energy design resources
design brief HIGH-PERFORMANCE NEW HOMES
High-performance new homes excel
in
thermal
comfort
and minimized energy use.
Summary
Homeowners see lower utility
Interest is growing throughout California and the United States in new
bills, home builders sell better
homes designed to provide comfortable living environments with lower
quality homes, and utilities realize
energy consumption and operating costs. Residential design focused on
peak energy demand savings.
proper orientation, optimized building envelope, effective heating, cooling, and lighting systems, as well as efficient appliance selections, significantly reduce home energy use. Adding solar energy systems to generate electricity by harvesting the sun’s rays, or solar thermal systems to heat water or air by capturing solar heat gain, further offset energy consumption and lower a home’s carbon footprint on the environment. Designing, building, and living in high-performance homes provides economic, quality-of-living, and environmental advantages for homeowners. Home builders enjoy increased appeal by constructing
CONTENTS
new homes that have improved thermal comfort and lower operating Introduction
2
homes, and those with solar energy and thermal systems, reduce both
Benefits and Incentives
2
peak energy demand and consumption on the system-wide electrical
Integrated Designs
7
grid. This Design Brief provides an introduction for designing high-
Solar Technologies
16
performance new homes by addressing the following topics:
Energy-efficient Equipment
19
Case Study
27
Conclusion
29
For More Information
30
Notes
31
costs. Utility companies also realize benefits because high-performance
I
Benefits and Incentives
I
Integrated Designs
I
Solar Technologies
I
Energy-efficient Equipment
Introduction Extreme energy demands can strain California’s statewide electrical grid and infrastructure, resulting in supply issues and increased procurement costs for utilities and consumers. More and more homeowners are consciously seeking ways to lower their energy consumption and associated costs without sacrificing comfort, and homebuilders are increasingly interested in offering high-performance new homes, coupling energy efficiency strategies with solar energy and thermal systems for their customers. To design a high-performance home in California, architects, homebuilders, and owners should focus on three objectives. 1. Embrace the local climate. Match design strategies and technology selection to positive climate characteristics. Look for opportunities to take advantage of local conditions and reduce loads passively using an integrated design approach. 2. Evaluate solar technologies. Look to solar systems, also referred to as photovoltaics (PV) systems, as an effective and environment friendly way to offset energy use. 3. Meet remaining loads efficiently. Evaluate highly efficient technologies to meet heating, cooling, lighting, and water heating needs. Use control strategies to reduce equipment idle time. Using this three-prong approach insulates homeowners against rising utility costs, improves the level of thermal comfort within the home, and increases the long-term value of the property.
Benefits and Incentives Benefits High-performance homes offer numerous benefits. The most significant ones are briefly summarized.
PAGE
2
HIGH - PERFORMANCE NEW HOMES
I
Increased comfort – Better design strategies and construction practices produce superior interior thermal conditions. For example, window type and placement considerations drastically affect the amount of solar heat gain. Optimized air-duct design and installation improves the ability to seamlessly maintain desired indoor temperatures. Tight construction restricts the gaps and holes in exteriors and reduces temperature fluctuations and draftiness within a home. Third-party inspections of insulation and equipment installations during construction pinpoint deficiencies.
I
Enhanced indoor environment – Employing certain strategies may further enrich the indoor environment. For instance, use of increased insulation levels creates better acoustics, the addition of a humidifier to the HVAC (heating, ventilation, and air conditioning) system improves indoor air quality, and the selection of indirect rather than direct lighting designs provides a more pleasing luminous environment.
Figure 1: New Homes with Building Integrated PV Roof Tiles Home builders are designing and building new homes with PV systems that are integrated directly into the roofing systems, providing aesthetically pleasing options for homeowners.
Source: Geltz Communications
HIGH - PERFORMANCE NEW HOMES
PAGE
3
I
Reduced Operating Costs – Combining energy efficiency designs and equipment with solar energy and thermal systems typically reduces utility bills from 40 percent to 60 percent. Much of the cost savings is predicated on the aggressiveness of the home design, equipment selection, and the PV system size. Family size and lifestyle also play a significant role. For instance, families with young and older members that are at home during most days tend to use more energy and are more sensitive to thermal comfort needs.
I
Positive Cash Flow – Financially, it is important to compare the cost impacts of energy efficiency strategies and solar technologies against the mortgage payment and the projected decrease in utility costs. To illustrate, if a high-performance home’s price is $15,000 higher than a similar conventional home, it will increase the monthly house payment by approximately $100, based on a 30-year loan using a seven-percent interest rate. Yet, the monthly gas and electricity costs may decrease on average by $125 per month. The result is $25 positive cash flow each month. Thus, a high-performance home, if judiciously designed and built, creates a positive cash flow for the homeowner.
I
Wise investment – Several studies in California are indicating an increase in the marketability and value of high-performance homes. One study that focused on homes in southern California found higher resale values for homes with energy-efficient features and solar energy systems as compared to conventional homes in the same neighborhood.1
Homeowners Carbon Footprint
I
Environmental impact – At 1,254 million metric tons (MMT)
The California Environmental Protection
annually, residential carbon dioxide emissions represent roughly 21
Agency (EPA) Air Board provides
percent of United States energy-related carbon dioxide emissions.2
consumers with a California Specific
Residential sector carbon dioxide emissions result from: (~1/3) direct
Carbon Calculator. The online web site
fuel consumption (principally natural gas) for heating and cooking,
easily determines a homeowners
and (~2/3) from electricity production used primarily to power
carbon footprint.
cooling, lighting, televisions, computers, and other household electronic devices. By producing “nega-Watts”3 or negative Watts
www.arb.ca.gov/cc/ccc/ccc.htm
(electricity never needed as the result of energy efficiency), home builders and owners contribute directly to carbon emissions reduction.
PAGE
4
HIGH - PERFORMANCE NEW HOMES
Incentive-based Programs With the emphasis on decreasing utility costs and minimizing the carbon footprint of new construction, several incentive-based programs are available to assist home builders and owners. The majority are utility-administered programs. The California New Homes Program, which is offered by Southern
Plan for Energy Efficiency First
California Edison, encourages the construction of houses that surpass
Energy efficiency strategies are the most
Title 24, which is California’s Energy Efficiency Standards for
cost effective way to reduce a home’s
Residential and Non-Residential Buildings, and meet ENERGY
environmental impact. In California,
STAR requirements. A new home that is ENERGY STAR-qualified
new residential solar energy systems
is at least 15 percent more efficient than homes built to the 2004
must be coupled with energy efficiency
®
(IRC),4
and has the potential to
strategies that are more stringent than
prevent 4,500 pounds of greenhouse gases from entering the
California’s Energy Efficiency Standards
International Residential Code atmosphere each
year.5
Two methods of participation are available under this program:
for Residential and Nonresidential Buildings (Title 24) to be eligible for monetary incentives.
I
Performance Method requires the whole home to be 15 to 20 percent more efficient than required by the 2005 Title 24 standards and earn ENERGY STAR certification.
I
Prescriptive Method requires that builders select measures from a list of energy efficiency options such as ENERGY STAR appliances, tight ducts, and high efficacy lighting. The homes must still meet required Title 24 standards.
Incentives for this program vary. Individuals interested in participating should contact the utility for current information. Besides financial incentives, Southern California Edison also provides marketing and outreach benefits, training, technical support, and program implementation support to home builders, who comply with program requirements. Other incentive programs are available such as Southern California Edison’s (SCE) Sustainable Communities Program, Pacific Gas & Electric’s (PG&E) Residential New Construction Program, and Sacramento Municipal Utility District’s (SMUD) SolarSmart New Homes. Southern California Gas Company also features a program focused on natural gas savings in the home. Each program provides HIGH - PERFORMANCE NEW HOMES
PAGE
5
Table 1: California Utility Residential Programs Pacific Gas and Electric (PG&E) Residential New Construction Program, www.pge.com/res/energy_tools_resources/efficient_new_homes/info_for_builders/ Sacramento Municipal Utility District (SMUD) SolarSmart Program, www.smud.org/residential/saving/solarsmart.html Sempra Energy Utility (Sempra) Advanced Home Program, www.sdge.com/construction/newHomes.shtml Southern California Edison California New Homes Program, www.sce.com/SC3/RebatesandSavings/BuilderandBuyer/EnergyStarHomesProgram/ Southern California Edison Sustainable Communities Program, www.sce-scp.com
varying incentives and benefits for new homes that are designed and built to be energy-conscious and environment friendly. Program guidelines and strategies are available from individual utility companies. The New Solar Homes Partnership (NSHP), under the auspices of the California Energy Commission, is designed with similar intent, which is to reward builders and homeowners embracing energy efficiency measures. The NSHP goes one step further by requiring the installation and commissioning of solar energy systems for participants to qualify for incentives. Rebates are offered based on anticipated PV electric production and are meant to reduce or buy-down the initial cost of the PV system. Qualification is two-tiered with either 15 percent better than Title 24 2005 standards or 35 percent better, with 40 percent improvement for cooling. Three major investor-owned utilities, SCE, PG&E, and San Diego Gas & Electric Company (SDG&E), are involved with the NSHP and administer it as part of their residential offerings within their service territories. In addition, the California Public Utility Commission (CPUC) plans to offer incentives for solar thermal technologies under the California Solar Initiative. San Diego Regional Energy Office (SDREO) also is scheduled to run an incentive program for solar thermal technologies in the SDG&E service territory. Central to the economics of residential solar technologies is the concept of net metering (See sidebar). Federal Tax Credits also may be available PAGE
6
HIGH - PERFORMANCE NEW HOMES
that reward homeowners for installing energy efficiency products as well as PV systems. A tax credit, which is different from rebates, directly
Net Metering is Important to Understand
reduces the tax burden of the homeowner. For complete and up-to-date information about available tax credits for energy efficiency and solar energy and thermal systems, consult the ENERGY STAR website at www.energystar.gov/index.cfm?c=products.pr_tax_credits. Homeowners should consult a tax advisor or the Internal Revenue Service for current information to fully understand the impact on individual tax returns. Other programs exist to guide builders and homeowners, though do
Source: Southern California Edison, www.sce.com
not offer rebates. The United States Green Building Council’s LEED®
Net metering allows homeowners to
for Homes is a voluntary residential certification program. The
sell renewable electric power
California Green Builders Program is another program that provides
generated at their home back to the
support and information. Build It Green is a non-profit membership
utility. In essence, the electric meter
organization whose mission is to promote healthy, energy- and
runs both forward and backward, and
resource-efficient building practices in California. These programs go
the homeowner is charged only for the
beyond energy efficiency and promote sustainability as it also relates
“net” electricity used. In California,
to topics such as water efficiency, material resource selection, and
utilities generally credit customers for
indoor air quality.
generation on a "time-of-use" basis.
Integrated Designs
Electricity, therefore, is both bought or sold at a rate set by the time of the
Climate Considerations Climate-responsive design seeks to take advantage of the positive climate attributes of a particular location to minimize energy loads and increase the hospitality of the indoor environment. California is divided into 16 climate zones (CZs), and certain building envelope features and heating
exchange. This is generally beneficial to the homeowner, since peak solar output is typically during the afternoon, coincident with the highest utility rates.
and cooling strategies are more effective in specific zones. The zones, shown in Figure 2, are extremely diverse, ranging from moist, cool locations in the upper northwest coastal area, which is CZ-1, to hot, mountainous, semi-arid regions that stretch from the Oregon border south to San Bernardino County, CZ-16. In general, most of California receives an abundant amount of solar exposure. The majority of climate-responsive designs should, therefore, attempt to reduce cooling loads by controlling solar heat gain, and harvest the sun’s energy through active solar electric or HIGH - PERFORMANCE NEW HOMES
PAGE
7
Figure 2: California Climate Zone
thermal systems. Decisions regarding building orientation, insulation levels, over-hang depths, window selection, natural ventilation, thermal mass, mechanical system design, and daylighting should be carefully evaluated for successful integrated design. The Pacific Energy Center has published a Guide to California Climate Zones and Bioclimatic Design,6 which provides detailed information on prevalent climate conditions to inform energy-conscious design in each climate zone.
Design Options Design options focused on providing holistic or whole-house energy Source: California Energy Commission
reductions should be considered from the beginning of a project. Many opportunities, if decided upon early, present substantial energy reductions by affecting other downstream decisions. Understanding the energy impact and cost effectiveness of each design option is important to successfully building a high-performance home. Orientation and Layout Where flexibility exists, home sites facing south, southeast, or southwest, provide the best opportunities for daylighting and passive solar design. In fact, “simply facing your home in the right direction can save up to 30 percent on your energy bill,” according to the Rocky Mountain Institute.7 In general, moderate amounts of southern windows with appropriate overhangs and thermal mass, which is material that can slowly absorb and release heat, will provide warmth during winter months without creating significant energy penalties during the summer. Also, south- and north-facing windows bring daylight into the home without combating harsh east and west sun angles. Minimizing surface area to volume for home designs—compact form with normal ceiling heights—generally increases efficiency and typically allows for downsized equipment, increased ventilation, and consistent temperature distribution. Buffer spaces such as vestibules, porches, and sun rooms may be used to temper weather extremes. In general, spaces intended to be warm should be placed on the south
PAGE
8
HIGH - PERFORMANCE NEW HOMES
side or west side of the house, and those intended to be cooler located on the north or east sides. Finally, it is important to consider
Transportation Related Energy Use
integrating onsite features such as trees or hillsides for shading, and
Prior to construction, deciding where
ocean or valley breezes for natural ventilation to lower annual
to build (or buy) a house may make a
cooling and heating loads.
significant difference in the long-term carbon footprint. Research shows that
Building Envelope
when compared to other household
The building envelope generally refers to the walls, roof, windows,
actions, taking public transportation
and foundation that separates a home’s interior from the exterior
can be up to ten times as effective in
environment, and contributes to the structural integrity,
reducing household related carbon
temperature control, moisture control, and pressurization of a
dioxide (CO2) emissions. Therefore, it
residence. High-performance envelope design includes selecting
is important to take a home’s
appropriate wall assemblies and insulation, properly installing
relationship to public infrastructure in
materials and sealing air leaks during construction, and choosing
mind when selecting a site.
windows with proper characteristics. Such envelope strategies work year-round to keep a house warmer in the winter and cooler in the summer, and can minimize the need for mechanical heating and cooling.
– The American Public Transportation Association’s Public Transportation’s Contribution to U.S. Greenhouse Gas Reduction
The performance of various building envelope elements is primarily a function of material properties such as R-value and thermal mass. Windows have additional performance characteristics, which are described in a later section. I
R-value is a measure of a material’s resistance to heat transfer by conduction—the greater the R-value, the greater the insulating value of the material.
I
Thermal mass is a function of a material’s ability to store heat. The higher a material’s thermal mass, the greater its ability to store warmth or coolth, which is the state of being cool. Thermal mass like stone floors or walls regulate temperature fluctuations within a space. In climates without significant temperature swings, thermal mass may not have a significant effect. For inland climates with hot days and cool nights, thermal mass and proper insulation can be combined to mitigate cooling and heating loads.
HIGH - PERFORMANCE NEW HOMES
PAGE
9
Two issues, moisture control and toxicity, affecting building envelope are not addressed in detail in this Design Brief, because both are not directly related to a home’s energy performance. Moisture control is a function of a material’s porosity and a wall assembly’s ability to resist moisture or air penetration, and is critical for maintaining a proper indoor environment and structural integrity. Toxicity concerns the off gassing of toxins by building materials. It is important to select wall assemblies such as insulated concrete forms (ICFs), or adobe that are low in toxicity. Advanced wood framing also may have low toxicity, if formaldehyde or other toxic agents are not used for binding. Table 2 provides a brief overview and Figure 3 presents visual examples of different wall assemblies. Figure 3: Wall Assemblies
Insulated Concrete Wall
Steel Framing
Structural Insulated Panels
Advanced Framing
Source: National Renewable Energy Laboratory (NREL), Department of Energy (DOE), www.nrel.gov
PAGE
10
HIGH - PERFORMANCE NEW HOMES
Table 2: General Properties of Various Wall Assemblies Building material
Thermal performance (higher R-value means better insulation)
Renewable and recyclable
Benefits or Issues
Adobe (earth)
Low R-value, but great source of thermal mass material in warm or mixed climates
Not renewable, earth is not easily replaced but is plentiful
Cost-effective if sourced locally, and can be part of good passive solar design. Requires insulation in extreme climates
Advanced wood framing
6-inch walls provide space for increased insulation. Spacing studs 24 inch on center rather than 16 inch and using efficient-framing techniques can reduce the amount of framing lumber used. However, wood frames can be a thermal “weak link,” causing thermal bridging (for example, a wood framed wall with R-19 insulation has an actual insulation value of R-16)
Choose renewable products that are sustainably harvested. Check for Forest Steward Council (FSC) endorsement; can be re-used at end of life in buildings or for mulch
Wall cavities need to be insulated; many residential home builders are adopting
Concrete (block or solid)
Low R-value but an effective thermal mass material for moderating indoor temperatures in climates with high diurnal temperature swings
Choose products supplemented with recycled fly ash or slag from steel manufacture; can be crushed for road base at end of life
Inexpensive but poor insulation can lead to high heating bills in cold climates
Insulated Concrete Forms – ICFs
High R-value. Built-in place forms consist of EPS or Extruded Poly Styrene (XPS) filled with rebar and concrete
Poly Styrene can have high recycled content. Choose concrete fill supplemented with recycled fly ash or slag from steel manufacture; can be recycled
High STC or sound transmission class rating for a wall assembly. Issues such as water or insect penetration need to be considered
Masonry
Masonry is not a good insulator, but it is a very effective thermal mass material, capable of storing warmth or coolth
Not renewable, but the raw materials are abundant; can be crushed for fill or reused at end of life
Price dependent on design and level of expertise required. Requires insulation in extreme climates
Steel framing
Popular in areas prone to natural disasters and termites; provides increased structural integrity; though high thermal conductor; poorly designed wall assembly will increase heating/cooling loads. Thermal bridging must be addressed by using knock-outs, spacing the studs on 24-inch centers, and using exterior rigid insulation
Steel may be recycled at end of life
Steel prices may be more stable than wood. Thermal efficiency of a steelframed system can meet and exceed the requirements of the California's building energy efficiency standards, if properly designed
Straw bale
Very high R-value and when combined with an earthen plaster can provide a substantial thermal mass
Renewable, and instead of cropburning, farmers can profitably divert otherwise wasted straw to a productive use; can be used for mulch at end of life
Cost-effective if sourced locally, and no additional insulation costs
Structural Insulated Panels (SIPs)
SIPs (foam insulation or compressed straw sandwiched between sheathing) can provide very high insulating values and reduce air infiltration by minimizing joints
Most are made using recycled wood chips in the sheathing and are manufactured to size, which minimizes waste; end of life use depends on material
Material is expensive but does not require framing or extra insulation, and requires
Source: Southern California Edison, www.sce.com
HIGH - PERFORMANCE NEW HOMES
PAGE
11
Insulation As a rule, insulating homes is important in any climate and, typically, the more insulation (i.e., the higher the R-value) the better. Properly installed, insulation decreases unwanted thermal gains or losses through the envelope throughout the year. For many locations in California, recommended insulation levels for roof and floor areas are R-38 and R-30 respectively. Exterior wall recommendations may be more moderate, ranging from R-13 to R-19. Information on various types of insulation is summarized in Table 3. Insulation works less effectively if it is not continuous or gaps exist. Using properly trained contractors and paying attention to construction detailing are important for ensuring quality installations. In California, third-party inspection companies will inspect and ensure that builders and their contractors properly perform insulation installation and air sealing.
Table 3: Types of Insulation Insulation Type
Method of Installation
Where Applicable
Blankets: Batts or Rolls • Fiber glass • Rock wool
Fit between studs, joists and beams
Walls, floors and ceilings
Loose-Fill (blown-in) or Spray-Applied • Rock wool • Fiber glass • Cellulose • Polyurethane foam
Blown into place or spray applied by special equipment
Enclosed existing wall cavities or open new wall cavities
Rigid Insulation • Extruded polystyrene foam (XPS) • Expanded polystyrene foam (EPS or beadboard) • Polyurethane foam • Polyisocyanurate foam
Interior applications: Must be covered with 1/2-inch gypsum board or other building-code approved material for fire safety
Basement walls
Exterior applications: Must be covered with weather-proof facing
Unvented low slope roofs
Reflective Systems • Foil-faced paper • Foil-faced polyethylene bubbles • Foil-faced plastic film • Foil-faced cardboard
Foils, films, or papers: Fitted between wood-frame studs joists, and beams
Unfinished ceilings, walls, and floors
Unfinished attic floors and hard to reach places
Exterior walls under finishing (Pay special attention to vapor retarders)
Source: Oak Ridge National Laboratory, DOE, Insulation Fact Sheet, 2008, www.ornl.gov/sci/roofs+walls/facts/Insulation%20Fact%20Sheet%202008.pdf
PAGE
12
HIGH - PERFORMANCE NEW HOMES
In general, insulating the attic or roof should be the first priority since the most extreme boundary conditions or temperature differences typically occur at or around these areas. However, other hidden areas need to be insulated by home builders and contractors. These spaces include finished and unfinished attics, all exterior walls including those between living spaces, and floors above cold spaces, even slab floors built directly on the ground. Though, appropriate ventilation of enclosed cavities such as attics, crawl spaces, and storage areas is necessary to prevent excessive moisture build-up. Figure 4 shows various areas to insulate and seal around the home. Figure 4: Hidden Places to Insulate and Seal in New Homes 1.
In unfinished attic spaces, insulate between and over the floor joists to seal off living spaces below. 1A attic access door
2. In finished attic rooms with or without dormer, insulate... 2A between the studs of “knee� walls; 2B between the studs and rafters of exterior walls and roof; 2C ceilings with cold spaces above; 2D extend insulation into joist space to reduce air flows. 3. All exterior walls, including... 3A walls between living spaces and unheated garages, shed roofs, or storage areas; 3B foundation walls above ground level; 3C foundations walls in heated basements, full wall either interior or exterior. 4. Floors above cold spaces, such as vented crawl spaces and unheated garages. Also insulate... 4A any portion of the floor in a room that is cantilevered beyond the exterior wall below; 4B slab floors build directly on the ground; 4C as an alternative to floor insulation, foundation walls of unvented crawl spaces; 4D extend insulation into joist space to reduce air flows. 5. Band joists. 6. Replacement or storm windows and caulk and seal around all windows and doors.
Source: Oak Ridge National Laboratory, DOE, Insulation Fact Sheet, 2008, www.ornl.gov/sci/roofs+walls/facts/Insulation%20Fact%20Sheet%202008.pdf
Radiant Barriers Another way to reduce summer heat gain and winter heat loss is by using a radiant barrier in the attic. Consisting of a reflective film placed between the roof deck and rafters in new construction, a radiant barrier is installed to face an open air space. The barrier reduces cooling loads since heat radiated from the hot roof is reflected back toward the roof, and reduces heating loads by reflecting heat back into the warmer living spaces. HIGH - PERFORMANCE NEW HOMES
PAGE
13
Duct Sealing Sealing and insulating air ducts can significantly improve the energy efficiency of a home’s HVAC system and mitigate common comfort issues. Leaky ducts are responsible for reducing heating and cooling system efficiencies by as much as 20 percent.8 During new home construction, busy contractors may not properly install, seal, or fully insulate all areas of the duct system. A duct pressurization test, often called a “duct blaster” or “blower door” test, can determine the amount and location of air leakage. Common leakage sites are around air registers and grilles, duct connections, panned floor joists or the use of floor joists as return ducts, and the actual connection to the heating and air conditioning unit. High Performance Windows Heat transfer through windows, in cooling-dominated climates, accounts for up to 50 percent of a typical house’s cooling load and, in heating-dominated climates, accounts for up to 25 percent of heating load.9 High performance windows can reduce solar and thermal gains in the summer and keep indoor heat from escaping to the outside during the winter. As an added benefit, high-performance windows prevent damaging ultraviolet light from entering a home. Important performance characteristics for residential windows are typically defined using the following criteria: I
Air Leakage (AL) – air infiltration occurs in and around the window assembly. AL is expressed as the cubic feet of air moving through a square foot of window area. The lower the AL, the less air transmitted through the assembly. Although air flow characteristics can be important, light transmittance characteristics typically dominate the energy performance of a window.
I
Frames – different window framing materials conduct heat differently. Least conducive framing material to most conducive is generally in the following order: wood, fiberglass, vinyl, and aluminum. In other words, wood is typically the best insulator and aluminum is the worst. Cost and maintenance for these materials vary.
PAGE
14
HIGH - PERFORMANCE NEW HOMES
I
Low-E – microscopically thin coatings that help keep heat inside during the winter and outside during the summer; the “E” stands for emissivity or re-radiated heat flow. Low emissivity coatings reduce radiative heat transfer while allowing visible light through the windows.
I
Multiple glazing (panes) – Multi-pane glazings, referred to as insulated glass (IG), provide an air gap between the glass panes. More panes mean better insulating characteristics. It also is possible to fill the spaces between the glass with argon or other high-performance gases to increase the insulating properties of the assembly.
I
Solar Heat Gain Coefficient (SHGC) – Expressed as a fraction between 0 and 1, SHGC measures the ability of a window to block the part of the solar spectrum that is associated with heat. The lower
Figure 5: High Performance Window Labels ENERGY STAR®-labeled windows meet a stringent energy efficiency specification and have been tested and certified by the National Fenestration Rating Council (NFRC). NFRC is an independent, third-party certification agency that assigns specific energy efficiency measures such as U-factor and Solar Heat Gain Coefficient to the complete window system, not simply the glass. ENERGY STAR qualified windows may have two or more panes of glass, warm-edge spacers between the window panes, improved framing materials, and Low-E coating(s). The ENERGY STAR and NFRC labels are easy to identify.
the fraction, the less solar heat is transmitted through the window. I
U-factor – the rate of heat flow through a window. A low U-factor number means slow heat transfer and an energy-efficient window assembly.
I
Visible Transmittance – this optical property measures the amount of visible light transmitted. Typically, values range from 0.3 to 0.8. A high VT is generally desirable to maximize daylight into a space.
The SHGC and U-value of the window assembly should be carefully considered relative to climate considerations and window orientation.
Only
certain
combinations
of
performance
characteristics can co-exist. Performance trade-offs may be necessary when selecting a window product for various locations. In heatingdominated climates, solar gain may be desired. In such cases, glass with high solar transmittance (high SHGC) are desired and provide passive solar heating benefits. However, the same windows provide unwanted solar gain during the summer months and require shading options. Deciduous trees, operable shades, or properly designed exterior shading elements can effectively provide this
Source: ENERGY STAR, www.energystar.gov and NFRC, www.nfrc.org
seasonal shading.
HIGH - PERFORMANCE NEW HOMES
PAGE
15
Figure 6: Flat Plate Collection
Solar Technologies In sunny California, solar provides a vast and renewable source of light, heat, and energy. It can be harnessed in a variety of ways to significantly reduce the use of utility-provided gas and electricity. Once strategies taking advantage of the local climate to reduce loads have been implemented, the next strategy in high-performance home design is to leverage the available solar resource, where technologically and
Source: NREL, DOE
Figure 7: Evacuated Tube Collector
economically appropriate.
Solar Hot Water Hot water heating can account for up to 15 to 25 percent of a home’s total energy use. Solar hot water systems can reduce these operating costs by as much as 90 percent. These systems have relatively high first costs, and most require a conventional water heater as a backup to ensure hot water is continually available. However, solar hot water systems provide significant cost savings over the lifetime of the system, which is typically 20 years or more. In fact, cost estimates using 2007 energy prices show approximately an eight-year payback for common flat plate collectors in the state of California.10
Source: NREL, DOE
Active solar hot water systems consist of pumps and sensors to move water or water/anti-freeze mixtures; heat exchangers and storage tanks harvest and store the heat from the sun using this circulating fluid. Systems are either open loop, circulating water that will be used by the household through the system, or closed loop, re-circulating heat transfer fluid in isolation through the system. In cold climates, anti-freeze mixtures are generally needed. Two types of solar collectors used in either closed-loop or open-loop systems are: I
Flat plate – insulated, weatherproofed panels that contain a dark absorber plate under a glass or plastic layer. The panels are designed to let sunlight in while preventing heat energy from escaping. Serpentine metal pipes run through the panels to transfer the collected solar heat to the circulating fluid, reaching temperatures of nearly 160° Fahrenheit (F).
PAGE
16
HIGH - PERFORMANCE NEW HOMES
I
Evacuated Tube – these collectors consist of an inner metal tube
Figure 8: Pool Solar Heating
contained in a vacuum and bounded by an outer glass tube. Evacuated tube collectors have higher efficiencies than flat plate and fluids can reach 170–350°F temperatures. While more efficient, this technology is more expensive and generally reserved for commercial applications or residences where hot water also is used for heating.
Solar Pool Heating Source: NREL, DOE
Solar pool heating is, perhaps, the most cost-effective use of solar energy in California and is already fairly common. Solar pool-heating collectors use unglazed, inexpensive low-temperature collectors and operate at temperatures slightly warmer, approximately 20°F, than the surrounding air temperature. Such systems are used to extend the pool season, and are generally more cost effective than both gas and heatpump pool heaters.
Active Solar Heating Homeowner Rights
Active solar heating systems harvest the sun’s energy to heat either a
State laws in California protect
liquid or air that is pumped or ducted inside the home. In a liquid
homeowner access to the the sun for
system, the fluid provides space heating similar to a boiler system. Air
solar systems. For more information on
systems work much like furnaces, and the hot air warmed in the panels
solar-related information and programs,
is frequently delivered directly to the space. Solar heating systems work
visit www.gosolarcalifornia.ca.gov.
only when sunshine is present and require electricity to power fans or pumps. As a result, these systems are typically designed in combination with traditional heating systems to provide back-up or supplemental heating. Operational savings can be significant, especially in areas with long heating seasons and a multitude of sunlight.
Solar Electric Solar electric systems convert sunlight into electricity. Although the systems have a relatively high first cost, the technology is non-intrusive and easily integrated into residential construction. PV systems require little to no maintenance, and are very reliable. Such systems are frequently placed near the peak of a south-, southwest-, or west-facing roof locations with reliable, year-round solar exposure. Systems are comprised of the following components:
HIGH - PERFORMANCE NEW HOMES
PAGE
17
PV Energy Payback
I
Solar panels, which convert sunlight directly to electricity.
Although photovoltaic technology requires
Photovoltaics are made of silicon, have no moving parts, and produce
energy to make the modules, frame, and
direct current (DC) electricity. In addition to solar panels, solar tiles
balance of system work; assuming a
are available that integrate directly into the roof material, supplanting
30-year system life, PV technologies
some of the traditional roofing cost.
provide a net gain of 26 to 29 years of
I
emissions-free electricity generation
Inverter, typically a wall-mounted box, which converts the DC electricity into alternating current (AC) for household uses.
making it one of the most environment friendly technologies available.
I
Electrical panel, which is typical for all houses, routes the electricity from the inverter into the house.
www.nrel.gov/docs/fy04osti/35489.pdf I Source: NREL PV FAQs
Net utility meter, which meters home energy use, turns backwards or digitally reduces metered consumption anytime the PV production exceeds home energy use.
I
Internet-based performance information provided by many solar electric system manufacturers. Homeowners may be given on-line access to view the real-time production of their PV systems.
PV system installations may be eligible for incentives from the state of California and tax credits from the federal government. Homebuilders and their contractors also should verify local code and permit requirements for PV systems. City inspectors and the electric utility may require special documentation, inspections, and permits. Some PV manufacturers provide turnkey services to home builders, meaning the manufacturers design the system and roof location, hire insured installers, work with the city inspectors and the electric utility, and submit documentation for available incentives. PV manufacturers typically provide product warranties, in some cases up to 20 years. Also, certified installers may provide additional system warranties, typically five years. Most residential systems are typically two to four kilowatts in size, and can be expanded over time. In general, a solar system should not be sized to produce more than a home’s annual electric needs. Net metering agreements in California typically allow customers to gain credit based on time-of-day billing rates. As a result, customers are able to get the retail value for the electricity they generate. However, utilities are not required to purchase any excess electricity produced during a 12-month
PAGE
18
HIGH - PERFORMANCE NEW HOMES
period. In a tiered rate pricing scheme (see Figure 9), the more electricity
The state of California’s “Go Solar”
used, the higher the unit cost of the electricity. Therefore, a smaller solar
initiative wants to place 3,000 MegaWatts
system might be the most cost effective because the electricity generated
of solar-produced electricity systems on
will offset the most expensive kilowatts, allowing the homeowner to
rooftops by 2017, which would represent
purchase lower cost electricity to meet the remaining need.
solar systems on one million homes (www.gosolarcalifornia.ca.gov ).
Figure 9: Tiered Rate Tariff for electricity prices shows the increase in the unit cost of electricity as more energy is consumed
Available on the Go Solar California website is a California Energy Commission Photovoltaic Calculator (CECPV Calculator.) This tool provides detailed hourly calculations for eligible inverter and collector product combinations using climate data for
Source: SCE
the relevant California Climate zone. It estimates monthly and annual
Since PV systems generate electricity during daytime hours, solar helps
production for the specified system,
all members of the community by reducing the electric demand on the
and calculates the appropriate incentive
electric utility infrastructure at its peak, which is typically summer
amount. Other tools and resources are
afternoon hours. Most importantly, electricity generated by a
available on the Go Solar California
photovoltaic system is clean, reliable, and renewable.
web site.
Energy-efficient Equipment After the design and building envelop have been optimized, and solar systems evaluated, the final step is to meet the remaining loads as efficiently as possible. Today’s homeowners employ a myriad of large and small appliances, home theatre systems, computers, communication devices, HVAC, and lighting equipment. Reducing electric loads throughout the house is essential to maximizing the benefit gained from the high-performance strategies and PV systems. Figure 10 is a general breakdown of electricity use in a typical California home. It indicates that lighting and miscellaneous loads, consisting mainly of plug loads, account for more than half of household electricity use. Cooling equipment accounts only for approximately 14 percent. Much of the electronic equipment in a home consumes electricity even when in the “off ” position. These loads are typically referred to as
HIGH - PERFORMANCE NEW HOMES
PAGE
19
Common in many residential applications, dimmers allow occupants to lower the room lighting as desired,
Figure 10: California Household Electricity Use This graph does not include gas consumption, which typically is used to provide heat and hot water.
which extends the life of the bulb while
Household Energy Use - California
saving energy. Though, lamps should be
Refrigeration
checked for dimming compatability. Ventilation
Timers turn lights on and off at
8%
11%
Office Equipment Heat/Cook/Hot Water Cooking 3% 3% 5%
pre-designated times and are particularly effective for exterior lighting
Cooling
14% 37%
applications. Available for interior and 19%
exterior applications, sensors turn on or dim lights as needed using technology
Miscellaneous
Lighting
which senses movement, heat, or light levels. For best practices in lighting design and control, reference the California Lighting Technology Center Residential Lighting Guide.
Source: California Energy Commission www.fypower.org/res/energy.html
“parasitic loads.” Noticeable energy savings can be achieved from unplugging instead of just turning off the equipment when it is not in use. Efficient power adaptors or transformers such as those required for computers and cell phones, time-based plug-in controls, and power
cltc.ucdavis.edu/images/news/
strips with motion sensors are on the market—all assist in reducing
Title24/lighting-design-guide-
parasitic loads. Additionally, ENERGY STAR-certified electronics are
version-2.pdf
widely available that use up to 60 percent less energy while providing the same level of performance.
Appliances National standards for energy-efficient appliances have improved dramatically over the last decade. An ENERGY STAR-qualified appliance typically uses 10 to 50 percent less energy and water than standard models. The best approach for ensuring energy efficiency is to select ENERGY STAR-qualified products including refrigerators, dishwashers, washing machines, dehumidifiers, water heaters, and ceiling fans. ENERGY STAR Guide labels provide quantitative information about an appliance’s projected energy consumption.
Lighting As seen in Figure 10, lighting typically accounts for more than a third of all electricity use in a home. For California, new homes must meet PAGE
20
HIGH - PERFORMANCE NEW HOMES
Title 24 standards, which have specific requirements for high efficacy
An LED product attracting attention
lighting and controls. Homebuilders and designers can take advantage
in residential applications is the recessed
of ENERGY STAR-qualified lighting products and new light-emitting
downlight kit. The off-the-shelf recessed
diodes (LED) technologies coupled with motion sensors, dimmers, and
downlight is dimmable, consumes 80
time-based controls to meet and exceed Title 24 standards for both
percent less electricity than an
indoor and outdoor applications.
incandescent, 45 percent less than a CFL, and lasts up to 50,000 hours. Both 4-inch
ENERGY STAR-qualified lighting products use approximately 75 percent less energy than standard lighting, while also producing up to
and 6-inch diameter products are available from various manufacturers.
75 percent less heat and lasting up to 10 times longer. For example, the average 100-Watt incandescent bulb costs about $.01 per hour to operate and has a rated life of 1,500 hours. The equivalent 27-Watt compact fluorescent light (CFL) costs $.0025 per hour and has a rated life of 12,000 hours. In general, installing CFLs rather than incandescents can provide paybacks of three years or less in medium to high-usage areas. It is important to note that lighting technologies should always be properly matched to the application. Currently, CFLs can overheat in enclosed recessed fixtures that are not specifically designed and rated for CFL use. Also, the use of CFLs in dimming applications is extremely limited at this time. However, for ambient and task lighting, CFLs and linear fluorescent are energy-efficient options. Fluorescent lighting is slightly different in appearance than incandescent lighting, and has a slightly longer “warm-up” time due to the technology used. Visual performance in lighting is characterized by Correlated Color Temperature (CCT), which is given in Kelvin and describes whether the light appears ‘warm’ or ‘cool,’ and Color Rendering Index (CRI), which is the ability to reveal the “true” relationship between colors. For both categories, fluorescent lighting has made significant improvements. Fluorescents lamps now have CCTs of 2700 to 3000 Kelvin, which provide a warm glow similar to incandescent lamps. Also, fluorescents are available with CRIs of 70 to 90, based on a scale of 1 to 100, while incandescents maintain CRIs of 100. Cold cathode fluorescent lamps (CCFLs) is another viable technology for recessed lighting that also is used for neon lighting and backlighting LED computer screens. The “cold” in cold cathode reflects the fact that
HIGH - PERFORMANCE NEW HOMES
PAGE
21
by operating at a higher voltage, the lamp avoids the use of a heating filament. As a result, a CCLF is up to 30 percent more efficient than a comparable hot cathode fluorescent lamp (CFL), and lasts up to two times longer. Other advantages are that CCFLs are fully dimmable with reduced energy consumption resulting directly from reduced input, are excellent white light sources, and provide predictable performance. Finally, light emitting diode (LEDs) is an emerging technology that is becoming available to the residential market in the form of LEDbased downlights, porch and yard lights, ceiling fans, under-thecounters lights, wall washers, and task lights. These products show promise for exceptionally low energy use and extensive lamp life. However, these novel products typically are more expensive. LEDs may achieve CRIs from 80 to 92 and CCT ranging from 2700 to 3500 Kelvin. LEDs are highly “tunable� with respect to color temperature and offer a variety of color changing products and dimming capabilities. For whatever type of lighting technology selected, high-quality performance requires proper lighting design. Key points for energyefficient lighting design are:11 I
Specify the desired light level and strive to not over-light a space. Using high-efficacy lights, it may be possible to produce the same light level using fewer fixtures. Efficacy may be expressed in lumens per Watt.
I
Ultimately, lighting quality rather than lighting quantity is what counts. The luminous environment is most affected by the distribution, color, and rendering quality of the lighting system. Room geometry and the color of interior objects also play a role.
I
For occupancy sensors and dimmers, correct application and installation are critical. In general, bathrooms, storage areas, garages, and laundry rooms are effective applications for occupancy sensors. Dimmers are more appropriate for high traffic areas. Also, sliding dimmers and toggle switches provide different effects; homeowner should choose the appropriate technology for the desired effect.
PAGE
22
HIGH - PERFORMANCE NEW HOMES
HVAC Systems A growing number of energy-efficient options are now available for smartly cooling and heating homes. Efficiency improvements for HVAC equipment and advanced control strategies are more widely available and affordable in the residential market. Cooling efficiency gains are important particularly in California where summer temperatures and cooling loads play a significant role in the peak energy demands placed on the utilities.
Energy Efficiency Terms The ENERGY STAR program provides many tips for proper selection of cooling and heating equipment. Most systems are rated using Seasonal Energy Efficiency Ratio (SEER) as a measure of equipment energy efficiency over the cooling season. Annual Fuel Utilization Efficiency (AFUE)
Cooling Innovative cooling strategies worth consideration include:
is a measure of the amount of fuel converted to space heat in proportion to the amount of fuel entering the furnace.
I
High Efficiency Air Conditioning. In general, central air conditioners are more efficient than window units, although proper sizing is critical to performance. California’s Title 24 2005 Standards require air conditioners to have an seasonal energy efficiency ratio (SEER) of 13 or above, although units are now available with SEERs reaching
A furnace with an AFUE of 90 could be said to be 90 percent efficient. Furnace efficiency ratings do not take into account duct losses, which may be as high as 35 percent.
nearly 17. Additional steps towards improving efficiency include
I
placing the condensing unit in a shaded area rather than in the direct
The EF (Energy Factor) is a measure of
sun. Designing for multiple zones is recommended, such as upstairs
the annual energy efficiency of water
and downstairs, to allow the operation to more effectively mirror
heating systems.
occupant usage and cooling loads.
In all cases, the higher the number,
Economizers. Mechanical devices added to air-conditioners that provide significant energy savings by relying on outside air to cool a home when
the greater the overall efficiency of the system.
the outdoor temperatures are sufficiently cool. For example, nighttime or early morning hours provide optimal times to use economizers. However, if not properly maintained or controlled, economizers can result in decreased energy savings12 by staying in operation too long. I
Evaporative Cooling. This strategy is a cost-effective means to provide cooling and is best used in dry climates. Quite simply, evaporative cooling uses the evaporation of water to cool air, using up to 25 percent less energy than a conventional air conditioner. Since water is the medium for heat exchange, the use of environmentally harmful refrigerants is avoided. Designs include direct, indirect, and two stage (or indirect/direct). Residential evaporative cooling systems are high-
HIGH - PERFORMANCE NEW HOMES
PAGE
23
performance alternatives to conventional air conditioning systems, and can be either individual units or ducted systems in a house. Local water quality makes a significant impact on maintenance and longevity of the system. Finally, residential evaporative cooling systems typically require coordination with operable windows or outside vents to provide balanced pressurization within the residence. I
Heat Pumps. Rather than generating warmth or coolth, heat pumps use electricity to move heat from a cool space into a warm space, making the cool space cooler and the warm space warmer. In the winter, these systems move heat from the (cool) exterior to warm the interior. In the summer, heat pumps run in reverse and remove the heat from the (cool) interior and expel it to the warm exterior. Heat pumps are particularly efficient in warmer climates, but are not effective in climates that experience extreme cold in the winter.
I
Ductless, Mini-Split-Systems. Mini-split heat pumps have one outdoor compressor/condenser unit and typically several indoor airhandling units serving multiple zones. Heat is moved using a transfer fluid. Such a system is particularly appropriate for a house without forced-air since only pipes rather than ducts supply the air handlers.
I
Geothermal Heat Pumps. These units use the ground, surface water, or underground water as the heat source and sink. Underground or submerged pipes temper a circulating fluid using the ground’s nearly constant year-round temperature. Significant efficiencies can be gained in extreme climates. These systems typically have high first costs since they require underground piping be installed.
I
Thermal Storage. Residential thermal storage systems are available that produce and store ice at night when utility costs are low and condenser efficiency is the highest, and circulates refrigerant piping through the ice during the day to produce consistent cooling. Typically, the systems supplement conventional air conditioning systems, using less or the same amount of energy. Time-of-use rates from the utility are required for these systems to be cost-effective, because thermal storage units may eliminate up to 95 percent of onpeak air conditioning demand.
PAGE
24
HIGH - PERFORMANCE NEW HOMES
Heating In many California homes, heating is less of an energy driver than cooling. Nevertheless, several system alternatives are available which provide increased efficiency. I
Active Solar Heating. (See Solar Technologies section) Active solar heating, either liquid or air, can be used in locations that have a high number of sunny days during heating season.
I
Furnaces and Boilers. Many homes are heated either using a furnace that distributes heated air through ducts, or boilers that distributes heated water through pipes. Both furnaces and boilers are available in high efficiency models. Efficiency for both is measured in AFUE. High efficiency systems, which typically require closed combustion, achieve AFUEs in the range of 90 to 97 percent.
I
Electric Resistance. While electric resistance typically converts 100 percent of the electricity into heat, in general this is an energy intensive and costly way to heat a space. If electricity is the favored supply energy, heat pumps are preferable in most climates and typically reduce electricity use for heating by more than 50 percent.
I
Heat Pumps. (See Cooling section) Absorption heat pumps exist for largescale residential, which are driven by natural gas, propane, solar-heated water, or geothermal-heated water. Heat pump systems are available that generate hot or cold water, and can be used in conjunction with radiant systems.
I
Radiant Heating. Radiant heating systems transfer heat, typically using water, although air or electric resistance can be used. The heat is sent directly to the floor, wall, or ceiling panels, which transfer the heat to the objects in a room through radiative transfer. Radiant floors also transfer heat based on natural convection. Such floors should remain exposed. Any material that insulates the floor, such as carpet, impedes the effectiveness of both the radiant and convective heat transfer.
In all cases, proper HVAC equipment sizing is extremely important. When a homebuilder or owner has carefully designed the home to take advantage of the local climate and reduced energy loads, using rule-ofthumb sizing for HVAC systems undermines energy savings and can HIGH - PERFORMANCE NEW HOMES
PAGE
25
Title 24 2008 standards for new homes
affect indoor comfort. A properly sized system will run the proper
will require mechanical ventilation
amount of time at optimum efficiency, while maintaining desired
systems. With new construction
temperature and humidity levels.
practices in the state becoming more stringent with a focus on energy efficiency, homes are becoming less
Additional Energy Savers Other strategies that assist in energy efficiency include the following.
drafty. The new requirement for mechanical ventilation helps to ensure
I
in under-ventilated spaces below dark roofing. Sufficient attic
proper indoor air quality. The mechanical
ventilation can decrease energy use especially when air-ducts or
ventilation can be provided simply by
HVAC systems are located in the attic.
installing a supply or exhaust fan in the bathroom, ducted to the outside, that will
Attic exhaust. Extreme temperatures may occur in attics particularly
I
continuously ventilate the whole house.
Ceiling fans. Suitable for several California climate zones, ceiling fans do not lower the actual air temperature, but increase comfort by providing air movement at a fraction of the cost of air-conditioning.
I
Ventilation fans. ENERGY STAR-qualified ventilation fans are available for kitchen, bathroom, and utility room applications. Some fans that include lighting use 70 percent less energy on average than standard models. These fans also are more than 50 percent quieter than standard models. The fans have high performance motors and improved blade design, providing better performance and longer life.
I
Smart Thermostats. Features such as time-based, two-staged, or lock-out controls allow owners to better manage their heating and cooling use. Homeowner can save around 10 percent a year13 on heating and cooling bills by simply setting back a thermostat 10 to 15 degrees for eight hours. Future thermostats may be outfitted with technologies that allow utilities to change the temperature setting remotely to limit peak demand and energy use for a community of homes under dire circumstances.
I
Tankless water heaters. Heating water directly without the use of a storage tank, these heaters avoid standby losses and heat only the water needed to meet demand. Family size and hot water use greatly influence the cost effectiveness of these systems.
I
Whole House Fans. Pulling air from open windows and exhausting it through attic or roof openings, whole house fans can provide houses with 30 to 60 air changes per hour and are far more economical than conventional HVAC systems.
PAGE
26
HIGH - PERFORMANCE NEW HOMES
Table 4: Summary of Heating and Cooling Systems System Type
Pros
Cons
Climate Specific Notes
Recommended High Efficiency
Cooling Central Air Conditioners
Conventional system; somewhat affordable
Energy intensive. Less efficient the hotter it is outside. Drive up demand
Standard for inland California homes
Natural Ventilation/Fans
Low cost
Cannot cool below ambient
Very effective in moderate climates
Evaporative Cooling
Significant energy savings No harmful refrigerants Inexpensive to install
Maintenance can be high and is a function of the quality of water used
Very effective in hot/dry climates
Heat Pumps
Significantly more efficient than conventional systems since heat (or “coolth”) is moved rather than generated
Can have problems with leaks, low airflow, and incorrect refrigerant charge
Efficient at providing cooling in hot climates
Economizers
Potential for “free” cooling
Improper controls or maintenance results in poor performance
Good in climates with high diurnal temperature swings
Radiant
Even, pleasant heat source
Slow response time. High first cost, requires exposed thermal mass
Furnaces / Boilers
Conventional systems
May require ducting
Standard for California homes with heating loads
Electric Resistance
100% of electricity converted to heat
Energy intensive and very expensive and to operate
Only advisable in areas with minimal heating loads
Heat Pumps
Can reduce heating energy use by 30 to 40 percent
Heating setbacks may not be as effective. Thermostats programmed for heat pumps are available
Very poor efficiency in extremely cold climates
> SEER 13
ENERGY STAR
> HSPF 8 > SEER 14
Heating
> AFUE 90%
> HSPF 8 > SEER 14
Source: Architectural Energy Corporation
Case Study In Lancaster, California, one developer plans to build multiple highperformance homes, designed to exceed Title 24 2005 standards by more than 35 percent. The energy efficiency measures include increased wall insulation from R-19 wall to R-21, upgraded window products from dual pane to triple pane, and an upgraded HVAC system from 92 percent AFUE and 14 SEER to 95 percent AFUE and 16 SEER. Solar electric systems are planned with the PV panels integrated into the south- and west-facing roof tiles. Three different house plans (A, B, C) with varying elevations and
HIGH - PERFORMANCE NEW HOMES
PAGE
27
facades have been designed, and the plans have qualified for California’s New Solar Home Partnership incentives along with SCE’s New Homes Program. Three PV systems, sized 2.3 kW DC for plan A, 2.6 kW DC for plan B, and 2.8 kW DC for plan C, use a 23-degree tilt, which is typical for a 5:12 roof pitch. Table 5 summarizes the energy efficiency features, PV systems, costs, and savings for each plan. The incremental cost estimates include the incentives and tax credits.
Table 5: Case Study Feature Summary Features
Conventional T-24 Home
High-performance Home
Attic Insulation
R-38 / R-19 at Furnace platform
R-49 / R-19 at Furnace platform
Wall Insulation
R-13 (2x6)
R-21 (2x6)
Floor Insulation (Abv Grg/Cant)
R-19
R-30
Low Air Infiltration
No
Yes
Radiant Barrier
No
Yes
Quality Installation of Insulation
No
Yes
Glazing (U-factor and SHGC)
0.45 U-factor 0.45 SHGC
SL (U=0.20, SHGC = 0.22), SH (U=0.20, SHGC=0.22), FX (U=0.16, SHGC = 0.24), Patio Dr (U=0.33, SHGC =0.34), French Dr (U=0.40, SHGC = 0.40)
HVAC Efficiencies / Tonnage
80% AFUE 13.0 SEER
95% AFUE 16.0 TXV SEER (up to 1 ton reduction in HVAC system)
Duct Insulation / Location
R-4.2 @ Attic
R-6 @ Buried in Insulation
Water Heater
50 Gal EF = 0.60
2 Tankless EF = 0.82 w/ R-4 pipe insulation on all major trunks
Lighting
2005 Package
2005 Fluorescent Lighting Package
Dryer
Electric
Gas
PV System Size
None
2.3 kW DC (Plan A) 2.6 kW DC (Plan B) 2.8 kW DC (Plan C)
Savings over T-24 (includes gas usage)
N/A
45.3% (Plan A) 46.6% (Plan B) 46.0% (Plan C)
Annual Electric Savings
N/A
61% (Plan A) 64% (Plan B) 64% (Plan C)
Total Peak Energy Demand / Demand Reduction
7.40 kW (Plan A) 8.98 kW (Plan B) 9.24 kW (Plan C)
2.8 kW (Plan A) / 62% Demand Reduction 3.35 kW (Plan B) / 62% Demand Reduction 3.0 kW (Plan C) / 67% Demand Reduction
Total Incremental Cost
N/A
$12,610 (Plan A) $13,024 (Plan B) $13,720 (Plan C) Source: California Energy Commission, Public Interest Energy Research, Contract #500-04-024
PAGE
28
HIGH - PERFORMANCE NEW HOMES
Analyses showed a positive cash flow for prospective homeowners with the energy efficiency package combined with the PV system. The incremental cost, when wrapped into a 30-year mortgage at seven percent interest, yielded a monthly house payment that was offset by the monthly utility bill savings. The result is a positive cash flow ranging from $58 for plan A to $88 for plan C per month beginning in year one. Cash flows14 are summarized in Table 6.
Table 6: Case Study Cash Flow Summary First Year Monthly Cash Flow Case Study Plan A
Plan B
Plan C
T-24 Home Monthly Energy Bill=
$265.44
$303.05
$316.70
High-performance Home Monthly Energy Bill=
$123.20
$132.00
$137.37
Total Monthly Energy Bill Savings=
$142.24
$171.05
$179.33
Amount Borrowed (Total Incre.Cost)=
$12,610
$13,024
$13,720
Interest=
7%
7%
7%
Monthly Payment on Incre. Cost=
$83.90
$86.65
$91.28
Monthly Cash Flow=
$58.34
$84.40
$88.05
Source: California Energy Commission, Public Interest Energy Research, Contract #500-04-024
Conclusion Integrated, climate-specific design, solar technologies, and energy-efficient equipment play significant roles in designing, building, and operating high-performance homes. Today, many high-performance homes are reducing utility bills 40 to 60 percent while increasing comfort. In the future, additional strategies and technologies will go even further to costeffectively decrease energy bills and provide environmental benefits for new homes. Construction practices will continue to improve; third-party inspections will become more common; and innovative energy-efficient technologies will gain greater popularity and become widely available. Prices for solar energy systems also will continue to decrease. With these advancements, high-performance homes are well positioned to become common-place for new construction in California and across the country.
HIGH - PERFORMANCE NEW HOMES
PAGE
29
FOR MORE INFORMATION Guides and Resources A Household Guide to Building Green, Citizen’s Environmental Coalition, www.resourcesaver.org/file/toolmanager/CustomO16C45F87831.pdf Building America Best Practices Series, U.S. Department of Energy Energy Efficiency and Renewable Energy, www.eere.energy.gov/buildings/building_america/ Database of State Incentives for Renewables and Efficiency (DSIRE), www.dsireusa.org Environments for Living, www.eflhome.com Flex Your Power, www.flexyourpower.org New Home Construction, Green Building Guidelines, Build It Green, www.BuildItGreen.org The Green Home Guide, LEED for Homes, www.greenhomeguide.org The California Green Builder Program, www.cagreenbuilder.org
Residential Software Tools Free software tools are available to aid in energy-efficient, climate responsive residential design: CECPV Calculator – estimates kWh production for specified solar systems; www.gosolarcalifornia.ca.gov/nshpcalculator/ Energy-10 – helps identify cost-effective, energy-saving measures for lowenergy buildings; www.nrel.gov/buildings/energy10.html Home Energy Efficient Design (HEED) – whole-building energy design tool that helps consumers make energy-efficient design and remodeling decisions; www2.aud.ucla.edu/heed Insulation Zipcode Tool – tells the most economic insulation level for a home; www.ornl.gov/~roofs/Zip/ZipHome.html FlexYourPower Resource Library – provides up-to-date information on various tools; www.flexyourpower.org/res/tools/resources.html
PAGE
30
HIGH - PERFORMANCE NEW HOMES
Notes 1
Farhar, B.C. and T.C. Coburn. 2006. A New Market Paradigm for Zero-Energy Homes: The Comparative San Diego Case Study. NREL/TP-550-38304-01. Prepared by the National Renewable Energy Laboratory for the U.S. Department of Energy. www.nrel.gov/docs/fy07osti/38304-01.pdf Baccei, Bruce. 2006. Impacts of Zero Energy Homes on Buyers and Owners. Solar 2006 Conference Proceedings, edited by R. Campbell-Howe. American Solar Energy Society, Boulder, CO. Coburn, Timothy, Barbara Farhar, and Lew Pratsch. 2006. Comparative Analysis of Utility Consumption and Costs of NearZEHs and Comparison Homes in California. In Proceeding of the 2006 ACEEE Summer Study on Energy Efficiency in Buildings, Washington, D.C.
2
Energy Information Administration, Emissions of Greenhouse Gases in the United States 2005, www.eia.doe.gov/oiaf/1605/ggrpt/summary/carbon.html
3
A term coined by Amory Lovins in 1989.
4
Features of ENERGY STAR Homes; www.energystar.gov/index.cfm?c=new_homes.nh_features
5
Pacific Gas & Electric New Homes Features www.pge.com/res/energy_tools_resources/efficient_new_homes/ features/
6
Climate Zone Map; www.pge.com/003_save_energy/003c_edu_train/pec/toolbox/arc h/climate/pdfs/California_Climate_Zones_01-16.pdf
7
Home Energy Briefs: #9 Whole System Design; Rocky Mountain Institute, 2004.
8
ENERGY STAR Duct Sealing Brochure www.energystar.gov/ia/products/heat_cool/ducts/DuctSealingBro chure04.pdf
9
ENERGY STAR High Performance Windows www.energystar.gov/ia/new_homes/features/HighPerformanceWi ndows1-17-01.pdf
10
Del Chiaro, Bernadette & Telleen-Lawton, Timothy, Solar Water Heating, How California Can Reduce Its Dependence on Natural Gas, Environmental California Research & Policy Center, April 2007.
HIGH - PERFORMANCE NEW HOMES
PAGE
31
PAGE
32
11
For additional information see the Residential Lighting Design Guide, California Lighting Technology Center, www.cltc.ucdavis.edu
12
Design Brief: Economizers. EnergyDesignResources, www.energydeisngresources.com/docs/db-02-econommizers.pdf
13
Thermostats and Controls, www.eere.energy.gov/consumer/your_home/space_heating_coolin g/index.cfm/mytopic=12720
14
ZENH Cash Flow: energy bills were analyzed based on SCE Schedule D tier rate structure: www.sce.com/CustomerService/QuickAnswers/Rates/
HIGH - PERFORMANCE NEW HOMES
Energy Design Resources provides information and design tools to architects, engineers, lighting designers, and building owners and developers. Our goal is to make it easier for designers to create energy efficient new nonresidential buildings in California. Energy Design Resources is funded by California utility customers and administered by Pacific Gas and Electric Company, Sacramento Municipal Utility District, San Diego Gas and Electric, Southern California Edison, and Southern California Gas Company, under the auspices of the California Public Utilities Commission. To learn more about Energy Design Resources, please visit our Web site at www.energydesignresources.com. This design brief was prepared for Energy Design Resources by Architectural Energy Corporation.
06/2008