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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
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
3 Answers

Alternatives to MHK1 for minisplit?

We've had a three-head Mitsubishi Mr. Slim system for about a year now, and we've noticed that it takes a fair bit of fiddling to get the unit to hold a set-point. The necessary offset in heating mode is something like 8 degrees F, varying with the outside temperature. During the shoulder seasons, it seems like we pretty much have to cycle the unit off and on or it will overshoot.

In Mechanicals | Asked By Logan Schmaltz | Jul 13 16
14 Answers

Does anyone have experience with Zehnder ComfoFlex?

We are building a new house and in the final stages of design. The design includes an HRV and Zehnder ComfoTube looked great until I discovered that it is not UL listed. So, I'm curious if anyone can provide feedback on ComfoFlex. There isn't much on the intertubes...

In Mechanicals | Asked By Trevor Fontaine | Feb 9 16
8 Answers

Unvented attic -- New roof, exploring options

Hi everyone,

We're in the process of getting our roof replaced on our 1964 single floor "rancher". The house currently has no venting at all in the attic and we're getting mixed responses from different vendors on whether we need ventilation or not. Read plenty of things online about the negative pressures that are typically created when using powered fans in the attic and would prefer to avoid them. Another installer recommended smart vents installed under the shingles and a new ridge vent.

In Energy efficiency and durability | Asked By Ryan Holt | Jul 16 16
7 Answers

Insulating a suspended floor: Caulk the seams or not, and is cellulose okay?

A friend of mine is building a tiny house on a trailer in Austin, TX (Climate Zone 2A), and has questions about insulating the floor.

First, should the seams of the floor framing be sealed with acoustical sealant before installing the insulation, to prevent air infiltration and increase insulation performance, or is some air movement good to prevent moisture accumulation and mold?

In Green building techniques | Asked By Michael Bluejay | Jul 16 16
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