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14 Answers

Add rigid insulation to a 2x4 ceiling with an existing polyethylene vapor barrier?

I've been creeping around this website for years. I love reading random articles and questions and learning this stuff for fun.

Zone 6. We live in Southern Maine (Scarborough to be exact, stop by and say hi!).
Our "play room" appears to have been built (or renovated) as part of the garage addition, date unknown. Our house is 1960ish.

- (Section A) About 300 sq.ft. of the room is a flat drywalled ceiling, 8' tall. 2x6 framed ceiling. "Attic" space

In Green building techniques | Asked By Seth Fernald | Oct 3 16
1 Answer

ERV ducting options for existing construction?

I have taken Martins advice from a past discussion and added an ERV to our home. Currently the ERV is setup in the easiest install method by adding the fresh air and exhaust air ducting from the ERV to our return air for our furnace. Our furnace blower has an ecm blower so we are not taking a huge power hit as it pulls about 100 watts. The drawback to this is that we have two independent HVAC units serving the home, each on opposite ends of the two story house.

In GBA Pro help | Asked By Jeremy K | Oct 17 16
2 Answers

Insulated Slab - Entrance and Edge Details

I am working on my first Insulated and heated slab for a garage addition. We are focused on getting the details right. To start we are in Northern NJ (Climate zone 5/4 Marine) We installed 2" XPS down the inside of the stem walls to the footer. Under the slab we have 2" XPS sitting under the Vapor Barrier and wire mesh and above the crushed stone capillary break. We are running into an quandary with the edge details:

The mason is insisting that we need to

In Energy efficiency and durability | Asked By David Colin | Oct 17 16
8 Answers

Old, empty house — preventing mold

I have a small, old house in Transilvania (Romania) that is empty. The windows do not close well,

In Energy efficiency and durability | Asked By Sue Park | Oct 15 16
2 Answers

Finding an engineer

I would like to put 8" of rigid foam over a gambrel barn roof, with long fasteners. However, I cannot find a standard guide to the numbers and spacing of screws for the roof. I was going to do screws every 12x12" (horizontally and vertically), but am concerned this may not be enough.

How do I go about finding an engineer to help calculate the appropriate quantity? This seems like a pretty specialized application, and I would want to use someone with experience. Is there a guide somewhere that lists names and numbers of companies who specialize in this area?

In Green building techniques | Asked By John P. | Oct 17 16
4 Answers

Underfloor hydronic: foil faced insulation or aluminum diffuser plates?

Hello: I have a hydronic underfloor system (double pex-piping within floor joist space). The installer used NEITHER diffuser plates to hold the piping NOR reflective insulation. The performance has been disappointing and after having read many of your posts and Q&A I am convinced I should do one or the other at least. The insulation in the joist spaces is R11, kraft paper facing to the basement.

In Mechanicals | Asked By Trevor Laubenstein | Oct 14 16
8 Answers

How best to install HVAC return duct on outside of house?

Basic facts: 3 level house built on a down slope hillside lot in 1994. HVAC zone one covers main and upper floors. Zone two heats lower floor bedrooms. Equipment room located on lower floor. Climate zone 3c---SF Bay Area home. Large SW facing windows heat up main floor (family room) and upper floor master suite.

In Mechanicals | Asked By Joe Geesman | Oct 4 16
1 Answer

Can I use rigid styrofoam on top of top plate to minimize thermal bridge from trusses


I was wondering if its suitable to install a truss on top of a sandwich styrofoam between 3/4 ply and the top plate of an exterior wall, Sort of like putting a SIP on flat. Can the SIP support the point load of trusses for lets say a roof needing to support 100 psf?


In Green building techniques | Asked By Stephane Aucoin | Oct 17 16
1 Answer

Green Bldg Advisor for higher education?

Do you have a program of providing full content of Green Building Advisor to libraries? At a large institution it is not feasible to manage an account with a single ID and password for use by faculty and students. Access by IP address ranges is necessary. Do you provide this type of institutional subscription? For many years your journals Fine Homebuilding and Fine Woodworking have been popular supplements to architectural education. Green Building Advisor could have similar value if access can be feasibly managed.

Henry Pisciotta
Arts & Architecture Librarian

In General questions | Asked By Henry Pisciotta | Oct 17 16
8 Answers

Adding insulation to floor vs adding insulation to walls

Hi, we have a basement that is partially below grade on two sides and on grade for the rest. The walls are cinder block, and the foundation is a concrete slab with a layer of gravel under it. There are 5 windows that are 35x37, double-pane, with air leaks around them. There is a propane furnace that ducts heated air to ceiling vents in basement rooms and floor registers on the main floor. Three of the rooms in the basement have electric baseboard heaters. The basement and main floor are both 1500 square feet. The only floor covering in the basement are then stick-on vinyl squares.

In Energy efficiency and durability | Asked By John Lambert | Oct 16 16
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