Retrotec Blower Door - Manual (Page 9)

Page 9 of 87
©Retrotec Inc. 2015
1. How the Blower Door System components work
A Door Fan is a specially designed calibrated fan which, as part of the Blower Door Fan System, is
temporarily mounted in a doorway. The fan is used to blow air into or out of a room, house, or building
to measure the air leakage of the enclosure. The term “room, house, or building” is often shortened to
“enclosure”.
The Door Fan System works by establishing a pressure difference between the inside and the outside of
an enclosure. The pressure difference forces air to leak through all of the holes in the exterior envelope
of the enclosure. The amount of air flow that is required to maintain a constant pressure difference is
equal to the amount of air that is leaking from the enclosure. A specially designed gauge can thus be
used to measure the pressure difference and calculate the amount of air flowing through the Door Fan,
which can then be used to determine the total size of all those leaks.
A typical Door Fan or Door Fan system is comprised of four main parts:
1. A Door Panel, which temporarily seals a typical doorway and provides a hole to mount a fan.
2. A calibrated fan, capable of creating a measurable flow of air.
3. A two-channel differential pressure gauge that can also calculate flow for a particular fan.
4. A fan speed controller to change the air flow through the fan (which can be provided by the
gauge)
A typical Door Fan system breaks down as shown in Figure 1:
Figure 1: The breakdown of a typical Door Fan system.
In this case, an aluminum frame holds a Cloth Door Panel in place, sealing the doorway. The fan is
mounted in the hole in the cloth, and is supported by the aluminum frame crossbar. The gauge is acting
as both the fan controller and differential pressure gauge.
In its role as differential pressure gauge, one channel of the gauge is connected to the fan through a
yellow tube to measure the Fan Pressure, (referenced to the pressure at the green port of the gauge),
which is the pressure required for the fan to bring the enclosure to the desired pressure. The other