Q&A: A Forum for Green Building Experts and Beginners

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10 Answers
Rigid foam for hot roof

I am interested in converting our bungalow attic to finished space, and it was not designed for venting. I've heard I can do a hot roof insulation method using spray foam. However, I am a DIY guy by nature, and was interested in methods I've seen using closed-cell polyiso rigid foam and spray foam cans to achieve the same result, at least in walls. I am curious about using this method on a hot roof. Surely it would cause head-scratching with code officers. Would it work, though?

In Energy efficiency and durability | Asked By Asa Bradford | Jul 13 14
17 Answers
How to keep cool in and heat out?

I am not in construction or an architect, just someone who would like to live in/build a small, comfortable, energy efficient home. I don’t need and could never afford a Passive House. Don’t even know if one would work where I live. I live in the low desert southwest near Phoenix. Living is very different here than in cold weather areas. And very different than Florida or humid areas of Texas. Outside temps over 100F in shade 5-6 months; highs 115F; nighttime lows 95F for at least 2-3 months. Low humidity 10 months. Little or no drought resistant shade trees.

In Green building techniques | Asked By Anneal G | Jun 27 14
3 Answers
Raycore - is it the product for me?

I was pretty much on board with buying Raycore for the 4500 s.f. home I am building in downstate NY, which is steel framed, so I actually don't need any structural value out of the exterior walls other than for supporting the windows and doors (and supporting the walls themselves). I am also going with a wire lathe and stucco on the exterior - Raycore told me I could direct apply the wire lathe and did not have to use any sheathing if I did not need the shear strength, but I am hesitant to do so.

In Green products and materials | Asked By Joe McCarthy | Jul 14 14
27 Answers
Finally got my heat loss numbers...ouch!!!

I thought I was on the right track but I am not so sure now ...42000 btu is the heat loss number .It is a 1200 sq ft slab on grade 1.5 storey .Total living space is 1900 sq. feet .It is 2by 6 blown in fiberglass with 2.5 inches of EPS on the exterior .We do have lots of triple pane large high windows on the lake side which is a north east exposure ...,that one large combo living,kitchen,dining room is a 17000 btu heat load .I was hoping to heat it with a Fujitsu mini split on each level ...Is that still a viable option ? I am in Peterborough Ontario which is a zone 6 ...thanks,Bob

In General questions | Asked By bob holodinsky | Jul 8 14
1 Answer
Cathedral ceiling roof assembly

The cathedral ceiling roof assembly on a recent addition to my house consists of vented fiberglass-filled bays with with an interior layer of 1/2" foil-faced polyiso under the 2x10 rafters.

Investigating a strong odor on hot days, I found that the builder...

Michael Roland,
Nassau, NY

In Green building techniques | Asked By Michael Roland | Jul 16 14
3 Answers
Isn't there an intrinsic problem with SCIP building systems i.e. thermal bridging?

Isn't there an intrinsic problem with SCIP (structural concrete insulated panels) that the reinforcing trusses bridge the insulation.

In General questions | Asked By Stephan Green | Jul 14 14
1 Answer
Should the rafter bay be sealed if there is a skylight installed in it?

Hi,
I’d like your recommendation on sealing rafter bays of a currently vented cathedral ceiling.

I’m doing a remodel of a small room (20 X 20 feet); the roof/ ceiling were built as a vented roof assembly complete with a ridge and soffit vents.

In General questions | Asked By Anthony Jackson | Jul 15 14
3 Answers
In an unsinsulated service cavity (created by running horizontal 2x lumber) is fire blocking required? Or is it a good idea?

My proposed wall assembly from outside to inside:

1. Ribbed steel siding
2. 3/6" fanfold battens to create air space
3. 1/2" cdx
4. 2x8 stud cavity filled with wet spray cellulose
5. 2" eps nailed to studs (interior uninterrupted rigid foam)
6. 1.5" uninsulated service cavity (created with horizontal 2x4s)
7. 3/8" acx plywood (interior wall finish)

The building is a heated workshop with some pretty high electrical needs for the machinery. Since it's not a residence, I could probably forgo the fire blocking.

In Building Code Questions | Asked By Rick Van Handel | Jul 14 14
3 Answers
How to attach XPS insulation to a wall that is partly covered with dimpled Delta MS?

I want to properly insulate a basement wall to which dimpled Delta MS has been attached up to grade level, as part of installation of interior weeping tile/sump pump installation.
How should I adhere xps or eps insulation to this wall, since the dimpled Delta is not exactly even with the concrete on the exposed part of the wall above it?
Or is it necessary to buy more Delta to go all the way to the top of the wall?
In either case, what is the best way to attach the insulation?
(I intend to frame a wall later in front of this insulation.)

In General questions | Asked By John Lawson | Jul 14 14
11 Answers
Basement Pros and Cons?

Basements are almost unheard of in Texas.
I always thought that basements were almost mandatory "up North" because of frost heaving problems.

I have recently noticed many cold climate examples that do not employ basements.

Most noteable..... German Passivhaus examples.
Almost all of the modern German examples do not include basements.

After seeing a video of Dan Morrison's basement .. I can see why youz guys may be reluctant to give up your basements ;-)
In Texas our Garages look much like your basements..... "Full of Stuff"

A basement is a deep crawl space...

In General questions | Asked By John Brooks | Feb 25 10
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