HRV and neighborhood wood stoves : is there a solution to prevent smoke intake?
New home, HRV intake is about 11ft off the ground (slab on grade, HRV intake is in the floor joists area). Closest neighbour (with wood stove) is roughly 100ft away. His chimney is about 20ft high. Today I noticed I could smell smoke around the house, which does not bode well for the HRV when it is fully commissioned. I know they recommend being low to the ground for HRV intake, but it was not possible due to the utility room setup. Floor joist height gave me a straights shot out with less restriction, and we also have some weird airflow in the area, with smoke lingering low or even being pushed down so low intake would not solve all the issues.
A quick search revealed some people use activated charcoal filters, which seem to work but are expensive and bothersome. A MERV 20 filter is recommended to filter out smoke particles, which also sounds expensive and restrictive.
I wanted to know if anyone had experimented with a smoke detector inside the HRV ducting, which would shut it off if it started to pull in woodstove smoke. I am not sure how sensitive they are, or if they would be able to detect smoke as soon as a normal person would smell it. Since in my case smoke in the HRV will likely be rare (correct wind speed and direction, winter time etc.), turning off the HRV when it sense smoke would make more sense than filtering every micron out of the air 100% of the time.
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Replies
Mai Tai,
Q. "I wanted to know if anyone had experimented with a smoke detector inside the HRV ducting."
A. I'm fairly certain that this idea won't work, because your nose will detect wood smoke at levels that are far below the levels that will trip a smoke detector.
If I were you, I would live in the house for at least one winter to see if this is even a problem. You may find that everything inside your home smells just fine, even if your neighbor has a wood stove.
You can also shut off the HRV manually when it is sucking smoke from the neighbor's. A few hours, or even half a day or so of shutdown isn't going to make much difference in IAQ.
Manual shut off is an option, but i find at least for open windows (different order of magnitude, but still), when I would smell it and close the windows it would be too late and the whole second floor would have a mesquite smell. It would be nice to get something automatic, even over sensitive would be fine. I suspect even at the low speed the HRV will over ventilate the house anyway, as it was sized for maximum bathroom humidity extraction, not IAQ requirements.
You could maybe use a sensor normally used for a VESDA system (very early smoke detection apparatus), which are just extra sensitive smoke detectors. They’re not cheap though, and as Martin mentioned your nose might still be more sensitive than even the VESDA detectors.
If the VESDA system is sensitive enough, it would be easy to interlock it with an HRV or other ventilation system by just inserting it as a control input.
I don’t think any of the common air filters will work. Ultrastatic filters are supposed to be good with very small particles, but they are expensive and need frequent cleaning to work well. They also don’t get everything. HEPA filters can filter out many smells, I’m i know from expierince they can filter out smoke, but they are expensive, clog relatively quickly, and are very restrictive to airflow. Don’t bother with any MERV rated filter — even the best won’t get smoke particles. Even drywall dust can get through most of them.
Bill
Mai, it has been a year and I am wondering how your HRV has fared with the wood smoke? Was it able to filter out the smoke and odour? Did you upgrade the filter? May I ask what brand and model of HRV you used? We have a wood smoke problem in our neighbourhood too. I have wanted to install a HRV with a HEPA filter so that we could have fresh air when it was smoky outside but no one has been able to give me a definite answer if it would be effective. Thank you.
What are the health effects of atmospheric wood smoke? Why should wood stoves be allowed to emit detectable smoke? Automobile emissions are severely regulated. Shouldn't wood stoves be as well? It's not that hard. We own a 40 year old German WESO stove. Within minutes of ignition the chimney gasses are invisible and odorless. Even with our exterior masonry chimney We've never had appreciable creosote buildup.
Thrifttrust,
There is no political will. Our community, North Vancouver, BC, is an older community and every single home that was built in the 50s to the 70s has a masonry fireplace. Politicians don’t want to alienate the voters..
Current EPA regulations allow only 4.5 grams per hour of particulate emissions, and that changes to 2.5 grams per hour in 2020. I'm not sure how that compares to European standards but I know that a lot of European heaters would come in around or under those limits. Rais and Morso are two that I am familiar with; my clients chose a Rais QTee2 for their new home recently, which is rated at 0.9 g/h. Compare that to older US-made wood stoves which may emit 15 g/h or more. (https://cfpub.epa.gov/oarweb/woodstove/index.cfm?fuseaction=app.search)
Gotta love it! "Why should we be allowed to emit detectable smoke?" Next it will be why are we allowed to exhale CO2?
Deleted
There's an old expression: Your rights stop at the tip of my nose. This is a quite literal example. CO2 while bad for the planet doesn't otherwise affect the quality of my life. When I was young, on a day like today, the air would be hazy with burning leaves. We no longer allow leaves to be burnt in the open in cities. I should not have to smell your woodstove, and as I pointed out, with straightforward good engineering woodstoves can be odorless.
Your methane emissions offend me and impact the quality of my life; please stop.