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Description
Whole house systems that combine extract ventilation and supply of fresh air in one system. Systems incorporate a heat exchanger to recover heat from extracted air, which is then used to preheat incoming air.
Unit cost of installation (3 bed semi)
From £1,800 dependant on size of system and ease of installation of ductwork.
Bulk cost of installation
Data not available
Indicative energy saving
Rather than saving energy there is often an energy penalty with these systems because of the energy consumed by the fan.
Maintenance
Regular cleaning and balancing of system required.
Lifetime
15 years for fan unit.
Technical suitability
Mechanical Ventilation with Heat Recovery requires a very airtight construction to function effectively. MVHR also requires ducting to be installed, which might present problems for retrofit. Fan motors should be low energy DC types, and the system sized to deliver a volume of air appropriate to the size of the dwelling.
Non-technical constraints
No specific issues.
Potential concerns with fuel poor
Users may perceive running costs to be high and therefore switch the fan off.
Ancillary benefits
Requirement for airtight construction means that the house will suffer fewer draughts. Manufacturers claim improvements in indoor air quality and help in controlling dust mite populations. A link has been suggested between allergic reactions, such as asthma, and house dust mite populations. Research is continuing in this area.
Trigger points for work
Major refurbishment. High levels of external noise requiring windows to be kept shut.
Technical Guidance Available
» CE124/GPG 268 'Energy-efficient ventilation in housing - a guide for specifiers'
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