MVHR is commissioned

We finally have a working Mechanica Ventilation with Heat Recovery system working! Graeme Bonds from Titon dropped by this evening and we balanced the system.

The anemometer in place

It reads 8 litres per second- a little more that we need in the WC.

There are two small fans, one supply and one extract that run continuously during the heating system. The incoming cold air passes through the heat exchanger which transfers the heat from the  moist outgoing air to it, returning the heat to the house.

When a house is well insulated, the proportion of heat lost through ventilation goes right up. The illustration below shows that in a low energy house with normal ventilation, the ventilation heat loss is equal to the fabric heat loss (through walls, windows, roof and floor). In a Passivhaus, the ventilation is controlled and heat is recovered. We won't know until we have been through a full heating season, but we know we started out on the far left of this chart, and are aiming for the Passivhaus retrofit standard, which is nearly as good as the new-build Passivhaus.

The humidity is lowered, increasing comfort in the winter. In warmer weather, a thermostat shuts down the supply air and runs the extract only - the windows are open for fresh air!