Understanding storage environmental stability during power outages: A key issue in sub-tropical climates

A functional test was conducted at The Government Records Service (GRS) of Hong Kong in the archival repositories in order to understand the performance of its building envelope in terms of hygrothermal stability and air-tightness. Before the test, 12 climatic data sensors in the target repositories and an external sensor on the roof of the building were installed. The testing procedures started with halting the air conditioning system for three days in August 2012, with typical external ambient conditions of 28.6° C temperature and 81.0% RH in average, to simulate the effect of a power outage. A first-order plus time delay model was employed to approximate the response of the interior temperature and RH at power outage. This model is essentially an exponential growth curve with extra parameters to account for the delayed response. It can be concluded that a back-up electricity source is not necessary, since power suspension for more than 12 hours has been extremely rare in Hong Kong. Given the present degree of air-tightness and the extent of insulation in all the repositories in HKPRB, the best strategy to mitigate the risk of power outage is to keep all repository doors shut at all times.