Weatherization Workforce Training Program

Transcription

1 Weatherization Workforce Training Program Diagnostic Testing > Blower Doors Blower Doors The blower door is the main tool for determining how leaky a home is, but it will do more than simply test for air tightness. In fact the blower door can be used for a multitude of other tests. It can help the weatherization team find air leaks to the outside, understand the condition of the home s duct system, and evaluate the overall safety of the combustion appliances exhaust systems. To better understand the important role the blower door can play in the weatherization process, this lesson will focus on: How the blower door works How blower door test results are used in the weatherization of a home What the specific parts of the blower door are How to assemble a blower door for testing a home s air tightness Learning to properly assemble, calibrate, and run a blower door test is no easy task. Even experienced operators, with dozens of successful outings, continue learning how to run more consistent and complete blower door tests. However, with a basic understanding of how the unit operates and what the intended results of the test are, anyone should be able to assemble and operate a blower door. How the blower door works A blower door is a powerful fan unit that mounts into the frame an exterior door. The unit can be disassembled and reassembled relatively quickly, is light and portable to transport, and includes sensors that measure air pressure inside and outside of the house. Once the unit has been assembled, calibrated, and turned on, the fan pulls air out of the house, depressurizing the home s interior. With air pressure lower on the inside of the home lower than on the outside, air is pulled into the home through all unsealed cracks and openings in the building. In simple terms, the blower door creates a slight vacuum The blower door when fully assembled. within the building envelope, which sucks air from outside the house through cracks, holes, and other gaps in the building envelope. The blower door creates a pressure difference of 50 Pascals between inside and outside. Fifty Pascals is roughly equal to a 20 mile per hour wind blowing against all surfaces of the building equally BMI & RHA, All Rights Reserved 1

2 Of course a home wouldn t be nearly as depressurized under normal circumstances, but by exaggerating the defects in the building shell, the blower door test makes it easy for the weatherization team to locate air leaks. This diagram shows how a blower door pulls air through cracks and gaps in the building envelope and pushes the air out the blower door fan, noted here as purple fins. The blower door s sensitive monitoring equipment measures how much air is passing through the fan. This measurement is used to estimate how leaky the home is: the leakier the house, the harder the fan must work to maintain the 50 Pascal pressure. The amount of air the fan blows is measured in cubic feet per minute or CFM. Once we understand how much air is passing through the fan, we can begin to map a strategy for sealing the leaks. Blower doors can also be used to pressurize the home. Pressurization will create a positive pressure on all sides of the building envelope. In this situation, air will be leaking out of the house by being forced into the building through the fan. In some situations, you may use a pressurization test, and in others, a depressurization test, and sometimes you will use both depressurization and pressurization. When the blower door test is running, there are several tests you can perform, some using the pressure measuring equipment, some simply with a smoke pencil, to pinpoint where the air leaks are. How the results of a blower door test are used in the weatherization of a home The blower door is mainly used to evaluate a home s air tightness. Air tightness is not about insulation; it mainly has to do with how well the building s exterior wall penetrations have been sealed. These penetrations include those made by electrical or cable television wires, or by water and sewer pipes. Air leaks can also occur around poorly caulked doors and windows, and even through gaps in the home s framing BMI & RHA, All Rights Reserved 2

3 Understanding the home s level of air tightness is critical for several reasons including: Air leaks will obviously increase energy use Leaks can bring unwanted moisture into the home. Excessive moisture can lead to rot and decay in framing and other materials, as well as mold and poor indoor air quality (IAQ) A drafty home is less comfortable, and has less consistent temperatures from room to room If the blower door test shows that the home is very leaky, or has been poorly sealed, then finding and stopping the leaks will dramatically improve comfort, durability, and energy efficiency. At the same time, if the blower door finds that the home is relatively tight, or has few air leaks, then the weatherization crew can spend its time and money on other improvements, like sealing air ducts or adding insulation. The blower door also creates pressure differences between the home s conditioned rooms and unconditioned areas like attics and crawl spaces. This pressure difference can provide information about the location and the size of a home s air leaks. For instance with the house pressurized, we should be able to use a smoke pencil to see air escaping into the attic. That tells us where we need to do our air sealing. Readings taken during the blower door test are very important because they help set a baseline for the weatherization project. By doing a blower door test before work begins, we understand where the holes are before we start work. Tests performed during the weatherization process can tell us if we re missing any major air leaks. A blower door test at the end will verify that we ve done the job correctly. Parts of the blower door The blower door can be disassembled into a few small, compact, and well-cushioned carrying cases. The basic parts of the blower door are: Frame Fabric curtain (tent or skirt) Fan Rings Pressure measuring devices Fan speed controller Along with these parts there will be electrical cords to power the unit colored tubing that is connected to either the pressure measuring devices or the blower unit. The blower door frame gets assembled and inserted into the home s exterior door frame. The nylon fabric goes around the frame and helps create an The blower door parts from left to right are flow rings, fan, tent (skirt), and disassembled frame. air tight barrier above the fan. Some people call the nylon fabric a skirt and others call it a tent. The blower door fan is used to move the air through the blower door assembly and will be installed to either 2009 BMI & RHA, All Rights Reserved 3

4 blow air out of the home during a depressurization test, or blow air into the home during a pressurization test. Flow rings are inserted into the fan and either restrict or allow more air to flow through the blower door fan. There are two kinds of pressure measuring devices used on a blower door: a digital manometer and an analog magnehelic gauge. Both gauges are equally accurate. A digital manometer measures the pressure between the indoors and outdoors as well as the pressure from the fan through the gauge. This is a nice piece of equipment because it has a self-zeroing feature that also can connect to different kinds of software to print out reports on the results of the blower door test. Digital manometers are very delicate and water sensitive devices, and should be handled with extreme care. With an analog magnehelic gauge you have to do the zeroing yourself if there are pressure differences at the baseline before you test. The magnehelic gauges were very common in the 1970 s but have not been manufactured for some time. Almost all new blower door units today use a standard digital manometer. The digital manometer has a self-zeroing, or self-calibrating feature. The analog or magnehelic gauge is a pressure measuring device for the blower door. This unit has the fan speed controller already mounted BMI & RHA, All Rights Reserved 4

5 How to assemble the blower door The first step in assembling the blower door is to remove the parts of the frame and position them on the floor. Step 1 Carefully unpack the blower door The next step is to connect the corners of the frame together so that they re securely fastened. Step 2 Connect corners of frame 2009 BMI & RHA, All Rights Reserved 5

6 The third step is to move the frame to the exterior door opening and adjust the frame size to the door opening size. Step 3 - Adjust the frame to snuggly fit the door. After that, spread the fabric, or skirt out on the floor. Once the fabric is spread, remove the frame from the door and lay it on top of the fabric and fasten the frame to the fabric using the Velcro fasteners at the bottom and the top. It is important to make sure that the fabric is snug around the frame. Fasten the frame to skirt BMI & RHA, All Rights Reserved 6

7 Next, insert the frame and the fabric into the door opening with the excess fabric folded to the interior. Adjust the blower doorframe so that there are not any visible gaps around the frame and that the frame fits tightly within the opening. You ll also want to make sure that the skirt is tightly fit around the frame so that it s taut and snug. Insert frame into door, tucking in excess fabric. Next, remove the gauges from the case and fasten them to the door. Secure gauges to door BMI & RHA, All Rights Reserved 7

8 After that, remove the fan from the case and insert it into the opening in the fabric skirt. Use the horizontal bar in the blower door frame and the Velcro to safely secure the fan so that it does not fall out of the fabric during operation. Remember, for pressurization the fan should blow into the house, for depressurization the fan will blow air out of the house. Make sure there are no obstructions around the fan before you install it into the door. The fan is a delicate and powerful unit that when operating generates a lot of noise. Be sure to inform occupants of this before starting the blower door test or operating the fan. Secure the fan to the horizontal bar in the blower door frame making sure it cannot fall out during the test BMI & RHA, All Rights Reserved 8

9 Next, remove the pressure tubes from the case and insert them onto the pegs of the digital pressuremeasuring device.. Depending on the test, the hose configuration will vary. For instance the first tube might connect the reference port on the gauge to the outdoors to measure pressure in the building with reference to the outdoor pressure. The other tube might measure airflow through fan. Connect the tubes per manufacturer s instructions. Depending upon the test you will be running, the configuration of the hoses will vary. Finally, plug the cord from the speed controller into the blower door fan, and from the electrical outlet to the speed controller. Make sure the speed controller is in the off position before plugging the power cord into the wall outlet. Be sure the speed controller is in the "off" position before plugging the unit into the wall outlet BMI & RHA, All Rights Reserved 9