Stunning precast concrete solar home incorporates latest technologies to provide superior energy savings and storm-proof strength.
By Ron Hyink
Throw off the yoke of conventional home design and start thinking forward. Wipe the slate clean and begin again with a completely sustainable design using currently available technology – and then build it!
A small group of architectural students did just that as they prepared for the U.S. Department of Energy’s challenge to build energy-efficient homes for its biennial Solar Decathlon.
A house to eNJoy
The “eNJoy house” – note the subtle New Jersey tag – is the concept of Team New Jersey, a collaboration of architectural students from the New Jersey Institute of Technology and Rutgers, The State University of New Jersey. The team not only designed an energy-efficient home made entirely of precast concrete panels – a first for the Solar Decathlon – but these students also helped manufacture and install the insulated walls.
“It’s a beach home for a retiring couple,” said Jennifer Switala, the student team leader for the project and recent graduate from the NJIT’s architectural master’s degree program. Presumably one of the inhabitants would be handicapped, and so there are entry ramps in the front and rear and no stairs, she said, adding that the home is completely compliant with the Americans with Disabilities Act. Even the kitchen countertop and sink, bathroom sink and shower are made of precast concrete, each of which will accommodate a wheelchair.
With the New Jersey beach in mind, the design takes into consideration a broad range of factors. First of all, the students wanted to work with a sustainable, energy-efficient building material that is relatively low in both cost and long-term maintenance. The easy answer for that was precast concrete, which naturally offers the utmost in thermal efficiency and lasts a long time without repairs or replacement (see the sidebar “Beautiful Design Plus All the Benefits of a Precast Concrete Home”).
“In general, people are nervous about concrete homes; they don’t think living in a concrete home can be comfortable,” said Switala. “So that’s what we wanted to try with this house – that it is comfortable and is much more cost-effective, more stable and, in the end, it works!”
While precast concrete’s thermal mass dampens exterior temperature fluctuations on the interior, the students incorporated roof overhangs into the design at just the right angles and lengths that allow – as well as restrict – how much sunlight reaches the exterior surfaces. In summer, when the sun rides higher in the sky than in winter, the roof’s overhang shades the southern exterior until evening. Operable windows can be opened to allow the coastal breezes to work with the integral cross-ventilation design and circulate air throughout the house. Impressively, on a hot, humid summer day, the home interior remains cool, and a slight air movement can be felt even if there is no breeze outside.
In winter, sunlight penetrates south-facing windows to help warm the interior; penetrating solar rays work in concert with radiant flooring to keep inhabitants comfortably warm.
No matter what the season, the concrete absorbs the sun’s heat during the day and releases it inside at night, keeping the home’s interior at a more consistent temperature (See “Thermal Mass: Precast Concrete can take the Heat,” page 30).
To augment electric light, small perforations containing insulated glass are strategically placed along exterior walls to allow ambient light into the home without risking heat gain or loss.
The roof of the 960-sq-ft prototype home seems to float on top of the house, thanks to its clerestory windows, which make the structure seem much lighter in weight and roomier inside than it actually is. The inverted hip roof design – affectionately dubbed “the boat” – funnels rainwater toward the home’s central core so that the water can be recycled for toilets and houseplants. The central core itself houses all the plumbing and electrical hookups and controls.
Throughout the house, technology abounds. From the roof with its solar panels to the floor with its radiant heating, the students designed the home to be self-sufficient (see the sidebar “Precast Concrete Design Makes the Most of Latest Energy Technologies”).
Design/build concept on steroids
Since nothing like this project had ever been accomplished, there was a learning curve in all phases – from concept and design to manufacture and transport.
Rather than simply design the home and send the plans out to a contractor, Team New Jersey students traveled to Northeast Precast LLC in Millville, N.J., 90 minutes away, to help build the forms and pour the concrete themselves. From that, they learned firsthand a great deal about how their designs are brought into the manufacturing process. Some of the snags that surfaced drove them back to the drawing board, but overall the house went together extremely well.
“You don’t really hear of architectural students getting into that level of the fabrication process,” said Richard Garber, associate professor with the NJIT’s College of Architecture and Design. “They were all over it and were very excited about it.” Garber, the faculty leader for the solar home project, explained that it added a twist in normal classroom procedures. “We teach a design studio, where all the students are given the same problem, and they all come up with individual solutions,” he said. For this project, however, the students worked together toward the same common goal, much like the environment in a professional architectural firm.
It was a college education like no other. “Going through the process of doing all the design work, doing all the documentation, doing the shop drawings, working at the plant, being on site during the construction – these students are coming out with an architectural degree, but they have five or seven years of experience on people who go through the standard architectural education process at this point,” said Garber.
John Ruga, owner of Northeast Precast, contributed all the precast concrete components for the project and provided the formwork and work space for the students at his Millville, N.J., plant. “It’s really a cutting-edge design,” said Ruga. “It was something that hadn’t been done before.”
Ruga said that he was fortunate to have grown up working with his hands and probably takes things for granted that other people struggle with. “I really felt with the students that this was a great opportunity to work with them to give them an experience they would never get otherwise,” he said. “They just wouldn’t have had the opportunity at all to learn how to do this. That was the enjoyable thing for us.”
Although Northeast Precast manufactures precast homes and commercial buildings every day with the patented THiN-Wall panel systems, it had its own learning curve for the solar home project. The most perplexing challenge was figuring out how to safely lift and handle the 30 precast panels, each of which was unique in shape, size and weight. Typically these insulated panels require lifting and handling systems that do not alter the thermal performance of the product, but none of the existing systems could eliminate thermal bridging.
To combat the problem, Ruga asked A.L. Patterson Inc. of Fairless Hills, Pa., to help create an entirely new lifting system. The new, patent-pending Quik-Lift Zero Series is a three-part lifting system that includes two wings cast into the panels and a reusable lifting plate. “After the panel is set, you reach in, remove the bolts and the lifter comes right out,” explained Ruga. “It works extremely well. Then what we did was insert a foam piece in place of the lifting device to fill the cavity in.”
The home also was designed with transportability in mind. It can literally come apart at the seams and be plugged back together, including the plumbing and electrical hookups. For example, the floor was cast in four separate, unique sections, and the roof in six sections. The entire home can be loaded up and strapped down on seven flatbed trailers.
The Team New Jersey students gained a rich learning experience from designing and building the solar home and felt their precast project could be used to help others as well. “We really felt that we should donate it to something, where it can be used for tours or a learning center or something like that,” said Switala. With public service in mind, this precast home will “reside” at the Liberty Science Center, located in Liberty State Park in New Jersey.
Beautiful Design Plus All the Benefits of a Precast Concrete Home
Precast concrete offers much more than just strength and protection from high winds and extreme weather. Some of the more prominent benefits of the eNJoy home include:
• Low maintenance
• High durability
• No repair or maintenance
• Extreme weather-resistant (tornados, tsunamis)
• High thermal mass
• Lower utility bills
• Insect-proof (even against the formidable Formosan termite )
• Reduces air infiltration
• Resists airborne moisture
• Resists abrasion
• Contains natural materials and recycled industrial byproducts
• Reduced heat-island effect
• Quick installation
• Painting and integral colors are possible but not required for durability
• Stunning modern architectural design
• Wheelchair friendly
Precast Concrete Design Makes the Most of Latest Energy Technologies
The Team New Jersey architectural students incorporated these energy-efficient technologies into the solar home design. All components are commercially available.
• Precast concrete (see the sidebar “Benefits of a Precast Concrete Home”)
• Solar thermal technology
o Roof-mounted system uses energy from the sun to heat water
o eNJoy house uses a closed-loop drain-back system with an evacuated tube collector
• Photovoltaic technology
o Roof-mounted system converts light to electricity
o eNJoy home uses 40 solar arrays to match or exceed electricity draws
• Dual heat exchanger
o Hot-water storage tank connects three systems in the house: the open domestic hot-water loop to the closed radiant floor and the solar thermal loops
o Located in the central core, the system heats up the radiant flooring in winter
• Air handler
o Used only when rapid space conditioning is necessary
o Located in the central core, the six-row heating/cooling coil provides the surface area for air to come into contact with conditioned water provided by the reverse-cycle chiller
o Also dehumidifies the air in extremely humid environments
• Energy-recovery ventilation
o Located in the central core, the cross-flow membrane heat exchanger preconditions incoming fresh air
o Incoming humidity is transferred to the stale exhaust stream, reducing humidity within the home
• Reverse-cycle chiller
o An air-to-water heat pump located outside the house
o Provides 45 F chilled water in summer
o Reverses in winter to provide 120 F water to the radiant flooring
• Radiant concrete flooring
o Concrete flooring contains coils filled with water used as a space heater in winter
o Heating with water is 3,500 times more efficient than air in transporting heat
o Delivers heat steadily, noiselessly and without hot spots
• Control systems
o A central computer controls the house systems via low-voltage signals based on information received from sensors
o Sensors monitor temperature, humidity, water and energy usage, user preferences and daily schedule
• Natural and artificial lighting
o All lighting is recessed
o Perimeter lighting imitates natural daylight and emphasizes the floating roof concept
o Vertical lighting fixtures emit the correct amount of direct light into the space
o A combination of low-E glass and suspended film technology gives the glazing system superior insulation over standard windows
o Perforations filled with insulated glass are strategically placed to brighten the darker corners of the house with ambient light while accentuating the architectural design
Ron Hyink is NPCA’s managing editor.
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