3064 -- Effects of Radiant Heat Exchange and Mean Radiant Temperature on Predicted Heating Energy Savings PDF

For energy conservation measures, savings prediction typically involves calculation of a relatively small difference between two large numbers; e.g., building heating loads with and without the measure. Therefore, effects that are of small significance in building load calculations may warrant use of correction factors in savings calculations. In this study, two such effects have been investigated. First, radiant heat exchange between room surfaces depends on envelope U-values and is not adequately described by combined radiative/convective heat-transfer coefficients. Second, retrofits tend to increase mean radiant temperature, thus allowing lower thermostat settings and increased energy savings while maintaining equivalent thermal comfort. Correction factors have been developed to account for these effects in heating load calculations and in savings calculations. The adjustments for radiant heat exchange reduce heating loads and savings while the adjustments for mean radiant temperature increase heating loads and savings. Hence, the two effects tend to cancel. The adjustments are larger for savings calculations than for load calculations and are most significant for poorly insulated buildings.

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