{HEAD ~ The U Factor} measures the rate of heat transfer or loss through {TAIL ~ a window} as laid down by the National Fenestration Rating Council 
{ HEAD ~ The U Factor } measures the rate of heat transfer or loss through { TAIL ~ a window } as laid down by the National Fenestration Rating Council
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH