Stephen McNeil, BRANZ

Stephen McNeil


Real world infiltration vs airtightness


Common methods of estimating infiltration from airtightness are rooted in older standards such as ISO13790:2004 and EN832:1998. This aspect of thermal performance is now accounted for in EN 16798-7:2017 (replacing EN15242:2007) by a more comprehensive method, which gives more realistic results. But if we are now striving for more efficient dwellings, should the more comprehensive techniques be used to gain a better view of potential losses.

This presentation gives comparisons of measured airtightness to measured infiltration for several buildings. The infiltration data was obtained during co-heating tests using a constant emission tracer gas method. The measurements took place over the course of at least two weeks, and a variety of wind conditions were captured. As part of the co-heating test, internal temperatures were held at 30°C, with required energy input constantly monitored. This gave valuable information on the role of infiltration in the energy budget of each of the buildings.

The results indicate that the simplified method for accounting for infiltration heat loss is over predicting the impact. In the longer term, considering impacts of air leakage on building durability will be the more important metric, once diminishing returns are reached in the energy space.

About Stephen McNeil

Stephen is a Senior Building Physicist at BRANZ. His research covers ventilation, airtightness, moisture issues and indoor air quality of New Zealand homes.

Stephen is has worked closely with the Fraunhofer Institute of Building Physics over a number of years, contributing to the development to the WUFI suites of software, and has extensively benchmarked it against experiments in BRANZ experimental buildings – with a particular focus on air carried moisture. His current interests lie in improving the building stock in NZ to reduce the burden on the health system, while mitigating the risk of unintended consequences in terms of moisture and overheating. He is a regular contributor to BRANZ Build Magazine, and author of a number of scientific publications in international journals and conferences.