One in four students in Hawaii currently study in poor-quality portable classrooms. The state plans to replace 10,000 of these units over the next ten years. This factory-built energy-positive portable classroom provides a high-performance, healthy educational environment while minimizing energy use through careful day lighting and natural ventilation, employing photovoltaic panels to generate substantially more power than consumed. The classroom also serves as an educational tool with natural forces and systems highlighted and building performance monitored and broadcast to students inside as well as to the web. The life-cycle cost is projected lower than previous generation energy-consuming portables.
This modular, offsite-fabricated, re-locatable classroom prototype was commissioned by the Hawaii Department of Education as a new model to replace the state’s current inventory of aging, poor-quality and energy-inefficient portables. The project was competitively awarded to a design-build team based on highly detailed performance analysis modeling and 30-year life cycle cost analyses. The building systems include extensive environmental monitoring systems broadcast to the web. A state-funded scientific team is evaluating the building performance through a two-year study. Based on scientific results and post-occupancy evaluation, the building will be revised as required for future units to be placed in numerous highly varied climate ecosystems throughout the state. The easily re-locatable building system is designed with flexibility and options for classroom comfort and energy efficiency in a wide range of climate conditions. Re-locatable classrooms are a major presence in Hawaii education planning.
The portable classroom is designed to provide an optimized educational environment for students and teachers while advancing sustainable design principles in construction and in classroom learning. The classroom is designed to conserve as well as collect and generates natural resources including electrical energy, daylight, wind energy, and rainwater. As well as being strong, efficient, and conserving, natural forces and resources are highlighted and exposed throughout the structure and all systems and performance criteria are monitored and broadcast to the web. The building acts as a learning tool for occupants, other schools, and the general public. The combination of maximized photovoltaic surface matched with low energy consumption creates a positive net energy production that is four times the building’s annual consumption.
The Energy Positive Portable Classroom optimizes photovoltaic roof surface orientation, naturally shaded north-facing daylight glazing, and modulated natural ventilation. All of these forces are balanced with the additional criteria of manufacturing and transport efficiency, functionality for classroom use, low operating costs, and ease of maintenance. The manufacturing and delivery process and the materials and products employed are all selected for minimum environmental impact and for maximum contribution to a healthy indoor environment. Wherever possible, materials are chosen to conserve resources, minimize initial and lifecycle maintenance costs, and to promote educational awareness of the natural environment and its relationship to comfortable and healthy living. The design focuses on performance issues directly impacting the learning experience of its occupants and the environmental quality of its community — thermal comfort, natural day lighting, indoor air quality, energy and resource conservation and generation.
The design provides excellent interior thermal, lighting, and acoustic performance based on current research in optimized learning environments. The classroom is designed to minimize heat gain and to use available natural daylight and natural ventilation rather than air-conditioning. Electrical systems are designed for contemporary and future digital teaching expectations, and for performance monitoring of energy consumption and interior environment charted against exterior weather conditions. Monitoring is web-broadcast and formatted as a child-accessible interface allowing students to interactively learn about their immediate environment and contextual sustainability issues. This web-broadcast data is integrated with curricula for various age groups and is publically accessible. As a comprehensive teaching tool, the building design exposes and highlights structural and performance components so that digital data is understood in reference to physical attributes of the construction. Materials, systems, and surfaces are designed for healthy air quality and global sustainability. Construction is accomplished in an energy- and resource-efficient factory, with a modular design facilitating future reuse on alternate sites, enhancing maximized sustainability throughout the life cycle.
The building is prefabricated in three easily transportable modules, reducing initial cost and energy and facilitating efficient relocation and reuse in the future, minimizing waste. A steel frame and steel and rigid foam, sandwich panel floor and roof system minimize material use; maximize insulation and heat reflection; and deter pests and mold in the cavity-free structure. A simple, double wall metal cladding, along with metal roofing shaded by solar panels above a three-inch ventilated airspace, creates a ventilated double skin greatly reducing heat gain. All glazing is operable and north facing and/or shaded to prevent direct sunlight and to optimize natural ventilation and comfortable airflow. Interior surfaces are low VOC products. Exposed beams are FSC-certified glue-laminated timbers combined with steel trusses to visibly trace primary structural forces. Interior surfaces are naturally finished, low VOC materials to provide good interior air quality. Day lighting analysis indicates that excellent work light levels are achieved throughout the typical school day in most locations without electric lighting. Thermal comfort analysis indicates the classroom will be comfortable in most high-heat climates without air conditioning, although an efficient mechanical air conditioning system is also available as an option for school sites where air quality or noise conditions preclude natural ventilation.
The angle and spacing of the clerestories is optimized for maximum solar exposure of the PV panels while facilitating indirect day lighting and natural ventilation. To optimize daylight levels, the windows are shaded from direct sun with exterior aluminum sunshades. Acoustical dampening is essential to interior experience and children’s ability to learn and distinguish spoken language is especially affected by background sound levels and surface echo. Floor, wall, and ceiling systems and all mechanical and electrical equipment are designed to limit sound generation and dampen sound reverberation. Surfaces, materials, views, light quality, and colors throughout the space are selected not only for health, sustainability, functionality, and hygienic ease of maintenance, but also to provide vibrancy, fun, and creative inspiration. Energy efficiency and energy production have been major focuses of design and construction for this building, which is designed to revolutionize the energy efficiency of typically energy-hogging portable classrooms.
Factory-built modular buildings can be not only equal or be superior to traditional buildings in quality, but the controlled manufacturing process greatly minimizes energy and material waste typical to site construction. Modularity of the construction system allows relocation and future reuse of the building without typical demolition and disposal waste of materials and embedded energy. High-quality windows, shading devices, and directed wind scoops, vented skins, and high-performance insulation and sealants reduce heat gain, which reduces energy waste, pollution, and release of greenhouse gasses. A high-quality white rubber roof and solar-shaded, low emissivity glazing and reflective metal ventilated skins reflect solar heat gain away from the building to keep it comfortable in hot weather and reduce heat-island warming of adjacent buildings and outdoor spaces. Occupancy sensors “learn” patterns of activity and optimize settings to conserve energy and maintain comfortable levels appropriate to daily cycles of use. Coordinated sensors and electronic control of the lighting system turn off lights when there is no activity in the room. The PV array on the roof surfaces shades the roof surface with a ventilation space below and generates four times the energy demand expected in the classroom, even while using substantial digital teaching technology and building performance monitoring systems.
The building was fully developed in BIM software and then modeled and analyzed in graphic and quantitative environmental analysis software. High performance goals in relation to ASHRAE 90.1-2004 were established and monitored by LEED AP personnel within the architecture and construction team and by building science consultants.
The team worked closely with university and industry-based building science-consulting teams in the design and performance analysis and monitoring. Modular, re-locatable buildings of this size are not yet included in sustainability certification programs such as LEED and Coalition for High Performance Schools, but the CHP standards and minimum equivalents to LEED Platinum standards and evaluation practices were applied as baseline project specifications.