Multifamily Blower Door Testing
With the recent increase in multifamily housing construction, combined with some builders’ desire to seek green certifications, establishing a user-friendly blower door test protocol that achieves repeatable results would allow multifamily buildings to achieve Passive House certification.
Blower door testing of multifamily buildings is not new. See “Measuring Leakage in Multifamily Buildings,” HE Sept/Oct 2007, p. 34. Recently I had the chance to do some blower door testing on a three-unit multifamily building. The building has three side-by-side units with no connections other than air infiltration through their adjacent fire-rated walls. It is on track to be a Passive House Institute US (PHIUS)-certified Passive House.
Challenge Homes are homes of the not-too-distant future. They are generally 40–50% more energy efficient than a current code home. They must be solar thermal- and solar PV-ready. They must be
Determine the Test Scope
Passive House certification requires that a building have ACH50 of not more than 0.6. We had done a variety of informal unit and whole-building tests with results very close to the 0.6 ACH50 requirement. None of those tests exactly matched the PHIUS protocol, though. Before hanging drywall, the builders wanted to make sure they were hitting the ACH50 target. We needed to do the real thing.
We received the following guidance from PHIUS regarding multifamily units:
The preferred method is to test the entire building at once, using three fans controlled simultaneously through the computer. However, auditors are allowed to do individual tests on each unit. If the individual test results are identical (in terms of net volume), you may take the average of the ACH50 for each. If they’re slightly different, add up the CFM50 for each unit, then multiply by 60 min/hr and divide by the net interior air volume of the entire project.
We were unable to test each unit individually because of interunit connections between units, so we decided to test the entire building at once. The prevailing protocol for PHIUS certification is ASTM E-779, a multipoint test—you pressurize and depressurize at five to eight pressure points, then do a linear regression to arrive at a CFM50 number. The regression is designed to compensate for large indoor-outdoor temperature differences, altitude, and windy conditions.
ASTM E-779 clarifies its applicability to multifamily buildings in its first section:
This test method is intended for the measurement of the airtightness of building envelopes of single-zone buildings. For the purpose of this test method, many multi-zone buildings can be treated as single-zone buildings by opening interior doors or by inducing equal pressures in adjacent zones.
We didn’t have any interior doors, so we had to devise a method where we could do three simultaneous blower door tests at identical induced pressures, record the results at multiple pressures, and do a linear regression of the resulting data to get an ACH50 number. PHIUS has one additional twist: You are supposed to do pressurization and depressurization tests, and average the results.
We had three sets of equipment—two blower doors and one Duct Blaster with a compatible blower door shroud. (Our targets in each unit were in the 100 CFM50 range, so a Duct Blaster was perfectly suitable.) The Energy Conservatory (TEC) manufactures all the hardware. Fortunately, TEC also has software that allows you to do semiautomated multiequipment testing similar to what we needed: multipoint pressurization and depressurization, with regression analysis.
TECLOG3, available by download from the TEC web site, can control up to 16 separate manometers through Wi-Fi, USB, or serial connections. The USB connections are limited to relatively short 15-foot lengths. Serial connections can be a few thousand feet long, according to TEC. We decided to use 100-foot CAT5 cables attached to a four-channel serial/USB hub attached to a Macintosh running Windows XP with VMware. The CAT5 cables have to be connected to the hub and the TEC DG-700 manometers using CAT5/serial adaptors. The DG-700 manometers are then connected to the fan motor controllers with fan control cables. You turn the controllers to the on position. The software then manages the testing process.
When you start a new TECLOG3 session, you typically first set up your configuration. In our case, we had three DG-700s, each with a unique serial number (see Figure 1). By selecting Scan for Ports/Devices, TECLOG3 discovered all three and displayed their serial numbers in the first three Device Settings slots when you double-click in those slots. We assigned them labels corresponding to the actual condominium unit numbers so that we could track each fan individually.
The next thing you have to do is tell TECLOG3 what parameters you want to track on each manometer channel (see Figure 2). The choices are Pressure, Interior Building Pressure, Envelope Pressure, Model 3 Fan Flow, Model 4 Fan Flow, and Duct Blaster B Fan Flow. For our test we chose Envelope Pressure for each manometer’s A channel—we needed to monitor each unit’s pressure at a series of pressure points. For each B channel we chose the hardware being used to pressurize and depressurize each unit.
Once you set up the configuration and channel settings, you can start a data-recording session. TECLOG3 displays the real-time data in a graphic format (Figure 3 shows the display for a single-fan test). There are various controls at the top of the screen for managing the testing, viewing the manometer values, and setting Periods of Record (PORs).
In order to view test results in a regression graph, or export them to other TEC software, you must record a beginning baseline, one or more sets of data at specific test pressures, and an ending baseline. For the beginning baseline, the fans are quiet and covered, just as they are for a normal blower door test. You select Baseline POR at the top of the screen, making the window in Figure 4 appear. You can indicate that this POR is a baseline or pressure reading, indicate the test number, and assign a label to the POR. Once you select the OK button, TECLOG3 records the manometer baseline pressures for a predetermined period of time (the default, which you can change, is 120 seconds). Baseline PORs are shown in green-hatched rectangles, as shown on the left-hand and right-hand sides of Figure 3.
Recording Your Tests
Once you have a starting baseline, you set up your hardware to record fan flow data. This might include, for instance, adjusting the fan rings to what you think are appropriate opening sizes. Once the rings are set up, you tell TECLOG3 to turn on the fans. You can control each fan individually, by selecting the Devices button at the top of the screen, or as a group, by selecting the Master button. For our testing, we needed to control them individually, so we unchecked the link box in the Device Settings section of the Configuration Settings page. The default setting in the software is to have all fans linked to the Master Controller that uses the average of all envelope pressures. If we did not unlink the DG-700’s from the Master, each fan would increase at the same rate and each unit would likely be at a different pressure. We want each unit to be at 50 Pa; we don’t want the average of the four be at 50 Pa.
You enter a target test pressure (baseline + induced pressure) for each fan and select Cruise Fan (you can also manually control each fan’s speed). TECLOG3 then turns on each fan and tries to achieve your desired test pressure. At the right of the screen, TECLOG3 displays the manometer data, including the fan sensor pressure, fan flow, and building pressure. As experienced testers know, you may have to modify the ring setup. You can do all this while the fans are running, then modify the TECLOG3 parameters to indicate the ring change.
Once you have usable readings on all your fans, you record a Fan-On POR (the solid green rectangles in Figure 3 are Fan-On PORs). All fan flows are recorded simultaneously for a specified period of time; the default is 30 seconds. These data are then used for the regression analysis for the ASTM E-779 protocol. If you are doing a multipoint test, you then repeat the process for your next pressure point, and record another Fan-On POR. Once you have all your pressure points recorded, you turn off the fans and record an ending baseline POR.
Figure 3 shows the graph for a multipoint depressurization of a single building. Note the starting and ending baseline PORs, and the data samples taken at –60, –50, –40, –30, and –20 pressures. The blue graph line is the zone pressure. The orange line is the CFM moving through the fan at that pressure (for instance, at 50 Pa, the building is leaking about 85 CFM). The right-hand section of the screen shows various parameters.
TECLOG3 lets you record two separate tests in one data file. This is particularly useful if you need pressurization and depressurization numbers for the same project. After the first ending baseline POR, you reset the equipment and rings and start the process all over again. When you do two baseline PORs in a row, TECLOG3 automatically changes from Test 1 to Test 2.
TECLOG3 keeps the data for each recording session in a separate file. You can view the test results in TECLOG3 (see Figure 5), or export them to TECTITE Express, a free software from TEC. (I haven’t used TECTITE Express, so I can’t comment on its features or capabilities.) You can also export the sampled data as a bitmap, enhanced metafile, JPEG, Windows metafile, or text file.
For our purposes, the TECLOG3 results, shown in Figure 5, were perfectly fine: a simple linear regression analysis of our multiple data points with a summary of the relevant computational parameters, the calculated ACH50, the effective leakage area (ELA), and the average data for each POR. From these results we were able to graphically prove that our project meets the Passive House ACH50 criterion for a whole-building volume of 32,024 cubic feet. Total pressurization is 287 CFM50, depressurization is 322 CFM50, for an average of 305 CFM50 and ACH50 of 0.57.
In this article, I describe some of TECLOG3’s features and capabilities, but I really only scratch the surface. You can use TECLOG3 for zonal pressure diagnostics or test according to other protocols, such as EN13829, the European Passive House blower door protocol, or USACE, the U.S. Army Corps of Engineers protocol. You can customize the graphics display, annotate the graph, and export the raw sampling data in a variety of formats. I haven’t used TECLOG3 for much beyond what I describe in this article, so I can’t comment on many of these other features.
TEC provides excellent support. It’s happy to take calls while you’re in the field and help you troubleshoot problems or assist you with your configuration. By the time you read this, TEC should have a series of webinars on its web site describing many of TECLOG3’s capabilities.
For more information about TECLOG3, contact The Energy Conservatory.
One feature missing from TECLOG3 is the ability to run a completely automated multipoint test based on the ASTM E-779 protocol. TEC’s free TECTITE program (not to be confused with TECTITE Express) has this capability, but it can only control a single manometer setup. With some practice, though, doing an E-779 test manually isn’t that tough. I know we couldn’t have successfully tested this project without TECLOG3.
This project could not have been completed successfully without the support and assistance of Allen Associates Construction and Habitat for Humanity Southern Santa Barbara County, both located in Santa Barbara, California.
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