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10 Answers

Heat pump water heater selection

My house is all electric in southern California and I plan to replace my electric water heater with a heat pump water heater. The plumbing professionals have little to no experience with these and are basically asking me to pick the water heater and they'll install it. From the research I've done it looks like the best choices include the Stiebel Eltron Accelera 300E and the Rheem Performance Platinum 80 gal. The Rheem is currenly on sale for $1600 at HD while the best price I saw for the Accelera is $2400. I believe my utility has a $250 rebate for the Rheem.

In Green products and materials | Asked By user-7014439 | Feb 11 18
31 Answers

Using hydronic in-floor heat in a superinsulated earth-bermed house

I'm planning an earth-bermed house at the 4,000 foot elevation in the mountains of eastern Washington. it will be single story, 8 foot 6" or 8" ICF walls on the sides and back. Back fill to 6" from the top of the wall.
The front will have a double 4" ICF front wall 2' tall and then double framed walls with thermal break to the top. This is south facing. front wall insulation is cellulose at about 18" thick but mostly windows 140 sq.ft on a 340 sq. ft. wall.
The floor will be 2" or 4" insulation with 4" concrete floor.

In Energy efficiency and durability | Asked By Grissom | Feb 13 18
13 Answers


We have a new construction home, less than one year old. Windows are the type that slide inward to clean, etc, vinyl, double pane. We have had temps drop below zero a few days in the past couple weeks. Whenever it gets below 0 degrees, we get condensation. Not the entire window, but along the bottom edge of the interior window, the space in between the bottom fixed window and the top slider, and in just a few windows it will frost in the bottom corner of the frame. Have checked humidty, and we run about 25%. Also have a call into the window rep, but haven’t heard back yet.

In Energy efficiency and durability | Asked By Kathleen J | Jan 2 18
2 Answers

Application of 2/3-1/3 rule when rigid foam is vapor barrier

I submitted a question a couple of weeks ago: "Rigid Foam Between Walls" in response to which I received numerous very helpful answers. Thanks again.

In General questions | Asked By David Williams | Feb 14 18
3 Answers

Bungalow porch: Should we insulate the ceiling?

We are building a Craftsman Bungalow in Farmington, Maine and the house has hip roofs and an open front porch. The porch roof is integral with the main house as it is shown in the attached figure.

My question is: Should the porch ceiling be insulated with a vapor barrier like the interior ceilings? We are planning on using Roxul insulation with a vapor barrier in the main house to get us an R-50 rating.



In General questions | Asked By User-6980234 | Feb 14 18
1 Answer

Whole-house fan in cathedral ceiling design

I'm building in climate zone 6B and I'm trying really hard not to put in AC. Our house is at 7000ft but we still get a few weeks of hot temperatures that are bearable during the day but are too hot for us to sleep at night. My thought was to do an air flush in the evening using a whole house fan.

In Mechanicals | Asked By Steve Mackay | Feb 13 18
5 Answers

New outbuilding, mold, crawl space encapsulation/ventilation plan

I'm building a 190sf art studio/office in Zone 5B (Central Oregon, drier/sunnier eastern side of Cascade range, sandy/volcanic ash soil, 24" frost line, ground freezes here). It has a one-year-old vented crawl space that developed mold beneath the plywood subfloor and I-joists. It sat with no roof and no ground moisture barrier through last year's snowy winter. Last Spring, I scrubbed the mold off with diluted bleach and spread 6mil poly over the ground, but did not attach the poly to the stem wall or seal up the vents.

In Energy efficiency and durability | Asked By KevinEJ | Feb 13 18
7 Answers

Recommendations on HVAC Design

Because local HVAC contractors typically oversize and aren't apt to land on the ideal solution for high performance homes, I am considering analysis by a third party like Energy Vanguard for my cold climate ductless heat pump system:


I would like to get some feedback on services like this and any recommendations of alternatives to them. I was quoted $900 for:

-Manual J room-by-room heating and cooling load calculations
-Manual S system specification with Diamond System Builder report for Mitsubishi

In Mechanicals | Asked By J M | Feb 13 18
21 Answers

Radon is 9.3 pCi/L even after radon mitigation — Is this OK?

Hi. I am having elevated ( 9.3 pCi/L) radon after mitigation done. I have an encapsulated crawl space ( insulated, air sealed, dehumidifier ) with piping running under vapor barrier-which terminates to an outside radon fan connected with a 4"PVC pipe. Would like to find out if it's Ok to install drainage ( perforated black pipe) piping under vapor barrier ( in encapsulated crawl) for radon mitigation. The piping is spilt off of a main trunk ( no continuous circle) to different sections under the crawl.

In GBA Pro help | Asked By Hotandhumid | Jan 22 18
6 Answers

Corrugated metal over mineral wool

Hi, I am looking for ideas for installing vertical corrugated metal over Roxul comfort board.

A bit more about the project:
Zone 5B,
2x6 @ 24" OC walls insulated with Roxul batts (R-23),
plywood, wrb, and
2" Roxul Comfortboard (R-8), corrugated metal siding running vertically.

Do I need to install vertical furring a layer of horizontal furring to attach the corrugated panels to? Can the metal be attached directly over the comfortboard?

Thanks for any thoughts/ ideas.

In Green building techniques | Asked By Stacey V | Feb 6 18
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