Civil Engineering Reference
In-Depth Information
of the building fabric with respect to
air leakage.
Figure 1.40 shows results of fan
pressurisation measurements on five
large commercial buildings in the UK
and compares them with buildings
tested in Canada, the USA and
Sweden. It can be seen that the Low
Energy Office (LEO) is twice as air
tight as the other UK office built in a
more conventional manner, and as
tight as the two offices tested in
North America.
Broadly speaking, a building with
an envelope leakage index of 5 can be
classified as having a good, low
leakage standard, while index 10 is
average. Buildings with index 20 are
poor and are likely to give rise to
complaints about uncomfortable
draughts and difficulties in keeping
warm.
Results from two old industrial
'hangar' type buildings showed them
to be over twice as leaky as one built
within the last decade under current
UK building regulations. But
comparison with tight Swedish
industrial buildings shows that a
further five fold reduction is
50
Older pre Building
Regulations
40
1979 Building
Regulations
Leaky
30
1990 Building
Regulations
Conventional
Low energy
20
10
0
Dwellings
Offices
Industrial
Leakage in m
3
per h per m
2
at 25 Pa
Swedish Building Regulations
North American examples
United Kingdom
Figure 1.40
Envelope leakage indices of buildings
measured by BRE
possible.
