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MEV vs dMEV
MEV and dMEV are two forms of continuous mechanical extract ventilation. MEV uses one central fan connected to the wet rooms by ducting; dMEV uses a separate small fan in each wet room. Both continuously remove stale air, and neither recovers heat. This guide explains the difference and which suits which home.
By VentRight Editorial · Last updated 2026-07-08 · Impartial · Sourced
MEV uses one central extract fan and ducting; dMEV uses a separate fan in each wet room. Neither recovers heat.
Central MEV vs decentralised dMEV — labels
- MEVCentral MEV — One central fan, ducted to the wet rooms, extracts stale air. Fresh air enters through passive vents. No heat recovery.
- dMEVDecentralised dMEV — A separate continuous fan in each wet room, with little or no ducting. No heat recovery.
What is the difference between MEV and dMEV?
MEV, mechanical extract ventilation, uses a single central fan, usually in a loft or cupboard, ducted to the kitchen, bathrooms and utility. dMEV, decentralised mechanical extract ventilation, replaces that with a separate small continuous-running fan in each wet room. Both run continuously and extract stale air; the difference is one central unit and ducting versus several local fans.
In both systems fresh air enters passively through background ventilators in the habitable rooms, and stale, moist air is pulled out of the wet rooms. The choice between them is mostly practical: whether it is easier to run ducting to a central unit, or to fit a fan in each wet room.
When is dMEV the better choice?
dMEV suits flats and retrofits, where running ducting to a central unit is difficult. Each fan is fitted in its own room with a short duct straight to outside, so there is little or no ductwork. It is simple, cheap to install, and easy to fit into an existing home, which is its main advantage over central MEV.
For a flat or a house where you do not want to run ducts across the property, dMEV is often the path of least resistance. The trade-off is a fan in each wet room rather than one central unit, but modern dMEV fans are quiet and low powered.
When is central MEV the better choice?
Central MEV suits homes where a central unit and ducting can be accommodated, often new builds or larger properties. One unit is quieter in the living space than several in-room fans, and can be easier to control and maintain from a single point. It is a tidier solution where the ducting can be run.
Because the fan is centralised, usually in a loft, the living spaces stay quiet and there is one unit to service rather than several. In a new build where ducting is planned in, central MEV is straightforward; in an untouched existing home it is harder, which is where dMEV wins.
Do MEV or dMEV recover heat?
No. Both are extract-only systems: they remove stale air, and fresh air enters passively through background ventilators. Neither recovers heat, which is the key difference from MVHR. If heat recovery matters, in an airtight home, MVHR is the system; MEV and dMEV suit reasonably airtight homes where the simpler, cheaper approach is enough.
This is worth being clear on when comparing systems. MEV and dMEV are a step up from intermittent extractor fans, giving continuous whole-home extract, but they do not touch the heat leaving with the stale air. In a very airtight home that heat loss matters, which is why such homes use MVHR instead.
Questions
- Is dMEV better than MEV?
- Neither is simply better; they suit different homes. dMEV is easier to fit in flats and retrofits with little ducting, while central MEV is tidier and quieter in the living space where ducting can be run.
- Does MEV recover heat?
- No. MEV and dMEV are extract-only systems with no heat recovery. Fresh air enters passively through background vents. For heat recovery you need MVHR.
- Is dMEV good for a flat?
- Yes. dMEV is often the easiest mechanical option for a flat, because each wet room has its own small fan with a short duct to outside, avoiding long central ductwork.
- What is the difference between MEV and MVHR?
- MEV only extracts stale air and does not recover heat. MVHR both supplies fresh air and extracts stale air, and recovers most of the heat from the outgoing air, which suits airtight homes.