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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
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
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
2 Answers

Open air returns in attic

I have two open air return in the attic. I'm wonder exactly what they are for?

In Energy efficiency and durability | Asked By Jim Bellar | Jul 20 16
2 Answers

Low-e storm window over low-e house window?

I was wondering if anyone knows the answer to this: Is there an advantage putting low e storm windows over low e windows? Low e raises the cost of the storm window and if the house already has permanent low e windows then would clear glass storm windows be the way to go?
Thanks for your time,

In Energy efficiency and durability | Asked By Chris Dunn | Jul 19 16
7 Answers

Should I tape my sheathing joints AND my rigid insulation joints?

I'm designing a wall assembly which will include plywood sheathing over the studs and rigid insulation over the sheathing. Should I have my carpenter tape the joints of the plywood AND the joints of the rigid insulation, or is that overkill?

In Energy efficiency and durability | Asked By Julie Kardatzke | Jul 17 16
5 Answers

Instantaneous gas water heater with small tank to meet PHIUS+ hot water performance requirement

We are well into the construction now, and don't have a lot of flexibility. For example, have 3'' venting pipes in place for what was meant to be Eternal condensing hybrid gas hot water heater with 2 gallon tank. The small tank helped to reach PHIUS+ requirements of not wasting more than 0.6 gallon of water before the water temperature at the furthers fixture reaches 75F. (We also designed very small diameter hot water pipes to help that goal).

In PassivHaus | Asked By Lucyna de Barbaro | Jul 18 16
8 Answers

Blower door tests and Equivalent Leakage Area

In reading Dr. Lstiburek's book Series "Builders Guide to... 'name your climate'", I concluded (though it was never specified quite clearly) that for 1000 CFM at 50 Pa the EqLA was 1 square foot. That would be about 7 CFM50 for each square inch of EqLA.

More recently, in an article by an editor of Journal of Light Construction, a duct blaster was used to conduct a blower door test in a very tight house. The conclusion was that the 50-65 CFM50 equated to an EqLA of about 2 ½ sq. in.. That would be about 23 CFM50 for each square inch of EqLA.

In Energy efficiency and durability | Asked By Ted Cummings | Jul 18 16
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