Weatherization Workforce Training Program

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1 Weatherization Workforce Training Program Diagnostic Testing > Conducting Blower Door Tests Conducting Blower Door Tests Conducting a blower door test is relatively easy, but before you turn on the equipment, there is series of steps you must take to prepare you, the blower door equipment, and the home for the tests. In this lesson you will learn: How the blower door will affect the home when it is in operation How to prepare the home for the blower door test How to zero-out or calibrate the manometer How to conduct a successful blower door test How the blower door will affect the home In order to understand why preparing the home is important, you first need to understand what the blower door will actually do to the home. The blower door can be used to positively or negatively pressurize the building. During a pressurization test, the blower door will blow air into the building and force it out through cracks and openings in the building envelope. During a depressurization, or negative pressure test, the blower door fan will suck air out of the house, creating a vacuum in the house. While the The blower door, shown here as purple fins, will depressurize the home to - 50 Pascals creating a slight vaccuum in the home. This will pull air in through all the cracks in the building envelope and help you identify spots to air seal. blower door fan is running, you can capture important measurements about the volume of air being moved into or out of the home, and you can also locate the air leaks in the building shell and seal them to make the home more energy efficient and air tight BMI & RHA, All Rights Reserved 1

2 When in operation, the blower door will create a pressure difference between the inside of the home and the outside. Although this pressure difference is large enough to move air, it is not large enough to cause any concern for the health and safety of the occupants. People with breathing problems, or who require oxygen tanks to breathe, should not be concerned about the blower door test. The pressure difference will not be great enough to pop the occupant s ears, nor blast windows from their frames. The blower door is loud, so talking while the test is running, especially near the fan unit, may be difficult. Also, because the blower door will probably be installed in the main entrance of the home, you will want to make sure that other points of entry are unlocked and accessible so that you and the occupants can come and go freely from the house during the test. This is very handy to remember, especially if you are conducting the test by yourself. Getting locked out of the home during a blower door test is not the best example of professionalism on the job site. It is also important to talk to the occupant before moving any furniture or accessing basements and crawlspaces. You want to be very careful not to damage any of the occupant s belongings, or to make them uncomfortable when moving around the home. Ask the homeowner about removing your shoes when you enter, and explain to them what you are going to do with the blower door test. The main complaint occupants may have is a significant change in the home s temperature. Because of the exaggerated air movement through the home, the blower door will be forcing conditioned air out and pulling unconditioned air in. For homes that are cooled by air conditioners this means that the home s interior will soon be the Some of the basic supplies you will need to prepare the house same temperature and humidity as the include cardboard, tape, foam blocks, and self-adhesive film. outside air. In the winter a blower door test can rapidly cool the home by displacing the warm heated air with chilly air from the outside. For this reason it is a good idea to only run the blower door fan unit when working on identifying air leaks, or taking measurements with the manometer. Supplies needed for preparing the home for the blower door test There are a number of supplies you will need to prepare the home for the blower door test. Because you never know what you are going to find once you get out in the field and on the weatherization project, it is a very good idea to always be prepared. Some of the basic things you will want to bring with you to the blower door test are: 2009 BMI & RHA, All Rights Reserved 2

3 Cardboard. When dealing with broken windows or other large openings in the building shell that are eventually going to be permanently repaired, it is nice to have cardboard and different types of tape and plastic to cover those openings up during the test. Foam blocks. Foam blocks can be inserted into intentional openings like supply or return registers or vents to stop the air from leaking. Tape. Some of the tapes available today have more adhesive than others and seal very well for things such as cardboard or attaching the plastic around openings. But if there s an area where the paint may chip off using a looser, less aggressive tape might be necessary. Film. Self-adhesive films or plastic can be used to be put over exhaust covers or vents on the outside of the building. In addition to these supplies you will want to have a pen, paper, and clipboard to record the measurements you get during the blower door test. It is also a good idea to create a checklist of all the alterations to the house you made to conduct the test, so that you can return it to its original condition when you are finished. Closing up the home for the test The accuracy of the blower door test is very dependent on how closed up the building is. The overall goal of preparing the home for the test is to allow air to flow freely from all conditioned spaces to, through, and out the blower door fan (during depressurization). This includes letting airflow through the forced air system, so sealing up the ducts and registers is not necessary. To ready the home for the blower door test you will want to prepare the physical space and allow for free airflow between conditioned spaces. A conditioned space is any part of the home that has heated or cooled air circulating through it. Conditioned air spaces include: Bedrooms Hallways Bathrooms Utility rooms Likewise you will want to close off any doors or access hatches to unconditioned air spaces. Unconditioned air spaces include: Crawlspaces Attics 2009 BMI & RHA, All Rights Reserved 3

4 Garages Attached porches that are screened in Here are some of the other important preparations you will need to do to the home before conducting a blower door test: Make sure that the home s heating and cooling system is in the off position so that is will not turn on during the blower door test. Make sure that pilot lights are off on the water heater, the furnace, or any combustion appliance. This is a critical safety issue. We want to make sure the pilot lights are off because when the home comes under negative pressure, pilot lights may be accidentally blown out which can result in natural gas or other combustible fuels being spilled directly into the living environment. Seal all exterior vents, including dryers, bath fans, and range hoods, so that they don t blow open during the test. Vents with baffles that open during fan operation should be taped shut. If there is a wood fireplace or a wood stove, we want to remove the ashes and close the damper so they do not enter the building during the blower door test. If ashes are not removed before the blower unit is turned on, they will be pulled into the living space and drawn towards the fan. This is sure to make a mess and not impress the occupant. Pour water down all plumbing traps, especially floor traps in basements or seldom used showers. When sinks or floor drains have not been used for a while, the water in the trap can evaporate. When you begin the blower door test, if the traps are dry, you could pull sewer gasses, including methane, into the building envelope. This can be a health hazard and a fire risk. Be sure to ask the occupant about any drains in the basement that you might miss when prepping the home. Close all exterior doors and windows latching them securely in place when possible. Closing off the spaces does not mean air sealing beyond what is already in place in the home, but if there is a broken window you will want to temporarily patch it with cardboard to help reduce the amount of air flowing in and through the blower door. Large gaps like open windows or broken doors will make the blower door test very difficult, if not impossible to conduct. Figure 2. Seal all exterior vents such as dryers, bath fans, and range hoods with clear selfadhesive film or tape. Figure 1. Pour water into drains to prevent backdrafting of sewer gasses during the blower door test BMI & RHA, All Rights Reserved 4

5 If you notice weather stripping missing from around a door, you should not repair it at this time because you will want to measure how much the air was passing through that gap in the building envelope. After the repairs have been made to the house you will conduct another blower door test to gauge effectiveness of your work. After you have finished the blower door test and are ready to leave, you will want to relight the pilots for all combustion appliances, remove film and tape from vents, and return the home to its original condition. One handy tip is to leave your car keys atop the water heater when you turn the pilot light off. This will guarantee that you remember to relight the pilot before leaving. Zeroing-out or calibrating the manometer Once you have successfully prepared the house, you are ready to calibrate the pressure measuring devices and start the blower door test. Calibration, or zeroing-out, is necessary to get an accurate measure of the volume of air leaking through the building envelope and the pressure differences between inside and outside. Depending on the type of blower door you are using, there are a number of different ways to zero-out the equipment. It is important to zero-out the gauges so that you know the baseline benchmark that you are working from. Zeroing-out the gauges insures that we re at zero pressure in the building with reference to the outside before we start the blower door test. If you are using an analog gauge you will need to manually adjust the pressure. To zero-out the analog or magnehelic gauge, use a small screwdriver to turn the screw at the bottom of each dial so that the measuring needle is at zero. Be sure to complete this step before turning on the blower door unit. Digital manometers have a self-zeroing feature that you can activate when you turn the unit on. Each model manometer is different, so be sure to consult the manufacturer s operational instruction manual to learn how to zero-out the specific manometer you will be using in the field. Attaching the tubing to the manometer and fan It is important that the tubing be properly attached to the manometer and to the fan. Placement and connection of the tubing is critical in order to achieve an accurate air tightness reading. The first tube should run from the reference port on the gauge, the A channel, to the outdoors. It measures pressure in the building with reference to the outdoor pressure. The next tube runs from the B channel side of the input to the fan, and measure the airflow through the fan. Make sure the tubing is not crimped or blocked. Even stepping on the tubing during the test can drastically change the readings on the manometer. Most blower door units have a small hole in the skirt to allow for the tubing to be inserted through and pulled to the outside to get the outdoor pressure reading. It is important that the end of the tube on the outside not be near the fan. If the end is too close, the air being blown out of the house will affect the test results. If the ends of the tubes ever get 2009 BMI & RHA, All Rights Reserved 5

6 cracked or frayed, you can clip them off, making sure that you have a neat, even connection between the tubing and manometer pegs. Tubing comes in a variety of colors and lengths, but as long as there are no cracks or holes in the tubing, color is for simple reference only and will not impact the test results. With Reference To (WRT) Often when setting up the manometer to conduct a blower door test, the term with reference to or WRT will be used. With reference to is an industry term that describes the relationship between where the manometer is (the areas being tested) and the zero or baseline (often the outdoors). For instance, when attaching the tubing to run to the outdoors, the measurement you are taking is indoor air pressure with reference to the outdoors. To properly set this up, the reference (REF) peg on the A channel of the digital manometer will have the tube running to the outside, and the Input peg will be open allowing for a reading of the space where the manometer is (inside the home). For some tests you can use the manometer to measure pressure differences within the home, like when testing the pressure around combustion appliances to prevent backdrafting of exhaust fumes into the living area. To conduct this test you might slip the reference tube under a closed door of the mechanical closet to measure that room s pressure with reference to the space you are standing in. Although with reference to (WRT) can take time to get comfortable with, it s a very important concept because it will help you understand and articulate what you are trying to test, and will also help you get more accurate results. WRT or With Reference To is an important, but often confusing term to understand when conduction a blower door test. The B-side of the digital manometer is used to measure the CFM, or Cubic Feet per Minute of air that passes through the fan. This measurement will inform you of the volume of air being sucked through cracks in the building envelope during a depressurization test. An analog or magnehelic manometer has the three gauges that measure three different things. The top gauge shows the house pressure WRT (with reference to) the outdoors, the middle and bottom gauges show the fan pressure as well as the CFM of air moving through the fan. After attaching the tubing, make sure the speed controller is in the off position, and to plug the blower door s electrical cord into a wall outlet BMI & RHA, All Rights Reserved 6

7 Also make sure that the area around the blower door is cleared before starting the fan unit. Obstruction to air flow will alter the test results, and dust or loose particles will get sucked into the blower door when it is running, so care should be taken. Starting a blower door test and reaching 50 Once you have cleared the area around the blower door, you can turn the knob on the speed controller to start tuning the fan speed. In a depressurization test the intent is to increase the fan speed until the home has reached a point of -50 Pascals of exaggerated pressure. A Pascal is a scientific unit of measure that was established by the French mathematician Blaise Pascal in the 16th century. It is the pressure standard that is used to do all blower door testing. A -50 Pascal pressure measurement is equal to a 20-mile an hour wind blowing on all sides of the building. All blower door tests use 50 Pascals as the interior baseline, compared to an outdoor pressure of zero Pascals. When pressurizing the home, there will be 50 Pascals more air pressure on the inside than on the outside. When depressurizing the home, there will be 50 Pascals less pressure on the inside than on the outside. If you have no trouble reaching 50 Pascals (positive or Make sure the area around the blower door is clear before starting the fan. negative) it means that you have done a good job of prepping the home and you can begin to record the measurements on the manometer. Sometimes though, you will have trouble reaching 50, and when this happens there are several things you can do. If you have a problem reaching 50 Pascals, it means that the home is allowing so much air through the fan that you cannot create a strong enough vacuum. This is like trying to pump up a bike tire that is full of holes, or siphon water through a leaky pipe. The first thing to check if you can t hit 50 is to walk around the building and make sure that all the doors and windows to the outside are closed. There may be a damper on a fireplace or a dryer vent that is open and that needs to be properly closed. Once you have checked the home you can come back to the blower door and restart the test BMI & RHA, All Rights Reserved 7

8 If you still can t get to the pressurization of 50, you can stop the fan unit and remove one of the flow rings from the fan to allow more air to move through. Keep removing flow rings until you can either hit 50 Pascals, or the fan is wide open and there are no more rings to remove. If you still can t hit 50 Pascals, then it is safe to say that there is a large leak in the building. Either you did not, or cannot, prep the building properly, or the building is leaky enough that you simply aren t going to reach the 50 Pascals of pressure difference. In this case you can use the Can t Reach Fifty Factors (CRF) chart usually printed on the speed controller of the blower door. The Can t Reach Fifty Factors (CRF) chart allows you to take the house pressure reading and multiply it by a factor to calibrate the CFM reading. This is done by rounding the pressure reading you can achieve down to the nearest 5 unit measurement, and then multiplying the CFM reading by the CRF factor. This process is actually much easier than it sounds. For example, if you are at a 33 Pascal pressure difference between the inside and outside, and cannot get the home to the 50 Pascal goal, round your reading of 33 Pascals down to the nearest 5 unit measurement, which in this case would be 30. Next, use the chart on the speed controller to determine your CRF Factor. According to the chart, if your house pressure is at 30, then you will use a factor of 1.4 Finally, multiply the CFM measurement on the manometer that you are reading at the 33 Pascals by 1.4 to get what it would equal at 50 Pascals. If you were reading a CFM of 3800 at 33 Pascals, then by using the Can t Reach Fifty Factors (CRF) chart you could estimate a CFM of X 3800 = 5320 Cubic Feet per Minute at 50 Pascals Figure 3. On the bottom of most speed controllers is a handy chart that can be used if you cannot reach 50 on the manometer. Remember, the ultimate goal of the blower door is to measure how much air is passing through the fan when the house is at 50 Pascals. Once you know the volume of air that the house is leaking at 50 Pascals you have an industry standard baseline to evaluate the home s building envelope, and a starting point for making improvements through the weatherization process. One of the unique features of the digital manometer is that it has a timing function that you can use to take a pressure measurement every one second, five seconds, or ten seconds. If there are adverse conditions outside if it is windy you may want extend that time out to longer periods so that it averages out any variations in wind speed. By using this average you can get the most accurate measurement. Along with adjusting the timing, if you encounter extremely windy conditions in setting up the blower door, it s very important to get the tube in a location that is least affected by the wind. If you have a 2009 BMI & RHA, All Rights Reserved 8

9 bucket or something else to cover that tube so it is at a stable pressure, you will get a more accurate reading of outdoor pressure. Maintaining and Caring for the Equipment All of the equipment used in the blower door test is expensive and fragile and needs to be treated as such. Storing each piece securely in its cases and transporting it carefully will make for more accurate readings and allow your equipment to last much longer. The digital manometer is the most fragile piece of equipment, so be very careful to make sure that that is never dropped, and that it is always carried within its case. Over time, the tubes may become stretched out or frayed from being inserted and taken off of the pegs, but it s ok to clip off the end of the tube so that it can make a tight seal. Be sure to transport the blower door equipment in the proper cases to extend the life of the equipment and get consistent, accurate test results. into the fan motor. The fan is also very fragile and includes pressure measuring devices. Take care handling and transporting it, and be very careful to make sure that that gets inserted into its case after the blower door test has been completed. The fan itself does not need to be oiled it is a closed, calibrated, sealed unit but make sure that no dirt or dust gets The skirt or tent that goes around the frame of the blower door can also become frayed or torn if it s not cared for properly. Be careful to make sure that the least amount of wear and tear occurs on the tent. The frame is fairly robust but can be damaged if it s dropped. It can also be bent if it runs into something. In Summary Before we had blower doors, we had no way of measuring the amount of air that leaks in and out of a building. With this contraption, we are able to specifically test how much air is leaking through cracks and openings in the building. Through the use of this blower door, we can air seal and tighten buildings and make them more energy efficient and comfortable. Once you understand how to use the gauges and the blower door system we can move on to further levels of testing BMI & RHA, All Rights Reserved 9