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16 Answers

Insulate a slab in a mild climate

We're building a 250 square foot in-law unit on a monolithic slab in zone 3c (bay area, calif.). The slab will be 6.5 inches above grade to meet code. The slab will also double as the finished floor. It will NOT have radiant floor heating.

Do you think it's a wise investment to add rigid insulation around the exterior of the slab and under the slab? If so, what r-value should we shoot for?

In Green building techniques | Asked By Nick Jensen | Aug 29 12
1 Answer

I have a gable roof with a gable vent in front, but there is now a cathedral addition

In south Mississippi, I have a gable roof with a gable vent in front, but there is now a cathedral addition in the rear, so there is no longer a rear gable vent. No ridge vent, no soffitt vents. It is an unconditioned attic with HVAC ductwork. The air handler is in a closet below the ceiling. The fresh air intake is located in the ceiling of the front porch which is a cantilever.

I have two registers going from the original rear gable wall into the new addition which is split into two equal rooms, each 14'x16'.

How do I create a satisfactory envelope?

In General questions | Asked By roger steinbrink | Jun 19 14
19 Answers

Best Approach: 19th Century Farmhouse Retrofit

I recently purchased a farmhouse in Western MA (zone 5) that was built in 1890. The house is currently heated by a vintage 1987 Williamson forced air furnace with newer uninsulated duct work. The house is supported by posts and beams in the basement but I believe it is balloon framed with rough cut lumber. There is no insulation in the 2(?)x4 walls. The foundation consists of about two feet of field stone at the bottom with the remainder brick. The brick is showing signs of freeze thaw damage on the inner wythe. The exterior has been re-clad with vinyl and the roof is in okay shape.

In Energy efficiency and durability | Asked By Brian Coppola | Sep 10 13
4 Answers

Overclad EPS foam on top of stucco-covered fiberboard?

I'm doing a deep energy retrofit of my New Mexico house (zone 5B) and it's time to plan out the walls. The existing exterior walls have stucco cladding with no deliberate drainage gap, over two layers of tar paper, over fiberboard. In my extremely dry climate, this wall seems to have proven robust in its 42 years of life so far, as I have found no evidence of moisture damage whenever I have ripped out drywall or chiseled away stucco.

In Energy efficiency and durability | Asked By Nathaniel G | Jun 15 14
11 Answers

Polyiso foam in basement: a rim joist question

Hi all,
Love this site, great hints
Now Im in Rockland county a little north of NYC and have a 2007 2 story colonial
I have added to the R38 with another 8" of cellulose and now am looking at the basement.
It is unfinished but I has r19 batts in the ceiling (unfinished)
So I was looking at putting 2" Poly Iso board glued to the basement walls, the ceiling height is 8ft so perfect fit for the boards

In Energy efficiency and durability | Asked By Darren Finch | Feb 11 14
3 Answers

Cut and cobble vented cathedral ceiling

We are finishing our attic on a tight budget. We just had new roofing installed 2 years ago and unfortunately did not add continuous exterior insulation at that time since we had an insulated attic (at the time). The floor-to-ceiling height is so low that every inch counts, so we are looking at cut and cobble to maximize R-value within a very small space. House is 1927 drafty everywhere, so unvented roof seems impossible to retrofit appropriately without spending a lot of time and money. We are in Portland, Oregon (moderate climate).

In Energy efficiency and durability | Asked By Miyeko Endy | Jun 18 14
1 Answer

How best to insulate the outside of the sheathing?

What say you wall system experts about this "new" product vs. my old favorite Thermax?


In Green products and materials | Asked By Morgan Audetat | Jun 18 14
1 Answer

I have an old wood window sill that I want to install PVC Trim over

After I scrape out, fill any rotted areas with a spackle or epoxy mix and sand what other prep do I need to do before attaching my pvc trim, caulking & repainting?

Because of the design of the frame there are infact 2 small sills where the storm windows used to be. When the windows were installed PVC trim was put around all sides of the storm window area with a quarter round base (to cover the sloped sill gap). The paint on the large sill has taken a beating, so I want to extend pvc trim over it.

In GBA Pro help | Asked By Mike Tew | Jun 18 14
9 Answers

Insulating PWF basement

The "new plan" is to insulate the outer wall of my PWF basement with strips of EPS between the studs since I've found the material at a cost lower than mineral wool bats.. I'll cut strips of the sheet goods and install them much like bats for a total of 7 1/2"thickness. Inside the foam will be 3 1/2" of mineral wool as an ignition barrier for a cavity r of 45. Since my outer insulation is not air permeable, I should not need an interior vapor/air barrier.

In Energy efficiency and durability | Asked By Jerry Liebler | Jun 17 14
1 Answer

Hot water distribution

I have an electric water heater that I’d like to move from one end of my house to the other and I'm wondering how to calculate any potential energy savings.

All of the water users including the kitchen, laundry, and bathroom are tightly clustered at the front of the house where our town water supply enters the foundation. But the hot water tank is at the opposite end of the house about 30’ away, for reasons that predate me owning it.

In General questions | Asked By Mark Fredericks | Jun 18 14
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