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longshanks 12-04-2012 03:44 PM

heat recovery ventilator retrofit?
hi from northern Canada

our house was built in 1996, and based on our low heating bills and cold climate, I'd say it is very well insulated and 'tight'. It has an insulated concrete form foundation, and is heated with forced air gas, and also a pellet stove as secondary heat.

I am interested in learning more about a heat recovery ventilator, due to the following:

1 - a recent radon gas test showed that our basement is @ 3Bq per cubic metre. The Canadian guideline was recently reduced from 8Bq to 2Bq, which means that we are slightly above the new guideline for radon gas.

2 - there is very little air circulation in the house, which contributes to poor indoor air quality. When running the pellet stove, there is often the smell of wood combustion in some of our basement living space. I've installed a couple new vent fans (kitchen, bathroom) but there is not enough fresh air coming into the house, particularly in the winter. The negative air pressure created by these fans is probably contributing to the radon issue.

3 - on days when the temperature is well below freezing, we get significant amounts of condensation inside the windows.

Does a heat recovery ventilator sound like a reasonable solution for these problems? And, will it be effective if it is installed using the existing forced air ductwork, or does new ductwork need to be installed?

thanks in advance for your help on this one.


yuri 12-04-2012 06:09 PM

I have a very tight house and installed a Lifebreath HRV. They make them for Lennox also and call them Healthy Climate. Google Lifebreath heat recovery ventilator and look at one of the install manuals. You can use it with your existing furnace/ductwork and they work very well. Need to have a Pro install it AND balance it properly or it won't work properly. Radon gas needs to be removed with a exhaust fan pipe under the slab system and an HRV won't help with that.

kaalapurushha 12-05-2012 11:27 AM


Originally Posted by yuri (Post 1066387)
Radon gas needs to be removed with a exhaust fan pipe under the slab system and an HRV won't help with that.

It should theoretically work if your HRV inlet air is being drawn from the basement area, where the radon concentration is highest. In that situation, you are exhausting 3 bQ and inletting 0 bQ from the outside

I thinking about doing the same thing.

yuri 12-05-2012 12:41 PM

Then you have a $3000 exhaust fan. An HRV is to remove moisture from the house, provide fresh air etc. Using it to remove radon is a waste of time and $$ IMO. Also you won't be able to balance it properly if it is just sucking from the basement.

longshanks 12-05-2012 12:44 PM

I understand that the HRV will not reduce radon concentrations as much as a dedicated sub-slab depressurization system, but the radon concentrations in my house are not that much above guidelines and it seems like the HRV might acheive the radon reduction along with other benefits such as air filtration and humidity reduction.

Our pellet stove is located in the basement. The basement is usually where the woodsmoke smell accumulates, as well as the highest radon concentrations. As kaalapurushha points out, if I could situate my HRV air inlets in the basement, it seems logical that the HRV would collect radon gas, particulate, and other contaminants, exhaust them outdoors, but retain some of the heat from the warm basement air and re-distribute it to the ducting upstairs... If I placed the HRV inlets only in the basement though, would that be enough to reduce indoor humidity somewhat?

Looking at the range of other solutions that I could try, the HRV seems like it has the most benefits.

yuri 12-05-2012 02:40 PM

The proof is in the pudding they say. You could try and find out. The best method to use a HRV is to take the dirty stale air off the return duct of the furnace about 6 feet away from the furnace and dump the fresh air back in the return duct close to the furnace. Taking it from the basement is robbing Peter to pay Paul but it may help. If a HRV is unbalanced ESPECIALLY in a cold climate like northern Canada it will freezeup all the time and not defrost properly. You could take one small 4" vent from the basement to help but I would not go any further than that. You can buy el cheapo clone HRVs at HDepot etc with plastic bodies and cheap cores but you get what you pay for and buyer beware. If you have an unbalanced HRV it can further depressurize your house and it sounds like you need more combustion air to the stove as it is not drafting properly. BEWARE ANY FOSSIL fuel can produce CO Carbon monoxide, wood, pellets, nat gas , fuel oil so you may have a dangerous situation if it smells smokey down there. If you get CO from the stove and suck it into the HRV it will then distribute it thru the house which is even more dangerous. There was a tragedy in Toronto or nearby a few yrs ago where a family died from CO from a leaking gas fireplace. The woman was a nurse and they all had flu symptoms and you think she would have suspected CO. Her 2 kids and hubby died and she is left alone. CO and fireplace/stoves etc is NO joke and can slowly poision you and give your kids permament learning disabilities. NO joke.

dudleydoright 02-22-2013 03:00 PM

added exhaust fans?
Quite possibly you have created a situationof inducing a negative pressure on the dwelling by the addition of your new fans. For a ventilator to exhaust a given volume of air a replacement has to be available other that as a back draft through the exishting natural draft flu pipes. If you have a couple new exhaust fans they could be doing one of two things.
1)Depressurizing the space enough to inhibit natural draft.
2)Sucking in vented smoke through a natural draft flu vent if the stove exhaust is terminated near the flu discharge.

With your exhaust fans running take a book of matches and light it and hold it at the draft hood connection of your water heater and furnace if a draft hood equiped style. Flame and smoke from the matches should veer to the exhaust or inside of the draft hood and if it wavers or veers toward the free air or outside you do not have adequate make up air with your exhaust fans operating. CO poisening is cumulative. If you do not understand then call a pro as life is worth more than a service call.

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