Heat Recovery Ventilation Explained
Seal a house up tightly enough to stop wasting heat, and you also stop it breathing. Heat recovery ventilation is designed to solve both problems at once.
Heat recovery ventilation, or HRV, is one of those systems that sounds like an unnecessary extra until you understand what it's actually solving. Once a home is insulated and sealed to a modern standard, it needs a different kind of ventilation — and HRV is built specifically for that job.
What does an HRV system actually do?
An HRV system continuously extracts stale, moist air from kitchens and bathrooms while supplying filtered fresh air to living spaces. As the outgoing air passes through the unit, up to 90% of its heat energy is recovered and transferred into the incoming fresh air before it enters the room — so you get a constant supply of fresh air without constantly reheating the house from scratch.
Why airtight and renovated homes need it
Modern building standards push new and renovated homes to be sealed and insulated far more tightly than older housing stock — great news for heat retention, but it also means the natural draughts that used to ventilate a house are gone too. Without them, moisture, cooking odours and condensation have nowhere to go, which is exactly the gap HRV fills.
It's worth being honest about where it doesn't help: an old, draughty house that hasn't been sealed and insulated properly won't see the same benefit, since it's already ventilating itself, inefficiently, through gaps that should really be closed up. HRV earns its keep once a building is airtight enough to need it — which is why it makes the most sense in new builds, passive houses, and homes being renovated to a high standard.
The benefits
- Up to 90% of heat recovered from outgoing air, rather than wasted
- Continuous supply of fresh, filtered air throughout the home
- Helps prevent condensation, damp and mould
- Works independently of your heating fuel — oil, gas, wood pellet, heat pump or electric, it doesn't matter how the heat in your home was generated
- Reduces the load on your heating system, since incoming air arrives pre-tempered rather than stone cold
Where it's installed, and the upkeep involved
HRV units are best sited in a utility room, hot press or wardrobe — somewhere with easy access for maintenance. We'd generally recommend running the system continuously rather than switching it off, since that's what keeps the air fresh and prevents the odour and condensation build-up you're trying to avoid in the first place. Day-to-day upkeep is mostly changing filters, with a professional service recommended about once a year.
See our full heat recovery ventilation service page for more detail, or ask us whether it makes sense for your particular property alongside your heating system.