Let's Play Stump the Chump!

August 29, 2013

Send in your stumpers!
You know—that problem house, symptom or combination of symptoms that confounded the homeowner and challenged all your building science savvy to solve. Send BPI a description of the problem—and the solution, which will be kept secret. If it's a genuine stumper, it may be published in the next HVAC2HP e-newsletter. Send stumpers to mkandel@bpi.org.

This stumper is reprinted with permission from BPI. 

Answer to Last Month's Stumper:

Joel Key, General Manager of Healthy Home Diagnostics, was quick on the draw for last month’s game. Readers will recall the problem was with a newly built house that didn't pass the building airflow standard. The blower door test revealed that the band joist area between the first and second floors, which by rights should have been inside the house, was directly connected to the outdoors. Joel’s answer: “My thoughts would be that the heated garage is below a vented attic and the plywood sheathing, while going below the insulation, is not extending all the way to the bottom of the band joist and or blocking was not added to each joist bay. Air was being pulled in thru the attic vents (eve, soffit, ridge, etc) through the insulation and gap under the sheathing right into the interstitial space between the floors.”

Thanks also to Macon Parker of Charlotte, NC, who sent us his solution to the problem: “Install a pressure boundary (with plywood or rigid foam) and air seal with spray foam. Additionally we have found that the insulation beneath the floor is often falling down and inadequate and we have dense packed this area with cellulose to act as a partial barrier, as it is often very cost prohibitive to remove drywall, air seal the band joist and install adequate supports for the insulation in the floor above the garage.”

This Month's Stumper:

Thanks to Thomas McAteer, an Auditor Supervisor with CMC Energy Services in Fort Washington, PA, for submitting this month’s head scratcher!

Thomas drew his inspiration for this stumper from baseload usage analysis and client education, two things he believes are commonly overlooked components of a comprehensive energy audit.

Thomas recalls a job in which a man and his wife had requested that CMC Energy perform an energy audit on their home. Thomas sent one of his Energy Analysts to perform the audit. The couple lived in a 1,200 sq ft, single story residential home, which was originally built in 1955, and had a baseload of 1830KwH.

The analyst surveyed the entire home. It was heated by a 2002 FHA natural gas furnace, and relies on a 2006 electric water heater without a timer. The home has a 115v, 12 AMP deep well pump that provides water. He notes that the range and dryer, which aren’t frequently used, are electric. The analyst examined the utility data to determine the above baseload, seasonal increase and monthly average usage, and documented all electric devices and appliances, including a 2006 21 cu ft top-freezer refrigerator. He paired this data with a thorough customer interview to create complete usage estimates. But he noticed a problem when, after taking every appliance and number of occupants into account, he was still approximately 1000 KwH over the actual baseload. He was stumped.

What could be causing this mysterious increase in non-seasonal usage?

Think you know what the problem is, as well as the solution? Send it to mkandel@bpi.org.

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