Monitoring of the building envelope of a heritage house: a case study

The paper describes the long-term monitoring of the hygrothermal performanc e of the building envelope of a heritage house located in Ottawa. The house , once the residence of two of Canada's Prime Ministers, now serves as a mu seum. To preserve the historical artifacts within the building, the specifi ed temperature and relative humidity (RH) for the indoor air are 21 degrees C and 35% to 50%, respectively. As the house must also be preserved, there was concern about the effect of the high indoor RH (moisture) on the durab ility of the building structure. The main objective of the monitoring was t o assess the effect of the conditioned air on the building envelope. Select ed wall sections and a window were continuously monitored from March 1995 t o August 1996. The monitoring included indoor and outdoor conditions and th e attic environment. Temperature, RH, surface wetting-drying cycles (from p recipitation or condensation), and air-pressure differential were monitored . This paper describes the monitoring approach and results. The results ind icated that the brick walls are unlikely to experience internal condensatio n problems as long as they are subjected to a negative air pressure differe nce. However, because the building is quite leaky, the negative pressure in troduced too much cold dry air from the exterior. It caused localized cold spots with condensation and ice formation on interior of walls and ceiling. Negative air pressure differences are not a solution unless the leakage pa ths are reduced. Crown copyright (C) 1999 Published by Elsevier Science S.A . All rights reserved.