midwest, but I haven't heard of anyone using it here in California.
It seems as weatherproof, as fireproof, lower maintenance, and lower priced. Ecologically, it seems like a slightly better choice due to its recyclability.

In Green products and materials | Asked By Nathan Kurz | Nov 11 13
3 Answers

What type of roofing material is best above a SIP roof with PV modules on top?

I am a home owner in the final design stage for a net-zero house. The house will be located in update New York near Albany at an elevation of 1360 feet and is probably closer to Zone 6 than Zone 5. The area can have heavy snowfalls and also ice storms.

The house will have SIP walls and an 8.25 inch R50 SIP roof. I plan to add 2 inches of polyiso insulation either to the outside or the inside of the SIP roof in order to increase the R-value to R62. The ceiling below the SIP roof will be a cathedral ceiling.

In Green products and materials | Asked By Robert Walker | Nov 9 13
5 Answers

Flashing finless (European) aluminum-clad windows

I have finless, wood-frame, aluminum-clad windows to flash, and have attached a detail of what I'm planning so far. I'm looking to address water that makes it behind the aluminum cladding and comes down along the outside of the wooden frame, at the bottom of the window. I want to move it outside of the wall assembly rather than leaving it to run down behind the clapboards.

In General questions | Asked By Bill L | Nov 6 13
6 Answers

Do I need a vapor barrier in an unvented roof assembly?

I am building a roof assembly with 2x10 rough hemlock rafters exposed on the inside with cathedral type ceilings and no interior insulation. Rafters are covered with 3/4" pine shiplap decking, then 5 1/2" of polyiso insulation (2 layers of 2 3/4", joints sealed and overlapped), then 1x3 strapping, then metal roofing panels. I'm wondering if I need to include a vapor barrier anywhere in this assembly, and if I should put tar paper on top of the polyiso and underneath the strapping? The polyiso is paper faced. I am in upstate ny.. thanks for any advice!

In Energy efficiency and durability | Asked By walter button | Nov 8 13
9 Answers

Failed wall assembly

I had some questions with regard to some pictures of a “failed” wall assembly that was shown to me. I included (attached) a few pictures.

The “back story” on this wall assembly.., a 20-25 year old wall assembly in Northeast Massachusetts which consists of:
From the outside of the building to the interior…
• Cedar vertical siding
• Tyvek house wrap
• ½” or 5/8” CDX plywood
• white mold (on interior sided) of ½” or 5/8” CDX plywood
• 2”x6” kd wall studs
• R19 unfaced fiberglass insulation

In Energy efficiency and durability | Asked By JP Palm | Nov 8 13
3 Answers

Using EPS for roof insulation?

I am building a home in zone 6A. It is a reclaimed barn frame that has gone through engineering, engineer wants double 9.5" LVL's 24" on center. I would like to use 8" 1.5lb EPS between the rafters giving the R value required. My thought was to spray foam the corner where the rafter meets the interior sheathing and while still curing slip the 12' lengths of EPS in. Then sealing any other seems w/ spray foam. This would also provide for 1.5" vented cold roof. The roof system would consist of (from interior out) pole rafters, 3/4" reclaimed wood sheathing, Grace triflex, then the EPS block.

In GBA Pro help | Asked By matt bowman | Nov 8 13
4 Answers

When an ERV/HRV dies, won't homeowners be poisoned?

Here is my concern about "build tight, ventilate right":

A homebuilder builds a "tight" house ( for argument's sake 1.5 ACH 50). To "ventilate right" he installs a "builder grade" HRV or ERV that lasts 5-10 years. Then it burns out. The homeowner is my mother in law who knows nothing about houses or building science. She didn't even know she had a ventilation fan and she wont' know to replace it. Or perhaps she can't afford to replace the ERV/HRV.

Will indoor air pollution accumulate in the "tight" house without ventilation and harm the occupants?

Thanks in advance!!

In Energy efficiency and durability | Asked By Randy Ransom | Nov 5 13
4 Answers

Thank you everybody. Blower Door Day

We did our blower door test today - 94 cfm50 which translates to .48ach50. We tested at the framing stage before the installation of the dense pack cellulose insulation. I am very happy.

I just want to thank everybody for their helpful advice through this building process. I was so nervous I was peeling old caulk off our caulk guns to keep busy while the test was being set-up.

The person who did the test immediately called up some of his co-workers and I heard him say "and this is before any insulation." He was impressed.

Thank you so much for your help.

In Energy efficiency and durability | Asked By Lucy Foxworth | Nov 5 13
4 Answers

Need advice on spray foam under roof sheathing of low-pitched roof in Texas

Is it 'more advisable' to use 2 inches of closed-cell spray foam, followed by the needed R-value inches in open-cell foam, in a non-vented, inaccessible, 18-inch truss space, on the underside of a low-pitched roof in a humid, Texas climate?

The roof will be 1/4 inch slope per foot, highly reflective, PVC, fully adhered membrane with Densdeck underneath and rigid polystyrene for creating needed slopes on top of Advantech decking/sheathing.

In GBA Pro help | Asked By Norman Luke | Nov 6 13
1 Answer

To insulate or vent overhangs or not in conjunction with a non-vented attic?

If you are going to to have a non-vented attic area because of spray foam installation, would you insulate and/or vent any overhangs, i.e. in a hot and humid climate? This seems to be debatable amongst builders.

In GBA Pro help | Asked By Norman Luke | Nov 7 13
Register for a free account and join the conversation


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