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