Mechanical Ventilation and Heat Recovery (non-domestic) is an approved Green Deal and ECO measure under the Building Services Mechanical category.
What is Mechanical Ventilation and Heat Recovery?
Without Mechanical Ventilation to provide fresh air, moisture, odours and other pollutants can build up inside a home. Mechanical Ventilation systems circulate fresh air using ducts and fans, rather than relying on airflow through small holes or cracks in a home’s walls, roof or windows.
Benefits of Mechanical Ventilation
- Better indoor air quality - Indoor air can be many times more polluted than outdoor air. Ventilation systems can be significantly improve a home’s air quality by removing allergens, pollutants and moisture that can cause mould problems
- More control – When homes rely on air flow through walls, roofs and windows for ventilation, there is no control over the source or amount of air that comes into the house. In fact, air leaking into the house may come from undesirable areas such as the garage, attic or crawl space. Mechanical ventilation systems, however, provide proper fresh air flow along with appropriate locations for intake and exhaust
- Improved comfort – Mechanical ventilation systems allow a constant flow of outside air into the home and can also provide filtration, dehumidification and conditioning of the incoming outside air
Typical Systems and Recommended Climates
Supply Ventilation Systems – Hot or Mixed Climates
Fresh air is drawn in through an air “intake” vent and distributed to many rooms by a fan and duct system. A fan and set of ducts dedicated solely to ventilation can be used, or an outside air intake can be connected to the main return air duct, allowing the heating and cooling system’s fan and ducts to distribute the fresh air. The benefit of connecting to the return air duct is that outdoor air can be air conditioned or dehumidified before it is introduced into the home.
As supply systems continually introduce outdoor air, a home can become slightly pressurised. As a result, these systems are typically not appropriate for colder climates where there is a risk of heated indoor air being pushed through any remaining holes and cracks in the construction assembly where it could reach cold exterior surfaces, condense and cause moisture problems.
Exhaust Ventilation Systems – Cold Climates
Indoor is continuously exhausted to the outdoors with one or more fans often located in bathrooms. As indoor air is continually drawn out, the home becomes slightly depressurised. As a result these systems are typically not appropriate for hot, humid climates where there is a risk of drawing hot outdoor air into remaining holes and cracks in the construction assembly where it could reach cool interior surfaces, condense and cause moisture problems.
Balanced Ventilation Systems – All Climates
With these systems, equal quantities of air are brought into and sent out of the home. This is usually achieved using two fans – one to bring fresh air in and another to send indoor air out. The two most common systems are “heat recovery” ventilation, (commonly referred to as HRV) and “energy recovery” ventilation, (commonly referred to as ERV). HRVs transfer heat from exhaust air to incoming air during the heating season and from incoming air to exhaust air in the air conditioning season to reduce the heating and cooling load and improve comfort. ERVs transfer heat and moisture between the exhaust and incoming air. This provides additional savings in the simmer by reducing the moisture content of the incoming air that would otherwise have to be dehumidified with the cooling equipment or dehumidifier. ERVs also provide additional comfort in the winter by adding moisture from the outgoing air to the incoming air to help avoid excessively dry indoor conditions.