Should I turn off my HRV in the Summer?

Well, even though it’s still cool out, I think it’s safe to say that summer is coming, and not a moment too soon IMO.  Which means it’s time to put away the snow shovels and pull out the rakes and mower.  Although there are a lot more things going on outdoors, there is some housekeeping indoors that needs attending to as well. Some people turn off their humidifiers and turn the humidifier dampers to “Summer” where applicable.  Others close all the vents in the basement to direct more of the cool air to the main floor, (although having Weather Tech Heating & Cooling add some ‘return air’ runs in the basement is a much better idea ;). Installing a new filter for A/C season is always a good idea and having our technician come out to service that air conditioner before the season is a great suggestion! 

A common question our customers ask us is about their HRV’s (Heat Recovery Ventilators) and what to do with it:

  • Should I run my HRV continuously?

  • Do I change the HRV settings?

  • Is it better to turn the HRV off completely?

It’s a great question and there are different camps of thought on this. The textbook answer is based on some ‘assumed’ variables. In order to answer this properly one must understand how an HRV works.

How Does a Heat Recovery Ventilator Work? 

An HRV’s job is to ‘ventilate’ the space it serves. Ventilation takes care of a couple of things, exhausting unwanted air from the home and bringing in more desirable air. This could mean exhausting excess humidity, smells, or simply ridding the home of (CarbonDioxide) CO2,  and replacing that air with drier, fresh smelling, oxygen enriched air. 

Any given HRV, if installed properly, will be sized according to the type and size of home it serves as well as the ‘load’ it will have. The load would have to do with  the number of occupants, or other variables that would necessitate an HRV.

Because our homes are getting increasingly more efficient and tighter with regards to the construction and doors and windows being installed, these needs listed above are amplified and no longer being mitigated through loose construction and drafty door frames. So much so that here in Manitoba, an HRV is mandatory with new home builds and even large renovations to existing dwellings. 

How do you balance a heat recovery ventilation system?

When sized properly as well as ‘installed’ properly, the HRV will be “balanced”. To balance an HRV means to ensure the amount of air being exhausted and the air being introduced into the home is equal. This is done with specialty tools and dampers within the HRV duct system. The problem with this equation is that it changes every time the pressure in the home is affected. 

For instance, if a kitchen range hood is turned on and increases the negative pressure within the home. Or if the gas water heater starts up and pumps combustion air from the home up the chimney. There are a number of things which can affect the pressure in the home and all of them to some degree change that perfect balance. Perfect balance would be great, but we’ll have to settle for the best case scenario the majority of the time.

Sizing the HRV for the home as a rule of thumb is ⅓ air changes per hour. For the most part, this can be done without running your HRV 24hrs a day. That’s why the newer style of digital controllers are getting installed. Much like the setback digital thermostats, they save energy/money by turning off the system and only running it at intervals needed to accomplish its task.

HRV Controller

Did You Know?

The Manitoba government is actually giving $150 rebates to help pay for these controllers to get installed too! 

Does running your HRV cost a lot of money to run?

Running your HRV does use electricity to operate but the larger cost of running an HRV would be conditioning the air that it brings into the home. Introducing ice cold air in the winter and having to heat and humidify it as well as winter air is usually dry.  Sometimes,  being dry is a desirable quality as one of the jobs of the HRV is to remove excess moisture caused by showering, baking, cooking, plants, hanging laundry, or simply from people living in the home, and replacing it with this dry air is how it mitigates the humidity problem.  

In the summer however, the fresh air brought in from an HRV is usually warm to hot and filled with humidity. These are both qualities that can be quite undesirable to have in the home. It also places a fair amount of extra load on your home’s air conditioner system.  Especially if it was sized without taking into consideration the addition of an HRV.  Air conditioners use a fair amount of electricity to operate and that can add up. 

This is why many people choose to shut their HRV OFF completely for the summer. The thought is that the CO2 ventilation will be accomplished by the use of the non HRV exhaust fans in the home and other means such as an open window etc. It is possible to set any HRV to a “stand by mode” which would have the HRV come on only when required such as a fan timer switch in the bathroom or manually in the evenings. 

home timer switchBasically it’s up to the homeowner and the needs and demands of their individual home. If you’re not the type to open their windows in the summer, perhaps leaving your HRV running and having that air exchange is a much needed thing. As for the Weatherman, I leave mine on stand by for the bathroom exhausts and open a window any chance I get! 

I hope this helps understand the lungs of your home (HRV) better. If not, please do not hesitate to send me your questions to and I will get back to you. If it is immediate service you require, simply call our 24/7 number to have an on-call technician take care of all of your HVAC needs!