A sealed house needs a plan for air

Draughty houses ventilate by accident. They also lose heat by accident. Once you seal a house properly, fresh air has to become deliberate rather than incidental.

How heat recovery ventilation works

Stale air is drawn out continuously and fresh air is brought in, passing through a heat exchanger so most of the warmth stays inside. The incoming air is filtered on the way through.

Why it matters in winter

It means you are not opening a window in July to clear condensation off the glass. Filtered air also makes a noticeable difference for anyone living with asthma, hay fever or a sensitivity to dust and smoke.