Saturday, November 26, 2022

white plaster dust and ERV: responses

Ian Engelman

I found a Heat Recovery Ventalator (HRV) from Grainger I like. It is
the 3FND8 at $590. Installation requires some duct work, but it runs on
My goal is to keep the heat, but ventilate the plaster dust….

4 responses to the ERV system question:

If you’re like most P&O facilities you are generating the white dust, it
doesn’t come from outside. What you need is better filtration on your
HAVC system. Or, add an additional air circulator with electrostatic
The ventilator you describe is for very cold or hot climates. Instead
of ducting outside air in at ambiant temp you have a heat exchange that
draws the heat (or cold, and I know there is no such thing as cold) out
of the inside air you are expelling from the building, and then heats or
cools the outside air before releasing inside. Effectively you are not
throwing away the energy you used to heat or cool the inside air being
expelled. If temperature difference between outside and in is not
great, then cost of system takes long time to recapture.
Not a bad idea for a shop doing lots of laminating, you can throw out
the stinky air but not the AC/heat.


Visit 900

After reading your subject line I realized that your trying to filter plaster dust out of the shop, rather than conserve heat. On the other hand, maybe you want to do both. They are in fact two (2) different projects. Outside air is clean. Therefore, ERV systems do not “filter”. Clean incoming air is traded for “dirty” indoor air, capturing the indoor heat in the process. Over time, the ERV/HRV will, if it does not have a self-protecting filter, need to be cleaned of plaster dust.

What I think you are looking for is a shop (or plaster room) air filter system. The difference is an air filter system does not involve outside air. You are just removing bad stuff from the room air.

In many shops, plasterwork is not isolated. The result is dust contaminates everything! The answer is all plasterwork happens in a separate room, that has a dust tight door and heated and cooled air is filtered before it returns to the furnace, to protect the people and other rooms. Further, another filter system, within the room, protects the people working the plaster.

The thing to remember is balance of air pressure. Any air expelled from the plaster area must be replaced. If you force out more air than enters you have negative pressure and clean outside air (air outside the plaster room) wants to come in. This is good. If your shop air is at a negative pressure, the dust from the plaster room is pushes into the shop. Bad.

A workable system can be rather inexpensive. Full-length storm doors that seal on all four edges can replace the plaster room door. Furnace filters should cover the plaster-room air return to the furnace (they need a good seal all edges. A box fan with a furnace filter on the intake side can remove a bunch of dust. Again, sealed edges. That is the secret. Any path the dust can take to avoid a filter, it will take (line of least resistance). Last word, Use HEPA or paper(3M)filters, not fiberglass.

> From here, you can spend thousands of dollars.

I have an HRV (heat recovery ventilator) in my home in Canada. I get
fresh outside air which comes in prewarmed in the wintertime, even when
it’s freezing outside. It runs on a timer or program setting. For
example you go to the washroom and instead of a fan you push the HRV
button which turns it on for 20 min. Same thing during a shower or bath.
In P&O you could run it on low or high speed during the day, or run
20min on, 40 off. You’d want an ERV if you are in a southern climate
with air conditioning needs. This is pretty much a must for any P&O
clinic. Not only do you get constant fresh air pumped in from outside,
you remove stale air from bathrooms, patient visiting cubicles and the
dreaded tech room. At my office we just have a noisy exhaust fan
running, which get’s turned off because it’s too noisy, and then it
allows a backdraft, drawing nasty smells all the way to the front
office. Go for the HRV / ERV!


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