What's the purpose of filters for MVHR systems? Are they to filter the incoming air for the occupants or the equipment? Or both? Can you get filters that filter our pollution or is it just relatively large particles like pollen? (We're probably installing Paul MVHR)

Dust is the problem, our filters are so efficient that we hardly get any dust in the house now.

There is a cost in maintaining them, I feel that it is worth it.

I would rather see the dust in the filters than in my nose or lungs.

Shevek asked: "What's the purpose of filters for MVHR systems? Are they to filter the incoming air for the occupants or the fans? Or both? Can you get filters that filter our pollution or is it just relatively large particles like pollen? (We're probably installing Paul MVHR)"

The basic reason is to stop dust clogging up the heat exchanger and collecting in the ducts, but you can also buy pollen filters.

The supplier kind of answers the question:

http://www.greenbuildingstore.co.uk/media/page_content/MVHR/Pricelist/MVHR-filters-pricelist-October-2011.pdf

Also, do you think a house ventilated with PVHR (like Ventive) would remove dust in a similar fashion to MVHR systems?

Posted By: fostertom

you can't 'extract' settled dust - so any kind of whole-house ventilation with well filtered inlet would eliminate external dust in the house, but would do nothing to remove the dust that's created indoors - dead skin etc!

Right, so why is it that people with MVHR systems tend to report having far less dust in their houses? Is it really just the incoming filter? And what about reports of dirty room extract filters. Why are they getting dirty if not much dust is not being extracted? (see CWatters comment above)

I find our MVHR house about as dusty as the old Victorian house before it. I expected a big improvement - the filters do get quite dirty. I don't dust often. I blame the cat.

As a broad premise, you would almost certainly want filters of around Eu5 or Eu7 grade protecting both the fans and the heat exchanger (so supply side and extract side).

above that the fan power required to drive air through increasing high grade filtration becomes a major burden.

You cannot get high levels of filtration on passive ventilation - the stack effect doesn't provide enough driving force

regards

Barney

<blockquote><cite>Posted By: RobinB</cite> I blame the cat.</blockquote>

I blame our cat for a lot. Her ability to hold large amounts of earth in her paws, carry it (without spilling any) up two flights of stairs, to then deposit it on our bed never ceases to amaze.

Posted By: ShevekWhat's the purpose of filters for MVHR systems? Are they to filter the incoming air for the occupants or the equipment? Or both? Can you get filters that filter our pollution or is it just relatively large particles like pollen? (We're probably installing Paul MVHR)

Most units come with a G4 Filter to protect the unit. An F7 filter may be an option and this would filter pollen to some extent but this reduces the efficiency of the unit as it has to work harder to get the air through. My Helios 500 has the option of fitting an F7 and I may get one for the summer.

Posted By: Simon StillI blame our cat for a lot. Her ability to hold large amounts of earth in her paws, carry it (without spilling any) up two flights of stairs, to then deposit it on our bed never ceases to amaze.

I think the trick is to lick your paws so the dust sticks to them, walk it upstairs, then curl up on the bed for a while until your paws dry and the dust falls off.

Scratching yourself is also good for generating a bit of dust and giving your staff something to do.