MEV, PIV, heat recovery and central vacuum — how each one works
Not every home or building needs the same system. Here is what each unit actually does, in plain English, with the numbers that matter — so you know what you're getting before we quote.
Extract only
MEV — Mechanical Extract Ventilation
Stale air extractedFresh air in via vents
One quiet central fan continuously extracts damp, stale air from the wet rooms — bathrooms, en-suites, utility and kitchen — through ducting to a single unit, usually in the attic or a press. Suited to homes with up to six wet rooms (roughly 300m² / 3,200 sq.ft).
Demand controlled 55–85% RH
SFP from 0.16 w/l/s
Unit 340 × 252 × 310mm
2 year warranty
Supply only
PIV — Positive Input Ventilation
Filtered fresh air inStale, damp air pushed out
A single unit filters outside air and gently pushes it into the landing or central hallway. The slight positive pressure dilutes and displaces moisture-laden air, forcing it out through leakage paths and wet-room extract points. The go-to fix for condensation and mould in existing homes.
Loft, wall & air-source versions
G4 pollen filter
Brushless DC — from 3W
Integral pre-heater
Heat recovery
MVHR with a counterflow heat exchanger
Fresh air to bedrooms & livingStale air from wet roomsCounterflow plate core
Two separate air streams — warm stale air out of the wet rooms, cold fresh air into the bedrooms and living rooms — pass through a plate exchanger in opposite directions. Heat crosses the plates; the air streams never mix.
Up to 92% heat exchange
SFP from 0.38 w/l/s
245–568 m³/h flow
SAP Appendix Q listed
Heat recovery
MVHR with a rotary (thermal wheel) exchanger
Fresh air to bedrooms & livingStale air from wet roomsRotary thermal wheel
A slowly rotating aluminium wheel sits in both air streams. As it turns it picks up heat — and a controlled amount of moisture — from the outgoing air and releases it into the incoming fresh air. Built in Sweden for BEAM.
Up to 86% efficiency
F7 pollen-grade filters
38–43 dB(A) at 3m
No condensate drain
Room by room
dMEV — decentralised extract fans
An ultra-quiet, low-profile continuous-running extract fan for a single bathroom, kitchen or utility. One fan suits ducted-in-room or through-wall installs, with trickle, boost and high-boost speeds.
From 15 dB(A) at 3m
1.1–2.5W running
SFP from 0.11 w/l/s
0–60 min boost overrun
Single room
Single room heat recovery (REC)
A decentralised heat recovery unit for one problem room. Stale moist air is extracted while fresh filtered air is drawn in, both passing through a heat exchanger inside the same unit.
Up to 90% thermal efficiency
REC Smart+ & REC Duo 100
Independent per-room rates
Easy maintenance
Developments
DCV — Demand Controlled Ventilation
An intelligent low-energy whole-house system designed for multi-housing developments. A central unit connects by ducting to extraction valves in the wet rooms, while passive fresh-air vents feed the habitable rooms.
Multi-unit developments
Ducted extract valves
Passive supply vents
Low energy on demand
Central vacuum
Central vacuum — the units & options
Three elements: a power unit in the garage or utility, concealed 50mm ducting to wall inlets, and a lightweight hose with cleaning tools. Nothing is recirculated into the air you breathe.
605–1,045 airwatts
Up to 50% more suction
62–68 dB units
2 year warranty
Not sure which one suits your build?
Tell us the property type, size and whether it's new or existing — we'll size the right system and talk you through the options.