Building or Buying Your Sustainable Home
Award-Winning, Affordable Passive House Design
By Rolf Priesnitz
In accordance with post-Katrina building codes, guidelines, and best
practices, the house is raised seven feet above grade, securing its
safety during flooding and providing shaded parking, storage, and
outdoor living spaces.
Illustration © sustainable.TO Architecture + Building |
Many times, ultra-high efficiency and very green buildings – especially
architect-designed one – are dismissed as privileges of the wealthy.
However, the Toronto-based architectural firm sustainable.TO Architecture +
Building has taken the top prize in an international competition to design
an affordable house for post-Katrina New Orleans. The house had to be based
on the Passive House Standard (see this column in
Natural Life Magazine’s
January/February 2010 issue) and on the 2030 Challenge, which is a Santa
Fe-based non-profit initiative that aims to have all new buildings be
carbon-neutral by 2030 (that is, to use no fossil fuel greenhouse gas
emitting energy to operate).
The award-winning “Low Cost, Low Energy House” features an airtight,
thermal bridge-free and super-insulated envelope combined with passive
shading in the summer and solar heat gains in winter; concrete floor topping
for thermal mass to radiate the heat into the space as required; highly
reflective Galvalume® wall and roof cladding; a balanced energy recovery
ventilation system and split-zoned high-efficiency heating and cooling units
with an ultra high-efficiency on-demand water heater and supplemental
radiant floor heating.
In order to fit into its surroundings in the existing neighborhood of the
Lower Ninth Ward, the one-thousand-square- foot house uses traditional New
Orleans “shotgun” styling. This was popular in the Southern United States
from the end of the American Civil War through to the 1920s. Typically, the
rooms of this style of house would be aligned in a row, with no hallways –
one would walk from one end of the house to the other by going through each
of the rooms. Among other things, this would provide for efficient cross
ventilation.
The long axis of the Low Cost, Low Energy House runs east/west. The south
facade’s deep roof overhang provides passive solar protection for the
house’s interior in the summer, while allowing passive solar heat gain in
the winter.
There are two bedroom and bathroom units on either side of the main
living space. The open living plan optimizes natural air flow and
daylighting. A corridor opens southward to a flexible cantilevered side
gallery that wraps around the house, providing shaded outdoor living space.
The flexible boundary between the corridor and gallery can adapt to the
changing needs of the family throughout the seasons.
Sliding panels on the south facade offer protection from the sun,
rain, and wind, and shaded outdoor living space.
Illustration © sustainable.TO Architecture + Building |
Windows are situated on opposite sides of the house for cross ventilation
and natural cooling. High sloped ceilings induce air flow, allowing hot
stale air to escape through operable vents.
Additionally, two UltimateAir RecoupAerator® Energy Recovery Units
exchange stale air with clean fresh air, providing ventilation and air
filtration. Return air pathway grilles and baffles located in the bedroom
closets and washroom doors allow for the movement of air from the bedroom
and living space to washrooms for extraction. Split-zoned Mitsubishi
Electric M-Series ductless heating and cooling units located above the
washrooms are energy-efficient and allow each indoor zone to operate
individually.
Reversible ceiling fans in each room manage rising convective heat in
both summer and winter. Aside from the passive solar heat, a hydronic
heating system embedded in the concrete floor also provides supplemental
low-energy heating. The concrete floor is also beneficial during the summer,
as it is naturally cool.
All exterior walls have a minimum R-47 envelope. Roxul® insulation is
used. It is made from recycled mineral slag, an industrial waste material,
which provides high thermal resistance and is moisture, mold, and
fire-resistant.
All of this adds up to an affordable, very green house that can be built
in a variety of locations, including flood zones. For more information,
visit www.sustainable.to.
Rolf Priesnitz is the founder and Publisher of Natural Life Magazine, and
also has over forty years of experience in the construction industry.
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