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3 Answers

Some help with estimation of wall assembly cost?

We are in the process of designing a passive house and are working with PH certified architect/consultant. But for now, builder's knowledge would be needed: a back of the envelope calculation for the cost /sf of this kind of wall assembly: fiber cement board w/ rain screen, fiber board, dense packed cellulose, OSB, dense packed cellulose, drywall. The wood framing will most likely be w/Larson trusses. The R-value we are trying to achieve is around 40. The house is a duplex with gross sf area of ~4500. Would be good to know the material & labor separately. Why do I need it?

In PassivHaus | Asked By Lucyna de Barbaro | May 16 13

2 Answers

Sealing a dry sump

My basement is fairly dry and well above the local water table
and hasn't had any water ingress over any of the major storm
events we've had, and has never had a sump pump. So I don't
really care about storm water; what worries me is the potential
for internal plumbing leaks as there's no way for the basement
to drain until it basically fills all the way up. So I'm
thinking of putting in a sump pump but into a small well that
*doesn't* connect to whatever gravel/earth/whatever is underneath
the slab -- it would be connected to the slab and sealed in and

In Mechanicals | Asked By Hobbit _ | May 16 13

14 Answers

Closed-cell foam on underside of roof with no AC: Do I need to vent?

I am working with a local energy efficiency contractor. They are replacing my old roof (which badly needs replacing) with a new roof. They will be spraying five or so inches of closed cell foam directly against the decking. This will fully seal my attic. My question is, how does this work if you do not have air conditioning in the house, other than window units in the bedrooms and one in the living room.

In Green building techniques | Asked By Rob Graff | May 7 13

1 Answer

Basement slab moisture barrier

I am finishing our 800 sq.ft. basement in Portland, OR (zone 4c). I am planning to lay a combination of carpet and linoleum and want to reduce the chances of mold from moisture that might seep up through the concrete slab, which varies in thickness from 2" - 4" in some spots. I have noticed a couple 6" diameter spots on the slab that seem moist during the rainy season, but no pooling of water.

In General questions | Asked By Matty McDermott | May 16 13

1 Answer

Does anyone have experience with or an opinion of the Dow Powerhouse solar shingle and cathedral ceilings/ roofs?

The cathedral ceiling/roof is unvented, closed cell insulated. Will this solar shingle properly vent moisture upward from the plywood decking? Will there be any problems with running the multiple wiring conduits to the inverter in the basement?

In Green products and materials | Asked By JOSEPH POLAND | May 16 13

3 Answers

Re-using brick pockets in an exterior wall

I am working on the design phase of a rowhouse renovation in Baltimore, Maryland. This rowhouse is 14'x50' and is an end-of-group, with an east facing exterior side wall. Existing floor joists sit in "brick pockets" in this exterior wall.

In General questions | Asked By Charles Chiampou | May 14 13

4 Answers

Can exterior foam be combined with interior spray foam?

If I have walls and/or an unvented cathedral ceiling that are insulated with closed-cell spray foam from the inside, can I also have rigid foam on the outside of the sheathing to limit bridging?
Just wondering if it's somehow a bad idea to have the sheathing sandwiched between two layers of foam.

Thanks, Chris.
(This is for Ottawa, Canada, equivalent to zone 6A.)

In Green building techniques | Asked By Christopher Solar | May 13 13

7 Answers

Thermal mass lessened with overlay over slab?

I have a passive solar off-grid home that works extremely well with a 2 in. concrete slab that is finished with decorative concrete stain/paint. However, the slab and stain/sealer are completely defective and very likely have to be replaced, but one party is proposing a concrete overlay product be put atop the existing slab. The overlay product (ArtCrete Deck Coat, I think it is) consists of two parts--1) Portland cement, aggregate, and a stain, and 2) a modified acrylic latex resin.

In Energy efficiency and durability | Asked By K Tot | May 13 13

3 Answers

Roxul

I am finishing a screened porch into a fully-insulated room, to be part of the house and used year round. I understand Roxul is an excellent choice for exterior walls. Is a vapor barrier necessary and, if so, can someone suggest how to install. Tks for your help.

In General questions | Asked By Roni Collier | May 14 13

9 Answers

Space and water heating for a micro-load house

I've been re-reading Martin Holladay's posts on water heating as I once again deal with a small-ish super-efficient house: 1900 ft2 with a heating load of less than 20 kBtu/hour. The homeowners have access to propane and electricity and here in MN, electricity is still generated by a lot of coal, although the homeowners are planning for a pv system.

At the moment I've narrowed heat/hot water system ideas down to three:
1. use a 6kW modulating electric boiler for space heat (hydronic radiant) and also to fire to an indirect tank for hot water. Also, use a drainwater heat recovery device.

In Mechanicals | Asked By Rachel Wagner | May 14 13

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