Over a quarter of new homes are now being fitted with Mechanical Ventilation with Heat Recovery (MVHR) systems (source NHBC), and this is set to increase over the next few years.

Ever tightening building regulations have led to a need to ensure that new homes have appropriate levels of indoor air quality and ventilation, whilst reducing the amount of energy used for heating the property. Specifiers are therefore seeing MVHR as a practical way of meeting what at first appears to be the conflicting requirements of achieving adequate ventilation and the high levels of energy efficiency required for new homes.

MVHR systems work by extracting warm, moisture laden air from the ‘wet zones’ of a home (kitchen, bathroom and ensuites) and passing it over a heat exchange cell to recover the heat before it is expelled to the outside. At the same time, cool fresh outside air is also drawn through the heat exchanger where it collects the recovered energy and is tempered before being released into the living room areas of a property.

It was recognised some time ago and further highlighted with the production of the report Indoor Air Quality in Highly Efficient Homes – A review, that increased air tightness had a potentially harmful effect on the quality of indoor air. This is due to the build up of moisture-laden air and potentially toxic compounds that are all around us. So when homes are being built to the higher energy efficiency levels, some form of mechanical ventilation is required, and MVHR, because of its energy efficiency, has proven to be an ideal solution.

Poor indoor air quality, which is often characterised by high humidity, can provide a breeding ground for dust mites, which can exacerbate asthmatic and other breathing related conditions, as well as skin complaints. Poorly ventilated homes can also become damp and suffer with condensation which eventually leads to mould growth, causing damage to the fabric of the building and respiratory health issues.

As well as studying damp and condensation, the Review looked at the build-up of pollutants in indoor air that may be released by building products, furnishings, consumer products, such as hair sprays and furniture polish, as well as pets. It concluded that as a result of continued exposure to these pollutants, or ‘Volatile Organic Compounds’ these could cause a variety of ailments, ranging from asthmas and allergies to an increased risk of lung cancer and heart disease.

Another reason for the increasing adoption of MVHR by the new build sector is the latest ErP Directive, which is encouraging a move to a more systems-based approach to ventilation. It was first introduced in 2013 and the second stage of the legislation which is due to be released in 2016, focuses on ventilation units over 30W.

This mainly impacts on Mechanical Extract Ventilation and MVHR systems and requires all ventilation units, except dual use versions to be equipped with a multi-speed or variable speed drive. In addition, all bi-directional units are required to have a thermal by-pass facility as an essential part of the design criteria, which prevents warm air being recovered in warmer weather.

Housebuilders are recognising that MVHR helps them to cost effectively contribute towards the improvements in CO2 emissions required by Building Regulations. With MVHR, the incoming air is filtered, improving internal air quality. It negates the need for window trickle vents, where windows remain closed for acoustic or pollutant reasons. It can also give an improved performance under the Government’s Standard Assessment Procedure for energy ratings in dwellings (SAP).

We responded to the rise in demand from specifiers and housebuilders by introducing MVHR systems that are ideal for new homes, preventing condensation, damp and associated health issues. Systems like the energiSava 300 and 400 offer high energy efficiency and feature a summer bypass facility, therefore making them fully compliant with the next stage of the ErP Directive for ventilation units.

It is these types of system that help to meet current and future building regulations requirements, whilst providing a constant supply of clean air and reducing humidity levels, therefore preventing condensation and associated issues. The trend towards fitting MVHR systems into new homes looks set to continue as the new build sector continues to recognise their effectiveness in improving indoor air quality.

For more information on achieving ventilation requirements for new dwellings, contact EnviroVent via the website www.envirovent.com or by calling 0845 27 27 810.

A Whole House Approach To Ventilation