Exploring retrofit alternatives for State Houses in Southern New Zealand: an intensive monitoring process

The previous findings of an energy efficiency retrofit programme of state houses in southern New Zealand regions indicated that low internal temperatures occurred during the winter months and that it was difficult to reach minimum levels of indoor comfort. Houses were found to be 0.4oC warmer (annual average increase) after a ceiling/underfloor insulation upgrade with 0.6 oC increase recorded in winter months when corrected for energy consumption and weather conditions. A small reduction in energy consumption was also found. The findings were quite surprising as the upgrade program had the goal of making houses warmer by reducing heat loss through improved thermal insulation in the houses. Householders provided very little heating to living areas and even less to bedrooms. Indoor temperatures were found to be very low and did not come close to the WHO recommendations. The present paper investigates alternatives to provide a higher level of thermal comfort. To this end two houses were "borrowed" from the Housing New Zealand Corporation (HNZC) in order to undertake intensive monitoring after a range of improvements were made to the building envelope. The houses were unoccupied and tested during the winter of 2006. The original lumped thermal resistance of the houses was identified by investigating a steady state analysis; undertaken during the night when there were no solar gains and using electric resistive heating to provide a temperature differential between indoors and ambient. The houses were then upgraded at different levels (including different options for wall insulation and double glazing) and each of the upgrades were retested to obtain new lumped resistance levels. Air infiltration was also being tested after each upgrade to identify any reduction in heat losses due to air ingress. Results presented in this paper are preliminary results only as testing is not yet completed. The upgrade process will next be modelled using a dynamic computer program (Virtual Environment). This model will allow predictions to be made for the house with different heating schedules and systems, modifications, and internal gains.