Tier One is the basic building design itself, using the form and structure of the building to minimize heat loss in winter and heat gain in summer. This tier is achieved through the architectural design of the building and the appropriate decisions made here can greatly reduce the building’s energy loads and increase thermal comfort.

Tier Two involves harnessing natural energies through the use of passive systems (systems which do not require additional energy to operate).  This tier also has a significant effect on the architectural design of the building with passive systems adding to the character and feel of the building and interior spaces.

Tier Three is the design of the mechanical systems that are used to compensate for the remaining loads on the building. The use of efficient heating, cooling and ventilation systems can further reduce energy use, but it is more advantageous to reduce loads through the first two tiers before relying on mechanical equipment.

Heat retention is simply keeping heat in the building. Heat gains come from many sources including internal and external loads. Internal loads include body heat from occupants, lights and equipment (televisions, computers, appliances, etc.).  Retaining that heat as well as supplemental heat provided by passive and mechanical means ultimately reduces the amount of supplemental energy required to maintain comfort levels.

The main method of retaining heat is the thermal resistance – or insulation – of the building envelope. The higher the thermal resistance the less heat is transferred through walls, roofs and floors by conduction. The building layout is also an important factor here as a building with a smaller ratio of exposed surface area to floor area will lose less heat to the environment. Appropriate building systems and proper construction techniques create a tightly sealed building which prevents heat loss through infiltration, or leaks in the building envelope. A toughly sealed building needs to be equipped with proper ventilation which provides for fresh air without heat loss.

Passive solar heating is a simple system of collecting, storing and redistributing solar energy. Passive systems do not use panels, ducts, pipes, fans or pumps, but rather windows to collect heat, and walls, floors and other building elements to store heat. Since passive systems use basic architectural elements to apply solar principles there is little or no additional cost, little maintenance and it is very reliable. One of the greatest advantages is the wonderful spaces that are created by bringing more sunlight into the building. With passive systems the solar collection system is a livable, usable space. Some of the passive heating strategies commonly employed are direct gain, collecting storage walls, wall convective loops, solar walls and sun spaces.

Mechanical systems typically burn a fuel to produce heat in a central plant, which is then distributed throughout the building. However, active solar systems which use sunlight to heat air or a liquid medium such as water are also considered mechanical systems. Active systems usually consist of solar collectors, a storage system and piping or ducts for redistribution. While pumps or fans, which are used to move the heat through the system, do require energy input there is no burning of fuels and the total energy consumed is much less than the typical mechanical system. A ground source heat pump is a similar system that relies on pumps, but in this case draws existing heat from the earth or a body of water. The ratio of heat gained to fuel consumed is the system efficiency which varies between systems and between different models of similar systems.

Heat avoidance employs some of the same principles as heat retention such as insulation and a tightly sealed building envelope but to keep heat from entering the building. There are also other methods to help keep a building from gaining heat. Properly shading windows so that too much direct sun doesn’t enter the building to cause overheating is one essential strategy that is integral to the architecture of the building. Other issues and strategies include building orientation, vegetation and control of internal heat sources. Proper daylighting, for example, reduces the need for electric lighting and its associated heat gain. The color of roofs, walls and surrounding hardscape is also very important as darker colors absorb more solar radiation which is then transferred to the building as heat.

Effective passive cooling is ultimately climate dependent. Strategies that are effective in hot dry climates may not be effective in hot humid climates. Passive cooling strategies include comfort ventilation, night purge ventilation, radiant cooling, evaporative cooling and earth coupling. All these techniques take advantage of the three natural heat sinks; ambient air, upper atmosphere and earth.

Mechanical cooling is achieved with a piece of equipment that pumps heat out of a building. While mechanical heating has been around for thousands of years, mechanical cooling has only been around for about 150 years. The most common form of refrigeration is the compressive method which relies on the large amount of energy required to change a liquid to a gas and the same amount released when it is changed back to a liquid. Using this principle heat is transferred from the interior of a building to the exterior. Evaporative coolers, heat pumps, and geothermal heat pumps are some of the most common cooling systems.

Daylighting can be used for both functional and dramatic purposes in architecture. Daylight is most effective when it is distributed uniformly throughout the space with no direct sunlight or glare. A good daylighting design always allows the electric lights to be turned off when sufficient natural light is present. Daylighting works with the natural circadian rhythms of the body and has been proven to enhance productivity in classrooms, work spaces and retail applications. Daylighting must be integrated into a project in the very beginning of the design process to optimize the benefits.

Electric Lighting can be supplied in many varieties these days.  The incandescent light bulb has not changed much in the over 130 years since its invention by Thomas Edison.  The efficacy of a light source is the ratio of light output versus energy input and is one of its most important characteristics. Incandescent lights have an output ratio of 7% light and 93% heat for each watt of input energy. Fluorescent fixtures on the other hand have a ratio of 22% light to 78% heat while other types of lighting have even better light to heat ratios.  It is important to choose the most effective type of lighting and lighting controls to meet the architectural requirements and to complement the daylighting system.