requirements by perhaps
75 percent by 2015. A few
The Pathway to
Net Zero Energy Homes
large prototype buildings
incorporating such tech
nology have been constructed
Zero Net Energy
with incremental costs of only
Onsite Energy Supply
5 to 7 percent, which is
generally recovered from
reduced energy bills in fewer
than five years.
Photovoltaics offer the
possibility of net zero energy buildings, when combined with 60 70 percent whole building energy
reductions. This goal may be achievable as a cost competitive housing alternative by 2020 (see Figure 9).
The estimated cost premium for such a system today is approximately 25 percent.
A net zero energy building in 2020 would likely include a careful site plan to optimize the use of
solar energy and take advantage of any sheltering terrain; a super insulated and airtight structure with
high performance building components with low embodied energy but high thermal storage; heat recovery
air exchangers and exhaust systems, coupled with integrated low GHG emitting energy systems that
produce electricity on site while productively using waste heat; highest efficiency appliances and HVAC
equipment; and smart controls that optimize the thermostat and reduce wasted energy.
In the longer term, research in the field of thermoelectric materials, in which heat can be trans
formed directly into electrical energy and that can act as solid state heat pumps, could play a useful role
in an integrated building. Such materials would enable self powered sensors for the control systems and
waste heat recovery for appliances. Given adequate breakthroughs in material science research, they
could also serve as localized heating and cooling systems, reducing the need to heat and cool much
larger volumes of air.
Towards a Climate Friendly