Ventilation Air for Healthy Buildings

In the last month both ASHRAE and the director of the Healthy Buildings Program at Harvard T.H. Chan School of Public Health – Dr. Joseph Allen – have released guidance advocating the same principle; buildings need MORE ventilation air to ensure a healthy environment.

The traditional problem with increasing ventilation air in buildings has been the increase in energy costs as well as higher CO2 emissions. Addressing the increase in energy usage can help eliminate the accepted practice of minimizing the intake of fresh air. This is how the SolarWall® technology came to be developed in the late 1980s; Conserval Engineering was working with Ford Motor Company and the goal was to develop a low cost solar collector that would heat for free, large volumes of ventilation air required in manufacturing and automotive assembly lines.

Heating Ventilation

SolarWall® heating became so successful at heating ventilation air that there are now over 5 million square feet of collectors installed on thousands of buildings, generating more than 300 MW of thermal energy. This means that when you increase ventilation air, you don’t need to increase your energy costs.

Fast forward to today, and recirculating building air without adequate ventilation air is a top consideration. We must rethink the logic behind restricting fresh air to save energy.

Let’s see what the experts are advocating:


HVAC systems can have a major effect on the transmission of disease, according to the “ASHRAE Position Document on Infectious Aerosols.” ASHRAE’s Environmental Health Position Document Committee provides recommendations on the design, installation and operation of HVAC systems, non-HVAC control strategies and facilities management support strategies. It also includes strategies that can reduce the risk of dissemination of infectious aerosols in buildings and transportation environments.

Once the basics are covered, such as the disinfection of frequently touched surfaces, the focus must be on those buildings that remain open.

Recommendations include:

• Increase outdoor air ventilation; with a lower population in the building, this increases the effective dilution ventilation per person.
• Disable demand-controlled ventilation (DCV).
• Further open minimum outdoor air dampers, as high as 100%, thus eliminating recirculation (in the mild weather season, this need not affect thermal comfort or humidity, but clearly becomes more difficult in extreme weather).
• Improve central air filtration to the MERV-13 or the highest compatible with the filter rack, and seal edges of the filter to limit bypass.
• Keep systems running longer hours, if possible 24/7, to enhance the two actions above.
• Bypass energy recovery ventilation systems that leak potentially contaminated exhaust air back into the outdoor air supply

SolarWall heating and ventilating systems are ideally suited for all these recommendations as the air is heated for free with zero carbon emissions. Existing controls can be easily reprogrammed to run longer and with more fresh air whenever the sun is heating the air.

Healthy Buildings Program, Harvard T.H. Chan School of Public Health – Dr. Joseph Allen

“Here’s what we should be doing. First, bringing in more outdoor air in buildings with heating and ventilation systems (or opening windows in buildings that don’t) helps dilute airborne contaminants, making infection less likely. For years, we have been doing the opposite: sealing our windows shut and recirculating air. The results are schools and office buildings that are chronically underventilated. This not only gives a boost to disease transmission, including common scourges like the norovirus or the common flu but also significantly impairs cognitive function.

A study published just last year found that ensuring even minimum levels of outdoor air ventilation reduced influenza transmission as much as having 50 percent to 60 percent of the people in a building vaccinated.

Buildings typically recirculate some air, which has been shown to lead to a higher risk of infection during outbreaks, as contaminated air in one area is circulated to other parts of the building (as it did in the school with measles). When it’s very cold or very hot, the air coming out of the vent in a school classroom or office may be completely recirculated. That’s a recipe for disaster.”

Read the rest of this article here.


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