Environmental Engineering Reference
In-Depth Information
include the sprayed in-place formulations where liquid reactants generate
the foam in situ . All insulation plays a very important role in conserving
energy usedtoheat/coolhomes. In theUnited States, space heating/cooling
is the second largest use of fossil fuel energy accounting for 19% of the
total energy usage. Efficient low-cost insulation of buildings results in
considerable savings in fossil fuel resources and therefore, also avoided
GHG emissions.
Heat losses in residential buildings occur primarily via convection from
the roof (~25-35%) followed by air leakage and walls (~15-25% each).
Adequate insulation in roof and exterior walls is therefore a significant
energy-saving investment. Table 5.7 compares thermal conductivity and
environmental merits of different insulation materials (Dewick and Miozzo,
2002).Theinsulationefficiencyistypicallymeasuredin R values(thehigher
the value, the better the insulation). Values of R ~ 4-5 for PU and extruded
polystyrene foams are higher than that for glass wool or wood ( R ~ 3.0-3.5)
as well as for plate glass ( R ~ 0.2).
 
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