In addition to the usual allergens - pollen, dust, bed mites, pets, etc. there is a serious risk from chemicals introduced through cleaning products, toiletries, furnishings, paints, mdf, air fresheners etc. etc.

It has been stated that indoor air is 10 times more polluted than outside air (Which?) and with families particularly children spending more time indoors rather than outdoors they are more exposed to risk so the air quality is an important issue.

It is essential in these new air tight dwellings to provide adequate ventilation. This cannot be satisfactorily achieved with traditional window trickle vents and extractor fans; trickle vents are affected by weather conditions particularly wind and intermittent extractor fans are only working whilst in operation apart from being noisy and unsightly. Controlled ventilation systems with heat recovery are by far the best option as they provide continuous ventilation all year round. Heat recovery rates vary between 70% and 90% so you can achieve huge energy savings for small running costs. In addition HRV systems can contribute to a zero carbon home by distributing any heat generated in the home (such as by the occupants, cooking, solar gain, etc.)

As a minimum, homes should have a whole house ventilation system (extract only) to continually extract damp polluted air. It is not always practical to open windows for ventilation.