BlowerDoor testing in large buildings
Airtightness testing in large buildings places particular demands on planning, measuring equipment and test procedures. Compared with detached and semi-detached houses, building volume, height, wind and temperature have a much greater impact on test conditions. BlowerDoor testing must therefore be carefully planned and prepared.
Special requirements
Large buildings typically have a high volume relative to a comparatively small envelope area (a low area-to-volume ratio, A/V). Because this can result in favourable calculated air change rates (nL50), it also makes sense to consider the air permeability relative to the building envelope area (qE50).
Depending on the building's size, several BlowerDoor fans may be used. They are often installed in different locations to enable uniform airflow within the building. Preparing a large building for testing is considerably more demanding and requires careful advance planning.
Wind and stack effect have a much greater influence on the test because pressure conditions within the building change with increasing height: wind creates different pressure zones on the façade, while temperature differences between indoor and outdoor air cause thermal buoyancy. A BlowerDoor test in a large residential or non-residential building therefore differs significantly from a test in a detached house.
Planning and building preparation
A successful test starts well before the actual BlowerDoor measurement.
The following are determined in advance, among other things:
- the section of the building to be tested,
- air connections between spaces within the building,
- suitable installation locations for the test fans,
- and additional pressure measurement points.
These arrangements are established in advance.
Especially in large buildings, preparation is an essential part of the overall testing process.
Multiple fans and additional pressure measurement points
If a single fan does not have sufficient capacity, several BlowerDoor systems are operated simultaneously. The fans work in synchronisation to generate the required pressure difference together.
Additional pressure measurement points allow the pressure distribution within the building to be monitored and help assess the effects of wind and stack effect during testing.
This makes it possible to reliably assess the airtightness of large and tall buildings.
Conclusion
BlowerDoor tests in large and tall buildings require careful planning and organisation. Multiple fans, additional pressure measurement points and structured building preparation help ensure that even complex buildings can be tested for airtightness in a reproducible manner and in accordance with applicable standards.
Frequently asked questions about BlowerDoor testing in large buildings
What needs to be considered when testing the airtightness of large buildings?
In large buildings, volume, height, wind and temperature differences affect test conditions. Pressure conditions can vary throughout the building. BlowerDoor testing in large residential and non-residential buildings therefore requires particularly careful planning, building preparation and monitoring of pressure distribution.
Why are several fans used in large buildings?
If one fan cannot provide sufficient capacity, several BlowerDoor systems are used at the same time. The fans operate in synchronisation to generate the required pressure difference together. Depending on the size of the building, they can be installed in different locations.
Why is envelope-area-based air permeability relevant alongside the air change rate?
Large buildings often have a high volume relative to their building envelope area. As a result, they can achieve comparatively low calculated air change rates. In addition to the nL50 value, it is therefore useful to consider envelope-area-based air permeability, expressed as qE50.