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Building Science

Performing an Energy Assessment: A Case Study

This often-free service is invaluable when it comes to rooting out sources of extraneous energy usage

This is my first time in this home, and it’s my first time meeting the people who own it. However, I know a little about them. I have two years’ worth of electricity-usage data that tells me they use a lot of power—especially in the winter. Granted, we live in Minnesota, and it requires a lot of energy to keep warm during the long winters but this home uses far more than most.

I’m conducting this energy assessment in late 2019. Visiting at this time of year ensures my best guess as to what I am seeing  and helps me tease out the reasons why electricity usage and/or heating fuel costs are exceeding a homeowner’s expectations. This assessment is a free service offered by the electricity provider serving this home.

When I arrive, I’m met with a common question, “Where do we begin?” I tell the owners of this large, McMansion-style home built in 2010 that I will be asking several questions. My aim is to learn all I can about how the house was built, what equipment is operating in and around the home, and how the homeowners occupy it—meaning their habits. All of the questions I ask are targeted at figuring out why they use up to 10 times the electricity of a more efficient home.

Right off the bat, I learn they have two geothermal heating systems, one supplying forced-air heating and air conditioning to the two main levels, plus a second hydronic unit heating the basement floor and garage—a clue! I also find out the house has six bedrooms, a total of 5200 sq. ft., and five occupants. A quick estimation of three finished floors with tall ceilings tells me the house is in the neighborhood of 40,000 cu. ft. That’s a…

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  1. user-723121 | | #1

    Spending up to 1k per month on electricity, it defies logic as to why they did not hire you for a complete evaluation. Superinsulation would have payed for itself by now with this home. You did a nice breakdown of the energy use and ways to save, hopefully they will follow your advice.

    1. Randy_Williams | | #3

      Thanks Doug, unfortunately I almost never hear what the homeowner decides to do. I wish more people would pay for the optional blower door test, for a couple hundred dollars more we learn a lot more about the home.

  2. bob_swinburne | | #2

    Hey! This is a really good article that I can refer clients to at the start of a project. The next step might be a blower door test which is easy to come by in Vermont thanks to Efficiency Vermont. Thanks.

    1. Randy_Williams | | #4

      Thanks Robert. I had to check out Efficiency Vermont, looks like a great program.

      1. Expert Member
        PETER G ENGLE PE | | #5

        I'm just finishing up a weatherization project for a condominium complex in VT. The folks at Efficiency Vermont were great. Very helpful, and the rebates really helped sell the owners on weatherization. With just a few targeted insulation and air sealing upgrades (primarily attics and crawl space rim joists), we're seeing 30%-50% air leakage reductions. Great program.

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