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6 Answers

Retrofit rigid foam outside CMU walls

I'm looking for resources to plan a retrofit of rigid foam insulation outside our walls. The vast majority of resources are about wood framed walls, but we have walls built from concrete masonry units (CMUs).

In Green building techniques | Asked By James Howison | Feb 21 12
29 Answers

Am thinking of the following wall and roof assembly in BC as a cost effective way to achieve a high R-value and tight envelope.

2x6 structural wall with roxul in the cavities and gaps in sheathing (drill holes as well) to promote drying to exterior. The inside of this wall is sheathed with 1 inch of polysio (air and moisture barrier). A 2x4 wall inside this provides chase services, a cavity for fiberglass batts, and protection of air barrier.
The 2x6 walls are straightforward construction, with most of the building wrap and rainscreen installed before lifting wall. Foam insulation is also easy to install with no penetrations.

In General questions | Asked By Reggie DuBois | Feb 14 12
6 Answers

Unvented attic with open-cell spray foam

Newbie here with a design question. Planning a retirement home about one hour west of Ft. Worth, TX, (Gordon,TX) climate 3B I believe. Having trouble with the proper unvented roof design using, as I'm told by most of the approved builders in my development, open cell sf (spot leaks if any develop). What are my most practicable, cost efficient methods of :

1) achieving my required R code value in the roof (R38 roof/R15 walls per USDOE website)
2) eliminating thermal bridging (if that is a concern in climate 3B?)
3) Use ADA air sealing of sheetrock

In Energy efficiency and durability | Asked By John Grutta | Feb 21 12
15 Answers

Assistance with Attic Mold on my clients' home

Let me start by saying that I am sorry this is going to be such a long post. But I have spent countless hours over several winters now trying to assess this problem. And I guess I feel that for any of you to be able to give me an informed opinion as to the cause(s) of my problem and any subsequent suggestions/solutions, I have to give a thorough explanation of the project background and site conditions. I’ve also attached a few photos to help visualize the situation. And so I come to you GBA experts, on bended knee, in the hope that you can generously impart some of your wisdom.

In Green building techniques | Asked By Christopher Fuller | Feb 17 12
3 Answers

Dual fuel heating system - thermostat?

We recently built an addition onto our house and instead of extending our existing AC-only system, we installed a second AC/heat pump system. The house also has an oil-fired boiler with baseboards.

We added two heating zones to the addition onto the existing hydronic heating system, so the addition has two heat sources - oil and heat pump.

In Energy efficiency and durability | Asked By Eric Yancey | Feb 21 12
6 Answers

Solving thermal bridging.

I am building a wood frame home in southern Maine. I am using a combination of 2" spray foam and unfaced fiberglass batt in the exterior 2x6 walls for a total of R25. Would installing 3/4" rigid foam board insulation between the exterior 1/2" sheathing and the cement board siding create any moisture issues in the sheating, given there is spray foam on one side and rigid foam on the other? I am concerened about thermal bridging.

In Energy efficiency and durability | Asked By Dana St.Ours | Feb 21 12
4 Answers

Planned communities

At a social event last night, a friend who owns a 25-acre parcel asked me about resources for developers (or groups of friends) thinking about building a cluster of houses where like-minded people can live near each other. My friend is wary of the endless meetings associated with co-housing, and is also aware of the issues that arise when a group of friends build adjacent houses, only to have situations change due to divorce, deaths, and inheritance.

So who can recommend Web resources discussing these issues -- questions about:

1. Subdividing land

2. Intentional communities

In General questions | Asked By Martin Holladay | Feb 20 12
1 Answer

Thermal mass volume

Another related question: When measuring square area of the floor that may receive sunlight, do we include all of the uncovered floor area next to the south facing windows, even though some of the floor, like that abutting the south wall, will never get direct sunlight?


In Green building techniques | Asked By Christa Campbell | Feb 21 12
1 Answer

Slab dimensions for passive solar

I found the following answer and need clarification on the last paragraph. When Robert Riversong says " floor area", does he mean the whole floor area of the house or just the floor that could be exposed to sunlight?

For both radiant thermal mass and passive solar thermal mass, the ideal thickness of a poured concrete slab happens to be exactly the same as the industry standard for residential applications: 4".

In Green building techniques | Asked By Christa Campbell | Feb 21 12
7 Answers

Is this truss lift??


The link is to images of this case. Click the "show info" upper right of slide show for captions.

This production house in S.E. Pa. has a trussed roof. It is 3 years old. The first season (October) a drywall joint opened up (1/4" +/-) at the change of ceiling plane in the picture where the flat ceiling meets the "cathedral" ceiling. The builder installed a foux beam over that area to conceal what they thought would be a seasonal event. Now the next joint over opens up seasonally.

In GBA Pro help | Asked By Robert Post S.E. Pennsylvania Zone 4a | Feb 20 12
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