Quantifying Sustainability for Success

Quantifying Sustainability for Success
Mike Dieterich | June 2016
 
 
 
Building for today makes us more prepared for tomorrow. Passive design features, like additional insulation, light shelves, shade walls, and innovative heating/cooling design reduce the amount of energy that an HVAC system needs in order to adequately heat or cool a space. Less demanding HVAC systems have lower upfront installation costs and are cheaper to operate. Money saved can then be put towards adding even more energy saving features to a building. A return on investment can be calculated to illustrate the value of an energy efficient system. Passive design strategies are as intelligent as they are cost effective. They reduce upfront costs, operating expenses, and required maintenance.
 
Construction Management is perfectly suited for considering these systems during the inevitable VE exercise. By using professional knowledge, CMs can steer owners toward systems with lower operational costs. A CM may also request that engineers investigate energy conservation measures as a way to decrease HVAC demands and their resulting capital costs.
 
This article features research from the D.C. Public Schools (DCPS) Modernization Program. This is a multiyear study that will be revisited as new technology emerges. Retrofitting and building measurements were used to establish benchmarks. After being commissioned, optimization research was conducted to enhance performance
 
Our project measured light levels at desk height, in nine locations throughout each classroom. Measurements were taken three times during a school day to determine how the light level changes in a classroom. Levels are measured in foot-candles (FC). Acceptable levels are between 35 and 50 FC. Most spaces were over lit or inappropriately lit for their purpose. Changes made to light distribution and fixture type cut back on the number of lights that each building needed by 30-40%.
 
The two acoustic properties we studied were background noise and sound insulation. Background noise is the sound level in a room in which no sound is intentionally made. Sounds from an HVAC system, mechanical equipment and the outdoors contribute to a room's background noise level. Learning becomes difficult when levels breach 45 decibels. Measurements should be taken with and without the HVAC system running to determine the amount of background noise it contributes.
 
Sound insulation is the amount of sound that is transmitted between adjacent spaces. It is measured between a classroom and a hallway, and between two adjacent classrooms. Proper building design results in a reduction of at least 40 dBA between a classroom and a hallway and at least 45 dBA between adjoining classrooms.
 
Water use is measured by counting a building's fixtures and then observing each fixture's flow rate. This metric helped us determine whether high-flow fixtures needed to be replaced by ultra-low flow fixtures. In Washington, D.C., storm water management is key to site success. D.C. requires all water from a 1.2 inch rain event to be reusable. This can be accomplished via green roofs, grey water toilet flushing, and bio swales.
 
To determine waste production, we recorded the amount of waste that each school sent to a landfill, recycled, or composted. Our analysis enabled more appropriately sized waste receptacles to be installed and strategically placed to better accommodate the creation of a zero waste school.
 
Sustainability is the result of effective design guidelines and proper commissioning.
 
The DCPS Modernization Program used energy audits and the Collaborative for High Performance Schools (CHPS) Operational Report Card (ORC) to establish its data points. The ORC evaluates a learning environment's performance by measuring its indoor air quality, energy efficiency, visual quality, acoustics, thermal comfort] water conservation, and waste reduction.
 
"Indoor air quality" measures an interior environment's temperature, relative humidity, and its carbon dioxide (CO2) and carbon monoxide (CO) levels, in parts-per million (ppm). CO and CO, levels are compared to those found in the surrounding outdoor environment.
 
ENERGY STAR® Portfolio Manager® was used to measure and compare each school's energy consumption to a national standard. Our analysis collected energy consumption data at l-5 second, sub-metered intervals, which helped us determine the spikes, base loads, peak loads, and start/finish times for each piece of equipment. By adjusting start times and temperature points, we reduced energy consumption by an additional 20%.
 
Energy audits also use thermography to discover air leakages. This is done by assigning an estimated R-value to a building's envelope. Thermographs of the envelope are then taken and analyzed to determine the relative temperature differences (hot vs. cold) of an envelope's features. Significant temperature differences indicate leakage points. Common leakage points are around window and door frames, hollow wall cavities, attic spaces, and other holes cut into the envelope. After being identified, leakage points are properly insulated and sealed
 
Occupant satisfaction is an overlooked, but equally important metric. To measure satisfaction, a survey, with questions relating to each of the aforementioned category, was issued. lf over 20% of responses to questions about a specific category indicated dissatisfaction, we revisited our approach to that category.
 
Money saved by following our model was put towards the installation of additional, passive energy saving features in each building, which further reduced HVAC demands and their consequent costs.
 
Dunbar High School, which is recognized as The "Greenest School in the World", is a notable case study. It earned the U.S. Green Building Council's (USGBC) highest distinction, LEED Platinum certification.
 

Dunbar scored 91 out of a possible 110 points possible for LEED, making it the highest- scoring newly constructed K-12 school in the world. Dunbar's new campus raises the bar for sustainable building design and environmental stewardship. 
 
Notable enhancements include:

►  482 kW photovoltaic array(provided through Washington, DC's first power purchase agreement) that generates enough energy on a sunny summer day to power all classroom lights for eight hour.

►  Washington, DC's largest ground-source heat pump, or "geothermal" system below Dunbar's athletic field, with wells extending 460 feet deep

►  The reopening of O Street as 6,152 square feet of rain gardens able to handle a 1.2-inch storm event

►  Pervasive natural light resulting from proper orientation and shading of the building.

►  Two 20,000 gallon cisterns and low-flow fixtures help save over 1,400,000 gallons of potable water/year.

►  Enhanced acoustics that help create a high-performance learning environment​

10 months after opening, Dunbar's engineer, architect, facilities manager, head administrator, and owner met to discuss operational procedure, schedule, and HVAC temperature set points. Decisions generated by this meeting reduced Dunbar's energy consumption by 40%in the summer and by 20% in the fall, ultimately saving the school an estimated 550,000 in yearly utility costs. The diagram illustrates Dunbar's HVAC usage before and after the meeting.
 
Quantifying sustainability added value to the DCPS Modernization Program by drastically decreasing the costs of operating a school. The planning process has been redesigned such that passive design features are now discussed at the outset. The short term cost of implementing these features is justified by the long term savings they yield.
 
As technology advances, our metrics will need to be updated. These metrics serve as an important tool for AEC professionals to use in their quest to create a more sustainable, cost effective built environment.
 

 

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