What should I do about a fire place?

In the current regulations guidance document Part L it is recommended that any fuel burning appliance should have an efficiency in excess of 86%. An open fire is estimated to be c20% efficient. An open fire will reduce the efficiency of a HRV installation by up to 10%. When the fire is burning air is being taken from the room and by convection goes up the chimney. This causes negative pressure in the house. As a result, cold air will be sucked in as soon as a door is opened. 

The availability of suitable fuel for an open fire in the future is also an issue. If it is proposed to burn timber we suggest using a wood burning stove. These can be sourced with a pre-designed combustion air inlet. This combustion air must come from the outside, via a duct that has a minimum diameter of 100mm, is suitably insulated and controlled by a damper. This duct can travel under the floor, directly through a wall (if the fireplace is on an outside wall) or is now available down through a specially built balance flue chimney. 

What effect will a free standing stove have on the HRV system?

If it has an independent external air supply as described above the effect will be nil. 

How should a gas fire be connected up?

Gas fires should be of the enclosed type (they look much like a flat screen TV). These can be fitted with a balanced flue down through the chimney.

Section J of the Building Regs state that any fuel burning appliance must have a permanent  external air supply available to it. By this, they mean a hole in the wall or a balanced flue as described above.

Flame effect fires are not usually suitable for a balanced flue.