The Solar Decathlon team at the University of Colorado is working to develop a new approach to sustainable housing design. Balancing energy efficiency and high quality, low-impact construction practices with architectural appeal, the approach merges subtle and cutting-edge technologies to create responsive designs for mass-market homes. The framework for this work is Base+, an adaptable construction methodology for repeatable, site-specific housing that showcases renewable energy systems and environmentally sound building products.
Our design approach embraces the spirit of the event to demonstrate that environmentally and energy conscious buildings are available today. We have developed a compromise among energy efficiency, adaptability, and architectural appeal without compromising lifestyle by embracing the following characteristics:
- Two prefabricated modular wings, built with structural insulated panels and high-performance windows, joined by a unique central space
- Green building products, e.g., recycled materials, engineered lumber, and rapid-growth wood
- Efficient appliances and integrated systems.
- Overall energy performance without conformance to traditional solar aesthetic
A core principle of our Solar Decathlon design approach is adaptability. Employing a modular approach, BASE+ buildings may be readily customized to address a wide range of climates, budgets, and homeowner needs. In addition, architectural and technological upgrades can be configured with BASE+ modules to scale a project up or down in size, cost, or performance capabilities. Our house, spec-built for the Solar Decathlon competition by CU students and Mortenson Construction, is our inaugural BASE+ project. Subsequent buildings will be factory-produced in quality controlled environments Ð minimizing costs, fabrication time, and construction waste - and shipped directly to site where they can be assembled with greater ease and speed than conventionally built homes.
In general, BASE+ homes are comprised of three basic building modules: Basic, Spec, and Utility.
The Basic Module
Basic modules are constructed from systematized wall, floor, and ceiling components called Structural Insulated Panels, or SIPs. SIPs are factory-produced panels with integral insulation that offer a high strength-to-weight ratio and superior thermal performance. As basic building blocks, these modules are efficiently factory fabricated in a variety of shapes to accommodate the programmatic needs of each project. On site, the Basic modules are combined to create building forms that appropriately respond to site & client needs. For the Solar Decathlon, two Basic modules will be used, housing the bed/bath and office/living areas, respectively.
The Spec Module
Spec modules offer the widest range of architectural customization and are intended to be the personalizing and defining architectural element of a BASE+ home. Spec modules take their architectural cues from each project's physical, environmental, and architectural context to establish the building's site-specific identity. For the Solar Decathlon, the Spec module will house the kitchen/entry, and will be constructed using a combination of SIP and frame construction featuring extensive use of high performance windows. As an entry piece to our house, the Spec will take advantage of the site's prominent position as a gathering place in the Solar Decathlon community.
The Utility Module (TechPod)
The Utility module, known as the TechPod in our house, is the energy and equipment module that organizes, distributes, and collects the technological systems of the BASE+ home. The TechPod is the home's energy center for monitoring and controlling thermal and systems performance, whose size, configuration, and form is derived from the technical needs of each project. For the Solar Decathlon, the TechPod is constructed with a modular metal frame that plugs into the other modules on site. Whereas the other modules will largely display subtle technological features, such as daylighting and passive solar design, the Decathlon TechPod will showcase the integration of a variety of active energy technologies into the home marketplace. A BASE+ TechPod for homes in other locations could follow a similar strategy or offer more visually subdued technological support.
The BASE+ Package Options
The BASE+ design allows each building to be tailored to the needs of the specific project at hand. At a minimum, BASE+ provides comfortable and sustainable homes, at affordable prices ready for market. These homes can take on a wide range of shapes, sizes, and architectural detail, determined by programmatic requirements and the desires and budget of the homeowner. Prospective homeowners may choose to additionally augment these designs with a range of technical options, as outlined below.
For most BASE+ buildings, the TechPod is one of the three main module types. However, for small projects that have minimal or no additional technical add-ons (such as PV), the services typically contained in the TechPod may be small enough to fit in a box within the spec or basic modules. The CU Decathlon entry will have a prominent TechPod on the north side of the home. All technical equipment will be housed in this TechPod excluding the HVAC equipment.
BASE+ PV SOLARELECTRIC
This option adds a building integrated solar electric system (Photovoltaic, or PV) to the roof of the BASE+ home. The PV system provides renewable, clean energy to the home; with excess energy being stored either in batteries in the TechPod or in the local utility grid. By integrating the panels directly into the building roof, the system can be largely factory built. The CU entry will be powered entirely with a photovoltaic array with energy being stored in a battery system located in the TechPod.
The Solar Decathlon competition is unique in that all electrical energy consumed by the house is derived from solar electric systems which must then be stored in batteries in the TechPod. Yet a substantial market exists for solar homes that are directly connected to the local utility grid Ð feeding power to the community during surplus hours, and drawing from the grid at night. This option provides BASE+ homes with direct utility interconnect, removing battery storage from the TechPod. This option will not be able for the Decathlon, as the village will not have a grid connect option.
BASE+ DHW SOLARTHERMAL
This option provides BASE+ homes hot water for domestic needs, such as laundry, showers, dishwashing, etc., with energy harvested directly from rooftop solar thermal collectors. For most climates, a relatively small area of collectors is sufficient to provide almost all annual hot water needs. (Supplemental heat is derived during these times from either conventional systems or the PV HeatRecovery package.) The decathlon home will include this option using evacuated tube solar collectors. The solar heated hot water will only be used for direct hot water needs and will not be used for space conditioning.
BASE+ PV HEATRECOVERY
Although typical building-integrated PV systems provide electricity to the home, their efficiency limitations are such that a significant amount of heat is also produced, often being left unused. This option provides a system for recovering this heat to be used to address a variety of heating needs in the building (clothes drying, building conditioning). This option will not be used in the decathlon entry. The team hopes to conduct more research in this area at a later date.
This option harnesses heat recovered from the PV HeatRecovery package and sends it to the mechanical system in the TechPod to regenerate a desiccant wheel. In this innovative scheme, heat is actually used to aid cooling the building. This option will also not be included in CU's design and research could be done in the future.