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2 Answers

What's the most efficient way to run a dehumidifier?

I have tried everything but short of a DER i can't reduce the humidity load of the basement so i have little choice to bring in a dehumidifier.
The one i am getting is oversized according to online sources, 500sqft needs a small dehumidifier but i am getting a 70 pint energy star rated frigidaire (long story). It uses 746W and pulls 70 pints a day at 1.85L/kWh.

In Energy efficiency and durability | Asked By Alan B | May 17 15
1 Answer

Superinsulated Slabs - Vapor Barrier

I'm designing a house for a site in Climate Zone 6B with high groundwater (~36-42" below existing grade during seasonal high water) and in an area of typically high radon. I've been exploring using a FPSF similar to what Alan Gibson described in his April 2010 article on Super-insulated foundations in JLC.


In Green building techniques | Asked By JMS Build | May 18 15
6 Answers

Exterior foam as WRB

I know this question has been asked so many times and I've done my research but can rigid foam be used as a trusted WRB? Specifically XPS? I am in a cold climate and have read in my research that XPS outperforms polyiso. My original plan was 4" of XPS with house wrap over the foam as I will also be installing new windows which will be "outies". I am just confused if the foam is sufficient with the taped joints or if the house wrap is necessary. So much research has been done but there are mixed results and I want to get right on the first try.

In GBA Pro help | Asked By Brian Otten | May 17 15
2 Answers

Moisture & mold


We have a high humidity and moisture in house.

Can gap in caulking causing the shower water to leak into crawl space and cause high humidity in the house.

We recently got a new washer and dryer so suspect that is the cause. But plumbers have ruled out any pipe leaks. We are not able to detect the source of water and everyone says gradual water seeping into crawl space can't cause moisture n mold. It has to be a lot of water. Is that true.

In General questions | Asked By Sim Singh | May 17 15
3 Answers

Do minimum thickness of foam rules still apply for the partition wall between an insulated attached garage and the house?

Climate zone 6 location near Green Bay, wi. Partition wall is advanced frame 2x6 wall construction with planned 2 lb density blown fiberglass. I would like to use 1" foil faced polyiso on the cold side of the wall to limit thermal bridging and also tape the panels for a primary air barrier.

In Energy efficiency and durability | Asked By Rick Van Handel | May 16 15
4 Answers

PV and EMF

I hope the title of this post isn't provocative, but I would like to ask an earnest question about photovoltaics and magnetic fields. The link below connects to a study of electric and magnetic fields near residential and commercial PV arrays.


In Green products and materials | Asked By Jeffrey S | May 15 15
1 Answer

Flashing best practices request

I have a 1965 home in Houston that I am doing a deep renovation on. One of the problem areas in the house is the intersection of the upstairs exterior walls with the downstairs roof. There was a vinyl siding with 1/4" foam sheathing.

Today I removed the vinyl siding and foam sheathing. I did not like the vinyl, did not like it's color, and had leaks where it met the roof.

In General questions | Asked By Brian Greul | May 16 15
10 Answers

Backup heat for mini-splits? Electric cove heaters?

I'm planning a house build and am seriously considering using mini-splits. The house will be in climate zone 7 with a -13F 99% design temperature, so I want to make sure I have a source of backup heat when the mini-splits turn off during really cold nights (-25F happens several nights a year), and also to make sure the bedrooms stay warm enough if the doors are closed.

In Mechanicals | Asked By Nick Hall | May 15 15
5 Answers

Garage mold: cause and design solutions?

I'm in Portland, Oregon, climate zone 4C. Last year we bought an existing house (vintage 1943), with an attached 2-car garage. The garage is unconditioned, uninsulated, and unfinished, with the exception of the wall connecting the garage to the house, which is finished, and presumably insulated. It originally was a 1-car detached garage, but in the late '90s, the previous, long-time owner built a kitchen addition connecting the garage to the house, and also expanded the garage to 2 stalls. The garage roof has ridge venting, as well as a few soffit vents.

In General questions | Asked By Doug Elliott | May 12 15
3 Answers

R-38 ceiling and spray foam

If one sprayed 5" of open cell spray foam on a ceiling area, that would equal to around R-17.5, correct?

Now code requires R-38 minimum for the ceiling in this area. There is no "performance value" of R-38 in 5 inches of open cell spray foam, right?

That would be a marketing line bunch of nonsense as 5" of open cell is R-18 avg. and anyone claiming it is performing like R-38 is lying. How would the code department buy into this nonsense?

In Building Code Questions | Asked By Peter L | May 15 15
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