A domestic MVHR (Mechanical Ventilation with Heat Recovery) system is a whole-house ventilation system that continuously removes stale air from areas like kitchens and bathrooms while bringing in fresh air to living spaces, using a heat exchanger to transfer warmth from the outgoing air to the incoming air without mixing them. This helps maintain good air quality, reduce condensation and mould, and improve energy efficiency by retaining heat that would otherwise be lost, making it especially effective in well-insulated, airtight homes.