Ventilation for new builds, extensions and lofts in Dorset

New homes, extensions and loft conversions need ventilation that meets the building regulations and is tested before sign-off. We design the system, install it at the right stage of the build, measure the airflows and provide the commissioning information building control asks for.

Dorset has every kind of building, from old terraces to new estates and business parks, and every job is designed around the building in front of us, not a standard kit.

New builds & extensions in Dorset at a glance

Area: Dorset
Towns listed: 14, largest Bournemouth
Postcode districts: BH21, DT1, DT2, BH17, BH18 and BH12
Price region: South West
Survey: Free survey (UK mainland)

What ventilation for new builds, extensions and lofts involves

Extensions and loft conversions have their own triggers: a new wet room needs extract, a new habitable room needs background ventilation or a connection to the ducted system, and energy-efficiency work can mean the existing home needs more ventilation too. We work for self-builders, small developers, builders and architects. Fitting ducts at first fix is far cheaper than retrofitting, so it pays to involve us before the ceilings go up.

MVHR for new builds

Design, first fix, second fix and commissioning for whole-home heat recovery.

MEV or dMEV

Continuous extract systems where MVHR is not specified.

Extensions and lofts

Extract for new bathrooms and kitchens, background ventilation for new rooms.

Guide prices in Dorset

Ventilation for new builds, extensions and lofts guide prices in Dorset
Work	Guide price
MVHR in a new build or full renovation (fitted at first fix), 3 to 4 bedrooms (per home)	£5,150–£8,250 inc VAT
Continuous-running extract fan (dMEV) with humidity boost, flow tested (per fan)	£360–£625 inc VAT
Airflow testing and commissioning sheet for extract fans (up to 6 fans) (per home)	£150–£305 inc VAT
MVHR or MEV commissioning test, every terminal measured and recorded (per system)	£255–£410 inc VAT

Guide prices using South 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

You are insulating and re-windowing an existing home
A self-build with an airtightness target
Ceilings are about to be boarded

Rules in England

English building work follows Approved Document F (2021 edition) for ventilation rates, installation and commissioning. For homes, it sets minimum extract rates such as 15 litres a second for a bathroom and 30 or 60 for a kitchen, and expects mechanical systems to be airflow-tested.

How the job runs

Drawings
Design
First fix
Second fix
Commission

Towns we cover in Dorset

Questions about ventilation for new builds, extensions and lofts in Dorset

Which rules apply to ventilation in Dorset?

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.

Does an extension need extractor fans?

A new kitchen, bathroom, utility room or WC in an extension needs mechanical extract to meet Approved Document F in England, and new habitable rooms need background ventilation or a connection to a ducted system.

When should MVHR be fitted in a new build?

MVHR ducts should go in at first fix, after the structure and before plasterboard. Planning it at design stage avoids clashes with joists and steels.

Which towns in Dorset do you cover?

All of Dorset, including Poole, Weymouth, Christchurch, Ferndown and Dorchester. If your town is not listed, send the postcode and we will confirm.

Are prices different in Dorset?

Our guide prices are adjusted by region. In Dorset we use South West rates, so MVHR in a new build or full renovation (fitted at first fix), 3 to 4 bedrooms is typically £5,150 to £8,250 inc VAT per home.