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Passivhaus: Dentists Get Their Green On by Adam Cohen, RA, CPHC, LEED AP

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A newly constructed dental clinic can achieve up to 67 percent in energy savings compared to the average U.S. dental clinic, while increasing comfort and air quality.

This was the experience of Drs. Sean Lynch, Randolph Dickey, and John Singleton in Roanoke, Virginia, whose practice is housed in the world's first Passivhaus-certified, low-energy dental office.

Passivhaus—literally, "Passive House" —is the world's strictest standard for building energy performance. A Passivhaus building is exceptionally airtight, with excellent mechanical ventilation and thermal performance. The principles and methods of the system are calculation-based and performance-driven, with a strict focus on operating energy. A key element is reducing space heating and cooling—often one of the largest factors in a building's energy consumption—and at the same time, retaining comfort and maintaining excellent air quality. First developed in Germany in the early 1990s, the Passivhaus standard has become the fastest-growing certification in the world, with more than 30,000 buildings constructed to date.

These dentists in Roanoke were looking to build a new, 5,400-square-foot office as they prepared to transition their 30-year-old practice to a new generation. My firm proposed a Passivhaus-certified building. My experience building 11 previous dental clinics had shown me that clinics are exceptionally well suited for Passivhaus construction. The nature of the Passivhaus methodology and the requirements of a dental clinic create synergistic interactions between Passivhaus design principles and dental clinic buildings.

Dental clinic
building analysis
During the initial design studies for the clinic, we spent 2.5 months gathering real-time data on the existing equipment's energy usage. This opportunity was very fortunate for the team, as this type of real-world data is hard to come by.

Once the design and monitoring were complete, we calculated energy models of both a standard code-built building and the proposed Passivhaus building. Our results showed that the Passivhaus building would use approximately 75 percent less heating and cooling energy, and an impressive 50 percent less overall energy than if the clinic were built to the current energy-code requirements.

The last piece of the puzzle we needed for the group's decision was a cost figure. With our track record of dental clinic design/build, we had very accurate real-time cost information. Our experience is that in our region the typical delivered cost for a new dental clinic is between $150 per square foot and $200 per square foot. The new Passivhaus dental clinic came in at $155 per square foot.

With a market-rate delivery price at the low end of the scale, and an energy savings of 50 percent, this became an easy decision for the group.



Improving staff and patient comfort
As we completed our analysis, we also found that not only did it make financial sense—the interior comfort and air quality would also be significantly better in a Passivhaus clinic.

The thermal comfort of the doctor and patient is a consistent area of concern in dental-clinic construction. Doctors generally complain of being too hot and often patients complain of being too cold. When we completed our Passivhaus building analysis, the reasons became clear.

When a dental procedure is taking place, one typically has a nervous patient, a working doctor, an assistant, and a dental light. When calculating the heat load in the small work area, we found that the heat generated by the people and light is significant. To overcome the comfort issue of the dentist, a typical solution is to introduce a large amount of high-velocity conditioned air in the area behind the chair to keep the dentist and assistant cool.

Unfortunately, this has the unintended consequence of making the stationary and potentially nervous patient cold, as the conditioned air causes the perspiration of the patient to evaporate.

To overcome the comfort issue of doctor and patient we designed a multi-pronged approach.

We introduced pre-conditioned fresh air along the ceiling of each operatory space at a very low velocity. We then installed a separate low-velocity displacement air conditioning system directed behind the dental chair. By designing the ductwork and diffusers for low velocity, the conditioned air slowly drops out of the register, reducing the evaporation of the patient's perspiration, increasing the patient's comfort.

Then we installed 100-square-foot, passive radiant cooling loops in the floor around each dental chair. This takes radiant heat from the dentist and assistant, leaving the patient comfortable, with the chair acting as an insulated barrier to the radiative cooling in the floor.

The doctors report that the operatory thermal comfort is exceptional.



Eliminating the dental-clinic smell
Patients in this clinic regularly comment on the lack of the dental-clinic smell.

Passivhaus is a fabric-first approach to building energy use, meaning it focuses on the building envelope first, to reduce loads on the building systems. It does this through the combination of robust and clever superinsulation, exceptional windows and doors and airtight construction.

The reduction of airflow through the building envelope results in an up to 50-percent reduction in heating and cooling loads, and this reduces the size and cost of the mechanical system.

As one tightens up the building envelope, it's necessary to bring in fresh air, not because a building needs to breathe (as I hear so often), but because the occupants of a building need to breathe. For this fresh-air intake, we use state-of-the-art, energy-recovery ventilators that bring in a constant supply of filtered fresh air. These ventilators provide both energy savings (by recovering energy in the exhaust air stream) and comfort (by balancing humidity and filtering the incoming air).

First-year results
We have been monitoring the total energy usage of the clinic for one full year. After 12 months, the building's energy use is an incredible 67 percent less than the average U.S. dental clinic!

Adam Cohen is an active designer/builder and green building expert who has presented technical papers at national and international Passivhaus conferences. He is a leading North American Passivhaus practitioner. Cohen's innovative work on market-rate delivery of commercial high-performance construction has made his expertise sought after for projects across North America. In addition to speaking, Cohen also serves as a consultant and teacher of advanced courses in Passivhaus ultra-low-energy design. He can be reached at (888) 376-3424 or adam.cohenaj@gmail.com.


Dentaltown Magazine
April 2024
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