subject: Real Energy Saving Case Study [print this page] Architectural roll-out work is one of my specalities. You know a client needs a whole lot of the same building all over the place. 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. 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. It was built identically with 3 changes. 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, we doubled the roof insulation from 3 inches to 6 inches, increasing 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 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. 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. I think the results are very compelling but you can judge for yourself. Electrical consumption was cut by 25% and gas consumption was cut by 62% saving $5,090 in the first year. That is $424 a month every month.
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. What, I am talking about is the fact that buildings are financed so $18,250 is borrowed and then paid back from cash flow, at 7% that is $141 a month for 20 years. $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. 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 more thing the client allowed me to share this data but not their name. I hope you understand.
