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: 160

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

Home Energy Pros

Home Energy Pros was founded by the developers of Home Energy Saver Pro (sponsored by the U.S. Department of Energy,) and brought to you in partnership with Home Energy magazine.  Home Energy Pros is sponsored by the Better Buildings Residential Network.

Latest Activity

w d posted a discussion

AERC testing and Solar Grates update

AERC of WCMA has been created to test the effectiveness of window attachments and to design an…See More
49 minutes ago
Profile IconRob Pender, Sheldon White and jerrycarter joined Home Energy Pros
1 hour ago
Morgan M Audetat commented on Tom White's blog post Embodied Energy: Minimizing Waste with Off-Site Construction
"What is new…"
1 hour ago
Mark posted events
4 hours ago
Jim Gunshinan's video was featured

GoGreen Portland 2014: The Myth of Apathy - Renee Lertzman, Ph.D

http://portland.gogreenconference.net Renee Lertzman, PhD is the Director of Insight for Brand Cool, a marketing agency supporting a sustainable world. An internationally recognized researcher, speaker, author, instructor and thought leader in…
4 hours ago
Jim Gunshinan posted a video

GoGreen Portland 2014: The Myth of Apathy - Renee Lertzman, Ph.D

http://portland.gogreenconference.net Renee Lertzman, PhD is the Director of Insight for Brand Cool, a marketing agency supporting a sustainable world. An internationally recognized researcher, speaker, author, instructor and thought leader in…
4 hours ago
Stacy Hunt posted blog posts
5 hours ago
Colin Genge posted an event

Air Leakage Testing for Home Inspectors at Online

July 7, 2015 from 1pm to 2pm
• What sort of effect will IECC adoption have on the building industry? Home owners? Inspectors? •…See More
7 hours ago

© 2015   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service