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The following fact sheet is part of the About Your House — General Series

Maintaining Your Heat Recovery Ventilator (HRV)

Your heat recovery ventilator (HRV) can help make your house a clean, healthy living environment, while keeping fuel bills down. But your HRV can't do all this without your help.


[00:00:09:00] On Screen: CMHC works with housing providers and communities to acquire the skills, training and resources needed to manage and administer all aspects of housing.

[00:00:24.70] On Screen: Maintaining Your Heat Recovery Ventilator (HRV)

Stories of Our Houses - Mohawks of the Bay of Quinte

[00:00:31:27] On Screen: What is an HRV and why is it important?

[00:00:36:57] Lori Maracle: We have 160 rentals and plus 25 more which is our elders lodge.

[00:00:49:77] Lori Maracle: We did our south subdivision, which started in 1988 until I think about 1995 when we started doing R2000, so we did have to through back all those homes, bring them up to R2000 standards and that's when we started putting in the HRV units in. All our new housing which is our north subdivision, they all have HRV units in them.

[00:01:17.47] Keith Maracle: HRV is a heat recovery ventilator system, so it is a ventilation system for the house. One of the big misconception about it that people have, is they think it's for the house. And it helps the house but it's actually to bring in fresh air for their families and themselves so they can live more comfortably in that unit.

[00:01:38:36] Mike Calamusa: HRVs are very important because of the, especially in areas where there is stagnant air. There are a lot of houses down here that have in floor heating and no air movement so we need the HRV. So you know two purposes, reducing humidity in the winter and fresh air all year round.

[00:01:57.33] Tina Brant: By not maintaining your HRV unit you will notice the difference in the air. The air may become stale; you may have condensation on your windows. You'll just notice the difference in the air change. And when I built my home, it was recommended that I also install one and I did.

[00:02:16.77] On Screen: It takes seven simple steps to keep your HRV happy:
What you will need:
Bucket with soap and water
Vacuum Cleaner
Small brush

[00:02:28.72] Keith Maracle: In maintaining this unit, this HRV unit there are seven steps that you as the homeowner need to walk through and need to understand, okay. As we're, as we're going through this, and that the first step in doing this when we come into the unit, is to make sure that it is unplugged.

[00:02:42.47] On Screen: Step One Turn off your HRV

[00:02:46.57] Keith Maracle: Cause if it is not unplugged and there's power going through it, there's a fan in there, there's blades onto it, it could, it could turn on. All of them have a safety on them but sometimes they may stick if they haven't been cleaned properly or that. The second thing that we would do then is we would take the door, the door on all units will come right off to make, cause if you take to try hold it up and sit it on your head to work on it, it doesn't work. So all you gotta do is give the door a little shot like that, it comes off. You stand at the side, now here's the unit. The fans I've talked about, there's one right there and there's one, and there's one up here. That's the fan blades that I've talked about. This is the safety switch, so when the door's off, this machine wouldn't run. So like I said before if the machine hasn't been cleaned very often, this will stick. So you take the door off and the machine is still running. So this is how we can test it later on. You can use that to test it later on to see to it that everything is going to work.

[00:03:48.47] Keith Maracle: So the next step that you would do, is you would take these filters.

[00:03:52.73] On Screen: Step 2: Clean or replace air filters

[00:03:53.50] Keith Maracle:
These little knobs on here always are to the outside, okay. That what comes against the door. So this filter here isn't in too bad of shape. This unit here has been cleaned but there's this is the contrast in them is this. This particular one here was in a house that was five years old. And the people didn't even know that they had an HRV or what it did. So as you can see there is quite a difference. This is pretty nasty and this is, if there is any air getting into the house at all, it's pretty nasty stuff. And it is not doing, it's not cleaning the air like it is designed to do.

[00:04:31.73] Keith Maaracle: So the easiest thing to do, you can do two things, you can wash this out but when you wash it out this gets wet, it is a sponge basically and if you put it back in it will clog up really quick. So what we would do with this is I prefer to see them vacuumed out, so a small vacuum like this or the shopvac that you have at your house. You would just, vacuum it out like that, one of tests that you can do after you get it done, is hold it up to the light. If you hold it up to light, you can see daylight through it. When you can see daylight through it you know it is nice and clean. Now it can be replaced.

[00:05:26.13] Keith Maracle: This is step three. In a house this size where you got all of that duct work.

[00:05:27.80] On Screen: Step 3: Check outdoor intake and exhaust hoods

[00:05:30.23] Keith Maracle: And you are going so far from one end to the other. You want as much fresh air coming in as you can get. So, with these ones here when they are new, or when it's warmer, don't try this in the winter time because it doesn't work. But all you do with them you just shove them aside and they come right off. This is the grill here you want to make sure that is clean. In the summertime you're cutting the lawn with the lawnmower if you got this running its sucking the grass in there, leaves start blowing around in the Fall they'll get caught in here, and stuff like that. So you just want to make sure that all of this stuff is cleaned off before you start doing any maintenance. So air is going into this one, and in this one here when the machine is running, air comes out of this one. It's blowing out of this one, and there is a screen also but it doesn't ever get filled up because air is blowing out through it, so it never sticks into it. So you take this off and clean this up and you then you can put this back on again. It just snaps back into place, like that. Now, you have cleaned the outside hoods. Now, you can go inside and proceed with the rest of your cleaning of the HRV unit itself.

[00:06:52.33] Keith Maracle: In step four of your HRV maintenance would be to check this condensate line.

[00:06:55.17] On Screen: Step 4: Inspect the condensate drain

[00:06:57.67] Keith Maracle: What this does is in the wintertime this will get frost on it. This core will get frost onto it. When the unit goes into defrost mode, of course frost is water, it will melt that water out and it will run down these two pipes here and it will run out. It is very important to check to make sure that it has this loop in it. All you need to do is pull it off the bottom like that and there is the line. This black sediment that is in here is what you want to wash out.

[00:07:28.33] On Screen: TIP Slowly pour in warm water

[00:07:32.30] Keith Maracle: Like that. As you can see it is caught in this trap. This is the same trap is what would be like underneath there. Then you'd just shake that back and forth and when that's done you just bring it back over and you hook it back up again and that's the completion of step four.

[00:07:50.23] Keith Maracle: Step five we are going to clean the heat exchange core. I'll show you how to do that, it's quite a simple process. We just pull it out of the unit, like this. What this does is the cold air comes in and goes through here, goes up through this side. The stale air from the building comes down here and goes up through here out through here, so the inside of this core, the air never meet, one flow of air is going this way, the other flow of air is going this way so this just heats up the cold air, warms up the cold air that's coming in, hence HRV, heat recovery ventilator, so it is recovering the heat from the air that is taken out. So we take it out like this and the first thing we do, is we hold it up to a light. We hold it up to a light to see light through it. That one is not too bad of shape. We turn it a quarter turn, and there again the same. Now this is one is the side where was coming in, so that is the side that we will vacuum that. There are two ways that this can be cleaned. One of the things, we never put air in this, never. Everybody says they have a little compressor, I'll blow that out. Don't ever do that because these are so fragile that you'll ruin the insides of it. The other thing you can do if you can't see through it, it's plugged up so you fill the laundry tub or a garden hose. Laundry tub is the best you can put soap into it, and what you do is take it this way, like that, and you just up and down, turn it over like that, up and down in the water, wash the water through it, give it another quarter turn, up and down, like that, turn it a quarter turn again, up and down. Then you have to set it on something this way, let it drip dry. Then turn it this way, set it on something, let it drip dry.

[00:10:04.23] Keith Maracle: Before we install this back in, we need to make sure that the inside of it is cleaned out. So what we do then is regular dish soap, a little bit of water. And give it a washing down. The first thing on the other side here if you want, if there is anything loose in there, you can vacuum it out first and then wash it out. And you would wipe the whole inside of it down. As you can see there is dust under, give the whole inside a good clean. It really doesn't have any difference in the workings of your machine but what it does, is keep any particles or any bacteria that's in there from being put into the air, if you keep the inside of this thing clean. Because it can still water lies, it can create some bacteria some kind and be put into the air. It's a good thing to give it a good, a really good wiping down and then you can just again wipe it with a paper towel. Once that's done you can put it back in. Very easy to put back in, as you can see on the end there is an arrow, that part goes up. You take this and you set it in the track like that on the bottom and you tip it up onto the top track, like that, and it just slides into place. Now, we've cleaned the core and everything is back in and ready to go.

[00:12:06.63] Keith Maracle: This is step six, in this particular set up,

[00:12:08.37] On Screen: Step 6: Clean grilles and inspect the ductwork

[00:12:10.53] Keith Maracle: the way this HRV is set up, it's got a pick up in the bathroom. It's picking up stale air and taking it back to the machine. So there is one in the bathroom, this is what we call a grease trap in the kitchen. And all it does, it folds down and this opens up and there is a filter in here that comes out. This one here we just take hot water and we run this under hot water, and it will, because it is grease and its hot water, it will wash. As you see there is quite a bit of stuff coming off of it there. So when you are done and gone, this is what it should look like. It's nice and clean so now we can get some air through it.

[00:13:08.13] Keith Maracle: This one is a whisper vent. And all we do with it, is it will pull out, we can pull it right out, see, like that. And this one is not in too bad of shape. And this is how you adjust it; pull it out like that, so again, this one here you would just give it a wipe into, inside like that. Or again if you had your vacuum cleaner, you could vacuum. This one here is just dust, okay. This is picking up the steam out of here when you are taking a bath or shower. This one here is picking up steam, that's all that it's doing. So that's how we clean a whisper vent.

[00:13:51.13] Keith Maracle: And now all we do is just take it and the inside of this duct is pretty clean, they have used some really good parts on these, on this particular one. And you just take it and set it and shove it back in place.

[00:13:59.30] On Screen: Check! If the vent was altered during cleaning, it should be returned to its original open position when replaced.

[00:14:06.47] Keith Maracle: That's cleaned and maintained.

[00:14:08.27] Keith Maracle: Okay, step seven, is we would service, take a look at the fans and see how much is on them. These fans are again pretty good. You would get a small brush like this, this happens to be a small metal brush. But you could use a small toothbrush. And you would just scrape up and down, like that, in there to get the fans cleaned out. As you can see there is quite a bit of stuff coming up and then you would just take the vacuum cleaner and vacuum out what fell out. The other one is up here, you need to do the very same thing with this one up here. Now that we have this all clean up and everything, we can replace our filters. Remember what I said, this knob always stays out. So there's one filter, this is our other filter going into over here with the knob out like that. We will replace the door, so again get our door lined up. Secure it in place. And always remember to plug the unit back in. And now it's ready to be turned on and operate. There's the unit back in operation.

[00:16:06.77] On Screen: Did you Know? HRVs need to be balanced?

[00:16:14.57] Keith Maracle: Well, first of all when they are installed, they need to be balanced. An HRV that's not balanced, I recommend to the people that they don't brother turning them on because if they're bringing too much air, they are bringing in cold air; your heating bill goes up. If you they are taking out too much air, it's sucking out all the heat out of the house, heating bill goes up.

[00:16:36.53] On Screen: Benefits of having a well-performing HRV: Better air quality, and reduced mold or moisture damage in homes.

[00:16:42.63] Mike Calamusa: A lot of people think that with this HRV running, its chilling their house down or costing them a lot more in fuel to heat the house back up as the HRV brings the temperature down, that's not true.

[00:16:57.30] Keith Maracle: The benefits of maintaining your HRV, number one is you are going to get nice clean fresh air for your family. Your family is going to be able to live with nice fresh air in the house.

[00:17:06.40] Lori Maracle: If we didn't have the HRVs, if we didn't have any of them in working order, all our units would just deteriorate. So this helps to keep all our stock up and keep it in good working order, so it will last for years to come.

[00:17:21.87] On Screen: Working together for housing solutions. For further information about CMHC and the capacity development initiatives it offers, visit

[00:17:46.77] On Screen: CMHC assists housing providers and communities to improve their housing conditions through its programs, housing information and network of housing experts.


It only takes seven simple steps to keep your HRV happy…

The Seven Steps to a Happy HRV

Step 1: Turn Off Your HRV
First, turn off your HRV and unplug it.

Step 2: Clean or Replace Air Filters
Dirty or clogged filters can lower ventilation efficiency. Try to clean your filters at least every two months. Filters in most new HRVs can be easily removed, cleaned with a vacuum cleaner, then washed with mild soap and water before being replaced. Older units have replaceable filters. If your HRV is easily accessible, this is a five-minute job.

Step 3: Check Outdoor Intake and Exhaust Hoods
Remove leaves, waste paper or other obstructions that may be blocking the outside vents of your HRV. Without this vital airflow, your HRV won't function properly. During winter, clear any snow or frost buildup blocking outside vents.

Step 4: Inspect the Condensate Drain
Check to see if your HRV has a condensate drain — a pipe or plastic tube coming out of the bottom. If it does, slowly pour about two litres of warm, clean water in each drain pan inside the HRV to make sure it is flowing freely. If there's a backup, clean the drain.

Step 5: Clean the Heat Exchange Core
Check your HRV owner's manual for instructions on cleaning the heat exchange core. Vacuuming the core and washing it with soap and water will reduce dust that can build up inside the core.

Step 6: Clean Grilles and Inspect the Ductwork
Once a year, check the ductwork leading to and from your HRV. Remove and inspect the grilles covering the duct ends, then vacuum inside the ducts. If a more thorough cleaning is required, call your service technician.

Step 7: Service the Fans
Remove the dirt that has been accumulated on the blades by gently brushing them. Most new HRVs are designed to run continuously without lubrication, but older models require a few drops of proper motor lubricating oil in a designated oil intake. Check your manual for complete instructions.

Your HRV should be serviced annually. If you are not comfortable doing it yourself, contact a technician accredited by the Heating, Refrigeration and Air Conditioning Institute of Canada (HRAI). Make sure the technician you call has been trained by the manufacturer of your HRV.

Check Your HRV Balance: the Garbage Bag Test

HRVs need to be balanced, with the fresh air flow matching the exhaust flow. If you do not know if your HRV was balanced when installed or if you have changed or added HRV ducts, you may want to check the balance with the following simple procedure. This test will take about 10 minutes.

Use a large plastic bag, typically 1.2 m (48 in.) long. Untwist a wire coat hanger. Tape the wire to the mouth of the bag to keep it open. You now have a garbage bag air flow tester. Go outside to where your HRV ducts exit the foundation.

Step 1
Crush the bag flat and hold the opening tightly over the exhaust hood. The air flowing out of the hood will inflate the bag. Time the inflation. If the bag inflates in eight seconds or more, go to Step 2. If the bag inflates in less than eight seconds, turn your HRV to a lower speed, and repeat the test. Then go to Step 2.

Step 2
Swing the bag to inflate it and hold the opening against the wall around the HRV supply hood. The air going into the HRV will now deflate the bag. Time the deflation.

Figure 1 — Test your HRV balance with an inflated bag

If your HRV is balanced, air going into the HRV will balance the air coming out of the HRV.

The inflation and deflation times should be roughly equal. If you find that the bag inflates twice as fast as it deflates, for instance, your HRV is unbalanced. If you can’t see a problem with the filters that would cause such an imbalance, you should call a service person to test and adjust your HRV.

Please don’t ignore your HRV! Just a little bit of your time is all it takes to keep it running smoothly.

The easy maintenance program below can be taped directly onto your HRV. Simply check off each box as you complete the indicated task.

Easy Maintenance Program

To start your easy maintenance program, simply disconnect the electrical power source, then open up the front panel.

April or May ( )
  • Turn the dehumidistat (the adjustable control on many HRVs that activates the HRV according to relative humidity) to the HIGH setting or to OFF.
September or October (circle_4)
  • Clean core and check fans
  • Check condensate drain
  • Check grilles and ducts in house
  • Reset dehumidistat (40 – 80 per cent)

Table 1 — HRV maintenance checklist

Year: Year: Year:
  Clean filter Clean hood screen Other   Clean filter Clean hood screen Other   Clean filter Clean hood screen Other
Jan       Jan       Jan      
Mar       Mar       Mar      
May      May    
July       July       July      
Sept      Sept      Sept    
Nov       Nov       Nov      

Figure 2 — Get to know your HRV — this is what a basic HRV looks like from the inside

Additional Resources

For more information about HRVs, contact Natural Resources Canada at 1-800-387-2000 or visit the Office of Energy Efficiency’s website at



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