Woodfire Passiv, Operation And Installation Manual

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Please also observe the necessary measures for the fire protection of the floor. Further
details can be found in Building Regulations Document J.
Please also refer to “Firepower Hearth Guidance” which can be found on the
www.firepower.co.uk website. This gives recommendations for instances where
we recommend that the size of the hearth is increased over and above the
minimum sizes given in the building regulations, and also contains some
suggestions for how you can make a feature of the hearth.
iii. Combustion air supply
The stove needs sufficient combustion air. This can be drawn from the installation room,
which must have a suitable fresh air supply from the outside.
Document J of the Building Regulations provides guidance, including information on the
minimum area of ventilation that must be provided to the room. Care and consideration
should be give to whether there are any ventilation or extraction systems in the house and
when a draught test or smoke spillage test is done these should be switched on so that
the “worst case“ is tested for. The installer should refer to the HETAS technical notes and
guidance on ventilation.
Relatively little air is required for combustion when the door of the stove is closed. It is
when the door is opened that air rushes up the chimney and there must be a matching
supply of air to the room, otherwise smoke is liable to escape into the room.
When installing a stove into a modern well-sealed house, or one which has been
extensively upgraded with well-sealed windows and doors, it is likely that there will not be
enough fresh air supply to the room when the door of the stove is opened. It is also likely
that the homeowner will not want to install a permanent vent to the room because that
creates a hole in their well-sealed house.
The Passiv stove can be connected to a direct air supply duct and, if the intention is to not
install a permanently open vent to the room, or to install an AirSmart system in its place,
then the installer must follow the procedure in Hetas Technical Note TN_0020 to confirm
that the supply of air will be sufficient.
Please also refer to our “Firepower Direct Air Guidance” document which can be
found on the www.firepower.co.uk website. This gives further consideration as
well as mandatory duct sizing information if a direct air supply duct is being
connected to the stove.
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