BPI's April Stump the Chump: What’s Wrong with this Picture?

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, Chump, Stump, building, newsletter, performance, the

Views: 428

Reply to This

Replies to This Discussion

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 remaing 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. 

 

 

Oh, and most likely, this is the north facing roof your looking at, unless you have tons of winter shade on the southern exposure.

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

Latest Activity

Barbara Smith posted videos
9 hours ago
CharlieK posted a discussion

Eco-Cottage Program Applauded By Housing Groups, Suppliers & Lenders

AmeriSus a leading player in the eco-kit home business kicked off a new program on MLK-day which…See More
13 hours ago
Diane Chojnowski posted a discussion

Call for Nominations: Tony Woods Award and Building Performance Hall of Fame

The Building Performance Institute, Inc. (BPI) is seeking nominations for the 2017 Tony Woods Award…See More
14 hours ago
Diane Chojnowski added a discussion to the group 1000 Home Challenge
Thumbnail

January Webinar: Intro to the 1000 Home Challenge

The January Intro to the 1000 Home Challenge webinar will be  Friday, Jan 20 at 10-11:30 AM eastern…See More
14 hours ago
Diane Chojnowski's event was featured
Thumbnail

Introduction to the 1000 Home Challenge Webinar at Eastern Time

January 20, 2017 from 10am to 11:30am
The January Intro to the 1000 Home Challenge webinar will be  Friday, Jan 20 at 10-11:30 AM eastern…See More
14 hours ago
Diane Chojnowski posted an event
Thumbnail

Introduction to the 1000 Home Challenge Webinar at Eastern Time

January 20, 2017 from 10am to 11:30am
The January Intro to the 1000 Home Challenge webinar will be  Friday, Jan 20 at 10-11:30 AM eastern…See More
14 hours ago
Barbara Smith's video was featured

NY State Weatherization Story

The Weatherization Assistance Program (WAP) is an energy efficiency and conservation program administered by the New York State Homes and Community Renewal (...
14 hours ago
Quinn Korzeniecki added a discussion to the group Building Performance Institute (BPI)
Thumbnail

Call for Nominations: Tony Woods Award and Building Performance Hall of Fame

The Building Performance Institute, Inc. (BPI) is seeking nominations for the 2017 Tony Woods Award…See More
15 hours ago

Home Energy Pros

Welcome to Home Energy Pros – the unique digital community by and for those who work in the home energy performance arena.

Home Energy Pros was founded by the developers of Home Energy Saver Pro (supported 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. Please honor our Guidelines

© 2017   Created by Lawrence Berkeley National Laboratory.   Powered by

Badges  |  Report an Issue  |  Terms of Service