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ERV or HRV that scrubs the incoming air?

AntonioO | Posted in Mechanicals on

Hello all, I’m planning a new home and need some help on a ventilation issue. A couple of my neighbors burn a lot of wood in the winter, so much that you smell like a BBQ pit after a few minutes outdoors sometimes. Is there any ventilation system on the market that would scrub incoming air–activated carbon maybe? Or can anyone think of way to alter ventilation ducts on a typical ERV or HRV to do so that is safe for the systems and for me?

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  1. user-212218 | | #1

    Fantech sells a couple of inline filtration boxes... the FB6 would fit well inline with an hrv/erv... About 100$ bucks... Stick in whichever filter you fell is necessary.

  2. Richard Beyer | | #3

    Fantech box filters do not remove smoke from the air, only particulate.
    Residential Carbon insert filters are a waste of money in my opinion. Been there! I installed pre and after Fantech boxes in my home with MERV 13 filters to capture pollen and particulate from incoming outdoor air and for filtering the air exiting the building.

    Cleaning the outdoor to indoor air with carbon requires skill and proper knowledge of your long term outdoor temperatures and humidity.
    Activated Carbon is one way to handle the problem you described with a downside, it is costly! 55 lbs of activated carbon will cost you @$250.00 without a machine to pull the air through it. The life expectancy of activated carbon is 3 to 12 month's depending on the amount of contaminates and moisture captured.

    In order to use activated carbon successfully you need to dehumidify the incoming air with a whole house dehumidifier to receive the maximum life (Usually 1 year) out of the activated carbon because carbon will collect moisture from the air passing through it. Cost for a whole house dehumidifier in the northeast @$1,100.00 (130 pints per day) plus $100 to $300 per month to operate if left on constant operation with an inline air exchanger (HRV). Also note... ERV's are not dehumidifiers.

    To set your home up to operate on activated carbon, dehumidify with a new HEPA series Venmar HRV can cost you upwards of $15,000 plus installed.
    Next trick is finding someone who understands how these systems work. A commercial HVAC contractor may be able to help you who is familiar with indoor pollution control at casino's and other high smoke environments. Definitely not a DIY task.

  3. AntonioO | | #4

    Thanks, Richard. I thought it might be difficult, but I didn't realize how much so. Just the idea of dehumidifying the incoming air before scrubbing it seems a herculean task. I'm still interested though; I'd really hate my to put in an ERV or HRV and have it sucking in air worse than that it's ejecting. In any event your post was very informative.

  4. charlie_sullivan | | #5

    I'm facing this challenge as well. My first thought it simply to locate the intake on the side of our building furthest from the offending chimney. Another thought is to monitor the outside particulate count and run the HRV system on high when it's bad and low when it's not.

    Richard, can you recommend some reading about the humidity requirements for the carbon? For those of us dealing with wood smoke, that's mostly a problem on cold days. On cold days, after the air gets through the HRV, it will be warm enough that the relative humidity should be quite low. Would that be enough to solve the problem? (I'm in zone 6, central NH)

  5. AntonioO | | #6

    I on the other hand am near the zone 4 / zone 5 boundary. And where I live damp winter days are quite common hence my comment on the challenge of dehumidifying the incoming air. To make matters worse, wood is one neighbors main source of heat. Though the temperature hasn't reached below the mid 40s F yet, the wood burning has already commenced for this heating season. Given that their other heating source is an oil fired furnace, I cannot really blame them for burning wood with heating oil around $4/gal around here.

  6. Richard Beyer | | #7

    Carbon Adsorption Efficiency.. Humidity

    Relative humidity is an important factor that can affect the efficiency of the filter.
    The molecules of gases with low boiling points will be less adsorbed, because the molecules of the water vapor will be adsorped in their place, leaving less free surface in the pores for the gas molecules to impact the carbon. Generally, relative humidity must always be kept below 60%.

    Considering your problem seems to be during the heating season this may not be a concern. If the intent is to block smoke during the summer season when RH is high then you have some research to do or you could simply be throwing money away. There are many great resources online regarding carbon filtration.
    Again, I suggest for you to contact a good commercial HVAC company. Sometimes DIY systems are more costly than they need to be and in some cases you can cause more harm than good.

  7. nvman | | #8

    Antonio, I am replying to this post a year late but I am just encountering all the same issues. A lot of wood smoke during the heating season in North Vancouver. One thing I discovered is that HEPA will not filter smoke. Maybe the large particulates but definitely not odour nor the fine/dangerous particulates.
    Did you find a solution?


  8. AntonioO | | #9

    Sorry I just got around to responding. The short answer to your question is: No, I didn't find a solution. But heating oil prices are down near $2/gal now and my neighbor seems to be using oil more and wood less--at least for now.

  9. dickrussell | | #10

    Antonio, perhaps you have to resort to being "socially creative." If the neighbors are using fireplaces for their woodburning, give them some good references on how poor those are at providing real heat. More likely, if they are using woodstoves, they aren't running them anywhere near hot enough for complete combustion, possibly leading to excessive creosote buildup in the chimney and the risk of fire. If the stoves simply are too old, they need replacement. Get together with those neighbors, explain the severity of the problem their woodburning creates for you, show them the costs of the various "solutions" presented here and that those solutions actually may not work well. Then offer to split the cost of new woodstoves with them; that could well be your cheapest and best way out of your situation. It might be good for relations with those neighbors, too.

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