HRV Or ERV

What each one does

HRV: recovers sensible heat only. The incoming air is warmed by the outgoing air and arrives at outdoor humidity, which in January is very dry.

ERV: recovers heat and some latent moisture, so the incoming air arrives slightly less dry in winter and slightly less humid in summer.

Both ventilate at the same rate; the difference is what happens to the moisture.

Both need the same maintenance — filters, core, hoods, drain, balance.

Both are available as a standalone ducted system or tied into the furnace ductwork.

And both have a bypass or defrost arrangement for cold weather, which is where their behaviour in a Toronto January differs by model more than by type.

The Toronto winter question

Most Toronto houses in deep winter have too much indoor moisture rather than too little, because the house is tight and people cook, shower and breathe. For those houses an HRV is doing exactly the right thing by drying it out. The houses that find an HRV too drying are usually over-ventilating or have a very low occupancy.

Which suits which house

Window condensation and high winter humidity: HRV, which removes moisture more effectively.

A house that is uncomfortably dry in winter with static and cracking woodwork: ERV is worth considering, alongside checking whether the ventilation rate is simply too high.

A house with significant summer air conditioning and humidity: ERV has a genuine summer advantage.

High occupancy relative to volume: HRV.

Low occupancy in a large house: ERV, or an HRV on a reduced rate.

And in either case the rate matters more than the type, because an over-ventilated house is dry regardless of which unit is doing it.

What matters more than the choice

That it is running at all, which is the single biggest factor.

That the filters are clean and the core is washed, because a dirty unit does not ventilate whatever type it is.

That it is balanced, so supply and exhaust match and the house is not being pressurized or depressurized.

That the grilles are in the right places — exhaust from bathrooms and the kitchen area, supply to bedrooms and living space.

That the exterior hoods are clear and not icing up.

And that somebody has shown the homeowner how to use the controls, which is skipped on a majority of installations.