Recent research has shown that U.S. commercial and institutional buildings
are not as airtight as assumed, and that envelope air leakage has a significant
impact on energy consumption and indoor air quality in these buildings.
This applies to all building ages, sizes, and constructions.
ONLINE TECHNICAL INFORMATION AND RESEARCH:
Online Calculator in US Units or Metric Units
for computing the parameters of large building air leakage tests.
The U.S. has not made any significant changes in
building envelope construction recommendations based on the latest
airtightness research results. The UK is now more
advanced in their recommendations.
ASHRAE Fundamentals Handbook, 1997, 25.19:
The envelopes of commercial buildings are often thought to be quite airtight.
For commercial buildings, the National Association of Architectural Metal Manufacturers
recommends infiltration rates per unit of exterior wall not to exceed 0.06 cfm/sf at a
pressure difference of 0.30 in. of water exclusive of leakage through operable windows.
Tamura and Shaw (1976a) found that air leakage measurements in eight Canadian office buildings
..... ranged from 0.120 to 0.430 cfm/ft2 (2.2 to 7.8 m3/h*m2). Other measurements taken
by Persily and Grot (1987) in eight U.S. office buildings ranged from 0.213 to 1.028
cfm/ft2 at 0.30 in. of water (3.9 to 18.7 m3/h*m2 at 75 Pa). Therefore office buildings are
leakier than expected. Typical air leakage values per unit wall area at 0.30 in. of water
are 0.10, 0.30 and 0.60 cfm/ft2 (1.8, 5.5 and 10.9 m3/h*m2 at 75 Pa) for tight, average
and leaky walls, respectively (Tamura and Shaw 1976a).
....air leakage in buildings is due not only to windows and doors, but to a wide range
of unexpected and unobvious construction defects. Many important leakage sites can be
very difficult to find.
This is an excellent condensation of airtightness research up to 1997.
EPA Energy Star is one of the
few U.S. government programs that make airtightness recommendations for large
buildings. Unfortunately it repeats the myths about buildings airtightness.
EPA misinterprets the 1997 ASHRAE Fundamentals Handbook airtightness recommendations
to suggest that a target of 0.06 cfm/sf @ 0.3"wc (1.1 m3/h*m2 @ 75 Pa) is reasonable
in the Energy Star publication
Building Upgrade Manual.
See pages 8-10 of the Building Envelope section of the Energy Star
Stage Two, Building Tune-Up. ASHRAE only quoted this NAAMM airtighness recommendation to
show that it was unrealistic given the current state-of-the-art in U.S. building construction.
Note that this recommended airtightness is more than 25 times tighter than
the average of recent airtightness measurements of U.S. commercial and industrial buildings reported by
Persily! Since the Energy
Star program does not mention testing, there is little chance that the wide divergence between
recommmended and actual airtightness would ever be identified. In addition, the
Energy Star building envelope tune-up guidance centers on windows, doors and insulation defects and not the
"unexpected and unobvious construction defects" identified as the main problem
by the ASHRAE Fundamentals.
Energy Star needs to update its building airtightness tune-up recommendations.
* indicates an Infiltec calculation based on CIBSE-T23 building tightness specifications
To convert these leakage indexes to 0.30 "wc or 75 Pa, multiply flow (not area) values by 1.30.
ACH and hole size calculations assume 30'x50'x8' house, 300'x500'x10' other buildings (industrial assumes 20' height).
Hole size calculations assume orifice flow.
Multiply (square inches/100 square feet) by 0.69 to get (square cm/square m).
FAN PRESSURIZATION TEST EQUIPMENT FOR TESTING LARGE BUILDINGS:
Several large fan pressurization test systems have been built by
research organizations in Canada and the UK. Recently Infiltec and
Building Sciences Limited
developed the next generation of fan pressurization test equipment for
Stacked Blower Door: Infiltec manufactures a stacking system for
mounting 3 blower door fans in a single door of a building. Each fan
can produce a calibrated variable flow of up to 6,000 cfm (2.85 m3/s).
When 3 doors are used, the maximum flow from the 9 blower door fans is over
50,000 cfm (24 m3/s) @ 0.04 to 0.30"wc (10 to 75 Pa) building pressure.
These fans are powered by the building electrical power, and a dual-sensor
digital micromanometer is used to measure pressure and flow.
The pressure and flow calibration are in both metric and US units.
See Prices and Specifications.
For more information, Email:
or Call: (540) 943-2776 in Waynesboro, VA from 7AM to 4PM ET.
G54 Mobile Gasoline-Powered Calibrated Fan: The Infiltec G54 mobile
fan has a calibrated air-flow of over 55,000 cfm (26 m3/s) @ 0.30"wc (75 Pa).
The G54 can be trailer mounted for portability, and it is powered by a built-in gasoline engine.
No external power is required. The fan air flow can be varied and measured
within 5% accuracy over the range of 15,000 to over 60,000 cfm (7 to 29 m3/s)
@ 0.04 to 0.3 inch wc (10 to 75 Pa) building pressures.
The fan is connected to the building by a durable 60" (1.5 m) diameter by 250" (6.5 m)
long flex duct. Fan flow and building differential pressure
measurements are displayed on built-in analog gauges, or they
can be measured with a custom calibrated dual-sensor digital micromanometer.
The building pressure and fan flow measurements are displayed in both metric and US units.
Pictures of the G54 in use can be seen in an
April 2003 test of a 9,000,000 ft3 (256,000 m3) food distribution warehouse in Manchester, UK.
See Specifications and Prices.
For more information, Email:
or Call: (540) 943-2776 in Waynesboro, VA 7AM to 4PM ET.
For further assistance, call Infiltec at (540) 943-2776 Or Email