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6 Answers

Question re furring strips, XP drywall, and finishing basement over 3" of polyiso

I have used recycled roofing polyiso panels (1.5" stuff), staggered them, and going to foam the gaps where I can and use acoustic sealant ("the black death") on gaps too small for foam.

Here is a big question, I want to put furring strips horizontally and just mount drywall over that:
1. Is it OK to just go with furring strips and not build out full 2X3 or 2X4 framing. Wasn't planning to fill the gap with anything between drywall and polyiso

Asked By Apollo S | Mar 23 15
3 Answers

Is it wise to put a product like Drainwrap behind a layer of rigid insulation?

We are getting ready to remove the existing layers of siding from an old (100yrs. +) home that appears to have diagonal board sheathing attached to the studs.

Our intention is to blow cellulose into the stud bays, then cover the board sheathing with Drainwrap integrating the window flashing into this layer, then adding 1" rigid foam with seams taped, and finally adding 1x furring strips and either Hardi or Lp lap siding.

The project is waterfront on a coastal bay in Maryland. The windows in the home are vinyl replacements in original wood frames.

Asked By mike labesky | Apr 1 15
14 Answers

Alternate cathedral ceiling retrofit

I have a project related to a thread titled "How can I best retrofit and insulate an existing cathedral ceiling?" In my case, the zone 4b semi-arid west texas 1978 home's cathedral area has low density glass batts (or none) along with 1x10 or 12 deck boards over 2x12 rafters. The shingles above this unvented space have some blistering, and I was going to replace them along with resetting two skylight curbs that are incorrectly installed and caused some sheet rock damage from skylight leakage.

Asked By Glen Poklikuha | Mar 27 15
7 Answers

Rigid foam roof insulation and polyethylene vapor barrier inside — problem?

Was planning on a r-25 insulated roof deck for a ski house in lower zone 6 NH with cold roof (strapping with plywood) on top of that to help prevent ice dams.
Existing cathedral ceiling is actual 8" rafters framed 24" o.c. with 6" paper faced fiberglass batts. In exploring the original construction (circa 1980) I also found a layer of POLY as an additional vapor barrier....which sabotages my R-25 rigid foam roof plan.....damn.

Asked By Dirk Gently | Mar 27 15
9 Answers

Modular house design overview

Hi All,

My presentation can be found at

I am going to build a new house this year in south eastern MA. To reduce construction time I am planning on going with a modular builder. To control costs I am acting as the GC and planning on doing the HVAC install, attic and basement insulation, and plumbing/wiring hookups. I am still looking into modular builders, hopefully I can find one who is willing to set the house and make it weather tight and allow me to finish the rest of the work.

Asked By mike haskell | Mar 11 15
2 Answers

Where is the building envelope?

Doing several additions with new gable roofs overlaying the existing roof. New and existing roofs will have foam the underside of the roof sheathing. The question centers on where the envelope should be on the triangular overlay portion of the new/old roofs and should that triangle be vented in anyway.

Asked By Robert Brown | Mar 24 15
7 Answers

New home and ductless minisplits

In the process of getting the Manual J done as per code requirement. The home is as follows:
Zone 4B - R-10 / R-30 / R-60 with R-8 windows - ICF walls - Slab on grade - 2 stories - 3,200 sq. ft. - Open floor design.

Looking to go with Mitsubishi ductless heat pump minisplits wall units (22 - 26 SEER). Two on the 1st floor and two on the 2nd floor.

How good are the ductless cassette units?

One room might get the cassette unit instead of the wall unit because of the room layout.

Asked By Peter L | Mar 18 15
2 Answers

Is fiberboard air impermeable?

A recent GBA post noted that some builders are finding that OSB isn't always air impermeable. I'd like to know if fiberboard, such as Biltrite or BraceRite, is air impermeable. Specifically, I'm interested in trying to use it as an air barrier, in an assembly where I need the sheathing to be able to dry, and fiberboard has a permeability of around 20. But can it be an air barrier, if I tape or otherwise seal the seams? I can't find this info on the company's website or anywhere else I've been looking.

Asked By Rachel Wagner | Mar 19 15
4 Answers

Can I still use polyiso to insulate a rim joist that is irregular?

I am about to jump into insulating rim joist in the my crawlspace, but as I am cutting pieces for it, I am starting to realize that foam often will not be 100% flush with wood and in some spots there will be resulting small cavity behind. Will that create a problem or is little bit of cavity behind fine, as long as I make sure all pieces of foam are foamed in just right?

Asked By Apollo S | Mar 13 15
7 Answers

Unvented low-slope roof with exposed beams

I am designing a 2nd-story addition to a home with a simple 2/12 pitch, shed roof to the east in Colorado, climate zone 5. The clients really want an exposed beam look so we have designed the roof with exposed glulam beams at 4' centers. Above the beams we currently plan for 2x t&g decking, 4" polyiso, and another 4" nailbase insulation with polyiso, unvented. Roofing material will be Sarnafil thermoplastic vinyl membrane roof.

Asked By Donna Riley | Mar 10 15
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