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

Malcolm Jackson joined allen p tanner's group
Thumbnail

Energy Auditing Equipment for Sale, Trade or to Purchase

Discuss the pros and cons of the equipment you are interested in prior to purchase. Post equipment…See More
1 hour ago
Amber Vignieri liked tedkidd's discussion What if more efficient homes were actually worth more?
4 hours ago
Amber Vignieri posted a blog post
5 hours ago
Eric Kjelshus replied to Rob Madden, Solar Home Broker's discussion Indoor Air Quality Monitors and Meters
"I have been using air advice for 5 yr or so - I end up with a report in 35 min I can e-mail or show…"
7 hours ago
Profile IconBill Gartner, Shane Matteson, Jay Cooper and 1 more joined Home Energy Pros
8 hours ago
Kim Burnett commented on Diane Chojnowski's group Home Energy Pros on Twitter
"Good morning, would you please add me. Thank you. Kim Burnett A+ Abundant Energy Experts"
yesterday
Kim Burnett joined Diane Chojnowski's group
Thumbnail

Home Energy Pros on Twitter

We've created a twitter list of members of Home Energy Pros who tweet about home performance and…See More
yesterday
Luke Langhals replied to Luis Hernandez's discussion ERV Configuration
"Very good reading. Thank you for posting this."
yesterday

© 2016   Created by Lawrence Berkeley National Laboratory.   Powered by

Badges  |  Report an Issue  |  Terms of Service