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!

3 Answers

What level of heat is recommended in an unvented crawlspace?

My project has 2200 sf crawlspace, 2/3 of which is 18" minimum and the rest on a down slope having a height up to 12' and which will house a water heater and furnace; and it has a 12" thick structural mat foundation., This seems like the ideal application for a conditioned crawlspace so that I can run forced air ductwork and piping, since there is not an attic. There is less exterior wall than there would be floor area to insulate, and just as your 2011 article says, the insulation would eventually fall out.

Asked By brian rawlinson | Mar 19 14
3 Answers

Comparing HVI and AHRI test results for ERVs

Our project is trying to determine which ERV units will be most efficient for our application, and we're looking at a variety of ERV products. Some are tested by HVI while others are certified by AHRI. We are struggling to accurately compare the difference between testing results offered by HVI and AHRI. There seems to be very little ability to cross-reference test results, making a comparison all but impossible. What techniques or systems have you found for comparing these two testing standards?

Asked By Jennifer Martin | Mar 19 14
8 Answers

Best way to seal off attic above drop ceiling? Plywood and seal, 1 or 2" foamboard?

I am trying to come up with a solution to seal off the attic of this 5800 square foot house. The top attic is two parts: one part that is drywalled (300 sq ft) and other that is not (420 sq ft). It has a drop ceiling and if you move the tiles away you can just push up through the 9 inch fiberglass batts into the attic.

So they technically are heating an additional 700 sq ft of space until I close it off to shrink the envelope to the roof of the third floor. I was originally thinking 2 inch Thermax, then blow an additional 14 inches of cellulose. But Thermax was getting expensive.

Asked By Jeff Alligood | Mar 19 14
15 Answers

Mini-split exterior heat collector unit in attic?

What parameters should be evaluated in considering the placement of the 'exterior' unit of a mini-split heating system in an attic which is generally warmer than the outdoor winter environment in Northern Vermont? Why not collect some of that heat from sun on the shingles as well as some of the usual heat losses in a 35 year old wood frame/fiberglass insulated house? Is there a 'recharge' rate factor that would probably deplete that heat source faster than it would normally be replenished?

Asked By Kerry Batdorf | Mar 17 14
1 Answer

Is the R-value of a PVC ceiling better than 6.4 mm RhinoBoard?

I need data on PVC ceilings' R-value and the advantages of PVC ceilings over RhinoBoard.

Asked By Johan Van Vuuren | Mar 20 14
18 Answers

CertainTeed vs James Hardie fiber cement shingle

We decided to go with a fiber cement shingle or lap. Wanted to get advice/experience with CertainTeed or James Hardie. Heard James Hardie material is difficult to work with and bad for the environment (when they make and off-gasing when cutting and nailing it). Thanks for your advice! - Karen

Asked By Karen Miller | Aug 16 10
2 Answers

Interested in environmentally friendly sealants

I am looking at sealing the concrete slab of my basement, a large living space.
1. I have examined three products: Enduroseal, Xypex and Lithi-tek LS 9500. All claim to emit no VOCs. Enduroseal hardens into nonsoluble silicate minerals. Xypex hardens into nonsolluble crystalline structure. Lithi- tek LS 9500 hardens at the nano level (I don't know more than that.) Are there other environmental considerations besides VOCs for a living space? Might they form dangerous dusts? How does one assess such products environmentally? Is there any authority to consult?


Asked By Chris Campbell | Mar 14 14
15 Answers

Does fastening WRB or building felt with cap staples work as an air gap for a rain screen approach?

I'm wondering if the space created by the plastic cap staples will work as a "cheapskate's" rain screen under vertical ribbed steel siding? I don't know the exact thickness of the cap staple, but from memory I would say it's a bit over 1/16".

My wall assembly is as follows: 29 gauge vertical rib steel siding, Typar WRB, 1/2" cdx sheathing (taped and caulked as exterior air barrier), 2"x8" stud wall with dense pack cellulose or cut and cobble polyiso cavity insulation), 2" rigid polyiso interior sheathing taped, and 1/2" acx interior sheathing.

This is for my wood shop.

Asked By Rick Van Handel | Mar 12 14
9 Answers

Without natural gas, is there a better option than electric baseboard heat?

I am currently designing a home to build, that is to be the best compromise of sustainability and affordability. This home is 800 s/f and will have a passive solar heat design, and a wood stove to use our local biomass resource of beetle kill pine, however I need a third heat system for the house (what the City considers to be the primary system). Although natural gas is very cheap in CO, we decided we would rather put the money to run a gas line and install a furnace toward a net metering PV system, since we have the optimal climate for this.

Asked By Curt Lyons | Mar 7 14
12 Answers

Metlund D'Mand hot water recirculation pump

I am thinking about installing hot water recirculation pump to reduce hot water usage. Metlund D'Mand hot water recirculation pump seems to be a good choice since it's passive and does not use energy until you push a button when hot water is needed.

Asked By Rian Bart | Dec 2 10
Register for a free account and join the conversation

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