Airtightness testing of very large buildings: a case study

Abstract

The airtightness of a building envelope impacts upon uncontrolled air leakage, associated ventilation energy losses and occupant thermal comfort. The scale of these problems in large buildings would be expected to increase in relation to the potential size of possible leakage areas. Recent changes to UK Building Regulations have required new, large, nondomestic buildings (/ 1000 m2 floor area) to meet a specified standard of airtightness. A building’s airtightness is conventionally assessed using a steady state fan pressurization technique. There was some discussion in the airtightness testing industry that the upper practical limit of large buildings capable of being tested might be around 5000 m2 due to technical issues relating to fan size, power requirements, transportation and noise. The feasibility of testing very large buildings (over 5000 m2) with a steady state fan technique has been questioned. This paper demonstrates that such testing is feasible by describing the development, calibration and application of a 2 m diameter fan pressurisation system. The fan was tested on the largest building in the world (floor area 57 440 m2) ever to have its airtightness determined by steady state fan pressurization. Practical Application: The changes to Building Regualtions Part L2 that came into effect on 1st April 2002 raised the profile of the pressure testing of large buildings for airtightness. There were doubts raised concerning the feasibility of pressure testing very large buildings but the paper demonstrates that it is technically and practically possible.