Houses zero of energy, made available

How is it for a challenge? To create a clear house zero of energy of source (in opposition to the energy of site) as defined by the ministry for energy the program of America of the building. To conceive to function with the extrème of the unforeseeable climate of Denver, by using technologies available immediately and easily available. To maintain the systems mechanical also simple and not very complicated like possible. To incorporate the strategies of energy-effectiveness which do not require owners at the house to be experts as regards bearable building work or not to lead any maintenance beyond that required house of “normal”. Not excessively difficult, you could say? To add that the design must be reproducible for the future habitat for houses of humanity, use inexpensive building materials, and allow the voluntary friendly techniques of construction. With always me? The anvil: The target is the sector accessible from housing. Impossible, you could say? Yes, but nonimpossible provocative for a team of integrated design engineers of NREL and the habitat for the personnel and the volunteers of humanity. The finished product is of the 1.200 square feet, the house reduced to three rooms of income which produces really more energy of source than it consumes! Considerations of design combination of the engineers of energy, of a director of construction a real director of development and volunteers of habitat on the strike helped by design that a balance between the ideals of technology based on energy modelling, inherent realities of cost in accessible housing, and the considerations implied in a voluntary construction industry are used as team-member. The advantage of work of the volunteer of the habitat directed the team of design to the approaches which supported of low material costs and high costs of labor of labour. While this approach to the minimum reduces the substantial cost of labor of labour, once combined with the accessible internal condition it limits the range of the bearable strategies available. For example, of the strategies such as the structured insulated panels (SIPs) and the isolated concrete forms were not considered because of their high cost. In the same way, the condition for offer-friendly techniques of construction and the facility of the counterpart eliminated the option to use the ball of straw. The condition of simple design eliminated the possibility of a heating from space and a combined solar heating system of water. In conclusion, the requirement in energy zero, given the cold climate of Denver and the high cost running of systems of picovolte, required some differences that the force of some purists of `consider discussed. Approach design - envelope Reçu the attention describes above, the team of design decided to concentrate initially on reducing the load to the house of energy as much as possible, and then to classify the system of picovolte to meet remaining electricity need has. The first place to be looked at? Yes, you guessed it - a passive solar orientation with superb envelope isolated from “one”. Starting with a standard habitat with three rooms, the design of 26 X 46 square feet with a crawlspace, the team increased the South-coatings freezing the sector and reduced the coatings of north, of is and Western freezing the sector. After, a wall of double-pin with the construction of glass fibre battery was selected to benefit from it is relative at cut price, technical offer-friendly and the low cost of labor of the labour of construction of the habitat. The glass fibre swollen installed in the attic carried out an estimate R-60 and the insulated floors carried out a R-30 estimate. While the double design of wall of pin, with the spaced structural pins external with 16 inches of O.C could not carry out the points of view of techniques advanced by houses of LEED, the interior pins spaced with 24 inches of gathering of O.C certainly the condition. The glass fibre R-3 handles the beater in the cavities external of wall and R-13 filling space between the external and interior walls as the interior cavities of wall help certainly to optimize the execution of energy. A siding steamer-permeable external of envelope of house and fibre cement, with and a poly interior barrier of vapor plus the dry partition are added value of entirety-wall-R very to “strongly”. The tests of ventilator gave a normal result speed of infiltration of 0.15 ACH, very indication of one “strongly”. Heating and ventilation With the house calorific energy has need rigorously reduced by it tte coquille superbe-isolée, l'équipe de conception alors concentrée sur le chauffage et le système de ventilation. Noter que je n'ai pas mentionné système chauffer, me refroidir et de ventilation. Encore un autre défi de conception ! L'habitat pour la métro Denver d'humanité a une politique de ne pas équiper ses maisons de la climatisation. Ceci a signifié que la conception finale a dû maximiser la réduction de la chaleur (par exemple en maximisant le gain solaire) sans augmenter la charge de refroidissement d'énergie. Pour fournir une quantité appropriée d'air frais à la maison tandis que le potentiel réduisant au minimum pour la déperdition d'énergie, l'équipe optait pour un système de la ventilation de rétablissement d'énergie (ERV) avec les moteurs électroniquement commutés efficaces. L'air d'échappements de système de la cuisine et de la salle de bains, et air frais d'approvisionnements à la salle de séjour et aux chambres à coucher. La perte de chaleur de la ventilation est réduite parce que le système d'ERV chauffe l'air entrant avec la chaleur de l'air d'échappement. L'équipe de conception a bientôt découvert qu'une charge thermique très basse est une épée à deux tranchants. D'une part de l'énergie très petite est exigée pour chauffer la maison. D'une part, la plupart de commo nly available heating systems are oversized for such low heating needs, and overly complicated or expensive systems cannot be cost-justified. After carefully considering a variety of high-efficiency heating systems, and much internal debate, the team decided to follow a hybrid approach of electricity from the PV system, and natural gas. Controversial Approach Some of us who are ‘purists’ may turn up our noses at the thought of a zero energy home using natural gas. However, the economics involved convinced the design team that a hybrid approach was the best solution (see side bar) The PV system selected by the design team uses the local utility grid for storage, thus eliminating the substantial cost of the storage battery. When the system is producing more energy than is being used, it delivers energy to the grid. When the system produces less energy than it produces, it draws electricity from the grid. When the system draws electricity from the grid, it is likely drawing fossil-fuel generated electricity. Although a larger sized PV system may minimize the volume of electricity drawn from the grid, the cost of larger systems is prohibitive. The design team opted to include natural gas in order to reduce the size of the PV system by 1.1 kW, making it much for affordable for a Habitat Home. The team designed the system to offset the natural gas used, thus achieving, and even surpassing, the goal of net zero source energy. The hybrid approach allowed the team to size the PV system that is affordable, offsets the use of natural gas as well as any grid generated electricity, and thus allows the home to achieve (and even surpass) the goal of net zero source energy. The hybrid space heating system combines a pointsource direct-vent natural gas furnace in the dining room and living area, with small baseboard electric-resistance heaters in the bedrooms. Water Heating The design team selected a solar water heating system – rather than a combined space/water hearing system – for simplicity, backed up by a natural gas tankless water heater. The team calculated that the 96 square foot collector area and 200 gallon water storage would result in an annual solar-savings fraction of 88%. They opted for the tankless natural gas back up heater after finding that the tankless system uses zero heating energy whenever the solar water tank is at or above 115 degree water delivery temperature. The Crowning Element Having reduced all possible energy loads as much as possible, the design team zeroed in on the lighting, appliances and miscellaneous electric loads (MELs). They installed compact fluorescent light bulbs throughout the house, and ENERGY STAR label appliances. This left the miscellaneous electric loads, from TV, hair dryer, toasters, computers, and anything else that could be plugged in by the occupants. Using Built America benchmark assumptions on MELs, the team settled on a 4kW PV system. Because the Built America assumptions on based upon a national average of a ‘typical’ American household, the actual occupant use and local climate may either block the home from achieving zero energy usage, or propel it to the ranks of ‘net energy producer’. The Verdict Initial test results were encouraging. From the February to July of 2006, the PV system produced 1,600 kWh more electricity than the house consumed. Factoring in the natural gas used for space heating and water heating backup, the house produced 75% more source energy than it consumed. Although a longer testing period is required, it’s a safe bet to say that the house will be an annual net energy producer rather than just achieve net zero energy user. However, this could change if the occupants begin using more than the average calculated into the Built America benchmark. And the home owners? While it is true that the house is a net energy producer, they unfortunately are not free from utility bills. There is the monthly charge for the natural gas, as well as fixed charges for the electric grid and natural gas connection fees. From October of 2005 to May of the 2006, the owners shelled out an average of $18.25 per month in energy bills. Because the fixed monthly charges averaged 80% of those bills, in actuality the family used on average $14.60 worth of energy. For those of us who suffered through $200+ monthly energy bills during that same period, those results are very compelling. KEY RESIDENTIAL SUSTAINABLE FEATURES Energy and Atmosphere Passive Solar Design • The house was designed with increased glazing area on the long South facing side, and reduced glazing area on the North, East and West facing sides. Renewable Energy • 4kW Photovoltaic system using utility power grid storage to eliminate need for and associated high cost of, storage battery Insulation • Raised heel trusses in attic allow 2 ft of blown fiberglass insulation, achieving R-60 rating for thermal envelope top • Floors insulated to R-30 • R-3 fiberglass batts in outer 2 x 4 structural stud wall cavities, and a second, interior 2x4 stud wall with R-13 fiberglass batts placed horizontally between stud walls and vertically in interior wall cavities • Outer vapor-permeable house wrap and fiber cement siding • Inner poly vapor barrier and drywall Space Heating • Hybrid natural gas/electric heating system, combining a pointsource direct-vent natural gas furnace in the living room and dining area, and small baseboard electric-resistance heaters in the bedrooms. This combination provides the added bonus of zone heating, as each appliance has its own independent thermostat. Water Heating • Solar water heating system with 96 square feet collector area and 200 gallon water storage tank as primary water heating system, with natural gas tankless water heater as a back up system Windows • Double – glazed, low –e glass installed in South facing windows, with U-factor of 0.3 and SHGC of 0.58. For the East, West and North facing windows, Double – glazed, low – e glass was also used, with a U-factor of 0.22 and SHGC value of 0.27. The U-factors of all windows exceed (ENERGY STAR requirements by 20%). Appliances • ENERGY STAR® appliances were installed. Lighting • Compact fluorescent light bulbs deployed throughout the house Indoor Environmental Quality Local Exhaust • Energy Recovery Ventilation (ERV) system with efficient electronically commutated motors, exhausts air from the kitchen and bathroom, and supplies fresh air to the living room and bedrooms. Outdoor Air Ventilation • The ERV system heats incoming fresh air with warmth of the exhaust air, thus significantly reducing heat loss from ventilation. Materials and Resources • Advanced Framing Techniques: Walls consist of inner 2x4 stud wall, 24 inches O.C.