HRVs work in cold climates, experts insist, but need to be operated properly

There's some debate among homeowners about how well Heat Recovery Ventilators — or HRVs — function in northern climates, yet the experts insist they work just fine. 

HRVs are air circulation systems that remove stale inside air and exchange it for fresh outside air. HRVs are designed to warm the incoming air with the outgoing air, making them ubiquitous in new, energy efficient homes.

Michael Taylor, an electrician who wires HRVs, recently weighed in on a Facebook conversation among homeowners in the Whistle Bend neighbourhood of Whitehorse who were concerned about moisture building up in their homes. 

Taylor had the same problem this winter in the four-year-old home he recently moved into, and blames his HRV system. He said it doesn't adequately remove inside moisture when the mercury dips below -20 C outside, particularly because the machine goes into what's called defrost mode, and temporarily stops circulating air.

"If I'm cooking something ... I'll start to notice that my kitchen windows and my dining room door, which is glass, will start to have condensation form on the windows. And depending on how cold it is, my windows and doors will freeze with condensation," Taylor said.

Taylor is concerned about moisture damaging his home and leading to mould issues. To deal with the problem, he said he's planning to install fans in his kitchen and bathroom that vent direct to outside, separate from his HRV system.  

Externally venting fans gaining traction in Alaska

Robbin Garber-Slaght, a research engineer with the Cold Climate Housing Research Centre in Fairbanks, Alaska, said properly installed HRVs should provide adequate ventilation for the size of home. But, she said additional fans are a good idea, to remove localized moisture and pollutants. 

"We're starting to — more and more — add bath fans into the bathroom that vent directly outside."

She said stove range fans in the kitchen are also particularly important for removing moisture as well as air pollutants. 

"The biggest source of pollutants — outside of a wood stove — is cooking. Any time you're cooking, you need to have a range hood [running]."

Garber-Slaght said too many people under one roof can lead to excess humidity over and beyond what an HRV can handle. More people results in more showers and cooking, plus the added humidity produced by people and pets. 

"The design specifications for ventilation ... don't take into account overcrowded homes."   

Read the manual 

Juergen Korn, a researcher with the Yukon Housing Corporation, said HRVs work well in northern climates, but notes there is a learning curve associated with their use. He said often people move into a new house and don't know how to operate their systems. 

"I would recommend anyone with an HRV read the manual," he said. 

"Most of the problems with HRVs are related to either improper installation and improper maintenance."

Korn said if moisture is building up inside the home, the settings on the HRV can be adjusted to lower the relative humidity in the home, or increase the speed of the HRV.

He said people having issues with their units should look at online resources found with the Canadian Mortgage and Housing Association and Natural Resources Canada. They can also contact an HRV technician verified by the City of Whitehorse. 

As for Taylor, he thinks the City of Whitehorse should require builders to install separate bathroom and stove range fans in all new homes with HRV units.

According to a 2014 Whitehorse bylaw, new residences are required to have HRVs. They must have a "sensible recovery efficiency" of at least 64 per cent when outside temperatures are -25 C. Ventilation must meet the requirements of the National Building Code. 

The city has not yet responded to a request for comment.