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House of Pressure

A house that sits on a table and that you can see through makes a fine teaching and learning tool.

March 01, 2010
March/April 2010
This article originally appeared in the March/April 2010 issue of Home Energy Magazine.
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The New River Center for Energy Research and Training (NRCERT) in Christiansburg, Virginia, is a division of Community Housing Partners (CHP), a nonprofit development corporation that serves the needs of low-wealth and low-income residents in the Southeast. NRCERT was established in 1999 to provide training to emerging professionals in the fields of in weatherization and whole-house performance skills. NRCERT also performs research for leaders in the field. This research has resulted in significant technical advancements for the weatherization and building performance industries.

NRCERT’s training emphasizes a whole-house approach to home performance, using detailed curricula and innovative models to support these training efforts. Its goal is to create homes (both new construction and retrofit) that are good for people, good for the environment, and good for business. Technicians are taught to reduce energy consumption, address the health and safety of occupants, and assess how the building envelope, appliances, and occupants interact with one another.

One of the teaching tools is the House of Pressure, which Anthony designed in 1995 for himself. He designed this tool to help visually demonstrate to his peers the complicated science of air pressure. At the time, Anthony was a weatherization crew member with New River Community Action.


Not Your Typical Dollhouse

The House of Pressure visually demonstrates pressure and air flow dynamics within a residence, using pressure diagnostics. It is a model of a single-family home, made of a clear, high-strength plastic laminate called Lexan that can be written on with a dry-erase marker. The interior of the House can be viewed from all four sides. It gives the instructor the ability to create and control air flow with working scale reproductions of the mechanical air distribution systems that are found in most homes.

The House features an operable forced air duct system, a clothes dryer, a bathroom fan, a fireplace, and a water heater. There are smoke generators in the water heater and the fireplace to demonstrate the dangers of backdrafting; and a smoke generator in an exhaust pipe in the garage to show the danger of CO infiltration from a garage into conditioned space. (The menacing theme of Jaws plays when backdrafting occurs, as a warning that smoke is coming back into the House!)

An automated performance testing (APT) device from the Energy Conservatory measures the air pressure levels in eight different locations in the House. It uses Microsoft Excel to project those pressure levels onto an LCD screen, so that audiences can view the pressure levels and the direction of air flow in every room. It’s like having eight manometers going at the same time, so when you make changes to one part of the House, you can see how they affect every other part, with immediate feedback from the APT.


Testing the Model Is the Same as Testing a Real House

To get accurate results, it’s important to understand how to set up and use diagnostic equipment—and the House of Pressure is no exception. An illustrated laminated sheet with instructions comes along with the model. The instructions show how to set up the measuring equipment to perform various tests on the model, and also how to use the equipment in the field. It even has color-coded hose hookups for using the digital manometer.

The House of Pressure can be used to

  • demonstrate blower door testing, using a digital manometer and a Minneapolis Duct Blaster;
  • demonstrate zonal and pressure pan testing;
  • show how duct leakage diminishes health and safety, comfort, durability, and energy efficiency by creating leaks in the supply ducts and/or the return ducts;
  • demonstrate the effect of thermal bypasses;
  • show pressure and thermal boundaries; and
  • simulate backdrafting conditions.


There are operable doors from the bedroom and bathroom to the central living area that show how air flow takes place in a house with a central return duct system. Pressure relief methods can be shown and discussed. Combustion appliance zone testing can be shown by following a worst-case test procedure using a digital manometer.


Evolution of the House of Pressure

Now a unique and dynamic training tool used nationwide, this high-tech model is a far cry from my original invention of 15 years ago. The first House of Pressure was made of file folders, and while it helped me demonstrate unintended air leakage, it wasn’t very functional. Anthony was hoping to create a teaching tool that was a little more hands-on. Basically, he wanted an effective way to explain and illustrate the ways that pressure, air flow, and building systems interact to cause energy, comfort, and safety problems in houses. When Anthony didn’t find that flip charts explained the concepts very well, he made his first model.

The second version of the House was made of cardboard boxes, with one on top to simulate an attic. By adding a Duct Blaster, Anthony was able to demonstrate zone pressures between the house and the attic. The third version was made of insulation board and had a furnace, exhaust fans, and combustion appliances. The only problem was that at 4 feet x 4 feet, it could not fit through a standard door! Over time, however, Anthony was able to incorporate increasingly more sophisticated materials and functions to evolve the model into the 2 foot x 4 foot x 4 foot wood frame structure that exists today.

The House of Pressure was designed to be large enough to put real test equipment inside, just as one would in an actual house, so that tests performed on the model would produce results easily translated back into real life. Anthony has traveled all over the country with the House of Pressure, and another great thing about it is that it can be used to teach all levels of audiences, from elementary school children to weatherization crews to graduate students. You can use the model to give a basic overview of air pressure, or to demonstrate highly detailed concepts. In fact, Anthony has used the model for presentations at regional and national DOE weatherization conferences, ACI conferences, and numerous state weatherization conferences and trainings.

Anthony never meant it to be something that he would build and sell to others. But once people saw the model at national conferences and such, word spread, and people started calling and wanting to order one. To date, Anthony has sold about 50 Houses of Pressure to individuals and organizations all over the country—including weatherization providers, contractors, realtors, universities, and government agencies. He even shipped one to Canada. (Anthony jokingly referred to it as the IHOP, or International House of Pressure.)

Prior to March, 2009, when stimulus dollars from the American Recovery and Reinvestment Act began reaching weatherization teams across the nation, NRCERT built and sold, on average, seven Houses of Pressure per year. From March to November 2009, the number of models ordered skyrocketed to a dozen. And people have ordered as many as six at a time! Anthony attributes this increase in sales to an influx in federal stimulus money for both weatherization and green workforce organizations and training programs.

Anthony used to make each model himself, taking about two weeks to create the frame and install the various mechanical components. However, as demand grew for the House of Pressure, Anthony found he needed to hire another person to build them. They are still completely handmade, and templates have helped to cut the building time almost in half.


The Model in Real Life

Anthony gets a kick out of how people customize their models. They are sort of like technical dollhouses, and folks sometimes add their own personal touches, like dolls and furniture, to the model. It’s great that they can make something fun out of a teaching tool.

Almost everyone who has taught classes using a House of Pressure agrees that is an excellent educational tool—one that can greatly reduce the amount of lecture time required to describe the information presented. It’s also a helpful tool to determine whether or not the lesson has been understood. Once he’s finished with a training session, Anthony has the students go back and physically demonstrate to him what he’s just taught them. That way he gets a pretty good idea of how well they were able to process the information.

Marquam George, associate professor of Construction Technology and program head at the University of Alaska Southeast, is another big fan. He says “The House of Pressure is worth a thousand slides. Nothing comes as close to visually connecting the interconnections of our buildings as the House of Pressure.” Marquam tells me that he has written to numerous school districts across Alaska, describing this tool and the science behind it, encouraging them to use it in their classrooms. “Many, many young students sent me their unused dolls for me to decorate our House of Pressure,” he adds.

Mark Meiling, president of ForeSight Home Performance, Incorporated, in Wauwatosa, Wisconsin, uses the House of Pressure to demonstrate to building professionals and potential clients the importance of upgrading new and existing buildings in order to reduce energy usage. He uses it in his exhibits at building/remodeling and energy shows, in training classes for weatherization crews, and in classes he teaches at area schools, such as Milwaukee Area Technical College. “One can more easily see how air pressures simultaneously change during multizonal series air leakage and worst-case depressurization testing by connecting the House to an eight-channel Automated Pressure Testing manometer or a Duct Blaster, and projecting the images, using Teclog, onto a screen,” says Meiling. This allows him to discuss the value of gathering reliable and predictable data to determine when air sealing and heating contractors have successfully completed their work.

Meiling goes on to say that the House of Pressure can be used to illustrate the use of technically advanced equipment and complex testing protocols, “so we can solve uneven heating/cooling and ice dams, while avoiding the costly unintended consequences of moldy roof decking and window replacement, and consequent health concerns from mold and backdrafting combustion products.”

Since more attention is being paid to a building’s energy efficiency and indoor air quality, the House of Pressure serves as an engaging and effective tool for both teachers and students of structural air pressure dynamics. By using real diagnostic equipment, the model provides contextually familiar feedback while demonstrating the complexities of a house’s air system in a physically measurable and memorable way. The House of Pressure is an important teaching and learning tool for the energy services industry, but it has also proved to be of value to those involved in construction, real estate, physics, conservation, and education. The multidisciplinary appeal of the House of Pressure shows how much a building’s air pressure and quality affect all of us.

Anthony Cox provides training in residential energy conservation and diagnostics for public and private sector staff with Community Housing Partners (CHP). He holds several advanced certificates in home performance—including Building Analyst Professional certification from the Building Performance Institute (BPI) and an Air Balancing certificate from the National Balancing Institute (NBI).

Melissa Byrd is CHP’s Public Relations Coordinator. She is responsible for the creation, implementation and coordination of public relations, internal and external communications, event planning, and marketing efforts in order to expand awareness and support for the organization’s housing and community development programs.


For more information:
To learn more about NRCERT and CHP, go to www.communityhousingpartners.org.
To order a House of Pressure, contact Anthony Cox at 540-381-9446.

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