Why an ERV alone won't fix humidity in South East Queensland

Fresh-air ventilation is the backbone of a healthy, airtight home. But we see a lot of people expect it to fix summer humidity too, and in South East Queensland it won't.

What an ERV actually does

An HRV or ERV runs 24/7, pulling stale air out of wet rooms and bedrooms and bringing filtered fresh air in, passing the two streams through a core so you keep most of the heat (or coolth) you've paid for.

An ERV (energy recovery) core also moves some moisture between the streams. That helps: it stops a lot of the outdoor humidity coming straight in. But it can only reduce the moisture it brings in. It can't take moisture out of air that's already humid.

The SEQ problem

On a sticky January day the air outside is holding a lot of water. An airtight house with an ERV lets in far less of it than a leaky house with open windows, but people, showers and cooking keep adding moisture inside. Nothing in the ERV removes it.

Indoor humidity that sits high for weeks is how you get mould in wardrobes, musty smells and dust mites. So in this climate we plan dehumidification from day one, not as a fix after handover.

What to pair it with

A ducted dehumidifier that works alongside the ventilation is the cleanest answer. Microwell's DRY duct units are built for this and include heat recovery. Size it to the house's latent load (the moisture), not just floor area.

A well set-up split system on dry mode can carry a small, very airtight house. It's cheaper, but it's noisier and less controllable.

For the ventilation itself, look at Passive House certified units like the Zehnder ComfoAir Q, Brink Flair or Dantherm HCV. On renos where there's nowhere to run ducts, LUNOS or Stiebel Eltron room units are the fallback, but they won't dehumidify either.

Details that trip people up

Insulate supply ducts that run through a hot roof space, or they'll sweat.

Put the unit somewhere you can reach. Filters need changing a couple of times a year, and nobody does it if it's buried in the roof.

Get the system commissioned: airflows measured and balanced room by room. A system that's out of balance can push humid air into wall cavities.