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7 Answers

Installing solar panels over rigid foam insulation

We are about to break ground on a pretty good house in Virginia (Zone 4). The attic will be included in the conditioned area for upstairs bedrooms, so we will be building an unvented roof. Roof insulation is planned as Roxul ComfortBatts inside and ~R20 in two layers of rigid foam outside, topped with OSB (Hunter nailbase panels).

All that sounded great until I considered putting solar panels on the roof. Fastening to the roof trusses through 3"-4" of foam seems like a hit-or-miss proposition.

Do any of you clever folks out there have advice? Thanks in advance!

In Green building techniques | Asked By Esther Streusand | Jan 23 16
3 Answers

Sealing gaps in fieldstone foundation

I have a 1900 colonial home in MA with a fieldstone/rubble foundation.

While air sealing recently, I discovered one area of the basement near the basement door, which has a 1/2-1" by 4 ft gap where the mortar has crumbled away over the years. Is there anything I can do temporarily to seal this up until I am able to repoint this come spring/summer?

I could spray foam it, but it would probably be a huge headache to remove the foam when it comes time to repoint the stone. Would backing rods and caulk be a better option?

In General questions | Asked By David Schrier | Jan 23 16
6 Answers

Condensation under WRB during construction

Built a 2 story, 1300 SF addition on a house in Portland OR which got dried in in early December. The addition has no insulation yet and heat is inadequate and inconsistent via wood stove and the central natural gas furnace that serves only the first floor. The stairwell to the second floor is centrally located and the wood stove is on the first floor adjacent to the stairwell opening. Second floor heating will be a yet to be installed mini split system. A portion of the addition is an unheated garage. Currently running multiple fans and 2 dehumidifiers day and night.

In General questions | Asked By Robert McKee | Jan 23 16
7 Answers

Design for sealing open dirt floor crawl space

Hi I have a 28' x 30' crawl space that has a dirt floor and CMU walls. Ceiling of it is exposed with pipes and wires running around everywhere. I live in western Colorado so it's dry most of the year. I get some ground dampness, but no flooding, during a few months of summer when my hillside gets saturated in places from a natural spring in the rock ridge above me. I have pipes outside of the crawlspace that provide drainage and I keep the soil sloped away from the home walls. My adjacent slab walkout basement has 4" gravel, 2" sand, and vapor barrier under the slab.

In Energy efficiency and durability | Asked By Andy Nels | Jan 21 16
1 Answer

Panasonic WhisperComfort ERV - not necessarily a "spot" ERV anymore!

Corbett Lunsford just posted the first of a series of videos on how to convert a Panasonic WhisperComfort "spot" ERV into a ducted ERV. Apparently this setup was described to him by Panasonic engineers, so it has some legitimacy behind it.


This video doesn't contain all of the details, but more videos will follow (you can subscribe and get notified), and this is such a unique modification for a uniquely affordable ERV that I thought it was worth pointing out.

In Green products and materials | Asked By Nick Welch | Jan 22 16
2 Answers

Gas boiler not staying working

I have an old natural gas boiler that I need to keep going for one more winter.

I have replaced the thermopile but the unit continues to shut off and the pilot is out after a a couple of hours. I had the unit cleaned and inspected but I have doubts about the technician. While vacuuming the dust with a small handheld vacuum he never put a bag on it and my basement was then covered in dust and the air quality was "Visible".

What do I have to do to keep it running? What pressure should the pipes be at-it seems to like to settle at 12psi even if i jack it up.

In Mechanicals | Asked By Hal Sartelle | Jan 22 16
1 Answer

Insulation: what's best?

Continuous Insulation.

So who knew continuous insulation was best along with airtightness for the last 40 years?

Bruce Brownell.

What's the best strategy today to insulate?

Read up on his strategy insulating on the exterior of the entire shell. Learn how to improve upon his ideas here, on the Web, and at Building Science.

Uninterrupted insulation beats the pants off in-stud insulation. Dana here at GBA mentions this all the time, and so does the site and their contributor that holds a PHD in related science.

In Energy efficiency and durability | Asked By AJ Builder | Jan 22 16
6 Answers

Mini-split primer - how best to operate

I just got a Mitsubishi MSZ/MUZ GE 15 unit installed. My house is in Seattle, 1-floor (rambler) 1500 SF with all doors kept open. I want to get smart on how best to operate the unit for efficiency and comfort. Normally keep house at 70 degrees in day and I understand that you don't want to set back the mini-split at night. Do I just leave it at 70 degrees?

The unit seems to be working well...I used a recent discussion on these boards to locate the unit 1 foot below the ceiling (thanks Dana Dorsett) and it looks to be working continuously and not cycling.

In Mechanicals | Asked By S K | Jan 22 16
10 Answers

What's the most efficient way to build an R-52 wall in Climate Zone 5?

Looking to build a passive-inspired net-zero home, 2,264 square feet, two stories.

What's the most cost-effective or beneficial way to get that higher R-value? Double stud - blow in, 2x8 fiberglass batt with 2-2" polyiso, ICF, etc.?

Also, what are the risks with WRB (roll on) on sheathing, 1/2" plywood, 2' on center framing? Is there a concern for movement, cracks, or air leaks, as there will be no poly on the inside?


In Energy efficiency and durability | Asked By Kris Currie | Jan 19 16
2 Answers

For a straw bale infill wall, is a box beam required if the wall extends more than 12 ft. in hight.

We are planning a post and beam straw bale home with a shed style roof. the length of the house is 53 ft. and the width is 33 ft. The roof will rise along the length of the building, starting at 13 ft. from grade and rising to 21 ft. from grade. So, The wall infill will be approx. 20 feet high at its max. height and we are planning to put a box beam at the 10 ft. height. This seems like a sound decision, yet if it is not necessary, then we may eliminate the box beam.

In Green building techniques | Asked By Gerardo Larsen | Jan 22 16
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