Net ZEB Case Studies - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 374

7.2.5 Conclusions and Lessons Learned
This case study examined the design process of a near-net-zero energy
house, presented measured performance results, and suggested how
net-zero energy status could be achieved through some design changes.
Simulations showed that only modest electricity savings are possible
without taking any uneconomical measures. Beyond that, additional active
building-integrated solar energy generation becomes the most practical
upgradetoachievenet-zeroenergy.Afterthedesignupgrades,discretionary
loads account for nearly half of electricity use. In houses for which the
envelope heat transfer and passive solar performance have been optimized,
one of the greatest remaining opportunities is to influence occupant
behavior by means of advanced controls, display of resource consumption,
and education. This represents a significant and necessary area for further
research. For instance, Gram-Hanssen (2010) reported that occupant
behavior can influence heating energy by as much as 350%. Two major
trends are expected to aid the movement toward widespread
implementation of low-energy houses: (1) the improvement of efficiency
and intelligence of appliances and equipment, and (2) the improvement
of active solar energy collectors. This means that even a house that is not
net-zero energy today may become so as old equipment is replaced with
higher-performance equipment over its life cycle.
ÉcoTerra's form and fabric were selected for optimal passive solar
performance. It has a south-facing width-to-depth ratio of 1.38, an overall
window-to-wall-area ratio of 15% (40% for the south façade), which is
equivalent to a solar aperture (south-facing window area-to-total floor area
ratio excluding the garage) of 9.1%. The windows are triple-glazed, low-e
coated, and argon-filled. To supplement heating and cooling in southern
Quebec's heating-dominated climate, a BIPV/T system was built. The upper
south-facing roof section consists of 21 laminate amorphous silicon (a-Si)
modules with an air space underneath, through which air is drawn and
warmed by the absorbed solar radiation. The energy content of this air
is used to warm (or cool during summer nights) a ventilated slab in the
basement, preheat domestic hot water, or dry clothes, depending on the
current demands. A ground-source heat pump with a COP of about 3.7 is
usedtosupplementthepassiveandactivesolarheating.ÉcoTerra'sbuilding
envelope was designed according to passive solar design principles.