Tips to Enhance Natural Ventilation in an Old Home 

By Kristin Boza 

Old, historic homes are beloved for their architectural beauty and ability to withstand decades of wear and tear. Yet ask an owner of a historic home about heating and cooling, and prepare to hear their trials and tribulations as they struggle to figure out how to heat and cool the space efficiently.  

Beverly/Morgan Park resident Al Mitchell is an expert in maintaining the integrity of historic homes while maximizing efficiency. Mitchell has degrees in architectural engineering and architecture, and he’s working on a PhD at the Illinois Institute of Technology focused on engineering and retrofitting historic homes. His day job is at Passive House Institute US, Inc., a non-profit organization working to make high-performance passive building the mainstream standard. 

Mitchell says there’s a way for Beverly/Morgan Park homeowners to implement a summer energy conservation measure (ECM) for little to no cost utilizing operable windows for natural ventilation.  

“Most of the homes built in this area were built before air conditioning became commonplace. Space heating by steam radiators was already commonplace, but there was no active strategy for cooling in the summer, so a lot of passive strategies were incorporated into the building’s design,” Mitchell said.  

Natural ventilation is defined as the use of wind and thermal buoyancy to create air movement in and out of homes without the use of mechanical systems, according to Mitchell.  

“The goal is to bring fresh air into the house. When the conditions are just right, people can open their windows to enjoy fresh air,” he said. “Thermal comfort is based on airspeed, clothing insulation level, air temperature, humidity, and activity level. Based on the typical meteorological year, an averaging of 30 years of weather data, for Chicago Midway Airport, people can be comfortable without air conditioning for about 12.5% of the year.” 

How can the average homeowner achieve thermal comfort? If the home has double hung windows, maximum air ventilation can be achieved by opening each sash vertically so it meets toward the middle.  

“The warm air rising up will collect along the ceiling and can be exhausted from the room out of the top, while the cooler outdoor air can come in at the opening at the bottom,” Mitchell said. “High transom windows above doors work in a similar manner. Casement windows can be opened at a 45-degree angle to the wind to function as a wind scoop and force wind into the space, providing cooler air and some airspeed.” 

The addition of ceiling fans can keep people cool, and box fans can aid in exhausting the warm air out of the windows, which is particularly necessary in hot upper floors. “Sometimes, it might be best to do a night flush by keeping windows open on a cooler night and closing them in the morning. This can save some time in the morning before air conditioning is needed for comfort on those really hot, humid days,” Mitchell said.  

Blinds, curtains, and exterior shades or awnings can also help cool a home naturally.  

“In the summertime, southern facing windows bring in a lot of solar radiation during the day, and the west facing windows bring it in during the evening. By strategically using shades, it is possible to prevent the heat from getting into that space,” Mitchell said. 

Despite this amazing advice, hot, humid days provide a challenge. Mitchell advises air conditioning to be the best strategy for comfort when it’s just not possible to cool down a house during a hot streak. 

Mitchell recently joined the Ridge Historical Society Historic Buildings Committee (HBC). Along with the committee chair, Mati Maldre, the committee advocates for historic buildings, such as the current successful effort to have the Eugene S. Pike House added to the Preservation Illinois 2022 list of the Most Endangered Historic Places in Illinois. The committee also offers the Historic Building Plaque Program, which recognizes eligible homes that have not undergone significant exterior alterations or additions, while maintaining the historic appearance from the street.  

“I hope to contribute to the committee especially in talks and presentations, trying to share the technical work I am researching, and help people work to make their home more healthy, efficient, and comfortable while maintaining the historic charm and character that creates a lot of neighborhood visual appeal,” Mitchell said.  

He notes that the committee has arranged talks and presentations in the past, focusing on historic architecture and its significance to help educate people and raise interest in preserving historic structures.  


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