\t\t\t\tThe History of the Blower Door.<\/p>\n\n\n\n
Perhaps no piece of equipment has changed the way energy professionals look at buildings more than the blower door. Over the past 15 years, entire diagnostic procedures have evolved around this relatively simple device that can make subtle, but measurable, changes in house pressures.
\nThe blower door as we know and love it today springs from technology first used in Sweden in 1977, where it was actually a blower window. The idea migrated to the United States with Ake Blomsterberg, who came to Princeton University to do research in 1979. \u201cWe started using it because we were trying to understand infiltration,\u201d says David Grimsrud, who was a researcher at Lawrence Berkeley National Laboratory (LBNL) in Berkeley, California, at the time.<\/p>\n\n\n\n
According to Grimsrud, the Princeton researchers decided to mount the fan in a door because door sizes are more uniform than windows. Ken Gadsby (who was and still is at Princeton) recalls that they based the height of the lower door panel on his inseam length! With the help of the blower door, the researchers discovered that hidden leaks accounted for a much greater proportion of air leakage in a home than the more obvious culprits, such as windows, doors, and electrical outlets\u2013a giant leap forward in our understanding of how a house operates (and malfunctions). Researchers at LBNL began to see how useful the blower door would be in weatherization and retrofitting work.<\/p>\n\n\n\n
Blower door companies started springing up to serve the new market. LBNL energy researcher Max Sherman even got into the business of manufacturing blower doors for a short time. \u201cThe Department of Energy put out a solicitation to buy ten blower doors, so my father and I started a company and bid on the contract and we won,\u201d Sherman remembers. These were big, heavy, clunky blower doors, made of plywood and Formica.<\/p>\n\n\n\n
\u201cWe were all working out of our garages,\u201d recalls Gary Anderson, cofounder of the Energy Conservatory. In 1986, Home Energy (then Energy Auditor and Retrofitter) identified 13 blower door manufacturers, with combined revenues for sales and testing nearing $10 million per year (see \u201cA Healthy Outlook for the Blower Door Industry,\u201d EA&R May\/June \u201886, p. 6).
\nHome Energy
\nestimated that blower door sales alone reached $1.2 million in 1985. The focus at that time was on making more powerful fans in more manageable sizes.
\nAnd Then There Were Three<\/p>\n\n\n\n
The industry has consolidated today, with only three North American manufacturers\u2013the Energy Conservatory, Infiltec, and Retrotec\u2013now vying for sales in a growing market.<\/p>\n\n\n\n
The Energy Conservatory<\/p>\n\n\n\n
Of the three, Energy Conservatory (manufacturer of the Minneapolis Blower Door) is easily the largest, selling 800 to 1,000 blower doors per year, along with Duct Blasters, digital pressure gauges, and other diagnostic tools and procedures.<\/p>\n\n\n\n
The Energy Conservatory was hatched over lunches between partners Gary Anderson, then an auditor in St. Paul, and Gary Nelson, an engineer at the Minnesota Energy Agency, during which they would discuss the latest discoveries in residential energy efficiency. The blower door was one advance that captured their imagination.<\/p>\n\n\n\n
\u201cIt got to be an expensive hobby,\u201d Anderson recalls. The pair retrofitted a two-story garage to use as a calibration chamber and strove continuously to create a design that would be more practical for mainstream contractors. That meant it had to be less expensive, lighter, and easier to use. They worked to make blower door testing more friendly, accurate, and efficient, and helped develop protocols for weatherization programs to prioritize air sealing efforts.<\/p>\n\n\n\n
In the late 1980s, the Energy Conservatory was involved in research that led to the understanding that duct leakage is a big problem\u2013not just for energy waste, but also because pressure imbalances caused by the duct system can result in backdrafting and indoor air quality problems. This realization led to the development of a duct leakage testing fan (the Duct Blaster) and a digital manometer for more precise pressure measurements.<\/p>\n\n\n\n
Infiltec<\/p>\n\n\n\n
Infiltec sells blower doors, in addition to developing energy software and conducting indoor air quality studies for the Environmental Protection Agency.<\/p>\n\n\n\n
\u201cWe sold our first blower door in 1980,\u201d says Infiltec\u2019s David Saum. Saum got into the business when his retired father was looking for ways to make his home more energy-efficient. Saum did some research and found articles on the Super Sucker, the window-mounted unit being used in Texas. \u201cWe decided that we could do better,\u201d Saum says. In addition to blower doors, Infiltec now sells duct testers, mostly for testing ducts in new construction. Infiltec has recently taken its blower doors to Russia to test multifamily buildings there (see \u201cTo Russia with Blower Doors,\u201d HE Sept\/Oct \u201895, p. 8).<\/p>\n\n\n\n
Retrotec<\/p>\n\n\n\n
The Canadian firm Retrotec concentrates on selling units for testing fire protection systems, and on teaching HVAC contractors how to use the blower door to boost their business (see \u201cHVAC Contractors Discover Blower Doors\u201c). Retrotec has also been in business since 1980. The founders originally opened their factory because they needed blower doors to use in research projects for Natural Resources Canada (the equivalent of the U.S. Department of Energy).<\/p>\n\n\n\n
\u201cAt the time, you couldn\u2019t buy a blower door,\u201d vice president Brendan Reid says. Retrotec now offers seven models\u2013all different configurations of the same equipment. Four of these are used in testing industrial fire protection systems. The company offers an optional panel system made of molded plastic sheets, which Reid says installs faster than the standard doors and looks better, although it is less adjustable. Retrotec also sells a sealed smoke puffer, and a duct leak testing system for new construction. With nine employees and two independent sales contractors, the company has annual revenues of just over $1 million.<\/p>\n\n\n\n
The Amazing
\nShrinking Sucker<\/p>\n\n\n\n
Old-timers in the industry can best appreciate the evolution of blower door technology over the years. They\u2019re the ones who remember struggling with a heavy, bulky fan and door panels. \u201cWe had a chance to use one of Max\u2019s blower doors,\u201d Gary Anderson recalls, \u201cand when we\u2019d lug the blower door out there, two things happened. We\u2019d be blown away by what we were learning, but at the same time, we were frustrated by how long it took.\u201d<\/p>\n\n\n\n
\u201cOur first blower door moved 4,200 cubic feet per minute (CFM) maximum flow, weighed about 55 lb, and was about 28 inches long,\u201d says Anderson. \u201cThen we made a 10-inch long fan that moved 6,400 CFM, increasing flow by 50% with a shorter fan.\u201d Refining the frame was the next major improvement in the blower door, and the Energy Conservatory went to a cloth-covered aluminum frame.<\/p>\n\n\n\n
Infiltec\u2019s design also evolved over time, switching from a DC to a much less expensive AC motor. They also introduced a flexible door panel and started using fan rpm instead of just pressure drop to measure flow, improving the accuracy of calibration.<\/p>\n\n\n\n
HVAC Contractors Discover Blower Doors
\nHome Energy
\n\u2019s readers are familiar with the use of blower doors for weatherization. HVAC contractors are also beginning to recognize the value of using blower doors to improve the quality of their work and to distinguish their company\u2019s service in the market. Many have found that they can make more profit by fixing the problems than by selling higher-capacity equipment to provide thermal comfort in a leaky house. The blower door helps them do that. It also improves their ability to address such issues as backdrafting and indoor air quality.<\/p>\n\n\n\n
People like John Tooley of Natural Florida Retrofit and Larry Palmiter with Ecotope have played an important role in bringing blower door testing to the HVAC industry. Since they and others learned of the hazards that can be caused by pressure imbalances in homes and ducts, they have worked to get the message out to people who work on houses. The energy waste and safety problems that can be diagnosed with pressure diagnostics are substantial, and contractors in many areas now understand that it\u2019s good business to use blower doors in their work.<\/p>\n\n\n\n
Blower door manufacturers provide training for those who will use their equipment. For example, Retrotec has specifically targeted HVAC contractors with a package that includes seven days of training, with manuals, videos, brochures, and telemarketing scripts. As Reid says, \u201cWe realized that if they didn\u2019t have the training and support, they almost never used the blower door.\u201d He adds that the 160 contractors Retrotec has trained in the last four years use the blower door to differentiate themselves from the competition and to add value to a proposal in a way that doesn\u2019t cost them a lot of money. \u201cWe\u2019re trying to show that a higher price is often a better value.\u201d<\/p>\n\n\n\n
Mediterranean Heating and Air Conditioning<\/p>\n\n\n\n
Mediterranean Heating and Air Conditioning, in Canoga Park, California, owns five blower doors, and it didn\u2019t take long for their investment to start paying off. \u201cThe first week after we got the blower door, we tested my house and found 500 CFM of leakage,\u201d representative Mike Gardner relates. \u201cI looked up in the return air chase and found it was open to the attic\u2013a 12 inch by 30 inch space, open to the attic. The more houses we tested, the more we found that that\u2019s common. Systems are losing 30% to 60% of capacity on the hottest days, and that\u2019s normal!\u201d<\/p>\n\n\n\n
Gardner uses the blower door as an educational tool, to help customers understand that they are losing air. \u201cWe use Polaroid cameras in the attic to show them where the duct leaks are,\u201d he says. After the Northridge earthquake, Mediterranean staff could easily verify whether ducts had been damaged.<\/p>\n\n\n\n
\u201cWe\u2019ve really had a shift in emphasis in what\u2019s important in the HVAC business,\u201d says Gardner. \u201cNow the most important factor in how a system works is the integrity of the air distribution system. You have to ensure that integrity, so that people get the performance they expect from the equipment you install.\u201d<\/p>\n\n\n\n
Gardner\u2019s company goes into about 10,000 houses a year. Blower doors will one day be a necessity in his business. \u201cIf you don\u2019t understand the problems associated with duct leakage, you\u2019re not going to be in the business,\u201d he says. A year ago Gardner knew of only one other contractor in the Los Angeles area who had a blower door, \u201cand it sat in the closet.\u201d Now he knows seven contractors in the area who use them. \u201cIt\u2019s an incredible competitive advantage.\u201d<\/p>\n\n\n\n
Holt Service Company<\/p>\n\n\n\n
Before they started using blower doors in their business, \u201cwe could not find the problems because they were hidden under the insulation,\u201d says David Holt, president of Holt Service Company in Columbus, Georgia. Holt, the third generation to oversee the operations of the family business, says his company has used blower doors for three years. \u201cIt makes us money and it solves a lot of problems for the customer. The true benefit to consumers is health, safety, and personal comfort. The financial aspects are nice, the icing on the cake.\u201d He relates the story of a woman who had serious respiratory problems for years, which disappeared after he sealed her duct system. \u201cWithin about ten days, she called and said, `For the first time in ten years I\u2019ve been able to sleep without getting up and getting my respirator.\u2019\u201d<\/p>\n\n\n\n
\u201cWhat\u2019s it worth for you to sleep comfortably in your home all night and not wake up all clogged up?\u201d Holt asks potential customers. \u201cYou don\u2019t have to breathe all this dust and mold, don\u2019t have to deal with all the moisture; you\u2019re breathing cleaner, fresh air; and there\u2019s no backdrafting.\u201d<\/p>\n\n\n\n
What\u2019s Next?<\/p>\n\n\n\n
\u201cThe equipment has pretty much evolved to optimum,\u201d says Anderson. \u201cThe fan weight has dropped from 60 lb to 35 lb, at the same time increasing flow.\u201d The next step is toward computerization and improved error analysis. A computerized, digital blower door will make data more accurate and repeatable at lower house pressures. It will also make it easier for researchers to track a wide variety of conditions. For example, David Grimsrud is now at the University of Minnesota, where he is conducting blower door tests by remote control, tracking measurements by computer to study backdrafting in buildings. His studies use the newest development by the Energy Conservatory: a 16-channel data acquisition system that processes input from carbon dioxide monitors and pressure and temperature sensors.<\/p>\n\n\n\n
Super Sucker, the Sequel<\/p>\n\n\n\n
In another interesting development, a monster blower door that takes the name of the window-mounted unit used in Texas all those years ago is being used to test large residential and commercial buildings in Canada. The Super Sucker is a whopping 55,000 CFM fan that is 40 ft long and 5 ft in diameter. It is transported to the site on a flatbed trailer, and it takes a team of five people to hook it up (to a pair of double doors) and perform the test.<\/p>\n\n\n\n
A Blower Door for Windows<\/p>\n\n\n\n
At the other end of the spectrum, the Canadian consulting firm CanAm Building Envelope Specialists Incorporated is marketing an individual window depressurization testing kit, called the MiniLab, which is used to identify and quantify air leaks around windows. This mini-blower door allows retrofitters to demonstrate improvements in air leakage when they replace or seal windows, and enables new home builders to specify and measure the performance of their windows.<\/p>\n\n\n\n
The History of the Blower DoorWindow leakage is tested by installing 6-mil plastic on the inside around the window frame, cutting a hole in the middle of the plastic and attaching and sealing a tube in the hole. The hose is then connected to the blower, which pressurizes the space between the plastic and the window. The device has flow meters and a Magnahelic gauge, like a blower door, to measure flow in CFM at a given pressure. New standards in Canada require windows to meet air leakage ratings at 75 Pascals (Pa) of pressure.
\nWho\u2019s Buying
\nBlower Doors?<\/p>\n\n\n\n
\u201cThe market has changed from year to year,\u201d says Infiltec\u2019s Saum. \u201cOriginally it was entrepreneurs during the energy crisis; then it changed to utilities and weatherization agencies; and then a few years ago, to the fire protection business.\u201d Blower doors are used to test fire protection systems that use halon gas instead of water (to prevent water damage in case of a fire). These systems used to be tested by setting them off and timing how long it took the halon to dissipate. The EPA banned this procedure when \u201cit was found that halon was the worst ozone eater by a factor of ten,\u201d says Saum. With a blower door, contractors can calculate how long it will take for the halon to leak out of a structure without actually releasing it into the atmosphere.<\/p>\n\n\n\n
\u201cTo some extent, we have begun to saturate the weatherization market,\u201d Anderson says. However, the blower door is also a valuable tool for HVAC contractors and builders. \u201cEverybody who goes into houses and changes the way the houses operate wants to be sure they don\u2019t do damage. HVAC contractors are becoming more aware than builders; they are much more familiar with the problems that can arise.\u201d Retrotec\u2019s Reid agrees, \u201cThere\u2019s high potential because of the numbers,\u201d he says, \u201cwith about 50,000 HVAC contractors in North America.\u201d<\/p>\n\n\n\n
\u201cWe\u2019re moving to a time in housing construction when we\u2019ll see more mechanical ventilation systems,\u201d adds Grimsrud, requiring the near elimination of infiltration, and heralding a demand for infiltration testing in the construction industry.
\nAnderson points out that most of the people who stopped by the Energy Conservatory\u2019s booth at a recent builders\u2019 show weren\u2019t familiar with blower doors, \u201cbut just about every one of them talked about moisture problems, backdrafting, fireplaces that won\u2019t draw\u2013all of which have to do with the airtightness of the envelope.\u201d<\/p>\n\n\n\n
\u201cThey definitely will benefit from this technology,\u201d Anderson continues. \u201cThe option is to build the house and then deal with the problems that show up. A blower door gives builders some control over these problems, because they know how tight the house is, how to deal with duct leakage, and how to size a ventilation system.\u201d<\/p>\n\n\n\n
\u201cThe most important legacy of the blower door,\u201d concludes Anderson, \u201cis the evolution of the understanding of the house as a system and how you can characterize and diagnose the problems using pressure analysis.\u201d<\/p>\n\n\n\n