Comparison of Calculated and Measured Air Conditioning Design LoadsFor Alternative Glazing Options in Production Homes in California

摘要

In the spring of 2000 two identical new homes were purchased from a local productionbuilder in a bedroom community near Sacramento California. Both homes came equipped withclear double glass. After a series of careful measurements to ensure the houses were reallyidentical, all the glass in one home was replaced with high performance, low solar gain, lowemmissivity (LSLE) glass. During July of 2001, the air conditioning system in the house withLSLE was downsized by one ton (3.5 kW) to demonstrate the real cooling load savings from theglass. The two unoccupied homes were kept comfortable and monitored with extensive hourlydata for over a year to document the energy and peak demand savings from the high efficiencyglass. The house with LSLE glazing and reduced air conditioning capacity met the cooling loadand saved 25% of the cooling kWh and over one third of the air conditioning system peakdemand (1.8 kW less) compared to the house with clear double glazing Air conditioning sizingcalculations were performed for the houses using a alternative versions of the industry standardsizing approach. Actual design loads were inferred from the capacity and operation of theinstalled air conditioners and compared with the calculated loads. This analysis shows that thecurrent ANSI Standard sizing approach overestimates the sensible loads by 18% to 25% and thesavings from LSLE glass by 38%, but other versions give acceptable results.