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2 Answers

Does anyone have experience of adding a "pre- warming" system to a tankless hot water unit to reduce cost/ increase efficiency?

I'm in a northern climate, house is small, one bathroom with a 3"high enclosed crawlspace. The crawlspace is normally around 60-70 degrees, the water from the street comes in at around 40 degrees in the winter. My best choice (convenience, no need for venting, install price, space) of an electric tankless efficiency is impacted by the temp of the incoming water.

Asked By stu mcleod | Dec 4 13
1 Answer

Need Whole Wall R-Value Estimate

Looking to get a whole wall R-Value for the following setup (commercial application):

10" I-studs with 3/8" OSB web (does this reduce thermal bridging?)
16" o.c. framing
Icynene foam insulation under the exterior siding

What would the total whole wall R-Value be for this setup? Any STC ratings on this wall system?

The option is between the above or utilizing an ICF wall (2.5" EPS x 8" concrete x 2.5" EPS).

Asked By Peter L | Nov 23 13
4 Answers

How to add cellulose to a wall with existing fiberglass insulation?

I have a 1968 back split in zone 6A (Central NY). The 2x4 exterior walls appear to be insulated with fiberglass. I would like to blow cellulose into the cavities to help reduce air leakage. I know I can blow the walls without removing the existing fiberglass. Should I blow between the fiberglass backing (both foil faced and kraft paper) and the inside sheetrock or keep the vapor barrier in place and blow the cellulose between the exterior sheeting and the fiberglass batt?

Thanks in advance for your help.

Asked By Alwyn John | Nov 21 13
14 Answers

Another conditioned Cape attic

Hello, I have a 1.5 story home, often referred to as a Cape or bungalow, in Ann Arbor, MI. My house was built in the 40s, and recently I've decided to get a new roof and some insulation quotes. I have a single shed-roof dormer on the back where the stairwell comes up, other than that the roof is fairly straightforward.

Asked By Kevin Line | Nov 12 13
9 Answers

Crawl space ventilating fan

Hello, all --

I have a 625 square foot sealed crawl space that I need to ventilate. I can't seem to find a ducted fan that will suit this application. I'm no internet moron, but maybe I am tonight? What do you all use? My local building code jibes with what Martin wrote about in his article "Building an Unvented Crawl Space."

“a continuously operated mechanical exhaust ventilation at a rate equal to 1 cfm for each 50 square feet of crawl space floor area.”

Asked By Jeff Nelson | Nov 19 13
4 Answers

Insulation of concrete walls (above and below grade)


My wife and I, after a lengthy search, have finally found a house that meets our wants and needs. However, I have one potentially serious concern, and that regards how the contractor insulated at least some of the 1922 home's concrete walls in the recent to-the-studs renovation. To be clear, in addition to the basement, this home has above-grade concrete walls as well (with a stucco exterior). I'm attaching a picture to show a portion of the main floor when taken down to the studs.

Asked By Doug Elliott | Nov 19 13
1 Answer

I want to add insulation to the cathedral ceiling in my shop

About 20 years ago I built a workshop. It has a metal roof installed over 1X4 strips that are nailed directly to the 24" oc 2X10 rafters. I had a local insulation installer spray cellulose insulation directly against the metal roof. The insulation began to fall off almost immediately and today approximately 1/2 of it is gone. I would like to put more insulation overhead and have considered either fiberglass batts or spray foam. I have always been taught to provide an air space above fiberglass but there is not an easy way to ventilate above this cathedral ceiling type area.

Asked By Anthony Bright | Nov 19 13
8 Answers

Polyethylene as an air barrier in very cold wall assembly

My question pertains to the use of a polyethylene air barrier (6 mil) within a double wall assembly (and ceiling) in a very cold climate. My concerns when we came up with this wall were obviously wall performance, related to moisture buildup and drying, as well as keeping the build relatively inexpensive both in materials/labor while at the same time providing me with a system provides high R-value while decreasing air leakage.

Asked By Matthew Michaud | Nov 13 13
4 Answers

Interior walls using rough cut lumber and insulation?

We are using a restored barn frame to build a home. Our thought was erect frame, then wrapping the frame with painted rough cut, then applying 15lb felt paper, then framing w/ 2x4 or 2x6. We would then insulate w/ fiberglass, apply OSB sheathing, house wrap and then the necessary R value of foil faced poly iso to conform w/ code, being careful to seal all joints. Is this a proper wall build up or is there a better way to do this?

Thank you for your time GBA pros have been very knowledgeable.


Asked By matt bowman | Nov 12 13
3 Answers

Using EPS for roof insulation?

I am building a home in zone 6A. It is a reclaimed barn frame that has gone through engineering, engineer wants double 9.5" LVL's 24" on center. I would like to use 8" 1.5lb EPS between the rafters giving the R value required. My thought was to spray foam the corner where the rafter meets the interior sheathing and while still curing slip the 12' lengths of EPS in. Then sealing any other seems w/ spray foam. This would also provide for 1.5" vented cold roof. The roof system would consist of (from interior out) pole rafters, 3/4" reclaimed wood sheathing, Grace triflex, then the EPS block.

Asked By matt bowman | Nov 8 13
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