The Green (or Sustainable) Building: Part IV - Water and Energy Efficiency

This, the fourth article in our series on green (sustainable) buildings focuses on the twin subjects of energy efficiency and water efficiency two fundamental areas of importance for green buildings. These are important not only because they reduce usage of and promote reuse of these precious resources, but because in so doing to minimize the building environmental impact. A well designed green building, can not only reduce its own environmental impact, but can improve a surrounding environment.

In case you missed the first articles in “The Green (or Sustainable) Building”, the first article in the series can be found at: The Green (or Sustainable) Building: Part I – What Is the Green Building DNA?.

Design for Energy Efficiency

In the case of new construction, part of the initial architectural design decisions made during the siting and building-orientation phase of a green building project are how to make the most of what the local environment has to offer and minimize the cost the local environment will extract. Design and architecture decisions made at this phase can have very significant and long lasting impacts on the ultimate performance of a green building. Green buildings should be designed to maximize their use of natural light and passive solar gain during colder periods of the year, while preventing unwanted solar gain in the hot summer months. Maximizing the availability of natural light can save a very large amount of electric energy that otherwise would have to be consumed providing artificial lighting. Likewise a good passive solar design can cut down or even largely eliminate heating and the passive heat sink can be cooled by cooler night air in the summer to help reduce cooling needs.

Many improvements to energy efficiency are also applicable to renovation projects that are more constrained by the limits imposed by the existing structure. Adding good insulation to the building’s walls, roof and windows and sealing leaks in a structure are probably the single most important energy saving opportunity there is for retrofitting buildings to improve their green profile. Our country could save vast amounts of energy and reduce our emission of global warming gases if we just improved the insulation of existing structures, sealed leaky cracks and installed multi pane energy saving windows. This is truly the low hanging fruit; an easy energy efficiency harvest that could not only save enormous quantities of energy, but can provide many hundreds of thousands of jobs in to our currently under-employed workers in the building trades.

Lighting

Equipping a building with light wells and/or skylights where appropriate can help bring light into a building’s interior even several stories into the interiors of buildings, replacing electric lighting usage during daylight hours. Of course installing energy efficient lighting systems with advanced lighting controls also greatly reduces energy use over time.

Heating and Cooling Systems

A building can be made more energy efficient by using a properly sized and energy-efficient heat/cooling system in conjunction with a thermally efficient building shell. Additional measures may make sense depending on the climate. Especially for buildings situated in climates that experience extreme seasonal temperature swings geothermal heat pumps also known as earth tubes or earth-sourced systems, use the constant temperature of the earth as the exchange medium instead of the outside air temperature. This allows the system to reach fairly high efficiencies even on the coldest of winter nights. Earth sourced dual loop systems also use the constant cool temperature of the earth to cool the structure down on even the hottest days of the summer.

Another air conditioning option exists for green buildings that can increases their energy efficiency by time shifting their energy usage for air conditioning to periods of off peak demand and away from periods of peak demand. The technology is called Off Peak Air Conditioning or OPAC and it works by using off peak power, which is also usually greener in makeup as much less expensive to cool a heat exchange medium, usually just by making simple water ice and then use this stored cold during the heat of the day, which also coincides with peak load demand periods on the grid to cool the structure.

Green Buildings that Harvest Their Own Energy

When appropriate designing in systems to harvest renewable energy, such as wind or solar, into a green building not only contributes to reducing the structure’s energy footprint but can raise the stature of the project and help make it a symbol of emerging green technologies for the future.

Promote Water Efficiency and Reduce Water Pollution

There are many ways in which a building can use water more efficiently as well as use water more than once as in grey water systems or rooftop water harvesting systems for example. For starters a green building should consider incorporating green roof technology and design into the building either for new structures or in renovation projects in order to reduce storm runoff from the roof and to filter rain water that does runoff through the roofs biological skin.

Alternate pavers for parking lots in place of conventional asphalt or concrete can help a site meet storm water quality goals. Materials such as gravel, cobbles, wood mulch, brick, grass pavers, turf blocks, natural stone, pervious concrete, and porous asphalt absorb rainfall and thus reduce storm water runoff. In addition to using permeable paving materials adding bio-retention areas, such as rain gardens and swales can effectively treat storm water in a parking lot. Bio retention systems channel storm runoff into shallow, landscaped areas where it is temporarily detained and slowly infiltrated into the groundwater.

Incorporate designs for dual plumbing to use recycled water for toilet flushing or a gray water system that recovers rainwater or other non potable water for site irrigation.

Some other water saving techniques are: Minimize wastewater by using ultra low-flush toilets, low-flow shower heads, and other water conserving fixtures; use re-circulating systems for centralized hot water distribution; install point-of-use hot water heating systems for more distant locations.

For landscaping: use a water budget approach that schedules irrigation during periods of lower evaporation; meter the landscape separately from buildings; use micro-irrigation (which excludes sprinklers and high-pressure sprayers) to supply water in non-turf areas; use state-of-the-art irrigation controllers and self-closing nozzles on hoses.