subject: An Energy Saving Study [print this page] An Energy Saving Study An Energy Saving Study
Architectural roll-out work is one of my specalities. In case you don't know what that means, it is when a client needs a lot of the same buildings all over the county. This work is mostly for restaurant architecture but this case study is about 2 banks. One of the most interesting things about this type of work is when I get to do experiments, making variations in the building and comparing the results. This is the story of one of those experiments. I think you will find the results interesting.
It all started when I was designing a lot of banks in the Chicago area. The buildings in question were about 4,100 square foot retail branch banks. The first one was located in Deerfield, IL and was a good quality commercial building that met all energy codes. Steel frame structure, 6 inch metal studs, brick veneer and 6 inch fiberglass batt insulation in the walls, the roof is bar-joist, metal deck and 3 inches of rigid insulation. The second bank was in Wheaton IL about 20 miles away, so both building get the same weather. We only changed 3 elements, the buildings were other wise identical. One, the wall insulation was changed to foamed in place low density polyurethane, this changed the wall insulation value from about R-18 to about R-20 but the air infiltration into the building drops to almost nothing with the foam because it expands and sticks to everything. Two, the roof insulation was doubled to 6 inches thick, changing the insulation value from R-18 to R-36. Third, the glazing was changed from 1 inch sealed glass units with clear low-e glass to 1 inch sealed glass units with tinted low-e glass. Each item was bid as an additive alternate so we could obtain hard numbers for what each item cost and not just rely on estimates. The foamed in place wall insulation cost an additional $9,150, the roof insulation cost an additional $5,300 and the tinted glass cost an additional $3,800, for a grand total of $18,250 or put another way that is $4..45 a square foot. To complete the experiment I tracked the energy usage for a year and put together a comparison chart to ensure it was money well spent. You can judge for yourself, but I think the results are stunning. Gas consumption was cut by 62% and electrical consumption was cut by 25% that is a saving $5,090 in the first year. That is $424 a month every month.
Now for some reason people always ask about pay back on energy savings, that is the wrong question, but the answer is about 3 years 7 months. The correct question is what is the affect on cash flow, and the answer is $283 per month for 20 years then it jumps to $424 per month. This is the correct question because building are financed and not bought for cash, the original $18,205 borrowed at 7% for 20 years cost $141 per month. $424 in savings take away $141 in dept payment is positive $283 a month. For this calculation I use $0.09 a kilowatt-hour and $1.00 a therm, both prices have fluctuated above and below these averages but I don't think it affects the out come on the experiment. Each of these three items thicker roof insulation, tinted glass and foam insulation are now standard for my buildings and with this hard date clients are easily convinced it is money well spent. One last thing the client released me to share this information but not the bank name. I hope you understand.
