Vent Axia DMEV Extractor Fans

dMEV stands for decentralised mechanical extract ventilation. Each wet room, such as a kitchen, bathroom, utility room or WC, has its own small fan that runs all the time at a low, quiet trickle speed and boosts when extra extraction is needed. Together, the fans in a home provide continuous whole-house extract ventilation, known in the Building Regulations as System 3.

A standard extractor fan only runs when it's switched on, usually with the light and then stops. A dMEV fan never switches off. It removes moisture and stale air steadily in the background, then speeds up automatically when you shower or cook. Depending on the model, boost can be triggered by the light switch, a built-in humidity sensor or a timer.

No. Vent Axia's Lo-Carbon fans use DC motors, which the manufacturer says use around 90% less energy than traditional AC fan motors. For example, the published specific fan power figures for the Lo-Carbon NBR dMEV C are between roughly 0.08 and 0.14 watts per litre per second. A bathroom fan trickling at 8 l/s therefore draws around 1 watt, which costs a few pounds a year at typical UK electricity prices.

Usually, yes, and there are many benefits to having a dMEV installed in the bathroom. Most Vent Axia dMEV fans fit a standard 100mm duct or wall opening, so they can go into the same hole as many existing fans. The main difference is the wiring. A dMEV fan needs a permanent live supply to run continuously, plus a switched live if you want it to boost with the light. An old fan wired only to the lighting circuit may need its wiring changed. We recommend using a qualified electrician, as some bathroom electrical work must be notified under Building Regulations.

It can make a real difference. Condensation and mould usually come from moisture building up faster than it's removed. Because a dMEV fan extracts continuously, moisture is taken away before it has a chance to settle on cold walls and windows. Models with a humidity sensor also boost automatically when humidity rises. Persistent mould can have other causes, such as cold spots, leaks or poor insulation, so if the problem continues it's worth getting the property checked.

They're designed to be very quiet at trickle speed, because they run all day and night. For example, Vent Axia's consultant specification for the 100mm NBR dMEV gives a minimum noise level of 13 dB(A) at 3 metres. Several models also offer a delayed start. This lets you use the bathroom in quiet for up to 20 minutes before the boost kicks in.

Lo Carbon Revive is designed for social housing and refurbishment. It has an intelligent humidity sensor that ramps the fan up gradually, so changes in speed are less noticeable. It also has a built-in data logger, which helps landlords investigate humidity complaints.

Lo Carbon Response is a versatile choice for kitchens, utility rooms and bathrooms. It has an adjustable humidistat (40–90%), a delayed-start option and a digital display. It can be wall, ceiling, panel or window mounted.

NBR dMEV is aimed at new build. It comes in 100mm and 125mm sizes, with trickle and boost speeds adjustable in 1 l/s steps and is designed to meet the 2021 Building Regulations ventilation rates.