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Blower Door Test - DOC


									   Habitat for Humanity

       Blower Door Test

                     Sponsor Contact:

                   Doug Taylor
                Habitat for Humanity
                 420 S. First Street
                  (765) 423-4590

 Rachel Austin             
Virginia Christian          
  Doug Crook              
Vijay Murugesan          
 Michael Schilz           
 Matthew Selvey            

                       April 20, 2002

The purpose of the blower door test is to measure the air tightness of a building. The air
tightness of a house is directly correlated to the energy use and comfort of the structure.

The test house, located at 1120 Washington St., Lafayette, is unique because of its wall
construction. The outer walls are built with foam blocks and a concrete core. This
provides an energy efficient house construction with low Effective Leakage Area (ELA).
The blower door test will enable HFH to quantify the air tightness of the house and qualify
the effectiveness of the construction technique.

The ELA is one of the major inputs into the Energy-10 software package used by the
EPICS HFH team to model energy consumption. A model will be created to simulate
energy consumption of the house. Rather than using a default value, an experimental value
for effective leakage area will be found and used to update those models. It will also
provide another data point for blower door analyses.

A test was performed on February 22, 2002. The true ELA of the finished house could not
be found due to the unfinished state of the house. The leakage area was approximately
twice that of previous tests performed by EPICS teams on HFH houses. The second test
was performed on April 4, 20002, when the house was closer to completion. A final,
atmosphere corrected ELA value of 66.4 in2 for the house was found.

The ability to perform blower door testing is an important skill that the EPICS HFH team
needs to maintain. This test will maintain that level of expertise for team continuity.


      Blower door – test article, including fan, rubber seal, wire mesh protection, and
       differential pressure gage (measured in inches water)
      Extension cord – provides power to blower door
      Duct tape – covers exterior holes and reduces air flow under door
      Hammer, screwdriver, nails - removing exterior door hinges
      Board (2x4) – allows for better door seal in case floor boards are present


A fan built into a plywood door was tightly placed in an outside doorframe. The plywood
housing has a relative pressure gage mounted on it, which enables the pressure difference
on either side of the door to be read (see Figure 1: EPICS HFH Blower Door).

                              Figure 1: EPICS HFH Blower Door

The doors and windows were closed, outside vents were covered with duct tape, the blower
door was installed on the inside of the house, and the fan was turned on in an orientation to
produce a vacuum inside the house. The pressure readings were taken once the pressure
difference was stabilized after approximately 1 minute. The pressure difference was found
in inches water (in. H2O). From the calculations and charts located in Appendix A:
Effective Leakage Area Calculations, the effective leakage area was determined.

Another task to be performed during the test was finding the main sources of infiltration.
This was performed by observers in the house, pinpointing locations where air was entering
the house. The main trouble areas are usually found near the seal between the door and the
doorframe, around windows, and around dryer vents.


Test 1
Performed: February 22, 2002

On February 22, 2002, Rachel Austin, Vijay Murugesan, Mike Schilz, Matt Selvey, and
Doug Crook performed a blower door test on the Strong Walls house, located at 1120
Washington St., Lafayette. Ray Dubea, Construction Coordinator from HFH, was also in
attendance. The first test was more of a dry run than an actual test. The house was
partially completed; the dry wall was up, and some of the walls were painted. There were
many common items missing from the house – light bulbs, plumbing fixtures, and a
completed HVAC system. This would affect the ELA test results. Also, this house
included a basement, which is unique to Habitat for Humanity houses and different from
previous blower door tests attempted by EPICS teams.

The blower door was obtained at the HFH office and transported to the test site. An initial
walk around was performed to ensure the house was secure. Doors and windows were
closed, and the dead bolt holes in the doors (due to the dead bolts not being installed yet)
were covered with duct tape. The front door was removed and the fan was put in place and
plugged into the interior wall outlet. The walls surrounding the door were painted, so
caution was used to avoid scraping the walls. Duct tape was applied to the bottom of the
blower door to create a better seal, and the rest of the door was held in place by Mike and
Vijay. Matt stayed inside the house, identified leaks within the house and covered some of
those holes. Doug was outside the house, taking data from the differential pressure gage
and Rachel videotaped the test.

The first test run was performed at 4:25 P.M. The differential pressure was 0.18 in. H2O
and achieved steady state conditions after 2 to 3 minutes. This was significantly lower than
previous tests. The test was discontinued after noting that the opening to the attic was
uncovered. The fan was shut off and the attic was covered.

The second run started at 4:29 P.M. The differential pressure was 0.23 in. H2O after 5
minutes. Matt found several places leaks within the house. The most notable of these were
light fixtures, the heating duct, electric wiring leading to the outside, and the unfinished
plumbing system. Matt covered several of these with duct tape, and the pressure difference
increased to 0.24 in. H2O after 10 minutes. See Table 1: Blower Door Test 1 Results for a
test summary.

Table1: Blower Door Test 1 Results

Test      Diff. Press.     ELA (in2)
          (in. H2O)

Run #1              0.18        238.1

Run #2              0.24         88.9

Those on the interior of the house noted that the pressure change was hardly noticeable.
There was a difference in the observed pressure between the basement and the upstairs
portion of the house. This could be due to the excess air leakage in the basement due to
exterior holes. In the kitchen, the blower door sucked the sewage fumes into the room,
which was an unexpected result. Also, a crack in the window had condensation after the
test due to the air leakage and humidity.

Test 2
Performed: April 4, 2002

The second blower door test was performed on April 4, 2002, at 2:00 P.M. at the Strong
Walls house (1120 Washington St., Lafayette) by Virginia Christian, Mike Schilz, Matt
Selvey, and Doug Crook. Also in attendance were Ray Dubea, John Sears (HFH
Construction Supervisor), Jake Keiser (Strong Walls LLC contact) as well as others
working on the property. The house was much closer to completion. The walls were
painted, plumbing and light fixtures were installed, the external holes for wiring and
ventilation were sealed, and the sewer trap was filled. These were areas that caused
leakage in the previous test. The HVAC system was not completed. The test was run two
times – one with the HVAC vent uncovered, and one with the vent sealed with duct tape.

A problem was immediately encountered when the blower door was put into place. Since
the previous test, the trim around the floor was installed. This created a significant gap
between the blower door and the wall. A 2x4 was placed on the floor next to the trim, and
the blower door was placed on top of it. This allowed the blower door to be place flush
against the wall and create a better seal. When the fan was started, no airflow was
observed around the blower door seal. Mike Schilz held the door in place, Doug Crook
collected differential pressure data, Matt Selvey evaluated the state of the house and
potential leakage areas, and Virginia Christen was in charge of video taping the test effort.

The first test took place at 2:15 P.M. Within 30 seconds, the internal pressure stabilized to
.24 in. H2O. The time to stabilize the pressure appeared to decrease from the previous test.
The fan was run for an additional minute to ensure the pressure value was stable. The fan
was shut off, and the state of the house was evaluated. An HVAC vent was found on the
north side of the house. This was covered with duct tape to prevent unnecessary leakage
from an incomplete system. The test was resumed, and a differential pressure increased to
.25 in. H2O (see Table 2: Blower Door Test 2 Results). Although this was not the predicted
value, additional leakage sources could not be found.

Table 2: Blower Door Test 2 Results

Test       Diff. Press.     ELA (in2)
           (in. H2O)

Run #1               0.24         86.8

Run #2               0.25         64.6

Those on the inside of the house did not notice any sort of pressure change due to the fan


Test 1

The Effective Leakage Area (ELA) was computed for the first blower door test using the
equations found in Appendix A. It was found that the ELA was 86.1 in2. When the density
was adjusted for local weather conditions (T = 38o F, P = 30.18 in. Hg), the calculated ELA
was 88.9 in2. This was over double the leakage found in previous HFH houses. This was
attributed to the missing light fixtures, unfinished plumbing, uncovered HVAC vents, and
other leaks due to the unfinished state of the house. The air flowing into the house could be
felt by placing a hand in front of these holes. These will be covered as the house nears
completion. However, the source of these leaks was relevant information for Ray Dubea,
the HFH construction coordinator.

Test 2

The ELA computed using the predefined procedure was found to be 64.6 in2. The weather
conditions for the day were similar to those of the previous test (T = 39o F, P = 30.40 in.
Hg). When these weather conditions were taken into account, the ELA was 66.4 in2. This
is a decrease of 25% of ELA, but still higher than prior blower door tests. However, the
square footage of Strong Walls house is twice that of previous houses. A direct correlation
cannot be made between this house and others due to the lack of completed blower door
tests and data points. To make an effective comparison with other Habitat for Humanity
houses, more tests would have to be run to identify patterns between house size and ELA.

The Energy 10 energy analysis program uses gross wall surface area to compute a default
input value for ELA (see Equation 1):

           ELA = 0.133 x (wall gross surfacearea, in squarefeet)       Equation 1

Using this formula, the expected ELA of the Strong Walls house is 160 in2, which supports
the hypothesis that the house is more air tight than the typical house.

Energy 10 Analysis

The Strong Walls house floor plans and results of the blower door test were entered into the
Energy-10 energy analysis program (see Appendix B for a list of input parameters and
further results). The analysis was run for two cases – a reference case with the ELA value
obtained from the blower door test. The “High ELA” case was computed using the ELA
computed for the first test when there were air leaks around the light and plumbing fixtures
(see Figure 2 Blower Door Test Energy 10 Analysis Results).

                   Strong Walls / Blower door results analyis
                                 ANNUAL ENERGY COST
                    Reference Case                             High ELA

 $ / ft²

           0.2                     0.194 0.196


                                                 0.020 0.020
                     fuel             kWh            Demand       Total

Figure 2 Blower Door Test Energy 10 Analysis Results

According to Energy 10, yearly energy cost will be approximately $740, or about $62 per
month. The high leakage home analysis was $39 more than the reference case,
highlighting the importance of maintaining a tight house.

Lessons Learned

A steep learning curve was encountered initially due to the inexperience of the test team.
Please see Table 3: Test Schedule for insight into the length of the test.

Table 3: Test Schedule
  Time                       Event
3:45 P.M. Pick up blower door at HFH office
4:00 P.M. Arrive and setup at Strong Walls house
4:25 P.M. Begin testing
5:00 P.M. Testing completed

Setup, including installing the blower door and checking the house to ensure it was secure,
took a large portion of the time. Pressure inside the house achieved steady state after
approximately 3 minutes. The setup time will be decreased as the experience of the test
team increases.

Several lessons were learned about the state of the house and when the test can be
performed. The house needs to be closer to completed before it can be tested, including
light fixtures installed, plumbing completed, and exterior holes for wiring and venting

Appendix A

          Blower Door Test of Three-Bedroom House
Recorded change in pressure is ### in. H2O

                         Air Infiltration Calculations
From 1993 ASHRAE Fundamentals Handbook Sec. 23.12 equation 27

L         2P

L = equivalent or effective leakage area, m2
ΔP = reference pressure difference, Pa
QR = predicted airflow rate at ΔP, m3/s
CD = discharge coefficient (equal to 0.6 for sharp edged orifice)
ρ = density of air = 1.23 kg/m3 OR ρ = P/RT

From blower door calibration curve and blower door test
ΔP = ### in. H2O * (248.8 Pa / in H2O @ 60o F) = ### Pa
(From blower door calibration) Qr=(-21154x2-6576.9x+3500 CFM)*(4.719e-4 m3/s/CFM)
        where x = in. H2O
For Strong Walls house

Effective Leakage Area, ELA = (### m2)*(1550 in2 / m2) = ### in2

                                                     Blower Door Calibration



Volumetric Flow Rate (CFM)


                                                                               y = -21154x2 - 6576.9x + 3500




                                    0   0.05   0.1               0.15             0.2                 0.25     0.3
                                                           Pressure (in H2O)

Appendix B

Strong Walls          Apr 19, 2002
Energy-10 Summary Page               Weather file: indy.et1
Variant: Blower door results analyis       Saved as C:\ENERGY10\EPICS, Var. 1

Description:                       Reference Case                      High ELA
Floor Area, ft²                    1773.3                              1773.3
Surface Area, ft²                  7431.6                              7431.6
Volume, ft³                        15960.6                             15960.6
Surface Area Ratio                 1.95                                1.95
Total Conduction UA, Btu/h-F       318.2                               318.2
Average U-value, Btu/hr-ft²-F      0.043                               0.043
Wall Construction                  8in brick/foam, R=50.0              8in brick/foam,
Roof Construction                  attic, r-30, R=29.4                 attic, r-30,
Floor type, insulation             Basement, Reff=23.4                 Basement,
Window Construction                3050 double, alum, U=0.72,etc       3050 double,
                                                                       alum, U=0.72,
Window Shading                     hfh - roof overhangs                hfh - roof
Wall total gross area, ft²         2171                                2171
Roof total gross area, ft²         4374                                4374
Ground total gross area, ft²       887                                 887
Window total gross area, ft²       114                                 114
Windows (N/E/S/W:Roof)             1/3/0/4:0                           1/3/0/4:0
Glazing name                       double, U=0.49                      double, U=0.49

Operating parameters for zone 1
HVAC system                        Heat and Vent with Gas Furn           Heat and Vent
                                                                         with Gas Furn
Rated Output (Heat/SCool/TCool),kBtuh    40/0/0                          44/0/0
Rated Air Flow/MOOA,cfm           505/0                                  556/0
Heating thermostat                70.0 °F, no setback                    70.0 °F, no
Cooling thermostat                 78.0 °F, no setup                     78.0 °F, no
Heat/cool performance                 eff=80,EER=1.0                     eff=80,EER=1.0
Economizer?/type                      no/NA                              no/NA
Duct leaks/conduction losses, total % 8/5                                8/5
Peak Gains; IL,EL,HW,OT; W/ft² 0.20/0.04/0.66/0.36        0.20/0.04/0.66/0.36

Added mass?                               none                        none
Daylighting?                              no                          no
Infiltration, in²                         ELA=64.6                    ELA=86.8

Results:                     (Energy cost: 0.400 $/Therm, 0.054 $/kWh, 2.470 $/kW)
Simulation dates                              01-Jan to 31-Dec     01-Jan to 31-Dec
Simulation status, Thermal/DL                 valid/NA                    valid/NA
Energy use, kBtu                              112553                      121666
Energy cost, $                                743                         782
Saved by daylighting, kWh                     NA                          NA
Total Electric, kWh                           6369                        6430
  Internal/External lights, kWh               1393/152                    1393/152
  Heating/Cooling/Fan, kWh                    0/0/599                     0/0/661
  Hot water/Other, kWh                        NA                          NA
  Peak Electric, kW                           1.3                         1.3
Fuel, hw/heat/total, kBtu                     NA/NA/90821                 NA/NA/99725
Emissions, CO2/SO2/NOx, lbs                   9830/51/27                  10019/52/28


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