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: 397

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

Photos

Loading…
  • Add Photos
  • View All

Latest Activity

Anthony Adams posted a status
"Trying to figure heat load for HVAC on bonus room over a garage. Lots of wall space exposed to arttic."
34 minutes ago
Profile IconTirso De Ubago, Hamed Ghanbari, Bob Eldredge and 1 more joined Home Energy Pros
8 hours ago
Hamed Ghanbari replied to Brian's discussion Everything you need to become a energy auditor for sale in the group Energy Auditing Equipment for Sale, Trade or to Purchase
"Hello, I am interested to buy a Minneapolis Blower Door DG700. How much is your unit? Thanks. "
12 hours ago
Hamed Ghanbari 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
12 hours ago
Colin Genge updated an event
Thumbnail

Measuring HVAC Performance webinar at Online

February 23, 2016 from 11am to 12pm
If you install, service or test HVAC systems you will want be there for this special webinar.…See More
15 hours ago
Colin Genge updated an event
Thumbnail

Testing for IECC Code Compliance for duct and house leakage webinar at Online

February 16, 2016 from 11am to 12pm
The International Energy Conservation Code (IECC) is in use or adopted in 47 states, the District…See More
15 hours ago
Jan Green posted a status
"I'm honored to be selected to speak at the 2016 RESNET Conference right here in sunny Scottsdale 2/29-3/2/16 with SRP & others!"
17 hours ago
Joe Konopacki posted an event

Duct & Envelope Tightness (DET) Verifier at Temperature Equipment Corporation

February 26, 2016 from 8:30am to 4:30pm
The Duct & Envelope Tightness Certification (DET) was designed by the Midwest Home Performance…See More
17 hours ago

© 2016   Created by Lawrence Berkeley National Laboratory.   Powered by

Badges  |  Report an Issue  |  Terms of Service