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6 Answers

Will R-70 cellulose sag ceiling drywall 24" o.c.?

My plans call for an R-70 ceiling of loose-pack cellulose in double-netted bays between trusses 24" o.c., with 5/8" Type X drywall holding it up as my air barrier. My installer says this will weigh about 2.55 lbs/sq/ft. Is this too much? Will it sag over time or pop screws? Do I need to use some special (expensive) low-sag drywall? I don't want to go to the expense and lost clearance of, e.g., an OSB layer above the drywall.

Anyone have experience with this?



Asked By Randy Jorgen | Jul 16 17
32 Answers

Minisplit sizing and number of minisplit heads for this apartment?

Hello Martin and Dana,

We continue to progress on our project and are about to have the rough electrical started. As a refresher, this is the 700 sq. ft. apartment inside a post-frame construction shop building in climate zone 3.( My last dilemma I needed help with was a question about insulation between studs along with exterior insulation)

I am talking with an HVAC contractor who specializes in Mitsubishi products. I realize you get 20 questions per week exactly like what I am about to ask, and I appreciate the patient help.

Asked By John Peeper | Jul 13 17
6 Answers

Best insulation and sealing for a tucked-under-garage ceiling?

We are purchasing a circa 1966 Cape in the Philadelphia are with the garage tucked under the master and guest bedrooms and two baths. The garage ceiling is currently covered with Homasote, but there are small areas where we can see an underlying plaster ceiling with missing chunks. The joists are 2x10s and there appears to be some fiberglass insulation batts in place.The HVAC ducts run below the joists and are mostly covered in Homasote, but several feet of ducts near the overhead door opening are exposed and uninsulated, but with remnants of asbestos.

Asked By Geoffrey Simon | Jul 17 17
2 Answers

We are purchasing a circa 1966 Cape in the Philadelphia area with the garage under two bedrooms and two baths

The garage ceiling is covered with Homasote but there are small areas that you can see an underlying plaster ceiling with missing chunks.

We are homeowners with an enduring passion for houses. We previously designed our own home in 1995, then enjoyed 20 years there. I am a retired Doc who reads FHB for fun!

Asked By Geoffrey Simon | Jul 14 17
10 Answers

Confused and worried about minisplit sizing

We’re building a house in Toronto, two stories (both about 1500 sqft each), first floor R26, second floor R32, second floor ceiling R70, with HRV, de-humidifying system, window-to-wall ratio 12%, windows mostly face east and west, windows are Fibertec high-efficiency, fiberglass frame, low e-coating. Whole house will have hydronic floors for heating. We’re planning Mitsubishi mini-splits for A/C, but we’re very confused about sizing and placing of heads (and outdoor units).

Asked By Thomas Kaempfen | Jul 9 17
3 Answers

Hardie lap siding vs. Boral siding

We are building a house in NH. Hardie is less expensive material, but more expensive labor. What about durability? Hardie has had a bad reputation. Have they improved their product? We can't find how long Boral has been available. Any word on problems with Boral?

Asked By Frank Torti | Jul 10 17
2 Answers

Accessing isolated part of attic

In all areas of my attic where the main attic/roof intersects a section of the roof with a perpendicular gable (e.g. at a dormer), there is an access opening for that sub-section of the attic. There is one exception, and I want to safely access the isolated section.

I can tell by both measurements from the center of the main roof, as well as confirmation by the absence of roofing nails, the section I need to cut, but I was wondering if anyone had any other tips on what I need to be careful of before cutting.

Asked By David Johnson | Jul 3 17
5 Answers

Water infiltration/condensation problems


The climate zone where my bulding is, is 7or 7A, It is located in the southern part of province of Quebec, Canada, village name is Saint-Philemon.

The buiding is 2 stories, 28x24 floor surface, south wall on each story has 2 windows 9'x7'.

Wall layers from exterior are : wood clading, wood lathe(1x3), air barrier, styrofoam (2''), sheating OSB 5\8, 2x6 spruce wall filed with mineral wool, plastic vapor barrier, wood lathe(1x3), sheatrock/gypsum.

Asked By PIERRE LEVASSEUR | Jul 1 17
5 Answers

Dealing with multiple WRBs and air barriers with external foam board

Building a home on the edge of zone 4 & 5 (in zone 5) with avg 60" annual rainfall and minimal snow. CA building prices are crazy (~$275/sqft by avg contractor in area), and this is our final home so want to maximize durability and longevity in a reasonably buildable green home. The buildable area on the lot is small, so need a thin wall to get the needed square footage while allowing a garage. Planning 2" PolyIso over 2x4 framing and 7/16 OSB, then 1x4 rainscreen and stucco for the walls.

Asked By Mitchell Costa | Jun 29 17
4 Answers

Insulating a 1930s home with foam and fiberglass


I have gutted my bathroom of my 1930 cape cod and am looking to insulate from the inside.

I live in zone 5a, upstate NY
The house exterior is brick, with a gap between the brick and the exterior sheathing ( which is 8 inch boards)

My thoughts are this

Asked By Jason A | Jun 26 17
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