Orientation:
The house is located on a plot which has
an open aspect to the south, but due to
the Planning constraints this is a short
façade; nevertheless, we have maximised
the window openings to gain the most
solar energy gain in winter. Overhanging
eaves and soffits provide shading in
summer to limit overheating. Along
with this a series of roof windows allow
light and warmth to penetrate reducing
lighting loads and provide heat gains and
natural ventilation control in summer.
Insulation:
The house is exceptionally well insulated
to achieve a minimum U value of
0.1W/m2K. There are no traditional
foundations, with the ground floor
raft floating on 200mm of insulation.
Windows and doors are triple glazed
with a U value of between 0.7 and 1.0 W/
m2K. The insulation on the walls wrap
round in front of each of the window and
door frames preventing cold bridging.
Air tightness:
There are no draughts! The house is
hermetically sealed so a whole house
ventilation system is used – see below.
No draught equals comfort!
Thermal mass and volume:
This house is largely built of concrete
to retain heat in winter and maintain
a stable temperature in summer. The
volume of the 3m high south facing
rooms allows the hot air to rise and
stratify, transferring the summer warmth
to the 200mm concrete first floor
structure. The stair void in the centre of
the house rises 8.6m drawing warm air
through the house and out through the
roof windows in summer.
Heating:
The air to water heat pump (COP of 3)
delivers warm water very efficiently to
the underfloor heating which serves most
of the ground floor rooms. There is no
heating to the upper floor as the house
is kept at a constant temperature with
the upper rooms achieving the design
intent of 2oC lower than the ground floor
rooms.
Ventilation:
As the house is sealed against wasteful
air leakage a heat recovery ventilation
system has been installed, gently
extracting warm moist air out of the wet
rooms and input fresh air into all the
living spaces, through a heat exchanger.
Generation:
Using the south facing PV panels
which generate 3,338kW hours/year,
electricity is fed back to the house to run
appliances, the heating and hot water
production. Excess electricity is sold
back to a green energy supplier, reducin g
the carbon footprint of the house to
11Kg/year. This amounts to 3% of the
carbon produced by an average UK
house of the same size.