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What is a Mechanical Ventilation with Heat Recovery (MVHR) system?

MVHR is a whole-house ventilation system that supplies fresh air while recovering up to 90–95% of heat from extracted air. It is particularly suited to airtight SIP homes where controlled ventilation is essential.

A Mechanical Ventilation with Heat Recovery (MVHR) system is a whole-house ventilation system that extracts stale air from inside a building and supplies fresh air from outside, while retaining most of the heat from the air being expelled.

At its core, an MVHR system is a balanced ventilation system with heat exchange. It consists of:

  • A central unit

  • A network of ducts running through the house

  • Extract grilles in kitchens, bathrooms and utility rooms

  • Supply grilles in living rooms, bedrooms and offices

  • A heat exchanger inside the unit

Warm, stale air is extracted from the house, while cool, fresh air is brought in from outside. Inside the unit, a heat exchanger transfers up to 90–95% of the heat from the outgoing stale air to the incoming fresh air — without mixing the airstreams.

SIP homes are inherently airtight and very well insulated, which makes them ideal candidates for MVHR. In highly airtight homes (typically with air leakage <3 m³/h·m² @ 50Pa), mechanical ventilation becomes essential because natural air leakage isn’t enough to maintain healthy indoor air quality.

MVHR helps to:

  • Maintain indoor air quality by continuously refreshing air

  • Retain heat that would otherwise be lost through opening windows or extractor fans

  • Improve SAP scores and EPC ratings

  • Balance temperatures across rooms

  • Reduce condensation and mould

  • Provide quiet, draught-free living

Installing MVHR in a SIP home requires early coordination. Duct routes should be planned alongside SIP design, with service voids, ceiling zones and floor zones used to accommodate ductwork. All penetrations through the SIP envelope must be airtight and sealed.

MVHR is not air conditioning — it does not heat or cool the air, only recovers heat. It does not increase energy use and becomes essential in airtight homes for air quality and compliance.

In SIP homes, the airtight and insulated nature of construction means traditional ventilation methods are inadequate. MVHR provides fresh, filtered air throughout the year without losing heat, making it well suited to homes aiming for low energy use and thermal comfort.