The 'Simplified Technique' is a method by which it is possible to determine approximately the infiltration and ventilation rates of large and complex buildings. The aim is to provide a reliable and easy-to-use procedure for non-specialists. This paper describes a working protocol for using this technique. Results from computer model studies are given to provide guidance on use of the technique and its potential accuracy.
A six channel, computer controlled, tracer gas detection system for the measurement of infiltration rates and air movement in large single-cell industrial buildings has been designed, constructed and calibrated. This has been used for over 50 sets of tracer decay measurements in five single-cell buildings ranging in size from 4000 to 31000 m³, The buildings included a sports hall, a vehicle maintenance depot, two factory workshops and an aircraft hanger. Infiltration rates and interzonal flows were derived from the tracer decay curves using methods based on multizone theory.
In this programme of work, methodologies for determining infiltration rates of large and complex buildings have been established. Theoretical considerations suggested that comprehensive information regarding interzonal air movements might be obtained from experimental techniques using multiple tracer gases. Field measurements to determine interzonal flows were carried out in office buildings using automated measurement systems developed for this purpose. Simpler techniques were found to be needed and were developed.
Seven federal buildings ranging in size from 1900 to 48000 m2 of floor area were pressure tested to determine the airtightness of the building envelopes. These tests are part of a larger project to evaluate the thermal integrity of the envelopes of federal buildings. The buildings were pressurized using the air-handling equipment in the buildings and a constant-injection, tracer gas technique to measure the airflow through the fans. In addition, selected windows in some of these buildings were pressure tested separately to determine the airtightness of individual components.
Induced-pressure measurements were made in the tower of an eleven-story office building usiInduced-pressure measurements were made in the tower of an eleven-story office building using a fan. The fan was used to depressurize the entire tower as well as a single floor. Sulphur hexafluoride (SF6) tracer gas was used totrace air movements from floor to floor during single-floor depressurization. Average flow coefficients for the tower and for the single floor were estimated from single point measurements. The effect of opening and closing office doors also was determined.
Air leakage measurements by the tracer dilution technique were performed in five military aircraft hangars. The hangars were located in regions of the country having diverse weather characteristics. In several of the hangars, distinct measurements were performed to assess the degree of homogeneity of the air-tracer gas mixture in these large volume structures. Air leakage rates in the range of 0.6 to slightly above 2.0 air changes per hour (ACH)were measured. Surprisingly, these values do not differ significantly from those which might be measured in single-family residences.