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4 Answers

Exterior rigid foam vs. double stud wall

I'm considering 2 types of exterior wall assemblies on a new build in climate zone 6 and am wondering which you think is superior. R value is very important obviously, but breathability, durability, and cost efficiency is also important:

1. (from inside out) Drywall, 2x6 wall w/ 1.5" open-cell spray foam against exterior filled with dense pack cellulose, sheathing, Tyvek Drain Wrap, 2.5" XPS rigid foam, 3/4" rain screen, and siding.

2. (from inside to out) Drywall, 2 2x4 walls w/ a 2" gap filled w/ dense pack cellulose, sheathing, Tyvek House Wrap, 3/4" rain screen, siding.

In Energy efficiency and durability | Asked By David Voros | Jan 27 16
6 Answers

Recessed lights & insulation

Hi all,

I recently had an insulation contractor come in and put 12 inches (additional) insulation into my attic spaces (3) and install some baffles because of some ceiling shadows we were experiencing.

In Energy efficiency and durability | Asked By Ryan Lambert | Jan 25 16
7 Answers

Insulation plan for bonus room above garage

I am in MN(zone 6), working on my new construction.
It has an attached garage with a bonus room above it. I don't plan on finishing it right away but would like to plan how I am going to insulate it.
I have sheathed the roof deck with 7/16" zip sheathing. It will be covered with Cedar shakes. I have already roofed almost half of the house and am slowly making my way towards the garage.
I am considering both vented and unvented assemblies.

One of the possibilities is:

Cedar shakes with 30 lb felt paper interlayed
1 1/2" above deck ventilation
Zip sheathing

In GBA Pro help | Asked By asim majeed | Jan 26 16
3 Answers

Polyiso under metal roofing

First off, thanks for such a wealth of information! I live in central Indiana. I'm in the process of insulating my cathedral ceiling. I have access to cheap paper faced polyiso. My plan was to cut and cobble 3" polyiso in rafter bays. The build up would be tongue and groove, 2x2 nailers with 1.5" polyiso in between nailers for thermal break of rafters, 6mil Vapor barrier, 2 3" sheets of polyiso with very thick paper fiberglass faced, 3" vented airspace, 2x4 purlins, foil faced bubble wrap directly under metal roofing.

In Energy efficiency and durability | Asked By Damion Bauder | Jan 26 16
8 Answers

Are there any builders, architects, engineers, or homeowners interested in industrial hemp building?

Energy and bio-friendly materials significantly solve many issues I see here, and despite code/cost and other issues, it is a solution many are embracing...

Hempcrete, hemp fiber insulation, hemp particle board, carpets, furniture are all available and becoming more mainstream alternatives with immense positive experiences. Anybody have experiences or interest in this?

In Energy efficiency and durability | Asked By Kristin Steen | Jun 16 15
3 Answers

What are the pros and cons of the Mitsubishi multizone ASHP?

Hi All- I'm part of a community program in Tompkins County NY advocating for both ground sourced and air-sourced heatpumps. I am still a little uncertain what to tell people when the participating installers recommend the multizone units. In particular, I am concerned about the MXZ series. They have good heating performance down to low temperatures, but, as pointed out in a previous blog here, they have the very high minimum heating capacity suggesting a lot of needed on/off cycling during the shoulder heating seasons.

In General questions | Asked By Jonathan Comstock | Jan 25 16
6 Answers

Is it worth an upcharge to go from 1.5 lb./cu. ft. density to 2.0 lb./cu. ft. density on fiberglass BIBS?

I'm having my walls blown and I was questioning the installer about installed density. I was looking for a 1.8 lb density as that's what most of the fg blowing wools seem to require. However, he is installing Owens Corning L77 wool that does meets rated r-value at a lower density than most other blowing wools I've looked at.


In Energy efficiency and durability | Asked By Rick Van Handel | Jan 26 16
3 Answers

Minimum overbuilding (foundation) for a thermally isolated sunroom

Hi. I'm chewing on an addition of what would be classified as a thermally isolated sunroom, just-above grade. I'd like to do this myself, and since I'm not a person who has been in the game for years as some of you have, probably what I'm asking about a minimal but code-compliant foundation here is old hat to some.

Here's what the code says for my city:

Insulation is not needed in
ceilings, walls, and floors that do not
separate the sunroom from
conditioned space and when the
sunroom is not capable of
maintaining, through design or heat

In General questions | Asked By Mojave Disaster, 3B | Jan 26 16
3 Answers

Wall systems decision

I am designing and home in the outskirts of Santa Fe, NM (climate zone 5B / elevation 6800 ft.).
I am interested in energy efficiency, low maintenance and overall best choice for this climate.
(note: we are planning to use geo-exchange heating and cooling + PV's to minimize energy costs as the site will only have electrical and propane fuel sources)
We all know pretty well the pros and cons of double wall frame construction for this area.

In GBA Pro help | Asked By Abelardo Ruiz | Jan 25 16
6 Answers

Insulation behind built-ins?


I'm installing some new cabinets along exterior walls in my 1850s farmhouse. The cabinets are floor to ceiling, and I thought it might be a good idea to put a thickness of roxul insulation between the rear of the cases and the exterior wall.

Any thoughts on this?

Problems you foresee, best ways to make it work?

Thanks for your help,


In Green building techniques | Asked By DJ Polojarvi | Jan 24 16
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