ERVs and formaldehyde
In the Allison Bailes interview with Dr. Iain Walker https://www.greenbuildingadvisor.com/blogs/dept/building-science/interview-dr-iain-walker-ventilation
the emerging concerns about formaldehyde transfer (or non-transfer) are discussed at the end. As stated in the interview, it’s hard for the purchaser to know the exact extent of the issue with particular units, but Dr. Walker does describe the 2 methods of exchanging moisture, wheel and membrane with the latter being preferred.
I will be using an ERV on a new build in Zone 4A and would be really interested to know which ones are currently using the membrane for moisture exchange. Or, conversely, specific models that do not.
Thanks in advance for any help or guidance you can provide.
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Replies
Greg,
First of all, whether or not formaldehyde transfer in ERVs is an issue worth worrying about is not yet settled. Many U.S. homes have detectable amounts of formaldehyde in the indoor air; if you operate an ERV, the levels of formaldehyde will certainly decrease, because you will be introducing fresh outdoor air while exhausting indoor air.
Just because a small percentage of the formaldehyde in the exhaust air stream may be transferred to the incoming fresh air stream, doesn't mean that the ERV isn't effectively lowering indoor formaldehyde levels.
That said, you can find out more about the characteristics of ERVs by visiting manufacturers' websites.
For example, this page on the Renewaire website states, "The RenewAire static plate, air-to-air exchanger transfers both heat and water vapor into or out of the incoming fresh outdoor air." You can safely conclude that the Renewaire ERV uses a type of membrane, not a wheel.
This page on the Airxchange website states, "Rotating between two airstreams within the ERV cabinet (exhaust air and supply air), energy recovery wheels transfer heat and humidity from the warm/humid airstream to the cool/dry airstream. Airxchange’s unique, segmented, and sustainable wheel design provides a simple yet effective means of optimizing energy transfer performance for the life of the HVAC system." So Airxchange uses a wheel.
This page from the VanEE website states, "VanEE ERV heat exchangers (cores) are made of enthalpic or polymerized paper and have a 5 year warranty when in residential products. The advantage of enthalpic or polymerized paper cores over other ERV systems such as energy recovery wheels is that there are no moving parts to break down or service and no added energy required to drive the wheel motor." So you can conclude that ERVs manufactured by VanEE use a membrane approach, not a wheel.
Thank you Martin for that thorough response.
In case anyone else is concerned about the same, it looks like the Venmar AVS E15 ECM ERV uses a "polymerized paper core" as well.
Good air quality and new construction.
I build. Think about the exposure builders and tradesman live in for a lifetime. I have no allergies. I have blown out thousands of nose fulls of sawdust. Pressure treated, SPF, OSB, plywood. I do not sand exotic hardwoods anymore (unless wearing a good air filter) as doing that almost stopped my breathing permanently once.
Back to my point. Anyone who desires a low VOC home will be doing the opposite by moving from an existing home to new construction. I just built a set of stairs at a new home. Now that it is just finished it's summer and all windows are closed. Enter that home and the new home smell is very apparent.
New homes need to be highly aired out and I bet it would take months or years to reduce levels to that of a ten year old home.
I let this homeowner know that at least the next few months they should get all the windows opened for many hours a week.
Sensitive people should air out new homes and IMO never move into a new home the day after the carpet is layed and the certificate of occupancy issued.
Aj
Are there instruments to detect, measure and monitor indoor air pollutants? Beside the nose, skin rashes and phlegm levels?
What opened my eyes to a major air quality issue was to visit a house with a self cleaning range hood. These units separate and collect for disposal, the airborne particulate from cooking and periodically, as needed, the homeowner removes and cleans the capture containers and filters.
What I don’t like is that most of them are 500-700 CFM. That creates a lot of negative pressure inviting fugitive (uncontrolled, unknown) outdoor, basement and garage sourced infiltration as well as potential back-flow of other combustion appliances, dryers, ERV's, etc.
This particulate capture design technology seems to been extensively developed in Asian countries where modern gas wok and charcoal frying (i.e. tandoori ovens) releases a high volume of compounded water particles, carbon and oil/fat.
Here is one that is 300 CFM
http://www.cyclonerangehoods.com/EN/product/classic/7
Keep pets and children well back from others:
http://www.cyclonerangehoods.com/EN/product/classic
What most folks don't understand is that if you can smell a thing, then it is in your breathing zone as a particle. Combustion off-gassing (gasses are simply clouds of particles) is probably the major home-operation, pollution concern that a homeowner can affect. Particularly during cooking; Turn on or us an auto filtration solution.
Our sense of smell can be quickly saturated by an assault of an odor and within moments to minutes we no longer recognize a distinct odor like we did when first exposed.
My wife has insisted we change out our current range exhaust for the self cleaning type. I noticed a before-after difference in the smell and oiliness of our friend's kitchen/house with the Cyclone.
What concerns me are the things Terry Lee talks about (above; "Iain Walker" (I’ll take this as legal advice"). Theses particulates are the effluents of new and evolve with aging and oxidizing building materials; not something a home owner has any ability to measure or control.
It’s a fools game (but necessary) to control pollution by dilution and filtration; we should be keeping it out of the house in the first place.