Blower Door Testing Basics
IAQ Diagnostic Tools for Tribal
Professionals
Testing
House Tightness
House Air Leakage Testing
Building Air Leakage/Tightness Testing
Closed house condition
Blower door creates negative pressure
Measure house pressure + air flow out
Use - 50 pascal pressure
High air flow @ 50 pascals = large air leakage
Low air flow @ 50 pascals = small air leakage
Exceptions to Negative Pressure
Blower Door Testing
• Test house with Pressurization when
presence of pollutants or irritants may
be pulled into a home:
 Vermiculite insulation
 Asbestos, fiberglass, Molds, etc.
• Cover exhaust fans and other
openings with back-draft dampers
Measure the pressure in building
Measure the volume of air out fan
Calculate the leakage area
Estimate air exchange
Fan Door Test
1) Depressurize building to negative - 50 pascals
2) Measure how much air (cfm)
required to maintain 50 pascals
-50
CFM
Larger leakage = Higher CFM
Fan Door Test
1) Depressurize building to negative - 50 pascals
2) Measure how much air (cfm)
required to maintain 50 pascals
-50
CFM
Smaller leakage = Lower CFM
Leakage Test Equipment
Door Panel & Frame
Fan & Rings
Pressure Gauge
DG-700 Pressure & Flow Meter
Device Select
Device
Configuration
Select
Mode Select
“Input” ports
“REF” ports
BD = Blower Door
OPEN
BD 3
Pa
PR/
FL
CFM
1
OPEN
BD 3
Pa
PR/
FL
CFM
1
OPEN
BD 3
Pa
PR/
FL
CFM
1
OPEN
BD 3
Pa
PR/
FL
CFM
1
DG-700 Pressure & Flow Meter –
Conventional Blower Door Connection
Red tube
“Input” port
to Fan
Green tube
“REF” port
to Outside
OPEN
BD 3
BD 3
“ Blower Door “
Pa
PR/
FL
CFM
1
Basic Blower Door Test
Interior With Respect
to (WRT) Outdoors - 50PA
- 50.
A
B
AH
A
Green Tube Outside
Channel A “Reference”
Red Tube Fan CFM
Channel B “Input”
B
Red Tube Fan CFM
Channel B “Input”
Green Tube Outside
Channel A “Reference”
Set-up
• Assemble frame and adjust to door size
• Remove frame and place nylon panel over frame
• Place panel and frame in door opening and
tighten
• Insert fan in panel
• Connect tubing to manometer, fan and exterior
• Depressurize to 50Pa and record CFM
in older homes, pressurize if necessary
During Testing
• Exterior windows and doors closed
• Fireplace and stove doors closed
• Close dampers (depressurizing the house
sucks gravity dampers closed)
• Interior doors open
During Testing
• Open access hatches to conditioned attics or
crawl spaces
• Exterior ventilation openings closed and sealed
• HVAC ducts and registers not sealed
• HVAC, water heater, OFF
What the numbers mean
Pressure (in Pascals)
Flow rate (CFM)
HOUSE SET UP FOR BLOWER DOOR TEST
Select convenient and appropriate exterior door for fan
installation:
• Patio, garage, back porch doors are good choice allowing
main door access to your vehicle
• Garage door, back porch door, etc must be open!
Open interior doors to all zones defined by the air barrier
Make sure all windows and exterior doors are securely closed
New Homes: fill traps if necessary !
Check household items near fan to ensure air flow will not cause
damage – plants, pictures, etc.
HOUSE SET UP FOR BLOWER DOOR TEST
• Set thermostat to prevent furnace, boiler, A/C from
operating during testing – note original setting and tag
or leave truck keys
• Turn down thermostat on gas/propane water heater to
prevent firing during test – note original setting and tag
or leave truck keys
• Close flue damper fireplaces and/or woodstoves and
carefully seal to guarantee ashes are not released
during blower depressurization tests
• Turn off all exhaust fans, clothes dryer, range hood
BLOWER DOOR TEST PROCEDURES
General procedures for performing a blower-door test
1. Install blower door frame, panel, and fan in an exterior doorway
with a clear path to outdoors.
(on windy days, try to place the fan parallel to the wind direction)
Install fan with “rings” toward interior of
building and set in de-pressurization mode
2. Route the Green tube outside at least 5 feet to the side of the fan
exhaust.
3. Connect the house-pressure Green tube to the manometer
Channel A “Reference” to measure house WRT outdoors.
.
4. Connect the fan pressure RED tube from the fan to
the Channel B “Input” port to measure fan pressure
WRT indoors
Note: the zone near the fan inlet is indoors for
depressurization and outdoors for pressurization
5. Turn on the fan and increase speed slowly to about
15 to 20 pascals pressure differential indoors WRT
outdoors
6). Thoroughly check fireplace/woodstove seals, and
check house for open windows & doors and other
potential problems
7) Increase the fan speed slowly up to 50 pascals pressure
differential indoors WRT outdoors
8) Read the CFM50 airflow from the manometer
(or from the second channel of a two channel
digital manometer)
Check flow rate on manometer and
add or remove rings on fan
tighter homes will likely need rings
be sure to change manometer
ring setting
( OPEN , A1, B2, C3 )
9) Very large or leaky buildings may not reach minus – 50
pascals
•
DG-700 manometer can automatically compensate at -35 Pa
or greater pressures.
•
Using other manometers, depressurize to highest multiple of
5 and multiply your measured airflow by the “can’t reach
fifty” (CRF) factors in the conversion table provided with
equipment.
10) Record the results
January 1, 2011 code requires all
new homes and multi-family units
to be fan door tested
The Specific Leakage Area shall
be less than .00030
Calculating Specific Leakage Area
(SLA)
• SLA = (CFM50 X .055) / (CFA X 144)
• SLA = (1790 X .055) / (2240 X 144)
• SLA = 98.45 / 322,560
• SLA = .00030 (code maximum)
Specific Leakage Area
code requires the SLA to be less than .00030
Convert the flow rate (CFM50) to SLA.
SLA = (CFM50 X .055) / (CFA X 144)
Where:
SLA = Specific Leakage Area CFM50 X .055
(CFM 50 times conversion factor = SLA reference pressure)
CFA x 144 = Conditioned floor area of the housing unit,
converted to square inches
Example: A blower door test has been done on a 2,000
square foot house with 1,100 CFM50.
SLA = (CFM50 X .055) / (CFA X 144)
SLA = (1100 X .055) / (2000 X 144)
SLA = 60.5 / 288,000 SLA = .00021
2- Point Blower Door Test
Test @ CFM 25 and CFM 50
Typical blower door test assumes .65 coefficient “N”
“N” must be between .5 and .75 for accurate
test
Formula:
“N” = (LN Q50/Q25) / (LN 50 Pa /25Pa)
2- Point Blower Door Test
Test @ CFM 25 and CFM 50
Typical blower door test assumes .65
coefficient “N”
Provides additional valuable information
A value below .65 suggests large holes
A value above .65 suggests smaller holes
2- Point Blower Door Test
“N” must be between .5 and .75 for accurate test
N = (LN Q50/Q25) / (LN 50 Pa /25Pa
- - or - N = (LN of CFM 50/CFM 25) divided by (LN of 50 Pa /25Pa)
Example:
Blower door test resulted in CFM 50 = 1,800 CFM 25 = 1,200
1,800 divided by 1,200 = 1.5
LN of 1.5 = .405
50 Pa divided by 25 Pa = 2.0
LN of 2.0 = .693
.405 divided by .693 = .585
N = .58 congratulations …. a valid test !!
Important Fan Door Values
CFM 50
(Cubic Feet per Minute at 50 Pa)
SLA
(Specific Leakage Area = .0003 code maximum)
ELA
(Effective Leakage Area)
ACH 50
(Air Changes per Hour at 50 Pa Pressure)
EFFECTIVE LEAKAGE AREA
Convert blower-door CFM50 measurements into
square inches of leakage area: Divide CFM50 by 10
ELA = CFM50 ÷ 10
ELA helps technician visualize the size of openings in
a home or section of a home
Calculating ACH 50
1.
Determine CFM 50 of house
2.
Calculate house volume (ft3)
3.
Multiply CFM 50 times 60 and divide by
house volume
ACH 50 = CFM 50 X 60 / ft3 volume
Example: Calculating ACH 50
1,850 ft sq home
8 ft ceiling height
CFM 50 measured at 2,000 CFM
What is the ACH 50 for this house?
ACH 50 = CFM 50 X 60 / ft3 volume
Example: Calculating ACH 50
1,850 ft sq home
8 ft ceiling height
CFM 50 measured at 2,000 CFM
What is the ACH 50 for this house?
ACH 50 = CFM 50 X 60 / ft3 volume
2,000 CFM X 60 = 120,000 Cubic Feet per Hour (CFH)
Example: Calculating ACH 50
1,850 ft sq home
8 ft ceiling height
CFM 50 measured at 2,000 CFM
What is the ACH 50 for this house?
ACH 50 = CFM 50 X 60 / ft3 volume
2,000 CFM X 60 = 120,000 Cubic Feet per Hour (CFH)
1,850 X 8 = 14,800 ft3
Example: Calculating ACH 50
1,850 ft sq home
8 ft ceiling height
CFM 50 measured at 2,000 CFM
What is the ACH 50 for this house?
ACH 50 = CFM 50 X 60 / ft3 volume
2,000 CFM X 60 = 120,000 CFH
1,850 X 8 = 14,800 ft3
120,000 divided by 14,800 =
Example: Calculating ACH 50
1,850 ft sq home
8 ft ceiling height
CFM 50 measured at 2,000 CFM
What is the ACH 50 for this house?
ACH 50 = CFM 50 X 60 / ft3 volume
2,000 CFM X 60 = 120,000 CFH
1,850 X 8 = 14,800 ft3
120,000 divided by 14,800 =
8.1 ACH 50
Estimating “Natural” Air Changes/Hour
Climate factor for NW =20
ACH “natural” = ACH 50 divided by 20
Example:
5.3 ACH 50 divided by 20
= .26 Air Changes Hour “Natural”
Note: ASHRAE 62.2 guideline = 0.35 ACH