The coronavirus pandemic has exposed a key weakness of contemporary building design: conventional heating, ventilation, and air conditioning (HVAC) systems require airtight buildings, which can contribute to the spread of respiratory diseases. But throwing open the windows (per public health recommendations) is difficult in very hot or very cold weather—or requires massive amounts of energy to keep air temperatures in the comfort zone.
An international team of researchers offers a way out of this conundrum: a newly designed radiant cooling system, consisting of tubes embedded in a specialized membrane to prevent water condensation in hot and humid climates. They demonstrate the problem with conventional HVAC and the potential for the new system to solve it in a new study published in the journal Applied Energy.
“We propose a different paradigm that allows for energy savings and increased fresh air to go hand in hand,” says study team member Dorit Aviv, assistant professor of architecture and director of the Thermal Architecture Lab at the University of Pennsylvania.
First, Aviv and her colleagues quantified the problem, modeling energy consumption from conventional cooling systems in six U.S. cities—Miami, Phoenix, Duluth, Chicago, Washington, D.C., and San Francisco.
“Our analysis shows that increasing outdoor air intake to meet COVID-19 guidelines in standard HVAC systems can double cooling energy costs,” Aviv says. The exact increase depends on the location, with cities in mild climates like San Francisco faring the best and those in hot and humid climates like Miami faring the worst.
Next they analyzed climatic data from 60 of the most populous cities around the world to determine the need for cooling. They found that the radiant system combined with natural ventilation could keep things comfortable 80 to 100% of the time, again depending on the location.
This suggests that the new cooling system is a feasible alternative to conventional HVAC. Many of the locations where the system has the greatest potential are in South and Southeast Asia, the researchers say.
What’s more, the radiant system is much more energy efficient. The team’s calculations suggest that their cooling panels can decrease energy costs by 10 to 45% compared to conventional HVAC. This figure depends not just on the location but on how much fresh air is brought into the HVAC system. So, the more outside ventilation that is employed to reduce coronavirus transmission risk, the better the radiant cooling system looks.
Radiant systems can also provide effective heating while enabling windows to stay open for ventilation, although in very cold climates a mechanical ventilation system might be necessary as a backup during part of the year, Aviv says.
And pandemic aside, the radiant system is useful because it avoids the over-cooling of air that is often necessary to achieve dehumidification with conventional HVAC systems in humid climates.
“Rising temperatures due to climate change mean that more regions will undergo extreme heat, which make cooling systems even more essential to large parts of the globe,” Aviv says. “We must address cooling in a more energy-efficient manner in order to stop the vicious cycle of perpetuating climate change with more emissions related to building systems energy consumption.”
Source: Aviv D. et al. “A fresh (air) look at ventilation for COVID-19: Estimating the global energy savings potential of coupling natural ventilation with novel radiant cooling strategies.” Applied Energy 2021.
Image: Based on a photo by Preconscious Eye via Flickr.