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Windows Upon our inspection of Boucke, one of the first things we noticed were the very thin windows and the large area they covered. Conversations with the custodial staff confirmed that the windows were very old, poorly fitting into their frames, and in need of replacement. The following shows the calculations regarding upgrading the windows of Boucke building to cut heat loss. Current Windows: Heat Loss / Season = Area / R * 24 * HDD HDD for State College = about 6000 Assuming the windows are uniform (as they appear to be): Length: 3.33 feet Height: 7 feet Area per window: 23.333 square feet Windows in the entire building: approximately 528 windows Area of windows in the entire building: 12320 square feet The R-Value for approximately 1/8 inch of glass: 0.91 * R-Value for outer air layer: about .17 Composite R-Value: 1.08
Heat loss for the Season: 12320 / 1.08 * 24 * 6000 = 1.6e9 BTUs Or roughly 1.6 Billion BTUs of heat loss, through these single paned windows alone!
How does this compare to energy efficient windows? Let’s take a look… R-Value for low e windows with 2 suspended films: 5.05 * So heat loss for the season becomes: 12320 / 5.22 * 24 * 6000 = 3.4e8 BTUs, This is a savings of roughly 1.3 billion BTUs per year! The heat loss with these windows is one fifth as much as single pane glass.
So how does this equate to money? Assuming Penn State pays about $10 for one million BTUs (a fairly low estimate), the annual savings turns out to be $13,028 per year! To calculate the payback period for upgrading all the windows, let’s assume that it costs half of one million dollars to purchase and install 528 new windows (roughly $1000 per window). At this price, it would take: 500,000 / 13028 = 38 years to repay the investment cost For a university that is almost 200 years old, that isn’t a terribly long time, but it isn’t necessarily very short either… Perhaps the best temporary solution would be to purchase coatings for the windows to increase their thermal resistance. Furthermore, caulking and securing the windows in their frames could prove to be a substantially beneficial change.
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