A need for clean air
We live in North Vancouver, BC.
I need to bring clean air and fresh air into our newly renovated home, with emphasis on clean as my wife is extremely affected by wood smoke and VOCs. She developed this condition near the end of the construction.
Lennox has an option of using an HRV in tandem with their powered HEPA/activated charcoal filter system (Healthy Climate High-Efficiency Particulate Air (HEPA) Filtration System).
The fresh air port of the HRV Ducts directly into the intake of the powered filter.
The powered filter then distributes it into the cold air return. It can be connected to the HE gas furnace by way of an interlock. The furnace fan runs 24/7.
Since most HRVs have a lower cfm rate, the powered filter takes additional makeup air from the cold air return.
Has anyone had any experience/opinion with the Lennox powered filter? Basically, I am ready to bite the bullet on this because I really need to get something in place.
I find that there is virtually no information available for my situation. Even GBA does not have information on clean air solutions. As for “experts”, I have talked to a few and they are all knowledgable on the importance of fresh air but they know little about clean air. All they know is HEPA. I would have to say that in all the talk of “healthy homes”, no one appears to have given much thought to truly clean air. I guess the issue will only arise when more energy efficient homes start getting built next to busy roadways.
Thanks,
Aaron
If I sound a little frustrated, please forgive me.
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Replies
I'd check with the HRV manufacturer to make sure it can be properly commissioned and that the warranty is still good.
FWIW, my HRV (Zehnder Comfoair 200) takes a MERV 13 filter, which I understand is similar to a HEPA filter.
Aaron,
I recently published on article on IAQ here on GBA. Here is the link: All About Indoor Air Quality.
While performing research in connection with that article, I spoke to Terry Brennan, a well-known building scientist who serves on the ASHRAE 62.2 committee. According to Brennan, the most important specification for any HRV, ERV, or supply ventilation system is that the equipment should include a MERV 13 filter to filter incoming outdoor air.
More details on assuring IAQ are provided in my article.
Stephen,
If I use a Lennox HRV, no problem for the warranty. Unfortunately, any MERV rated filter or HEPA filter cannot filter wood smoke. You really need activated charcoal/carbon. And a pleated filter coated with the charcoal, is useless. You need a filter filled with several pounds of activated charcoal. Preferably impregnated with potassium permanganate.
Martin,
I believe your article talks about IAQ in general with suggestions on how to prevent air quality issues during construction and through lifestyle changes but with little in the way of environmental issues. It takes a MERV 17 filter minimum to filter combustion smoke. This is beyond the capability of residential heating systems.
At some point, ASHRAE should develop a standard to address actual air quality not just how many air changes are required. What if the exterior air is polluted?
Aaron,
I had a similar concern about smoke from neighbors' wood stoves, and Zehnder configured an HRV with a charcoal filter for me, in an add-on box attached to their manifold system. I haven't actually commissioned the system yet, as there are other parts of the project that got delayed, and the neighborhood smoke situation fortunately improved, because of the weather this year and the neighbors' habits. But I like the configuration they spec'ed and that part is installed and looks good.
I'm not sure which of the equipment you are talking about is already installed--do you already have an HRV with shared ducting? I think it's generally better to separate the ventilation and heating/AC ducting, but if you already have everything but the filter configure more or less as shown that seems like a good solution.
My hope is that busy roadways will start getting cleaner as we switch to electric transportation ... and they are already a lot cleaner than a dense neighborhood where wood heat is popular, and skills for clean burning and modern stoves are lacking.
Charlie,
Is there a name and model for the box?
Is it called a Comfowell?
I don't have anything installed yet.
We have quite an open floor plan so we would have a simple installation.
I know you should duct to bedrooms and exhaust from kitchen and bathrooms but since the house is finished, I am not going to worry about it.
Looking at the list of components I got from Zehnder, I see the filter is a "ComfoWell Activated Carbon Filter CW-FC 520, and I'm pretty sure the housing for it is a ComfoWell Filter Casing CW-F 520.
Aaron,
You wrote, "I believe your article talks about IAQ in general with suggestions on how to prevent air quality issues during construction and through lifestyle changes but with little in the way of environmental issues. ... What if the exterior air is polluted?"
Outdoor air pollution is a big issue, of course, but my article did address the issue. Scientists have determined that the most dangerous components of outdoor air from a human health perspective are small particles (PM2.5). Those are the particles that the MERV 13 filter is designed to address.
When occupants have special health issues -- you mentioned that your wife "developed this condition" and that she "is extremely affected by wood smoke" -- and there are specific local issues (especially issues arising from nearby homes that have wood stoves), then clearly, generalized IAQ advice may not apply. Charlie Sullivan gave you good advice about considering the installation of a charcoal filter.
This web site strives to provide advice that is broadly applicable and science-based. Most owners of green homes want high indoor air quality, and I think that the advice in my article is sound. That said, I don't know of any equipment that can solve all issues connected with outdoor air pollution, and people with special medical concerns may need individualized solutions to address their needs.
Aaron- If you send Zehnder your drawings, Zehnder will design the system for you, supply all parts needed and then come to the house and commission the system. It isn't cheap, but if IAQ is a priority, you might consider Charlie Sullivan's solution.
Martin,
I beg to differ with you as to your advice given regarding wood smoke.
Your article provides no additional information except to note that wood smoke is a contaminant
I am not saying that it is not a good article but when you point me to it, it is not providing any solution or proving any additional information.
Again a MERV 13 filter only provides the coarsest of filtering for wood smoke. Yes it gets the 2.5 particles but not much else.
I understand as moderator of this website, it is incumbant upon you to provide advice but you may not always have an appropriate article or the knowledge.
I think this is one situation where there is a dearth on information on GBA because there have been few requests or inquiries about truly clean air.
I have read all that I can on GBA.
Charlie and Stephen are about the only ones that have ever posted similarily.
And I am taking Charlie's advice and contacting Zehnder to get more information on ther filtering system.
Aaron,
I'm glad you posted your question here, and I'm very glad that Charlie and Stephen provided you helpful advice. That's what the Q&A section is here for. It's a successful example of the GBA community working as it should.
I also appreciate your suggestion that GBA continue to report on the topic of indoor air quality. It's a good suggestion, and we'll do our best to continue providing information on the topic.
I wish you the best of luck as you finalize your specifications for your ventilation equipment. Keep us posted about how well the equipment meets your needs.