June 2010 - NHBC Home

Sustainability
Extra
The Code Level 6 aircrete panel house under construction
Heating systems
Selected to meet the energy/CO 2
targets of the different
Levels of the Code, a variety of systems have been
installed at Miller Zero:
• The 10% reduction in CO 2
emissions required at
Code Level 1 was achieved with a conventional gas
condensing boiler and radiators.
• For Level 3 (25% CO 2
reduction), an air source heat
pump used in conjunction with radiators was selected.
• For Level 4 (44% CO 2
reduction), a ground source
heat pump connected to an underfloor heating
system was used.
• For the Level 5 (100% CO 2
reduction) and Level 6
(zero carbon) homes, the solution chosen was a
biomass boiler. Fuelled by wood pellets, a single boiler
shared between the two homes is located in
an adjacent garage.
Ventilation
All of the homes have been built with high standards
of air permeability in mind and, in order to ensure that
this does not give rise to poor indoor air quality or high
humidity levels (and associated risks of condensation
and mould growth), mechanical ventilation systems have
been specified for all five homes.
The equipment is located in the first floor airing cupboard
to reduce duct lengths and incorporates heat recovery
to minimise the amount of heat lost from the outgoing
exhaust ventilation air. The units also feature a summer
by-pass option for the warmer months of the year.
Renewables
The planning application included a small-scale wind
turbine, located in a communal area. However, whilst the
local authority was supportive of the development in
general, approval for the turbine was not granted.
Other than the biomass boiler serving the Level 5 and
6 homes, the only other renewable technology installed
was photovoltaic panels. The monopitch roof of the Level
5 home accommodates panels with an area of 14m 2 ,
whilst the Level 6 home has 38m 2 of panels – well over
twice the size. The peak output from the PV installations
is 1.7kW and 4.8kW respectively.
Non-energy/CO 2
Code challenges
A variety of other features have been specified to satisfy
the other elements of the Code. These include water
efficient fittings and appliances, rainwater harvesting,
many storey-height windows to maximise daylighting
levels as well as providing space for recycling, etc. Great
attention has been paid to detailed design, specification
and construction on site to pick up required number of
points in all categories.
Lessons learned
This project has already given Miller Homes an
invaluable insight into the challenges of designing and
building homes to meet the increasing demands of the
Code and future changes to thermal requirements of
building regulations. The exercise also demonstrated
the significant additional costs involved, amounting to
incremental increase as higher levels of the code are
achieved up to £50,000 for the Code Level 6 unit.
Subject to permission being given by the owners, built-in
sensors will be used to monitor the performance of the
homes in use for a 12-month period, during which, the
reaction of the occupants to the variety of technologies
installed will also be recorded. The owners will also be
able to closely monitor their own current consumption
of energy using ‘smart meters’ that have been provided.
The biomass boiler for the
Code Levels 5 and 6 houses
The air source heat pump of the Code Level 3 house
A mechanical ventilation with heat
recovery unit above the hot water cylinder
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