Matching Pairs Air Distribution Systems - section 3Online version NCCER Air Distribution Systems - section 3 trade terms by Valerie Jimenez 1 Radial system 2 R-value 3 Perimeter-loop system 4 Reducing-Trunk duct system 5 Extended-Plenum duct system Provides the best performance when properly sized, the pressure drop is maintained from one end to the other due to decrease in trunk size. Uses round or rectangular trunks for the main supply and return, the ducts remain the same size and can be installed in a crawl space or attic. Used in structures built on concrete slabs, it has a continuous duct embedded in the slab. A number that is used to indicate the ability of insulation to resist the flow of heat. The higher the R-value the better the insulating ability. Each perimeter outlet is fed directly from the supply air plenum. The duct work can be installed in a concrete slab, crawl space or attic.
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