Real Energy Saving Case 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. Mostly this is restaurant architecture but in this case the client was a bank. 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 these results compelling.

I had the chance to build 2 nearly identical banks in the Chicago area. These were retail branch banks about 4,100 square feet each. The first bank was in Deerfield IL and was built with good quality commercial construction. The building had a steel frame infilled with 6 inch metal studs, filled with 6 inch fiberglass insulation for the walls, the roof was metal deck and bar-joist with 3 inches of insulation board. The other bank was built about 20 miles away in Wheaton IL so it experienced the same weather. We only changed 3 elements, the buildings were other wise identical. One, we used different wall insulation we changed from fiberglass batt insulation to foamed in place low density polyurethane insulation the insulation value changed from R-18 to R-20, the real difference is the air infiltration into the building. The foamed in place insulation expands and sticks to everything sealing the walls tight. Two, the roof insulation was doubled to 6 inches thick, changing the insulation value from R-18 to R-36. Third, we changed the windows from 1 inch clear low-e sealed glass units to tinted low-e 1 inch sealed glass units. Each of theses changes was bid as an additive alternate so we have hard number of what these things cost and not just 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. Next I tracked the energy consumption for a year and put together a comparison chart to see if it was money well spent. I think the results are very compelling but you can judge for yourself. Gas consumption was cut by 62% and electrical consumption was cut by 25% that is a saving $5,090 in the first year. On a monthly basis that work out to $424.

People always ask the wrong question when it comes to energy conservation. They ask how long is the payback. The answer is about 3 years and 7 months. The question people should ask is how does this affect cash flow, and that answers in $283 per month for the first 20 years and then it increases to $4242 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. So you take the energy savings and subtract the cost of the money, that’s $424 minus %141 for a positive savings of $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. I have now made each of these items standard in my projects and with this data I have no trouble convincing clients 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.

Burt Andrews is an Architect with over 20 years of experience in designing restaurants and retail stores. You can read more of his restaurant ideas at his blog about restaurant architecture archisaur.us. He is a principal at Larson and Darby Group in charge of the St. Charles, IL office.