Introduction - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 1

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Introduction
Andreas Athienitis, William O'Brien, and Josef Ayoub
1.1 Evolution to Net-Zero Energy Buildings
Buildingshaveevolvedovertimefromlargelypassivesystemsintostructures
with increasingly high levels of environmental control, partly through the
addition of man-made insulation materials, such as fiberglass and
polystyrene. The adoption of electric lighting in early twentieth century
buildings, contributed to a reduction in window areas and reliance on
artificial lighting, particularly in the period from 1950 to 1970. But in the
1980s, the development and acceptance of sealed double-glazed windows
with an insulating airspace, or insulating windows with special coatings to
reduce heat transfer and optimize transmission of solar radiation (Athienitis
and Santamouris, 2002), led to the adoption of larger fenestration areas (up
to 60% of the façade area) in both the residential and commercial buildings.
These large fenestration areas - as much as 90% of the façade area - lead
to high heating and cooling energy consumption. Thus, fenestration and
daylighting significantly influence the design of commercial buildings. The
drivers of the design of residential buildings are shifting from space
conditioning to appliances, lighting, and integrated energy systems, as
building envelopes and HVAC become more efficient and passive techniques
are employed.
Since the early 1990s the potential of solar radiation incident on building
surfaces to satisfy all their energy needs has contributed to the idea of
net-zero energy buildings gaining widespread acceptance as a technically
feasible long-term goal (for most regions). A net-zero energy building (Net
ZEB) is normally defined as one that, in an average year, produces as
much energy (electrical plus thermal) from renewable energy sources as it
consumes . When the energy production is on-site the Net ZEB definition is
most strict.
The visible part of the solar spectrum (nearly half of total solar radiation) is
useful as daylight. Almost all of solar radiation can be converted to useful
heat for space heating, as well as other useful purposes, such as heating
water and drying clothes, or even solar cooling using passive and active solar