The force is used to determine the density of the insulation, which, in turn, is used to determine the thermal resistance or {HEAD ~ R value} of {TAIL ~ the insulation} 
of
The force is used to determine the density of the insulation , which , in turn , is used to determine the thermal resistance or { HEAD ~ R value } of { TAIL ~ the insulation }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL