As the immediate needs for more environmentally friendly and energy efficient buildings become more and more apparent, a logical question begins to come into focus: Where does it end?
Many in the design and construction community believe the answer is Zero Energy Buildings. Zero Energy is a term used to describe a building that consumes as much energy as it generates in a given year or net zero. Conversely, carbon emissions, which are directly related to the energy consumed, are zero. This is not to be confused with the notion that the building consumes zero energy all together. This would be nearly impossible given all of the HVAC, Lighting, and Life Safety System demands that are needed to operate a building, especially a commercial one. The key is to reduce the amount of energy consumed to the lowest possible amount and then create that amount of energy on-site by renewable means.
Here is a DOE’s database of Zero Energy Buildings in the US Today: http://zeb.buildinggreen.com/
It all starts with the building envelope and conservation:
This encompasses the entire surrounding perimeter of the building including the roof, the walls, fenestration (windows/glass), and the foundation below. The envelope is the first building system which must be optimized to achieve the most efficient building possible. Several new building envelope concepts have emerged, most notably the use of air/vapor barriers and insulation on the outside of the building in lieu of the traditional installation on the interior of the building. Driving this concept is the fact that thermal bridging has been found to drastically reduce the functional R-Value of an exterior wall when substrate and exterior finishes are attached directly to the framing of the building with no layer of thermal protection on the outside. Not only must a building envelope be well insulated but it must also need to be sealed well enough to prevent air leakage. Air leakage is one of the top reasons for energy loss in existing buildings today.
Click here for a link to a great resource, the passive haus institute on more information to maximize envelope efficiency: http://www.passivehouse.us/passiveHouse/PassiveHouseInfo.html
System Optimization & Proper Sizing:
The next step to achieving net zero energy consumption in a building is through the optimization of the mechanical, electrical and plumbing systems that operate the building. Virtually on a monthly basis new mechanical, electrical, lighting and plumbing equipment are released to the market with increased efficiencies. Designers are finding new ways to integrate these systems and make them efficient as possible. Also, these systems need to be engineered to be properly sized and configured based on the envelope and the anticipated demands of the occupants. After occupancy, the use of building management systems, smart controls and variable settings on equipment have all helped to integrate these systems and provide constant feedback on the amount of energy being used at a given time. The proper sizing and smart usage can combine to reduce the energy consumption by nearly 50% by using highly efficient systems and equipment.
For more information and great articles on optimizing energy efficiency in buildings: Check out the M-Files Blog http://blog.mcclureco.com/
Studies and energy models have shown that maximizing both the envelope and the major building systems can reduce the energy consumption of a building by 70% (over the baseline energy usage established by ASHRAE 90.1). Where does the remaining 30% come from?
On-Site Energy Generation:
The final step of achieving net zero energy consumption is through the generation of on-site energy for use by the building or the purchase of renewable energy through a green power provider. The plausibility of generating your own energy or using renewable energy sources has increased recently due to a heightened awareness and a drop in costs (avg solar array runs between $3.50 and $5.00 per watt). Systems that incorporate energy recovered from these various systems are becoming more of a common place for those planning to construct a new building: Solar, Geothermal, Cogeneration, Energy Recovery, Micro turbines, Wind and hydroelectricity. Utilizing this energy locally first, at the building location, is where the remaining 30% reduction occurs.
Whether Net Zero is Feasible or Not, Raising the bar is a Must:
Buildings and optimizing their performance must be a focus for the design and construction communities because they have the single largest impact on the environment today (and the costs of operating our buildings). Our collective commitment to creating buildings that perform optimally from a comfort, consumption and generative stance is imperative. Finding creative ways to reduce energy (as much as fiscally possible) and then operating these buildings in an optimal manner is a must. I am confident that the technologies and the strategies will continue to evolve and netzero will eventually become commonplace.
The Living Futures Institute (Creators of the Living Building Challenge) has now implemented a Net Zero Certification Program, for more information, go here: http://living-future.org/netzero/