Heat recovery room ventilators

Description
Extract fans with a built-in heat exchanger which pre-heats incoming fresh air from the warm extracted air.

Unit cost of installation (3 bed semi)
£250 dependant on size and method of installation.

Bulk cost of installation

Maintenance
Periodic cleaning.

Lifetime
15 years.

Technical suitability
Similar to extract fans but with a heat exchanger that recovers ~60% of the heat from the outgoing air. Units are usually dual speed providing continuous background 'trickle' ventilation at low speed with 'boost' extract capability which is controlled either manually or via a humidistat.

Care should be taken if installing extract fans in dwellings with open-flue combustion appliances because in some circumstances the operation of the fan could cause spillage of combustion gases back into the room. This can occur even if the combustion appliance is in a different room to the extract fan(s). Mechanical extract fans should not be installed in the same room as solid fuel appliances. Technical guidance referred to below should be consulted if open-flued appliances are present in the dwelling.

Non-technical constraints
User perceptions of running costs and noise might reduce usage in rapid extract mode, but units much quieter in operation at slow speed means that they are less likely to be disabled in this mode.

Potential concerns with fuel poor
No specific issues.

Ancillary benefits
Extraction of moisture vapour from source results in lower risk of condensation and damage to fabric of building and occupants' possessions from mould growth.

Trigger points for work
Refurbishment of kitchens and bathrooms.

Technical Guidance Available
» Approved Document F 'Ventilation'
» OFTEC Technical Information Sheet T1/112 'Oil fired Appliances and Extract Fans'
» BRE Information Paper 21/92 'Spillage of flue gases from open-flued combustion appliances' 1992