We know, we know. There’s a lot right with this picture, such as the gorgeous view of Lake Tahoe in the background and the awesome powder for skiing. But from a whole-house-as-a-system perspective, what’s wrong with this picture? What is the owner trying to do, and what would be a better solution?

Thanks to our own Larry Zarker, BPI CEO, for sending in this dandy shot. He offers the following Winston Churchill quote to explain what’s going on here: “You can always trust the Americans to get it right, after they have exhausted every other possibility”.

 

Think you know what the problem is, as well as the solution? Send it to us at lmcdowell@bpi.org.

Tags: April, Building, Chump, Newsletter, Performance, Stump

Views: 175

Replies to This Discussion

Congratulations to Craig Bird of Preston Insulation in Tucson, Arizona for winning last month’s “What’s wrong with this picture?”contest. Craig was not only the first person to send in the correct answer. His answer was far and away the most comprehensive, and dare we say, the most elegant in illustrating what in the world of home performance was wrong with the picture, and what should be done about it.

The picture shows a snow-bound house in front of Lake Tahoe, its roof zig zagged with heat strips.  Says Craig:

“The problem is ice dams.  The home most likely had melting of roof snow which then refroze and created ice dams possibly causing water damage or excessive ice buildup at roof edges. This caused the homeowner to install energy intensive heat strips to melt the ice dams and jack their electric bill through the roof during snow events.  

 

This is caused by:

1)     Air leakage from penetrations near exterior wall

2)     Heat sources close to exterior wall such as heating ducts or recessed lighting cans

3)     Insulation in contact with roof sheathing causing thermal bridging to roof deck

4)     Lack of soffit ventilation

 

The solution:

1)     Air seal exterior top plate with spray foam. It is also important to air seal any other penetration which is delivering heat to the underside of the roof deck.

2)     If recessed lighting is installed near exterior walls, the cans should be ICAT rated to prevent air flow through the fixture. An inexpensive air tight trim kit may also be purchased to avoid changing out fixture itself. Heating duct boots can be sprayed with 2 part foam to prevent heating of roof deck.

3)     Install soffit ventilation at code recommended level at EVERY BAY that is affected.

4)     Install insulation baffles at all soffit edges in order to provide a path for ventilation and carry away any remaining heat transferred from house and cool roof deck. This also prevents insulation from contacting the roof deck (causing thermal bridging).

 

Since it is often difficult to get full insulation amounts at the soffit edge due to clearance, an optimal solution would involve installing ventilation baffles and using spray foam insulation against the baffle and as far in until a full amount of blown insulation may be used. This solution also seals any air exfiltration through the wall top plate at the same time. 

RSS

Videos

  • Add Videos
  • View All

Twitter

Latest Activity

Carrie Sturrock updated an event
Thumbnail

Making an Old Home More Livable: Where to Start and When to Ask for Help at Webinar

September 15, 2016 from 11am to 12pm
Making an Old Home More Livable: Where to Start and When to Ask for HelpUpgrading and weatherizing…See More
4 hours ago
Profile IconTommy Spain and Carl Johnson joined Home Energy Pros
4 hours ago
Kit Yturralde posted a blog post

Crawl Space Dehumidifiers Vs. Portable Dehumidifiers

If you start looking at the prices of crawl space dehumidifiers compared to portable dehumidifiers,…See More
9 hours ago
Profile IconBarbara Smith and Carl Johnson joined Tom White's group
Thumbnail

Weatherization

Share your concerns and successes as a weatherization professional, or information for this…See More
yesterday
Carl Johnson replied to Joel Greenberg's discussion The Truth About Windows? in the group Weatherization
"I think the appeal of replacing windows is largely on the aesthetics for most homeowners. Nobody…"
yesterday
Carl Johnson commented on Amber Vignieri's blog post Chicago Winter No Match for Retrofitted Logan Square Building
"Beautiful home! Did Josh replace the windows as well or no? Living in Chicago myself, I know about…"
yesterday
Carl Johnson commented on Diane Jackson's blog post Two Addison Projects Win Housing Innovation Awards
"These homes look great! Congrats!"
yesterday
Paul Scheckel posted a blog post

Renewable Rant: Traditional Energy!

Why, when I open up a newsletter or market evaluation report about “traditional energy” markets, do…See More
Monday

© 2016   Created by Lawrence Berkeley National Laboratory.   Powered by

Badges  |  Report an Issue  |  Terms of Service