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4 Answers

Venting rafter bay with skylight

Building living space in attic - sloped cathedral ceiling to 8' high level, then flat
using Velux windows and fixed skylights in roof assembly.

How do I vent the rafter bay when the rafters are cross-blocked at the skylight framing?
E.g., rafters @ 16" oc - skylight rough opening 46 1/2 x 46 1/2".
"Rafters" are 16-inch I-beams.

Venting: soffits consist of 1x4 clear cedar spaced 3/8" apart. Installed perpendicular to house wall.
Black landscape cloth (perforated) continuously fixed underneath lookouts as bug-screen.

In GBA Pro help | Asked By Rainer Semsch | Mar 12 12
6 Answers

Basement Floor Underlayment foam or no foam

I am installing a floating cork floor on my basement slab and have decided to use a dimpled underlayment. One product instruction says to maintain a gap at the vertical edges, the other says to foam the edges.



I'm leaning towards the foam for the same reason I foamed around the XPS against the concrete walls - to avoid the conditioned interior air from contacting the concrete.

Foam or not to foam...?

thank you

In General questions | Asked By Frank O | Mar 11 12
1 Answer

Insulated Slab

I have a few questions about an insulated slab detail found in 'strategies and details" section (http://www.greenbuildingadvisor.com/green-basics/slab-foundations). What is the ideal substrate underneath the rigid insulation board and where, if necessary, should a vapor barrier be placed? In the past I have constructed in this order... slab, vapor barrier, 4" of gravel (passive radon vent integrated if EPA zone 1 or 2).

Thanks for the help!


In GBA Pro help | Asked By David Epley | Mar 12 12
4 Answers

Blown-in cellulose in a finished garage ceiling (conditioned space above)

Hi all,
Been putting this off til warmer weather and nows the time I push the button or not
Ok I have a 4 yr old 2 story colonial in NY (20 miles N of NYC) so the usual questions we see on the forum, why is the room above the garage so cold.
So Ive cut some holes and found the builder had put F/G Kraft paper batts in R30

In Energy efficiency and durability | Asked By Darren Finch | Mar 11 12
9 Answers

Avoiding thermal bridge under doors at slab on grade?

Due to extensive shallow ledge, I'm designing a slab on grade foundation for a seaside home in Massachusetts (Zone 5A). Because of gently sloping topography, neither a thickened slab edge nor a frost-protected shallow foundation seems possible, so I intend to use a frost wall with a slab separated thermally by rigid insulation.

In Green building techniques | Asked By John Rockwell | Mar 10 12
13 Answers

Is there a "direct vent" clothes dryer or kitchen hood?

It seems to me we focus on creating super tight envelopes and then cut holes in it to purposely blow out an enormous amount of air with clothers dryers and kitchen hoods. We either create negative pressure in the home or bring in unconditioned air with make up dampers. HRV's and ERV's now solve that issue with bath fans, but isn't there anything out there for dryers and hoods? My thought is there should be some kind of venting system like the direct vent on the back of a fireplace where the incoming air gets conditioned by the outgoing air.

In Green building techniques | Asked By Andrew Homoly | Oct 6 11
3 Answers

Is there much of a difference between .27 and .22 in the solar heat gain in new windows for Fort Worth, TX?

We are purchasing new windows for our home in Ft. Worth, TX and want to know if it is worth spending an extra $20 to $30 per window to improve our solar heat gain rating from .27/.28 to .21/.22.

In Energy efficiency and durability | Asked By Craig Schaefer | Mar 9 12
4 Answers

Moisture barrier & insulation for barn loft

I have a 30 x 40 two story barn that the upstairs loft had been insulated with fiberglass batts and drywalled for a temporary residence. The floor of the loft is 2x8 rough cut joists 16" center with 5/8 plywood flooring. It had been insulated from below with fiberglass batts that has been damaged by birds and rodents. The loft is now used for storage and I plan a workshop area that would only occasionally be space heated for short periods of time, so I can't justify putting a huge amount of money into insulation.

In Energy efficiency and durability | Asked By J. Gaub | Mar 9 12
8 Answers

Spray foam and batt insulation combination

We are renovating our 2nd floor bedrooms due to moisture problems and are seeking the most efficient and cost effective means to insulate. We live in the lower thumb area of Michigan and the the rooms have 2x6 cathedral ceilings. The previous method used was 6" R-19 kraft faced batts with durovent baffles(improperly installed/long story), with soffet and ridge vents. I do not wish to add to the 2x6's and shrink the rooms so I need to maximize the use of the 2x6's. I would like to use 2-3" of closed-cell spf and fill the rest with either 3.5" r-15 batts or 2.5" rigid foam board.

In Energy efficiency and durability | Asked By Jim Rogers | Mar 6 12
37 Answers

Night-time setback w/ radiant floor

I was talking to a heating contractor about a radiant floor system, and we don't agree regarding night-time setback. I'd appreciate some light shed on this.

The system has a typical slab on grade with R-10 under it and PEX tubing cast in, and another area of framed floor with PEX underneath with aluminum distribution plates. The boiler is a 30kw electric with multiple elements and outdoor reset.

In Mechanicals | Asked By David Meiland | Feb 10 12
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