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7 Answers

Open-cell foam in exterior wall cavities?


We want to insulate several rooms that have plaster interior and no insulation in the wall cavities (as verified in other portions of the house that were gutted). The exterior of the house is 8 inches of field stone over tar paper and sheathing boards. The house has sizeable roof overhangs and no apparent moisture issues. The insulation contractor is recommending injecting open cell foam in the wall cavities (drill and patch holes). Is there any issue with open cell foam retaining moisture from the exterior?

Thanks for the help

In Green building techniques | Asked By Douglas Wathen | Mar 20 16
6 Answers

Attachment of a stone fireplace surround -- fasteners?

Is it a code requirement or recommended practice to install mechanical fasteners to fireplace surrounds, or is mortar alone satisfactory? I'm not talking about massive columns and mantles. Just thin granite slabs (not tile) without a mantle. More specifically:

In General questions | Asked By John Walls | Mar 18 16
6 Answers

HPWH impact on load calcs

If one installs a heat pump water heater (HPWH) in the conditioned space, how does that impact the calculation of the design heat load and design cooling load?

For example, if the specs say that it uses 500 watts in heat pump mode and has a COP of 2.5, should the heat load include the (2.5-1)*500 = 750 watts that comes out of the house air? Or, is it not necessary to include the whole amount because the HPWH runs intermittently?

I am guessing that you can't take a credit for it in the cooling load since it won't necessarily be running.

In Mechanicals | Asked By Reid Baldwin | Mar 20 16
16 Answers

Vapor sandwich with foamboard on both sides of framing?

I have a 2x4-framed wall with very little cavity space for the cellulose insulation I plan to install, because windows comprise a lot of the wall, and because headers above the window take a lot of what's left. My plan to increase the insulation was:

- Install 3/4" foamboard, sheathing, and siding to the exterior.
- Add 2x2's to the interior framing, converting it to 2x6 framing.
- Install cellulose into the cavities.
- Glue 2" of foamboard to the headers.

In Green building techniques | Asked By Michael Bluejay | Mar 14 16
4 Answers

Do I need to fill nail holes from pneumatic nailer on pine plank walls before I seal with polyurethane ?

We had a sunroom added to our lake cottage this last December. Their carpenter put 8" pine planking on the walls against the house where vinyl siding was, to give the room a cabin look. We were out of town for this phase of the project . We're not sure if it's normal to see where he nailed the planks together or not , it doesn't look horrible or too bad , we just need to know what to do before I put polyurethane on. Any helpful tips will be appreciated. Thanks

In General questions | Asked By Danny Hendry | Mar 19 16
6 Answers

Install foam board and housewrap?

I am going to replace the old masonite siding on my house with LP Smartside and have a few questions. Currently my walls go (from the inside out) gypsum board, poly, 2x6 framing with unfaced fiberglass batts, black fiber board for sheathing, tar or felt paper, and then the siding.

I was planning on ripping the existing tar paper off and putting tyvek on the the entire house. Then I was told to put 1" foam board over the Tyvek and then the new LP Smartside lap siding over the foam board. I live in Montana so we have cold winters and hot summers with little humidity. Is this a good plan?

In General questions | Asked By Adam Johnson | Mar 17 16
17 Answers

Can I dehumidify without adding heat?

I live in New Orleans and I have a 6x8ft room that I keep an antique musical instrument in...and some more modern ones I practice on. I try to keep the temperature between 65 and 75 and the humidity between 40 and 60%.

I have a window AC that can cool the room just fine, but the dehumidifier puts out so much heat that this room uses more electricity than everything else I do.

Is there a way to keep the dehumidifier and AC from fighting?

In Energy efficiency and durability | Asked By Luke Brechtelsbauer | Mar 16 16
11 Answers

Separate ducted mini-splits for each floor or a multi-split for the whole house?

Hi all,

Building a house in Central KY (zone 4A) and trying to research what the appropriate strategy for zoning the HVAC. The traditional approach would be a conventional heat pump for each floor, allowing you to adjust the use for each floor when not occupied.

In Green products and materials | Asked By Clay Whitenack | Mar 17 16
6 Answers

Kraft paper on batts with polyiso

I am building a separate accessory structure in Southern California. It has an unvented cathedral ceiling. It has an asphalt shingle roof sheathed with radiant barrier. The plans call for closed cell rigid R-12.5, then batt R-30, then 5/8' drywall. My plan was to use 2" polyiso tight against the radiant barrier (roof sheathing). The polyiso would have the foil toward the inside (against batt). Is it better to install the batts with or without kraft paper and which way should the paper face? Toward the drywall or toward the polyiso.

In Energy efficiency and durability | Asked By Aaron Terry | Mar 17 16
18 Answers

Moisture management for tiny house subfloor?

My husband and I are just about to start building a tiny house on a trailer in Nashville, TN, and I'd like to make sure our subfloor does a good job of protecting against moisture, as well as drying out when necessary. Any advice would be greatly appreciated!

Our current setup, from bottom to top, is:

- Steel trailer frame
- Metal flashing
- 2x4 framing filled with Roxul, anchored to steel flanges on the trailer using bolts
- 3/4" Advantec with taped seams, which will connect to ZIP system sheathing as our air barrier
- Cork floating floor

In General questions | Asked By Michaela Riley | Jun 20 15
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