Field measurements of heating system efficiency and air leakage in energy-efficient manufactured homes.

Detailed field measurement of air leakage and electric forced-air heating system efficiency in nine Pacific Northwest manufactured homes built to adapted Model Conservation Standards were conducted during the 1994 and 1995 heating seasons. The research measured directly both heat delivery efficiency and system efficiency (as defined by ASHRAE in its HVAC Systems and Equipment Handbook) with a short-term alternating coheat test. For this test, a home is alternately heated with the furnace and then with an array of small electric heaters placed in each room which has a supply register. The test switches between these two metl1ods every two hours, recording temperature and energy usage data every ten seconds. An automated control algorithm controls the furnace and coheaters to keep tl1e home at essentially the same temperature during the eight hour test. A blower door test and duct tightness test are also performed, as are a tracer decay test (to measure effective ventilation rates with the air handler on and off) and other measurements. The homes performed better than contemporary site-built homes (24 of which were tested with the same protocol during 1991-1993), but system efficiency losses were still substantial, on the order of 20% of the annual heating load.