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11 Answers
Sizing a Heat Recovery Ventilator (HRV)...can it be too big?

> My new house with in-floor radiant and basement is approximately 28,000 cubic feet. I calculated a 200 cfm HRV unit:

cubic ft of house = 28,000

28,000 x .85 (to account for interior walls and furniture) = 23,800

23,800 x .5 (air change rate) = 11,900

11,900/60 (to convert air changes per hour to cfm) = 198.33

> My HVAC guy recommends a 300 cfm unit and is not concerned with oversizing the unit as much as undersizing it (he's used to installing 2,000 CFM heat pump systems in a house my size).

Is there a problem with OVERSIZING a HRV?

In General questions | Asked By Frank | May 6 10
7 Answers
"Mooney wall " for greater insulation value

Has anyone had an experience using a "Mooney wall" in either new or retrofit application? I came across this webpage and found it to be interesting, but wanted to ask the experts here for further discussion of the merits of such an application.

http://www.builditsolar.com/Projects/Conservation/MooneyWall/MooneyWall.htm

In Energy efficiency and durability | Asked By JR | May 5 10
7 Answers
Attic space insulation

I have friends who are renovating their 600 SF condo. They are on the top floor of a 4-story multi-unit residential building. The building is brick and completely uninsulated. I think it was built in the 1920's.

There is a 3-1/2 foot cavity between their ceiling and the underside of the flat roof. On the side of the building within that "attic" space there are a few vents for free flowing air circulation. That "attic" space is contiguous above all the other condos. They asked me if they should insulate above their space.

My concerns are:

In Green building techniques | Asked By David Pill | May 5 10
8 Answers
What's the best thickness for polyiso roof insulation?
Construction detail.jpg

I am working on a pool house design and have questions for roof insulation. Please see the attached drawing. Please see where Polyisocyanurate is indicated.
1. Are the locations of the rigid insulation correct?

In Energy efficiency and durability | Asked By Akino Sakaoka | May 4 10
3 Answers
In a warm climate, what are the advantages and disadvantages of spray foam versus radiant barrier in attics?

What works best and why?

In Energy efficiency and durability | Asked By Brad Alexander | May 6 10
3 Answers
Stone and Timberframe Renovation

I am looking at a 1,200 square foot one story renovation of a 150 year old stone rubble building with timberframe roof in Western Massachusetts - climate zone 5.

Exterior stone bearing walls are 1'-8" thick with direct applied plaster interior. The exposed timbers are built like a truss with planking spanning four feet with very small (5" wide) slate roofing applied directly to the planking.

In Energy efficiency and durability | Asked By Jon Wyman | May 5 10
8 Answers
I have a problem with peeling paint on a 1920 house in Nashville, Tenn.

The house was gutted and remodeled 2 years ago. the wall construction is 2x4 studs, 5/8 drywall, no vapor barrier, 1/2 x 6 beveled spruce siding applied directly to the studs- no sheathing, no building paper, no housewrap. The stud cavities are filled with open cell foam applied directly to the siding. The paint job was poorly done with reports of the paint being applied without primer over siding that had been previously stained(age and condition unknown),and also reports of drywall mud being used to patch and skimcoat areas.

In Energy efficiency and durability | Asked By tom kibby | Apr 30 10
0 Answers
Concerns about installing a condensing modulating boiler with an indirect hot water tank in a turn-of-the-century house

First, I want to check if there are any red flags about installing a condensing modulating boiler w/ indirect hot water in an old home with cast iron radiators in Minneapolis. I need to add an additional zone for a previously unconditioned space with plumbing. There I am planning to add a single wall hung radiant panel. My understanding is the cast iron radiators typically operate with water temps at 180 degrees F, the wall hung radiant panel at 150 degrees F, and the hot water will be heated just above 120 degrees F.

In Mechanicals | Asked By j chesnut | May 5 10
2 Answers
Passivhaus Translations

I thought I would start another thread specific to the discussion of translating Passivhaus documents.

I really like these educational panels(posters)
http://www.passivhausausstellung.de/#download
Is there an English version?

In PassivHaus | Asked By John Brooks | May 5 10
1 Answer
Are 16" o.c. eave chutes (a.k.a. baffles, Proper Vents) still made?

I'll be installing chutes, followed by 2-part foam at the perimeter. I'd rather get full-width chutes between the rafters rather than breaking the perforated 24" o.c. ones in half.

We bought a 1938 single story home. I plan on documenting the energy retrofits. (Maybe even create a blog?) We've already had a "Home Performance with ENERGY STAR" inspection done. First project is to remedy the ice damming. Would using layers of Thermax at the edge, then foaming that into place get a higher R-value above the top plate than only foam?

In Energy efficiency and durability | Asked By Jon Beers | May 4 10
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