The Basics: Mechanical extract ventilation (MEV)
With some existing buildings mechanical extract ventilation can be used without the need to install additional trickle vents. MEV is also appropriate for properties which have ‘dirty air rooms’ such as kitchens and bathrooms that do not have outside walls. MEV systems use ducting from the bathrooms and kitchens to the outside. The stale air is removed using extract fans. The need to run ducting through the building means that MEV is may not be easily retrofitted to existing buildings.
MEV extracts air continuously at a low rate and it is important that the system is designed so that it complies with Building Regulations Part F. Hausmate’s job is to boost the extraction rate when sensors detect a rise in humidity or low air quality. Applying demand controlled ventilation (DCV) technology, Hausmate can also close trickle vents to minimise ventilation heat losses when the air quality is good. Using DCV ensures that ventilation only takes place when the air quality is poor, saving energy and reducing heat losses.
MEV and micro heat pumps
MEV centrally extracts warm dirty air from a building. The energy from this warm air is usually lost to the atmosphere, but to be even more energy efficient when using MEV, Hausmate can integrate a micro heat pump in the exhaust duct. This heat pump then takes the heat from the dirty air and uses this energy to help heat hot water, saving energy and reducing costs.
This has a number of advantages for low energy buildings. The first is that often hot water is the biggest user of energy in a low energy house and a micro heat pump can solve that requirement in a efficient way.
When compared to MVHR the capital cost of a heat pump may be similar but the heat pump will work throughout the year, where as MVHR is only useful for the winter months and an alternative method of hot water heating is required.
MEV works by introducing fresh air to the building through trickle vents in the living and bedrooms and then extracting the stale, bathroom and kitchen air centrally.