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: 360

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

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.

Latest Activity

Jim Gunshinan posted blog posts
7 hours ago
H.O. Electric posted a photo

about us-team

H.O. Services is your residential Electric-Plumbing-Heating-Cooling Specialist. We are an…
7 hours ago
H.O. Electric added a discussion to the group News & Announcements
Thumbnail

Stay Cool With Easy To Install Ductless AC System!

Stay Cool With Easy To Install Ductless AC System!   Save $300.00 Off A New AC System For A Limited…See More
7 hours ago
Richard Wells commented on Diane Chojnowski's group Facebook Pages
"Three thousand home energy efficiency audits, and nearly a thousand retrofits in four short…"
8 hours ago
Richard Wells joined Diane Chojnowski's group
Thumbnail

Facebook Pages

Does your company or organization have a Facebook Page?This group is for pros who have facebook…See More
8 hours ago
David Baerg replied to Blake Shurtz's discussion Air sealing wood-burning fireplace from the crawlspace below
"Hi Blake, Do you mean around the underside of the hearth?  Are you trying to seal between the…"
9 hours ago
Tom White's video was featured

Rebirth Realty: Restoring Detroit properties for Venture for America Fellows

Its been a long, cold winter, but we've made significant progress in the restoration of 760 Virginia Park. Join Tim Dingman on a walkthrough to see what we've done.
10 hours ago
Kim Tanner added a discussion to the group Multifamily Buildings
Thumbnail

Blower Door Applications Guide

TEC and Camroden Associates have released their big building testing manual, Blower Door…See More
10 hours ago
Profile Iconmichael coleman, Dan Liska and Rob Moreno joined Home Energy Pros
11 hours ago
Christopher Morin's blog post was featured

5 Things New Energy Efficiency HVAC Contractors Need to Know

1. Do not sell on Price! Use 'Simple Payback'The price of High-efficient equipment will undoubtedly…See More
yesterday
Jim Gunshinan's blog post was featured
yesterday
Kim Tanner commented on Diane Chojnowski's group Home Energy Pros on Twitter
"Follow The Energy Conservatory on Twitter! We'll follow…"
yesterday

© 2014   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service