MVHR Ventilation for Insulated Homes: Why It Matters and What It Costs

The Problem: Well-Insulated Homes Stop Breathing

As homes are insulated and draughts are blocked to reduce heat loss, a new problem emerges: moisture, CO₂, and indoor pollutants have nowhere to escape. Without adequate ventilation, relative humidity rises above 65%, encouraging mould growth and condensation — particularly around thermal bridges like window reveals and external wall junctions.

Opening windows solves the air quality problem but throws away up to 40% of the heat you've worked to retain. MVHR (mechanical ventilation with heat recovery) solves both problems simultaneously: it continuously extracts stale air from wet rooms and recovers 90–95% of its heat before exhausting it. Fresh filtered air is simultaneously drawn in and pre-warmed.

How MVHR Works

An MVHR unit typically sits in a loft or utility room. Insulated ducts run from the unit to extract points in kitchens, bathrooms, and utility rooms, and to supply points in living rooms and bedrooms. A cross-flow or counter-flow heat exchanger transfers heat from outgoing stale air to incoming fresh air without mixing the two airstreams.

Modern MVHR units achieve heat recovery efficiency of 90–95% with whole-house electricity consumption of just 30–60 W — roughly equivalent to a single LED light bulb running continuously. This makes the heating contribution from MVHR free or nearly free at any reasonable electricity price.

MVHR Costs in 2026

A whole-house MVHR system for a 3-bedroom semi-detached house (90 m²) typically costs £3,500–£6,500 installed, including all ductwork, the unit, supply and extract valves, commissioning, and balancing. Premium units from Zehnder, Dantherm, or Vent-Axia cost more than budget units but offer quieter operation and higher efficiency.

MVHR is most cost-effective when installed as part of a whole-house retrofit or new build. Retrofitting into an existing occupied home adds complexity and cost due to routing ductwork through finished spaces. Insulated rigid ductwork in the loft plus flexible connections to rooms is the standard approach for retrofit.

MVHR and Heat Pumps: A Complementary Partnership

An MVHR system recovers heat that would otherwise be lost through ventilation — reducing the total heat demand the heat pump must meet. In a well-insulated house, ventilation heat loss can account for 20–30% of total heat demand; MVHR reduces this contribution to near zero. This means the heat pump can be sized smaller, reducing capital cost and improving efficiency at part-load.