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28 Answers

How to stop a Cathedral ceiling from sweating

Newly constructed home in upstate New York (Cold Climate) with cathedral ceilings throughout. R38 paper faced batts with Sheetrock and T&G pine cover the entire ceiling. After the long winter months have past the warmer weather causes water to come streaming down the inside of the valleys and down the walls for at least 5-6 hours. A roofing contractor said it was caused by ice damning so I replaced the shingles, s&i guard etc. in both valleys and I had a leak this past Sunday afternoon (no rain or snow). I don't know what to do besides rip down the ceiling and spray foam.

In Interior design | Asked By scott davis | Dec 6 11
3 Answers

Has anyone studied or quantified how XPS foam shrinks?

I am working on the foundation for a new house I am building for my family. Under the pad I am putting a 3.5" layer of reclaimed XPS. Then I got thinking that I should put something over top of that to overlap any seams. So the lumber yard had 4X8 sheets of .5" of XPS which isn't a lot of R-value but I mostly wanted something over the seams in the thicker reclaimed XPS. I know EPS is better for the environment, but they didn't have any. Anyway I took my time and really made sure the joints were tight and everything laid in nice without any gaps.

In Green products and materials | Asked By Dillon Vautrin | May 31 16
11 Answers

Building an energy-efficient metal building

We are in the process of planning a metal pole barn used for manufacturing. We need to have metal panels on the inside (or similar) for wash down. We currently have a similar metal pole barn which is not energy efficient. What is a good way to make better use of the insulation / materials to make the building as energy efficient as possible? We also need to maintain a constant temperature of 55-65 degrees if possible.

In Energy efficiency and durability | Asked By Becky Parrish | May 30 16
70 Answers

Do heat pumps and super insulation complement or compete with each other?

After reading the article on "how much insulation is too much", I found Marc Rosenbaum's stats on 11 cold climate house configurations interesting. He points out that the difference in energy savings is very small between a minimally insulated and poorly air sealed house and a super insulated and very tight air sealed house. This is because he starts with an 2.5 cop heat pump and a heat pump domestic water heater. He sets the miscellaneous loads (appliances and lighting) at 4800 kwh year. The domestic hot water at 1850 kwh year, and the only variable is space heat.

In Green building techniques | Asked By ven sonata | May 29 16
5 Answers

Attic insulation: how much of a concern are uncapped wall cavities?

On a retrofit of a leaky balloon-framed building in upstate NY, we found that most walls, both interior and exterior, did not have top plates and were open to the attic. All had fiberglass insulation in them already. Assuming that these walls are tight and aren't exfiltrating, I am wondering whether heat loss through convective air movement in this situation is likely to be significant. In some areas access is very difficult, so I'd like to have a sense of how much benefit there is in sealing these cavities.

In Energy efficiency and durability | Asked By Bennett Sandler | Jun 2 16
4 Answers

How should I deal with attic insulation where roof meets wall?

I'll be blowing cellulose into a vented 1920's attic in Oakland Ca. zone 3c. Roof has no overhang, rafters begin on top plate. There's also a small daylight gap where top of gutter board and bottom of roof sheathing meet. Would filling that intersection and contacting roof sheathing and rafters be a concern?



In General questions | Asked By carl haberberger | Jun 1 16
4 Answers

Ways to graph air conditioning run times?

I'd like to be able to graph and visually see the cycling pattern of my traditional split system heat pump here in Central Florida. The thought is that if I can determine that it is off, say, 25% of the time in the afternoon on the hottest summer days, that I could probably downsize the tonnage by 25% when it comes time for replacement. Of course, I would want to make sure that my system was properly charged and operating before conducting such a test.

In Mechanicals | Asked By david jensen | Jun 1 16
3 Answers

Could plastic attic ventilation baffles on a 5/12 roof create a moisture problem?

The article on attic ventilation baffles notes two pretty good commercial products, Accuvent and Smart Baffle. Both are made of plastic, with essentially zero vapor permeability. With a steep pitch roof, that's fine. Any vapor that come up through the ceiling, through a leak or through vapor diffusion through the drywall, can keep going up through the insulation and reach the vent space above the insulation, so there's no moisture trap.

In Green building techniques | Asked By Charlie Sullivan | May 31 16
3 Answers

Insulating walk-out basement

I'm insulating a walk-out basement in a new construction. The house is of a double wall design, and will be filled with dense pack cellulose. I understand that for the foundation walls that I can not apply cellulose directly, however I had thought that if I apply a layer of closed-cell either sprayed or laid in in sheets then I should be able to fill the rest of the cavity with cellulose, assuming that there is no concrete exposed. My question is how many inches do I need to use to assure I have no problems with the cellulose?

In Green building techniques | Asked By Geoff Frood | May 29 16
1 Answer

Window flashing when using SPF instead of rigid foam

The retrofit I'm planning will add exterior insulation in the form of SPF. Will add vertical furring strips suspended 1" or more from the existing siding/sheathing for mounting the new siding. For windows, will use the window buck approach and 'outie' window mounting style unless another style has advantages for ease of installation, durability etc. 'outie' would match the existing appearance, could change for the right reason.

In General questions | Asked By TIM LANGE | May 31 16
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