Heat Recovery Ventilation

Current building regulations require that new properties are built with high levels of insulation and air-tightness, ensuring that they are substantially more energy-efficient. At the same time the minimum ventilation requirement of trickle vents in windows and extractor fans in bathrooms and kitchens can result in poor indoor air quality as condensation and stale air generated from cooking, cleaning and bathing etc remain trapped inside the property. Mechanical Ventilation with Heat Recovery (MVHR), provides a solution to these problems, significantly improving ventilation and air quality, and at the same time will recover the heat that would otherwise be lost outside.

Typically MVHR systems are implemented with a central fan and heat exchange unit (or more than one in larger properties) with internal pipework running through ceiling voids and loft areas to most rooms and vented to the outdoors through wall or roof vents.

Extract pipework takes moisture-laden, stale air from ‘wet’ areas, such as kitchens and bathrooms. The heat from this stale air is recovered in the heat exchanger, and used to warm fresh air from outdoors delivered via the separate supply pipework into the living areas of the home.

It is important that the system is designed and installed to ensure an efficient and effective solution. Ducting runs and bends should be kept to a minimum with careful design so that the fans can be run at the lowest possible speed whilst still providing adequate ventilation. A well designed system will also provide an automatic speed boost when the humidity within the property increases above a set-point.

In addition it is possible to provide a level of cooling in the summer months by bypassing the heat exchanger when the outdoor temperature drops below the indoor temperature overnight by bringing the cooling fresher air directly into the property.