Basic Sustainable Design
Principles
Energy
Efficiency
Material Efficiency
Water Efficiency
Regional Design
Energy Efficiency
An
energy-efficient house minimizes energy costs, increases
occupant comfort, provides a healthier living environment, and reduces
negative impact on the environment. Creating
an energy-efficient home requires planning, foresight, and follow-through.
The end result can be comfort and energy savings for years to come.
The
way a building uses energy can best be understood as the interaction of
several related energy systems that continually respond to changing
climatic conditions and the comfort requirements of the occupant.
These basic energy systems are explained in the design patterns
identified on this site. The
patterns that directly impact the energy efficiency of a building are:
Site
Site selection can
be have a significant impact on the design on the houses.
Although land for affordable projects is usually selected based on
price, the site can preclude several sustainable features. Making the most
out of what the site has to offer can be the difference between an energy
performer or an energy guzzler.
Orientation
 Orientation
of the buildings will allow for passive solar gain and day lighting.
Windows facing east and south allow for early warming of rooms
during the winter. While
south-facing windows will aid afternoon warming, they may not be as
desirable in some climates. West-facing
windows need to be carefully designed so they do not add to overheating
the house due to the low angle of the setting sun.
Foundation,
Walls, and Roof
 The
envelope of the building has a great impact on how much energy is required
to heat and cool the building. The
challenge in designing the foundation,
walls, and roof is to minimize conductive heat
loss or heat gain, depending on the outside air temperature, while
minimizing the uncontrolled movement of air into the building.
The comfort of the building during the
heating season will depend in large part on interior surface temperatures
of the floors, walls, and roof as well as the amount of cold outside air
entering through leaks in the envelope.
Heating,
Ventilation, and Air Conditioning
Once
the building envelope has been addressed we can turn our attention to the
heating, ventilation, and air conditioning (HVAC) system.
These systems use more energy, cost more to operate, and are more
complex than other energy systems in the house.
Reducing
the heat load of the house allows for the installation of a smaller
heating and cooling system. But
they need to be properly sized; a system that is not properly sized can
increase the cost of the heating system as well as the cost to operate it.
 The
type of energy source selected to heat and cool a building is very
important. There are three
options: electricity, combustion (wood, natural gas, propane), and solar. If electricity is chosen, then the exterior envelope of the
building needs to be ultra-efficient.
When combustion energy sources are selected, special attention
needs to be addressed in the areas of backdrafting, or spillage and
leakage of combustion fuels. Solar
tempering and passive solar heating should be considered an integral part
of integrating house and heating system design.
The
mechanical ventilation system is the element of residential design that is
most often overlooked or ignored all together. The options for ventilating
energy-efficient houses are discussed in the Pattern
13. Those options
include fans installed in the bathrooms and kitchens, and
“heat recovery ventilation” (HRV).
Lighting and
Appliances
 U.S.
Department of Energy research found that lighting and appliances consume
14 percent of the energy used in a residence.
Occupants want houses that are bright and inviting.
Energy-efficient houses use natural daylight in areas of high
occupant use such as living rooms, family rooms, and kitchens.
The
type of appliances installed in a home can have a large impact on energy
use, as can entertainment systems, stereos, and computers.
Appliances that carry the Energy star label are tested and marketed
for the energy-efficient operation. The
Energy star appliances might cost more initially, but their energy savings
and long service life make them a smart choice.
Landscaping
 Landscaping is an
integral part in helping an energy-efficient house to perform better in
the winter and stay cooler in the summer.
Using the lay of the land to shelter the building to keep harsh
winter winds away and allow summer breezes should be considered.
Carefully selecting and strategically planting deciduous trees can
provide maximum winter solar gain, as well as effective summer shade.
Building Operation
One
of the most important elements in an energy-efficient building’s
performance is the manner in which it is operated by the occupants. Energy-efficient buildings are not a new concept, but the
materials and equipment used are and occupants need to be educated on how
to make them perform. Just
like a new car owner must learn about all the features in their
automobile, a new building owner needs to know about all the features in
their new home and how they operate and inter-relate.
Before
studying the design patterns included this site, you may wish to review a
few energy basics. Heat energy is lost from a building in three ways.
They are conduction, convection, and radiation.
Conduction
describes
the process where heat
energy is transferred directly from the warm side of a
material to the cooler side of the material.
The greater the temperature difference the greater will be the
movement of heat. Materials
that do not conduct heat readily are good insulators.
The better the insulation properties of a material, the higher will
be its insulating value or “R-value.”
The term for heat moving through framing members is called
“thermal bridging.” Thermal
bridges are places where there is little or no insulation in the building
envelope. These areas include solid headers over windows and doors,
beams in exteriors walls, and solid blocking for corners and partition
walls.
Convection
is the movement of air caused by the properties of warm air to rise and
cool air to fall. Convection
leads to stratification of air in tall spaces as the warm air collects at
the top of the space. Convection
is a factor in the heat loss from within various building components that
include air spaces such as glass or attics.
Infiltration
is a term used
to describe the movement of air in and out of a building.
Infiltration is one of the most significant ways heat and cooling
energy is wasted in houses.
All
warm objects radiate heat energy to cooler objects. An example would be a person standing in front of a wood stove.
The stove’s hot surfaces radiate heat to the person. The process
of radiant heating can cause
discomfort if there temperature of the surrounding surfaces is too
different. This occurs in sub-freeing temperatures next to a large window
or sitting too close to a hot wood stove.
Getting the Best Bang
for the Buck
It
is important to take a balanced approach to addressing energy efficiency.
Too much attention to a single energy system or component can lead
to lost opportunities. There
is a point of diminishing returns when investing in energy improvements.
For example, increasing exterior wall R-values beyond a reasonable point
would be unwise if there are more cost-effective energy-efficiency options
for windows or ventilation system.
Energy-use analysis software can be a very useful tool in making
balanced and cost effective design decisions.
Looking
and investigating all of the options available during the design phase
will pay off in the long run.
Next
Section: Basic Sustainable
Design Principles: Material Efficiency
|
