Daylight Harvesting

What is it?

One of the more common automation systems that is often used in schools is daylight harvesting. This approach to reducing electric light when daylight is available also has the benefit of reducing energy. Typical daylight harvesting systems use photosensors to detect the amount of daylight coming in through windows or on surfaces and adjust artificial lighting accordingly. While manual lighting and shading systems exist, automated systems ensure that the light levels meet minimum illuminance levels throughout the day coupled with occupancy sensors, only providing light when it is needed. Daylight systems can be integrated into automatic shading and building automation systems for enhanced control. 

How big an investment are Daylight Management Systems?

The control systems cost on average $0.55-0.75 per square foot of building area. This cost includes dimmable ballasts, fixtures, and controls. Additional costs will be incurred to include shading devices and integrate with building automation systems.

What are the sustainable benefits?

School districts spend between 20-25% of their energy costs on lighting1. Optimal daylight is typically between noon and 4pm which is the same time when other building systems are being maximized. By utilizing daylight harvesting systems, schools can decrease total energy costs by up to one-third, including reductions in demand charges as well as cooling loads in addition to the lighting reductions2. Further savings can be achieved by coupling daylight harvesting with building automation systems for integrated control with HVAC systems.

Several studies have demonstrated the benefits to student performance through natural daylight. The Heschong Mahone group found that students working in the most natural light had increases of 20% in math and 26% in reading assessments, compared to students working in limited daylight. In addition, learning rates were 21% better in classrooms with the most daylight compared to those with none3. 

Daylighting strategies that are enhanced by shading and other building features such as light shelves that can also help to reduce glare. Direct sun penetration into classrooms, especially through unshaded east or south facing windows, is associated with negative student performance, likely causing both glare and thermal discomfort4. Sources of glare have been shown to negatively impact student learning, especially math, where instruction often takes places on the front teaching wall. By adding blinds or curtains, teachers also have more control of distractions which can impact student performance3.

1 XcelEnergy - Guide to Energy Conservation and Savings for K12 Schools

2 Ander, G. (2011, August). Daylighting. Whole Building Design Guide

3 Heschong Mahone Group - Windows and Offices: a Study of Office Worker Perofmance and the Indoor Environment

4 2017. Schools for Health: Foundations for Student Success. Harvard T.H. Chan School of Public Health.

Commissioning

What is it?

One of the fundamental ways to ensure that a building is operating as designed is a process called commissioning. Commissioning in its most simple form is ensuring that the building systems, including mechanical, electrical, and envelope, are properly installed and tested to achieve optimal performance per the specifications and owner’s requirements1. Ideally the commissioning process should begin in early design to develop the scope, budget, plans, and schedule. Existing buildings can also benefit from this process, called retro-commissioning, utilizing an assessment of utility bills and operational procedures, and diagnostic testing. The most comprehensive approach includes both training for building operators so that they can continue to maintain optimized performance as well as documentation of the process.

How Big an Investment is Commissioning?

The cost to hire a commissioning agent depends on the size and scope of the project. Hiring a commissioning agent early on in design ensures that the most value is achieved from the process. According to the General Services Administration, total building commissioning costs range from 0.5% to 2.25% of total construction costs, depending on the size, type, and complexity of the project.  Projects can see costs closer to 3% if full commissioning, including the envelope, is performed. According to the Lawrence Berkeley National Laboratory, the normalized median cost was $1.16 per square foot for new buildings and $0.30 per square foot for existing buildings.

What are the sustainable benefits?

The commissioning process has a number of benefits beyond meeting the owner’s requirements for design of a project. Buildings that are commissioned have lower costs and during construction and fewer change orders. Throughout the life of the building, their equipment functionality is improved, extending the life of equipment. Commissioning saves on average 13% in energy costs with paybacks in approximately 4 years for new construction and 16% for existing buildings with payback in 1 year2.

There are also co-benefits including increased valuation in the building as well as results stemming from increased training by building operators. This results in increased comfort of the occupants, indoor air quality, water efficiency, and safety and security. 

1 2016. The Whole Building Design Guide. “Building Commissioning.”[1] https://www.wbdg.org/building-commissioning

2 Evan Mills, Building Commissioning: A Golden Opportunity for Reducing Energy Costs and Greenhouse Gas Emissions, July 21, 2009, Lawrence Berkeley National Laboratory, http://cx.lbl.gov/documents/2009-assessment/LBNL-Cx-Cost-Benefit.pdf

Performance Based Modeling

According to the EIA, buildings consume nearly 50% of the energy generated in the U.S. and produce 44% of the carbon emissions[1]. Certifications and codes help to drive reductions in the built environment, but as we look to meeting the energy needs of the future, designers can take a leadership role in doing our part for the industry.

Reducing energy use in our buildings can be done in a number of ways, but taking a critical look at the beginning of design allows for maximized impacts. Previously energy modeling was a skill that was reserved for engineers, and often involved complex details and a substantial amount of time. As an alternative, performance based models, where conservation targets are considered as soon as pen hits paper, is gaining popularity.

Building orientation and massing provide important opportunities for reducing energy in early design decisions. While designers often use rules of thumb, modeling allows you to see the direct impacts of adding shading devices or increasing the amount of glazing on a façade. It also becomes a component of the integrative design process, ensuring synergies between building systems are optimized.

Traditional energy modeling requires building improvements in later stages that then compete for priority. Early modeling of energy allows for flexibility and innovation by analyzing the impacts of various design scenarios and learning from each one. Taking it a step further, the process can be enhanced when coupled with benchmarking or Measurement and Verification once a building is completed, allowing the owner to ensure that the building is performing as designed. The analyses can also assist in maximizing daylighting by identifying over and under-lit spaces and priorities the type of shading and glazing needs for each façade. According to recent studies by Harvard School of Public Health, daylight has significant impact in the thinking and performance of students. There is a significant correlation between daylight in classrooms and student performance, particularly in material ready assessments as well as increased alertness and physical activity.

The continuous improvement process allows both the designer and the building to raise the bar of performance and track it over time. The result is schools that save on operation and maintenance costs. According to a survey from Turner Construction, sustainable schools can achieve direct savings of $12 sq. ft. going directly back into the school in the way of energy savings, lowered water costs, improved teacher retention and lowered health costs all for an increased cost of less than 2% more than conventional schools (approximately $3 per square foot) to make them green[2]. 

[1] U.S. Energy Information Administration (2012).

[2] “2005 Survey of Green Buildings,” Turner Construction. Available at: http:// www.turnerconstruction.com/greenbuildings