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33 Answers

120 year old uninsulated home siding retrofit

Hi all,

LP Smartside 76 series 8” 7/16” lap siding has been purchased by our contractor and now I am finalizing details.

Please review for compliance, efficiency and best practices and fill in my blanks. ;-) We plan to live here for a long long time and want to make sure we do it right.

Strip cedar shakes and old lap to 3/4" diagonal bracing or studs if bracing is rotten.
Replace rotten diagonal bracing with __?__.
Install tyvek as an air barrier
Install 1.5" R6 Roxul Comfortboard with 1x4 strapping screwed 1.5" into studs 16" OC

In Plans Review | Asked By bridgette downer | Jan 10 18
10 Answers

Another try at a ceiling service cavity framing

I now want the duct ed mini split IDU(s) and ducts within the ceiling therefore what I thought was an economical construction (lattice of flat wise 2x4s) really is not, especially if I'm to have code acceptable ducts. I simply need a taller cavity, 3" isn't enough, 6" is probably minimum. My latest thought is to use a variation of a Larsen truss (2x2 chords and OSB strips on alternating sides forming the "web") installed horizontally. The "Larsen's" top chord is fastened through the upper air barrier material (probably drywall) with screws into the bottom chords of the roof trusses.

In Energy efficiency and durability | Asked By Jerry Liebler | Jan 15 18
3 Answers

What do you think of the flex duct on this job?

We added some HVAC ducts to our basement's existing metal ducts as we plan to finish it. I have three questions about the Flex Duct they put in.
1.) Is flex duct ok to use in a basement like this?
2.) Is the way they installed the marked "A" okay? Looks a little sloppy to us how they tried to twist it into a bay, but what do you think?
3.) Are these both insulated? And, if not, should they be and is that something they can easily add?
Thanks in advance!

In General questions | Asked By Masb | Jan 16 18
13 Answers

Vinyl windows with synthetic stone

Hoping this isn’t a bad question.....any advice for detailing Synthetic Stone around vinyl windows (some have integrated J channel, some have brick mounding with integrated J channel).

In General questions | Asked By Birdie L | Jan 7 18
5 Answers

Climate Zone 3C: Crawl space, roof, and wall systems review

I'm in the design phase of a remodel of an existing 2 story house, CZ3 coastal, zip code 95062. The scope includes a new foundation and gutting the house with some interior walls moving, but for the most part keeping the existing exterior shape and roof line. Goal is a high performing house (well insulated, air sealed, mechanically ventilated, high IAQ and minimal heating and cooling loads). I've attached a line drawing of the shell for reference.

In Green building techniques | Asked By Phil Boutelle | Jan 9 18
6 Answers

Crawlspace rim joist

Hey All,
Have a crawlspace in zone 4A zip 08731. Installed a mini split a few years ago and it’s doinf a fine job heating the house until the crawlspace becomes cold due to no insulation down there. I eventually plan to do 2” of polyiso on the outside of the house but until the funds are ready to do that and the windows I am looking for a temporary hold over. Can I do 2.5” of EPS on interior of rim joist with foam sealing the edges and can it stay in place when the eventual exterior polyiso is installed?


In General questions | Asked By Chris King | Dec 26 17
5 Answers

Best way to install rigid foam insulation below floor joists from crawl space?

I have had to remove fiberglass batting from my crawl space due to the intrusion of rodents. This has left the underside of our floors uninsulated. I am thinking of replacing with 4" polyIso foam board. However, I am not sure what is the best way to install it:

Should I "cut and cobble" between the floor joists? This will be time consuming and will lend itself to thermal bridging. Or should I secure to the bottom of the floor joists? Doing the latter will leave a 6" gap between the rigid foam insulation and the sub floor. Is that too much?

In Energy efficiency and durability | Asked By Mike from Lafayette | Jan 15 18
13 Answers

Thought experiment: 30k cistern as thermal mass in passive home

Hi, we have a mountain lot in Colorado at 7500 ft elevation with lots of south facing solar heat gain, and we're planning on building a passive home. We're required to install a 30k gallon cistern for fire protection. A 30k gallon buried cistern seems to be extremely expensive, while a 30k gallon bladder type cistern is very cheap and could be installed inside the home's envelope in a crawlspace. Assuming the passive home is well balanced for on average for a year, could the huge amount of thermal mass help moderate an even temperate, or would it become a problem?

In PassivHaus | Asked By Mike AbiEzzi | Jan 9 18
5 Answers

Acceptable moisture content levels in wood tongue-and-groove boards?

To all,

Searching this site and the web. Surprisingly, I could find very little on what is an acceptable level of moisture in wood V groove T&G 1x6" paneling. FYI the wood species is Red Pine (Norway Pine)

The ceiling areas the wood will be placed has a 1 1/2" space behind it and the air barrier.

I have found some wood at 1/3 the price of kiln dried, and in the lengths I need. However, the wood was air dried, and currently is showing 10-12% moisture content. I think kiln dried is about half that.

In General questions | Asked By Steve Lenertz | Jan 15 18
6 Answers

Basement / crawlspace insulation

Basement of an addition has two levels. Most of the space is at normal height but about a third is raised to only about three feet high. Needed to do this because of the nearby ISDS. Energy auditors are recommending rigid foam on these "crawlspace walls" and not all the walls. Does this make sense?


In Green building techniques | Asked By Jonathan Blaney | Jan 16 18
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