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10 Answers

R-35 wall assembly for a 4C Marine climate zone

I am about to build on a 85" rainfall, 6000 HDD and no cooling system (I can withstand a little heat in summer)

I'm thinking of (from outside in)
* 1" wood siding
* 1" of air gap with 1x3" furring
* asphalt paper as WRB and air barrier
* 3" 2pcf EPS as R10 sheathing,
* A 10" double frame wall filled with a total * of R-24 polyester insulation
* asphalt paper as air barrier and vapor retarder
* 3-4" interior wood finish

(see attached image)

In Green building techniques | Asked By Jose Castro | Oct 29 14
8 Answers

Dehumidifier: running too much OR poor energy efficiency?

I just installed a 30 pint dehumidifier in the basement of my single story 900sqft house.

It uses about 4kWh per day to maintain a set-point of 55%, as measured by a Kill-a-watt.

I'm in Chicago, Zone 5.

My electricity bill without the dehumidifier from March-April was about 200 kWh/month.

Last month, with the dehumidifier turned on midway through saw a usage of 240kWh/month. A/C has not been used yet.

How can I determine if that 4kWh energy usage is due to it just running too much (e.g., too small for conditions?) or if the equipment just takes too much energy to run?

In General questions | Asked By Jeff Watson | Jun 6 16
33 Answers

Dehumidification vs. ventilation in an existing house

I have done significant air sealing of our 1930s cape cod house in Virginia (climate zone 4) and it only recently dawned on me through reading various GBA blog posts that this air sealing is probably the cause of our high indoor winter humidity levels (ranging from 55% to 70%)

I understand that adding ventilation is the correct way to go, and the bathroom exhaust fan approach seems the most cost effective. However, before doing this I have a few questions.

In Energy efficiency and durability | Asked By Timothy Godshall | Jan 4 15
7 Answers

How to choose someone for an energy audit?


I am looking to do an energy audit of my house. What should I look for in regarding selecting a company/individual - certifications, etc. What qualities would a good auditor have - what questions should I ask and what should they be asking of me - utility bill history, etc.


In Energy efficiency and durability | Asked By Joe Watson | Jun 8 16
3 Answers

Is an air space between a ceiling and SIPs a problem?

I have a timber roof system that goes like this.
timber rafters
plywood with a flooring glued to it and fastened down on top of the timber rafters
suredeck membrane (to protect the plywood) and double as vapour barrier
2x6 strapping on top of the plywood to facilitate electrical
8 1/8" sips
synthetic membrane and peel stick for eaves protection
laminated shingles
Should I be concerned about the 1.5" space between the top of plywood and bottom of sips.
We are going to be extra ornery about air sealing the sips.

In Green building techniques | Asked By Marty Munroe | Jul 20 16
33 Answers

Direct vent vs. power vent gas water heaters

A recent blower door test/audit has alerted me to the fact that my natural draft hot water heater can backdraft in worse case scenarios (range hood/clothes dryer/bath fan on). It seems to reverse back to a correct draft after a few minutes. It's only about 6 yrs old, so I hate to replace it, but not as much as I hate the idea of the back draft.

In Mechanicals | Asked By Erik Addy | Mar 8 16
4 Answers

Insulating cold water pipes

I'm getting a lot of condensation on my cold water pipes. The house is plumbed with pex, and most of the condensation is collecting on the copper and/or brass fittings.

In Mechanicals | Asked By Calum Wilde | Jul 20 16
1 Answer

Any new insight on Air Krete?

I've read the other posts, which are a few years old.

Does anyone have any new advice or guidance using the product? I have a client that is interested in the product. Specifically looking for any known issues or installation advice.


In Green products and materials | Asked By Cliff kornegay | Jul 20 16
20 Answers

Insulating rim board with rigid foam: best practice?

Zone 5B, main level + full basement. First floor I built with 2x6 walls, and used mineral wool insulation with a smart membrane. Not that that should effect this question, but just giving a bit of info about the construction.

Scenario : I have 12” thick i-joists, spaced 16” O.C., and want to insulate the rim-board void for two reasons: Noise reduction, and R-Value. Noise transfers surprisingly well from the outside, especially rain/hail and wind making the siding rattle.

In General questions | Asked By Nicholas C | Jul 9 16
10 Answers

Attaching Roxul (Comfortboard 80) to exterior foundation wall

My wife and I are building a "green" home (mix of Passive House, Pretty Good House, and Net Zero). For the basement foundation (9' basement) we intend to use spray-on waterproofing then two layers of Roxul Comfortboard 80 mineral wool (3" + 2" = 5" total) on the exterior side.

In Green building techniques | Asked By Eric Whetzel | Jul 14 16
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