Continuous extract fans (dMEV) in Lancashire

A dMEV (decentralised mechanical extract ventilation) fan is a low-energy extract fan that runs continuously at a quiet trickle speed and boosts automatically when it senses humidity or a light switch. Because it never fully switches off, moisture is removed steadily instead of building up between showers.

Every job in Lancashire gets a written quote before it starts and a commissioning record when it finishes. We cover Blackburn, Blackpool, Rossendale, Morecambe and Lancaster and the villages around them.

dMEV fans in Lancashire at a glance

Area: Lancashire
Towns listed: 29, largest Preston
Postcode districts: BB4, BB5, FY2, FY5, BB6 and BB7
Price region: North West
Survey: Free survey (UK mainland)

What continuous extract fans (dMEV) involves

On trickle speed they are barely audible and use very little power; on boost they reach the higher continuous-extract rates in Approved Document F (in England, at least 13 litres a second for a kitchen, 8 for a utility room or bathroom and 6 for a WC). Landlords and housing associations often choose them because tenants cannot switch them off and forget them. Under Approved Document F, continuous mechanical extract systems need commissioning: the airflow on both trickle and boost is measured and recorded.

Commissioned and recorded

Trickle and boost rates measured and written on a commissioning sheet.

Bathroom and en-suite

Through-wall or ceiling fans with humidity-controlled boost.

Kitchen

Higher-rated continuous fans where a ducted hood is not practical.

Guide prices in Lancashire

Continuous extract fans (dMEV) guide prices in Lancashire
Work	Guide price
Continuous-running extract fan (dMEV) with humidity boost, flow tested (per fan)	£330–£575 inc VAT
Airflow testing and commissioning sheet for extract fans (up to 6 fans) (per home)	£140–£280 inc VAT

Guide prices using North West rates. Prices include VAT at 20%. A guide price is not a quote: we confirm a fixed price in writing first.

When to get it looked at

Occupants switch fans off because of noise
Mould keeps returning in a bathroom with a working fan
You manage rental homes and want ventilation that cannot be switched off

Rules in England

In England, ventilation is covered by Part F of the Building Regulations and its guidance, Approved Document F (2021 edition). It sets extract rates for kitchens, bathrooms and utilities and asks for mechanical ventilation to be commissioned and recorded.

How the job runs

Survey
Specify
Fit
Commission
Record

Towns we cover in Lancashire

Questions about continuous extract fans (dMEV) in Lancashire

Is the survey free in Lancashire?

For new installations on the UK mainland, yes. The survey is free and the quote that follows is fixed and in writing. Servicing, testing and repair visits are charged, and we confirm the cost before booking.

Is it expensive to run a fan all the time?

No. dMEV fans use very little electricity on trickle speed, typically a few watts, so running costs are low compared with the condensation and mould they prevent.

Are continuous fans noisy?

A correctly sized dMEV fan is very quiet on trickle; most people only notice it on boost. Noise usually means the wrong fan or a poor duct.

Which rules apply to ventilation in Lancashire?

In England, ventilation in new and altered homes is covered by Approved Document F of the Building Regulations. Landlords also have duties under the Housing Health and Safety Rating System, and workplaces must be ventilated under the Workplace (Health, Safety and Welfare) Regulations 1992.

Which towns in Lancashire do you cover?

All of Lancashire, including Blackburn, Blackpool, Rossendale, Morecambe and Lancaster. If your town is not listed, send the postcode and we will confirm.