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F.7 standards for air leakage – Retrotec USACE User Manual

Page 298

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F4 ENERGY & PROCESS ASSESSMENT PROTOCOL

Timely measurement and sealing is essential while the building is under

construction or undergoing major renovation to ensure that air leakage detail-
ing is accomplished at the right stages so that methods may be altered early to
ensure that problems are not repeated over and over. This may be best done
by companies or agencies with air leakage testing and air-sealing experience.
For more information on building areas with a potential for air leakage, see
Appendix E.

Several countries have specifi c requirements and standards for building

air leakage, other don’t. Builders naturally fear the unknown costs of this type
of requirements. Typically, a marginal increase in cost with new construction
(primarily for development of architectural details and testing) result in build-
ings where air leakage can be properly controlled for all purposes. Studies
conducted by CERL and NREL (Zhivov 2009) showed that improving the
building airtightness in existing buildings undergoing renovation, may result in
energy savings between 5% and 25% depending on climate.

F.7 Standards for Air Leakage

Different international bodies use various units to characterize air leakage. To
make comparisons, Table 1 shows the requirement adopted by the US Army
Corps of Engineers for air leakage of 0.25 cfm per sq ft of the air barrier at 0.3 in
w.g. (1.27 L/s*m

2

) @ 75 Pa of pressure difference converted to other commonly

used units. Conversions will change for different buildings when comparing air
change rates since volume and areas are not directly related. Where different
reference pressures are used, conversion results will vary somewhat at the n
value or exponent of the fl ow equation (fl ow = C X Pressure

n

).

TABLE F1. UNITS CONVERSIONS FOR 0.25 CFM75/ FT

2

TO OTHER COMMON UNITS MADE

FOR A BUILDING 120 X 110 X 8 FT, 4 STORIES, N=0.65

0.25 cfm/ ft

2

at 75 Pa

Used by ASHRAE and US Army Corp

0.19 cfm/ ft

2

at 50 Pa

Used by some US researchers and an ASHRAE article

1.06 in

2

EfLA/100 ft

2

at 4 Pa

Used by US building scientists to calculate natural air exchange in houses

2.53 in

2

EqLA/100 ft

2

at 10 Pa

Used in Canada and other countries

1.12 Air Changes per hour
at 50 Pa

Widely used for houses but not useful for comparisons in high rise buildings because
volume to area ratios change so much.

3.51 m

3

/hr/m

2

at 50 Pa

Used in the UK to rate the permeability of commercial buildings

1.27 liters/s/m

2

at 75 Pa

Used by researchers in US, Canada and Europe for high rise buildings