Many of us spend at least half of our time at home in our houses and apartments. By providing good quality air at home we not only increase the well-being of the residents but also improve their health. The purpose of ventilation is to provide clean good quality air by removing the stale, polluted air from our homes. The main task is of course to ensure that the indoor air is healthy and safe to breathe. Ventilation today is also about energy and saving energy costs by adding heat recovery and/or renewable energy to the ventilation system.
A human being usually consumes about one kilogram of food and two litres of water each day – but at least 15 000 litres of air. Of this, up to 90% may consist of indoor air. For air to be clean to breathe, it has to be replaced with outdoor air every two hours. An effective ventilation system within a dwelling will protect the building fabric and occupants against potentially harmful condensation and mould growth and other airborne pollutants that are present in today's dwellings. Heat recovery is a process of continuously preheating incoming cool supply air by warming it with the outgoing exhaust air. Warm air is not simply exhausted through the open window but transfers most of its heat to supply air in a highly efficient heat recovery exchanger before being exhausted. At no time do the airstreams mix as the heat radiates through the plates of the exchanger.
Stale air is contaminated with humidity, toxins and smells extracted from the kitchen, bathroom and toilet. Outlet grilles in toilets and wet room areas, such as the bathroom, en-suite, utility and kitchen allow a constant or demand air volume to be extracted.
Fresh air is fed directly from outside into the ventilation system through a filter. The heat taken from the extracted air is used to warm the fresh filtered air in the exchanger and then flows through ducting. By undercutting doors and fitting transfer grilles fresh air circulation is ensured throughout the dwelling.
Saving Energy with MVHR
The level of effectiveness in saving energy depends on a number of highly variable and difficult to estimate factors. These are the level of air tightness in a home, the way the home is heated, the heat energy saved by the system, the energy used by the system, the type and cost of fuel used to heat the home and the cost of electricity used to run the system. MVHR systems are designed to run 24 hours a day, seven days a week, 365 days a year. Quite simply they have to be quiet in operation and acceptable to the occupants.