Mechanical Heat Recovery Ventilation

The house is designed to be as air-tight as possible for energy conservation. This involves painstaking attention to detail in filling, taping and sealing gaps, a "vapour control layer" (aka polythene sheeting) in between the insulation layers and having no trickle vents in the windows.

Clearly the house needs fresh air and this is achieved with a MVHR or Mechanical Heat Recovery Ventilation system. This is a unit with two fans - one to suck damp stale air from bathrooms and the kitchen, the other to blow fresh air to all the bedrooms and lounge etc.

The clever bit is a heat exchanger in the unit that uses the heat of the stale air to warm the fresh air. This means that although the fans run all the time the energy required to do so is less than the energy it would take to heat cold air coming in through traditional window vents. That's the theory anyway!

Step 1: Hire a professional installer!

Step 2: Cut holes in the roof (thank goodness for rubber tiles)

Step 3: Install roof vents

Step 4: Main inlet and exhaust ducts

Step 5: Install main unit

Step 6: Insulate ducts that run through un-heated areas

Step 7: Buy some more bits! (If only the plan was right!)

Step 8: Duct to downstairs rooms

Step 9: Build false ceilings to carry insulated duct to upstairs rooms

Step 10: Build noggins for duct exits to receive the inlet/outlet valves (post plastering)