The Green Thumb: Dial ‘S' for Sustainability - Part Two
Last time we began this discussion of the full meaning behind the term “Sustainable.” We saw that there is indeed a significant difference between terms such as “Green” and/or “Environmentally Preferable/Responsible” and “Sustainable.” This time, we’ll continue with a look at two key issues concerning sustainability: Energy Consumption and Indoor Air Quality
Energy ConsumptionIn the world of sustainable design, there are two types of energies to consider, Embodied Energy (EE) and Operational Energy (OE). Embodied Energy represents all the energy required to manufacture finish materials, extract raw materials, human labor, transportation and energy consumed to produce a finished building. In present day terms, it represents about 10 percent of the total energy consumed over the entire life cycle of a typical commercial building in the United States.
By far, the lion’s share of energy consumed by a building (90 percent), is represented by OE and is the key to reducing energy use in buildings. Maintaining comfort levels through HVAC equipment and running appliances are typical OE consumers. Obviously, there is a significant imbalance between EE and OE but, through good building design, one can affect the other.
The cost to construct a commercial building represents about 10 percent of the cost over the entire life-cycle of the building (construction through demolition), whereas the cost to operate and maintain (O&M) a commercial building represents about 90 percent. This is one of the reasons why sustainability is widely considered a very conservative approach to building. If the building uses half the energy required of a similar building, the building will not only save the owner money in the long run, it will actually produce income for the owner via paybacks such as selling excess electrical generation back to a utility.
Lighting represents the largest share of energy used in commercial buildings. To reduce lighting OE, designers can do several things, including specifying low-EE materials and utilizing natural lighting.
After lighting, computers and appliances are the largest energy consumers in commercial buildings. HVAC equipment such as fans, vents etc. come in third. In the northeastern U.S., cooling rather than heating represents about 80 percent of the total energy used to maintain suitable climate levels within interior spaces.
Thus, anything that minimizes heat gain within the building envelope also serves to reduce the energy required to cool it. Likewise, the tighter and better insulated the building envelope, the less energy will be required to keep it warm in winter. Very often, perimeter-heating elements can be reduced and/or eliminated entirely in very well insulated, tight building envelopes.
CUTTING ENERGY COSTSTankless water heaters, additional insulation in attic spaces, double/triple glazed windows and water saving devices such as low-flow shower heads all combine to save OE in residential buildings. About 40 percent of OE is used for heating and cooling in residential buildings. By thoughtful design and material selection, up to 60 percent of residential OE can be reduced. Lighting is also a critical component of the OE equation for residential buildings. Lighting with design elements such as adjustable louvers, clerestory windows and skylights that bring in natural light save OE and create a more inviting, healthy environment.
However, building design should avoid introducing direct sunlight into an interior space. Direct sunlight contributes greatly to solar heat gain and glare. On the other hand, indirect sunlight not only significantly reduces lighting OE but also improves people’s moods.
An AIA initiative for the year 2010 proposes a reduction by half of current energy consumption to construct and operate buildings. The goal of the 2030 Challenge is no less than zero-emission/carbon-neutral new buildings by the year 2030. Chicago Mayor Richard Daley Jr., along with the U.S. Conference of Mayors has heartily endorsed these initiatives. The Canadian-based GreenGlobe system (also used in the U.S.) focuses both on OE and EE. However, the USGBC’s (U.S. Green Building Council) LEED (Leadership in Energy & Environmental Design) green building rating/certification program focuses credits/points on OE rather than EE since OE is easier to document.
INDOOR ENVIRONMENTAL QUALITYIndoor Environmental Quality refers to all the factors that affect the health and well being of building occupants, including acoustics/noise-control, lighting quality, air exchange, humidity levels, comfort levels and Indoor Air Quality (IAQ).
According to the EPA, Americans spend about 90 percent of their time indoors, where pollution levels can be up to 10 times greater than outdoors, at concentrations up to 100 times greater. IAQ that is polluted with high levels of VOCs (such as formaldehyde) can cause serious health concerns. This is why many building products are low/zero VOC.
There are three main contributors to IAQ problems: Indoor pollutants, inadequate ventilation and high humidity levels. Mold spores require a 28 percent moisture content to begin growing on both organic and inorganic building material surfaces, but require only 20 percent moisture content to maintain growth.
Healthy building proponents endorse a three-tiered approach to minimizing indoor pollution: Eliminate, Separate and Ventilate. In other words, first try to eliminate those materials that will release VOCs such as formaldehyde. Next, if you can’t eliminate the IAQ offender, try to isolate it from the living space (i.e. in wall cavities). Last, provide proper ventilation which does not solely rely on natural ventilation-Mother Nature is not all that reliable in this regard. Therefore, provide mechanical ventilation via HRV (Heat Recovery Ventilator) technologies.
As we have seen, IEQ is critical in creating a built environment that fosters good health and the overall welfare of building occupants. As for energy consumption, when you consider the fact that, over the entire life cycle of a commercial building, the cost to initially construct it represents only about 10 percent, whereas the cost to operate and maintain it represents 90 percent, it’s making more and more sense to design and build with sustainability in mind.