May 13, 2014 6:24:00 PM
By Lori Johnston
The VISION House® at Walt Disney World has a message: Green living doesn't have to be a fantasyland. The creator, Green Builder® Media, says the home demonstrates how to incorporate mainstream green products and systems for everyday sustainable living. LED lighting from Sylvania, engineered hardwood wide plank floors by Armstrong, Boral's cultured stone, bricks and permeable pavers and photovoltaic solar panels from Hanwha Solar are among the products on display in the VISION House in INNOVENTIONS at Epcot®. If you're visiting the theme park during the summer, the indoor display offers a break from the heat, as a Disney guide leads tours from the front exterior to the open living room, dining room and kitchen, then to the laundry room, bathroom and bedrooms, ending on the patio (still inside the building). These five eco-friendly and energy-efficient items caught our attention and caused tourists to gawk, too.
May 2, 2014 1:19:00 PM
Apr 29, 2014 9:45:00 PM
In a traditionally designed and built home in the US, space heating and cooling are typically the largest energy uses. In a home strategically designed and engineered to be energy-efficient, it is often the domestic hot water that eclipses the space conditioning in energy consumption. This means that to approach a truly low-energy or zero-energy home, hot-water energy use must be aggressively addressed. After analyzing multiple options, the ReVISION House Vegas project team selected a very high performing combination system intended to meet all the projected domestic hot water demands, while providing the performance levels needed for a net zero-energy home: solar-thermal preheat and a Rinnai tankless gas water heater.
Apr 29, 2014 9:00:00 PM
Designing and building homes able to approach net-zero-energy first requires that overall energy use be reduced as much as practical. Determining major energy loads is the first step in developing a strategy to reduce those loads both practically and cost-effectively. In the hot-dry climate of Las Vegas, summer-time cooling most often represents the most significant energy use, and therefore reducing it is a top priority.
Apr 29, 2014 8:49:00 PM
Apr 29, 2014 5:31:00 PM
Most of the strategies, technologies, materials, and design choices discussed in relationship to the ReVISION House Vegas focus on the energy-efficiency, or more broadly, the “sustainability” of the post-retrofit home. However, the true barometer of sustainability is measured by the ability to endure over time, thus the assuring the durability of whatever it is we value. It is with this in mind that the ReVISION project team selected DuPont Weatherization system products to provide the envelope moisture control for both the wall and roof systems. With over 25 years of residential performance on over 5 million homes, the DuPont™ Tyvek® line of protective membranes, breathable weather resistant barriers and flashing systems are the world’s leading weather protection products. The ReVISION House Vegas uses several of the Tyvek family of products in helping us reach our zero-energy goal, and do it for a long time!
Tyvek™ StuccoWrap® is a non-woven, breathable housewrap specifically designed and engineered for use below stucco surfaces. Its unique crimped surface texture provides a 3-dimension surface with continuous peaks and valleys assuring that a continuous drainage path is provided below whatever stucco surface is used for the final finish. Knowing that the finished stucco coat is only the first-line-of-defense and that a “weather-resistive-barrier” is also needed under the exterior finish, the project team chose StuccoWrap® for its ability to provide reliable redundant protection, and also because it is prescriptively indicated as a manufactured approved choice by Dryvit, for use below its exterior insulation finish system (EIFS), which was also used for the ReVISION House Vegas.
Apr 29, 2014 5:00:00 PM
Aiming for and achieving the energy efficiency levels needed to reach net-zero-energy performance in a home requires first that the building’s thermal envelope be designed and built to minimize the capacity and energy requirements of heating and cooling equipment. Super insulated walls with outstanding air-sealing and weather-resistive capabilities are key. When applying these requirements to a home retrofit, the task becomes even more difficult as far fewer options exist within the context of an existing building. In the case of the ReVISION House Vegas, we add yet another obstacle; the desire to improve the thermal envelope from the exterior, leaving the interior finish substantially intact.
Before reviewing options for potential wall insulation solutions, the project team used EnergyGauge USA modeling software to determine the range of optimal insulation values needed to reach our performance goal. Once the needed R-values were identified, the insulation choices became clearer. With only a 3-1/2” space to work with in the 2 x 4 walls the amount of potential cavity fill insulation is limited. The limited cavity space and the requirement for excellent air-sealing led the team to select open-cell spray polyurethane foam which yields a nominal R-value of 13.6. As this R-value is lower than our modeled optimal value, additional supplemental insulation is needed, and since it can’t be placed toward the interior of the wall assembly (where interior finishes are to remain), an exterior insulated solution was chosen: in this case Dryvit’s exterior insulation and finish system (EIFS), the Outsulation® RMD System.
Apr 29, 2014 4:15:00 PM
In designing and building a net-zero-energy-home, the energy that the home uses annually must be exactly balanced with the energy the home can generate over that same year. This relatively simple equation is not as easy or obvious to resolve at it may seem. The first step is to understand what the energy uses will likely be for a house in a given climate zone, then devise strategies to assure that the home and its systems are as energy efficient as practical with the goal of ultra-low energy consumption. After strategies have been selected and adopted targeting the low-energy goal, and the annual energy use is predicted through energy-modeling, a properly sized renewable power system can be specified.
For the ReVISION House Vegas, the net-ZEH equation took on an additional variable: that of accomplishing zero-energy in the context of retrofitting a house that has already been built. The original equation stays the same but the efficiency options become more limited because we are working with an actual house and not a blank sheet of paper. And that existing house, according to EnergyGauge USA energy modeling, used 15,692 kilowatt-hours (kWh) a year. Add to that natural gas consumption of 478 therms a year, and total energy consumption is the equivalent of 29,451 kWh annually. If left as-is, the ReVISION House would need a cost prohibitive 18kW PV array covering virtually the entire roof surface to generate that much power in a year!
Apr 29, 2014 3:57:00 PM
Reducing energy use in buildings is ultimately predicated on reducing the energy loads as much as practical so that the systems that consume energy, such as heating and cooling have less work to do and therefore use less energy in accomplishing their tasks. It should come as no surprise that for this strategy to work in the hot-dry Las Vegas climate with its extreme summer heat, reducing the cooling load is a priority. To accomplish this, wall and roof insulation are especially critical, both in providing the needed R-values, and in preventing unwanted air-infiltration.
Before retrofit, the 1960’s vintage ReVISION House used conventional fiberglass batt insulation both in the 2 x 4 walls and in the 2 x 10 roof rafters. A small vented attic space, containing the heating and cooling ducts was insulated at the attic floor and the vertical knee walls leaving the ducts in 120-140 degrees F unconditioned space. Pre-retrofit testing revealed numerous significant gaps in the insulation and very high levels of air-leakage. A different approach was needed to obtain the ambitious performance goals set by the ReVISION House Vegas team.