TOM'S ARCHITECTURAL BLOG: ARE WE BEING HOODWINKED AGAIN?
Induction unit with decorative cover panel.
In June 1999, then-President Bill Clinton signed an Executive Order directing the “greening of the government” through efficient energy management. In May 2001, then-President George W. Bush signed an Executive Order directing all agencies of the federal government to reduce energy use during peak energy-use hours by 10 percent. Falling in step, in October 2009, President Obama signed an Executive Order – the FEDERAL LEADERSHIP IN ENVIRONMENTAL, ENERGY, AND ECONOMIC PERFORMANCE – directing federal agencies to “increase energy efficiency; measure, report, and reduce their greenhouse gas emissions; conserve and protect water resources; eliminate waste, recycle, and prevent pollution; leverage agency acquisitions to foster markets for sustainable technologies and environmentally preferable materials, products, and services; design, construct, maintain, and operate high performance sustainable buildings in sustainable locations; strengthen the vitality and livability of the communities in which Federal facilities are located; and inform Federal employees about and involve them in the achievement of these goals.”
Induction unit with cover panel removed.
There have been more Executive Orders that are just too numerous to summarize here. But have you wondered how all of the agencies of the federal government have attempted to comply with all of these presidential mandates to reduce energy usage in government buildings and become more “green”?
REDUCED THERMOSTAT SETTINGS
Being a civil servant in the design and construction branch of a government agency, I have seen the rollout of this implementation firsthand. Just last week in a staff meeting, it was announced that that the temperature set points for the thermostats in all buildings at the center where I work will be reduced to 68 degrees F (low) and 78 degrees F (high), a reduction of two degrees for each set point. How this will save on energy use when employees are currently using individual space heaters in the winter is yet to be seen. But what I want to write about is an emerging “green” technology called “chilled beam” which will be installed in a new building scheduled to begin construction this fall on the campus where I work.
DEFINITION OF INDUCTIVE AND CONDUCTIVE TECHNOLOGY
Induction unit with cover panel removed. Note the round connection for the supply air, and the coils for “re-heating” or “re-cooling” of the supply air.
A long time ago, I worked with a mechanical engineer that described air as “being stupid.” What she meant by that statement is that air has inherent properties that allow us to predict its performance based on its temperature and moisture content (humidity level). For many years, when designing HVAC systems for large commercial/institutional buildings, mechanical engineers have used systems that can be categorized as either inductive or conductive, or in other words active or passive. For systems that use induction units, conditioned air is supplied by mechanical means using supplemental fans and motors. The fans blow air under pressure through small ducts that are concealed in the walls to the induction units. Because the air is often traveling a considerable distance through the building, the induction units may be equipped with another small fan that blows the air over another small coil of tubes to either “re-heat” or “re-cool” the air at the point of delivery in the room.
With conductive units, air temperature is conditioned by coming into contact with a conditioned element, either left exposed in the room or concealed in a more decorative cabinet, causing the air molecules to naturally circulate using the old adage “warm air rises, cool air sinks.” Radiators are the simplest example of this type of delivery method.
Radiator. Example of a conduction unit.
The majority of the buildings on the campus where I work were constructed in the 1960s using induction units that can be found in each space located immediately below a window. Each building is equipped with huge mechanical units that circulate either chilled or heated water (depending on the season) supplied by a central plant and circulated through a vast network of underground pipes. This system is efficient because:
- There is no overhead ductwork so the height of the plenum space is reduced. This equates to a shallower floor-to-floor dimension resulting in reduced construction cost.
- Because the building can be shorter, there is a reduction in the amount of materials consumed to construct the building. This, again, results in a reduction in the overall construction cost. And…
- Fans and motors used in the delivery method are smaller thereby reducing the amount of energy consumed over the lifespan of the building.