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!

4 Answers

Polyiso along slab edge

There was a picture in the latest Finehomebuilding magazine of a wall profile of a newly built house. I'm going to try and attach it below. It shows polyiso foam along the slab edge of the basement. They used xps under the slab. I thought that because it can absorb moisture, polyiso shouldn't be used anywhere but above grade. From the picture it is positioned right on top of the footing along the slab edge. Is that ok?

Asked By Brian W | Sep 26 15
2 Answers

Ground gutter/curtain drain techniques

I have a 1920s home in Columbus, OH. As is typical of the neighborhood, it's a small footprint (~800 sf) and more vertically oriented (finished space on 4 floors). The house has an existing gutter system, but the west wall (picture attached) still receives water exposure during heavy rainfall. We have an interior french drain system that functions - water will come through the weep holes during heavy rain, but there has not been water infiltration on other parts of the wall.

Asked By Matt Bierlein | Sep 24 15
3 Answers

Bathroom ceiling and walls

Working on a project in Quebec. It’s an older home and we are remodeling in steps. We rebuilt one wall of the house, leveled and rebuilt a sub floor in this area. This process required us to tear out the bathroom and two closets on each side of the bathroom. This entire section of the house appears to be an add-on at some point in time and the roofline over this section runs at a slightly lower pitch than the main roof. The ceiling in this area is treated as a cathedral type since the rafters hit the top plate at around 6 feet.

Asked By Rob Henderson | Aug 16 15
3 Answers

Should i go with chimney vent or powervent water tank for cost savings?

The current chimney vent tank needs replacing, its 8 years old, the anode was never replaced and its rusting internally :(

The current is a natural gas tank, 40gal, chimney vented, its a 6 inch outer diameter, and i have had no back drafting issues of any kind since the furnace was replaced with a high efficiency last year.

Asked By Alan B | Sep 26 15
18 Answers

Air barrier in middle of double wall in mixed climate?

I'm in central Arizona, at the cold end of the Climate Zone 2B range, where I have around four months of moderate heating and five of moderate to heavy cooling.

Asked By Jeff Cooper | Sep 20 15
5 Answers

Does surface wiring on exterior walls make sense with batt insulation?

I've read a lot about the difficulties of properly installing batt insulation. If I kept my plumbing out of exterior walls, and used surface wiring on exterior walls, would that greatly simplify installing rock wool batt insulation? Or, would there still be other obstacles?

If surface wiring would improve the performance of batt insulation, other than the purported aesthetic issues with surface wiring, is there any other reason to oppose its use?

Asked By James Timmerberg | Sep 25 15
6 Answers

Zip panels vs. liquid WRB

I was curious - what option might be more cost effective?

1.) sheathing with OSB and then using the Prosoco joint compounds and CAT 5 liquid WRB over the entire surface...


2.) sheathing with zip system panels and then using the Prosoco products to seal the seams.

Asked By Brian W | Sep 25 15
5 Answers

Tilt turn windows with good visible transmittance

Can anyone recommend manufacturers of quality, energy efficient, tilt turn windows with good visible transmittance. If I'm going to put a hole in my wall for a window, I don't want to fill it with a thick frame and dim glass. The NFRC website lists 64 manufacturers of tilt-turn windows, and I don't know where to start. I'm designing for zone 5. I am cost sensitive, but willing to pay for quality.


Asked By John Ranson | Sep 24 15
2 Answers

What are good thermal break details on things like hose bibs, gas meters, and exterior lighting penetrations?

In PERSIST/REMOTE wall construction with 4 to 6 inches of rigid foam outside the sheathing, furring strips over the foam, and siding attached to the furring strips, what are good ways to handle things like water pipe for faucets, natural gas supply lines, and metal electrical conduit penetrations? I don't know how to provide a good thermal break consistent with mechanically strong (metal) piping, solidly attached to the structure, exposed to the elements on the exterior that punches right through to conditioned space on the other.

Asked By Stuart Friedberg | Sep 25 15
54 Answers

Dare to DIY a mini split install?

Hi all,
Can editors step out from behind the curtain to ask opinions, too? I'm planning to redo my garage shop this Fall and although my primary heat for the space is a woodstove, I'd love to have some supplemental heating, and cooling in the summer would be great, too. I'm no schlep when it comes to remodeling work, but have never installed or seen a mini split install. Would I be a fool to try the install myself or have the kits gotten streamlined to the point that its basically plug and play, complete with factory-charged units and quick connect line sets, etc?

Asked By Justin Fink | Aug 22 13
Register for a free account and join the conversation

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