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3 Answers

Will radiant heat system PEX tubing melt polyethylene vapor barrier?

The heating contractor we hired to install a hydronic radiant heat system for our backyard cottage project did not put a polyethylene vapor barrier on top of the gravel, under the 2" rigid foam insulation. The rigid foam insulation panels he installed have a mylar-like film on the under side, which he thinks is sufficient. We live in VERY wet Western Washington so I'm wondering if this will in fact be enough.

In GBA Pro help | Asked By Mightorta | Nov 12 17
1 Answer

How can I address condensation in my arched cabin walls

I built a 20x24 arched cabin(Gothic arch,2 inchsteel frame, 2x4 endcaps) in 2016. We were told that the provided insulation was r-49, but subsequent conversation with the manufacturer , solar gawd, said we are more like r 30, with two layers on the outside and two layers on the inside of the cabin ribs. We planned to make the end caps r 30 but the local contractor refused to install the rigid foam we had bought so we only have r 15 fiberglass in the wall.

In Mechanicals | Asked By waterfront165 | Nov 12 17
4 Answers

Heat pumps for cold climate

Is anyone aware of any conventional split system products (not mini-splits, but to be installed with a conventional air handler) available on the market with a cut-off temperature below -8C (17F)?

I am aware of the Mitsubishi Zuba central but the capacity of this product is much higher than what I need.

Thanks in advance,


In Mechanicals | Asked By Gio Robson | Nov 8 17
3 Answers

Best way to insulate interior of existing above-grade block wall in SE PA?

I am renovating my southeastern PA house that was built in the 50s. The entire structure is concrete block wall with stone and stucco exterior. On the interior, there are 3/4" wood furring strips and plaster walls. The house will continue to have hot water baseboard heat, and I will be adding ductwork and whole house air conditioning.

In Green building techniques | Asked By Tim Romanowski | Nov 11 17
13 Answers

Need an opinion on the practical side of perm ratings

Thanks so much for your time and advice. I plan to build in a high humidity environment, with off-grid PV power. Central dehumidification is a must, and is by far the biggest electrical load. I don't have a feel for whether plywood sheathing/OSB (perm range of 1-4?), combined with large wall surface areas, will allow a significant amount of moisture to creep into the house 24/7, requiring significant additional dehumidification beyond what we'd expect from normal interior sources (humans, showers, cooking, open windows, etc).

In Energy efficiency and durability | Asked By MarkM3 | Nov 10 17
6 Answers

insulation strategy for an unvented cathedral ceiling

I recently bought an old summer home in Freedom, NH, climate zone 6a. It is about 100 years old and currently has no insulation. The rafters are 2"x7" (mostly, they vary a bit in dimension) 24" on center. I would like to create an unvented cathedral ceiling in the attic space. My goal is around R50 without building down the ceiling too much. The plan I have come up with so far is this:
3" of XPS (in 2 layers) against the underside of the roof sheathing, edges sealed with foam
4" of closed cell SPF to fill out the rest of the bay
2" of XPS over the inside face of the rafters

In Energy efficiency and durability | Asked By abram pearson | Nov 10 17
2 Answers

How do I insulate steel support beams in a wooden framed house?

I have a two story house that is being build. For hurricane reasons, we have steel beams from bottom to top sized 5 1/2 x 5 1/2 inch. The steel is only covered with a air tight material of 3/4 inch thickness, see picture. It will be finished with cement board on outside and drywall and plaster on inside. The whole house has 4 of these support beams. Next to this, in between windows, there are two support beams of steel, 2x6 inch bottom to top as well, see picture of framed house. The windows will be wood with alu cladding, the wood being 4 inch square.

In Energy efficiency and durability | Asked By Jan Bultman | Nov 10 17
24 Answers

Are my minisplits modulating or short cycling?

Hello- first of all this site has been an incredible resource. I did most of my own research in adding 4 mini splits to my 1940's home. It was primarily for AC and heat for the shoulder seasons as we really enjoy our 1 pipe steam heat (although older boiler). I went with 2x Fujitsu (not XLTH) condensers with 2 heads each. A 12k per floor (open kitchen area, top of stairs, attic playroom), and 7k in the master.

Home has been retrofitted with new windows, open cell in the rafters, blown-in in the walls, etc...so definitely on the tighter side for it's age.

In Mechanicals | Asked By Kjmass1 | Oct 4 17
4 Answers

How to get Passive House educated?

Hi everyone,

In PassivHaus | Asked By DHTaylor | Oct 21 17
5 Answers

Heat pump water heater—in Maine?

We are nearing the end of construction on our house. We're on an island in Maine.

The house is 2,400 sq ft., including about 600 s.f. of walk-in basement in one half of the downstairs. (The downstairs walls are ICFs with additional blueboard insulation, 2" in the basment and 4" in the finished space. There are 4" of blueboard under the slab. Upstairs walls are double studs with 11 1/2" of dense-packed cellulose.)

Our only heat sources are two mini-split heat pumps: one upstairs, one at the opposite end of the downstairs from the basement. We have a 9kW solar array on the roof.

In Mechanicals | Asked By Jason Mann | Nov 10 17
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