1、Gas Use Roadmap to Zero Energy Homes Ryan Kerr Doug Kosar Member ASHRAE ABSTRACT The objective of this paper is to report on an analysis of natural gas usage scenarios in high performance homes through to net-zero energy. The technical analysis of energy usage trends led into investigations regardin
2、g the impact these homes have on gas and combined utilities, equipment manufacturers, builders, and homeowners. To best address the spectrum of utilities and building markets, a national Zero Energy Homes research methodology was used as the platform for analysis. The U.S. Department of Energys (DOE
3、) Building America program has been researching Zero Energy Homes for over 10 years. The programs least cost approach was used to develop technology pathways for high performance homes in four major climate regions. Results suggest that gas use in high performance homes, especially in cold climates,
4、 is reduced at an accelerated rate compared to electricity. In a highly efficient Chicago design, the simulated gas usage was reduced by 73 percent, whereas electricity was reduced by only 51 percent. This trend holds true for most homes built above the baseline as major appliances and miscellaneous
5、 plug loads (e.g. consumer electronics) are reduced at a lesser rate than space and water heat. While Zero Energy Homes may be far away in many regions, 30-50 percent whole house energy saving high performance homes may be a near-term reality. In 2008, ENERGY STAR New Homes represented 17% of the na
6、tional market and that number is growing. While most investigations of high performance homes or zero energy homes focus on electric utilities, this analysis suggests that the accelerated gas use reductions make the impacts on gas utilities a more near-term reality. Today, in areas where high perfor
7、mance homes have a real market presence, significantly reduced gas utility revenue combined with emerging electric alternatives are eroding the traditional economics of gas main and service connections. This paper will explore the role natural gas plays in the push toward zero energy homes, includin
8、g high efficiency equipment trends and utility attachment policies and revenue scenarios. INTRODUCTION AND BACKGROUND There is an increasing focus and push toward zero energy homes by federal and state governments, utilities, utility commissions and code making bodies. This push is being met by incr
9、easing pull from consumers as the value of energy efficiency, green building and environmental preservation take root. This report will consider the implications of a significant push toward high performance homes, eventually Zero Energy Homes, on the gas industry. There are several trends driving h
10、igh performance home building and further market penetration, including: Improving Codes (e.g. California Title 24, Washington State, International Energy Conservation Code (IECC) Rate Payer Efficiency Programs Tax Rebates and Incentives (e.g. Federal, State, Municipal) Market Pull (e.g. ENERGY STAR
11、, U.S. Green Building Councils LEED for Homes) Residential Energy Research Programs (e.g. Building America program) LV-11-C041340 ASHRAE Transactions2011. American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Published in ASHRAE Transactions, Volume 117, P
12、art 1. For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAES prior written permission.To best address the spectrum of utilities and building markets, a national Zero Energy Homes research methodology used by the
13、 DOE Building America program was adopted as the platform for analysis. A net-zero energy home is defined as a residential building that combines energy efficient envelope design and equipment selection with on-site renewable energy production, such as solar electric and/or solar thermal systems, to
14、 achieve a net-zero annual energy consumption on a source energy basis. This concept has been embraced by the DOE Building Technologies Building America (BA) program as its long term goal (until early 2010, when emphasis shifted to retrofit). Currently, the programs baseline for new construction is
15、30% energy savings, and is at 40% whole house energy savings (before solar electric) in most climate zones. Whole house energy savings are calculated relative to the Building America Benchmark (Benchmark). The Benchmark is roughly equivalent to a 1993 Model Energy Code (MEC) home. This means that a
16、new code home, especially in places like California or Washington, is better than the benchmark. However, the benchmark is important because it offers a constant reference point to compare homes longitudinally. To design cost effective homes, Building America uses a “least cost” design approach. Thi
17、s approach uses a minimum energy code compliant research homes annual mortgage payment plus yearly gas and electric utility costs as the baseline for cost-effectiveness. In this respect, as efficiency measures are added and included in the cost of the home, the mortgage portion of the annual costs r
18、ise, but the utility portion is reduced. As low cost features, such as a compact fluorescent lights (CFL), are added, annual costs are reduced, but as efficiency measures become more expensive and their annual energy return diminishes, the annual mortgage cost associated with these features outweigh
19、s the utility bill savings. Using this methodology, it is imperative to introduce only the most cost-effective features for any given home. RESEARCH METHODOLOGY The technical building energy analysis underlies all the results and recommendations of this report. Rigorous modeling was performed on sin
20、gle-family home designs to develop regionally appropriate results. The ultimate goal of the analysis is to identify cost-effective technology packages using regional, technical, and cost appropriate efficiency measures that will demonstrate the role for natural gas in Zero Energy Home construction.
21、Photovoltaics were not included in the analysis because they are currently not included in whole house savings in the Building America Program. There are five major Building America climate zones, four of which see the majority of new home starts and existing home retrofits. For each climate zone, a
22、 major metropolitan area was selected that represented both the climate and economic opportunity for new home builders. The four identified climate zones and cities are: Cold- Chicago; Mixed Humid- Atlanta; Hot Humid- Houston; and Hot Dry/Mixed Dry- Phoenix. With the cities selected, it was then pos
23、sible to identify regionally appropriate homes for analysis. Building America projects and reports, conversations with national builders, the ENERGY STAR program, regional building styles, and regional codes were used to determine home styles and base features. For example, foundation types vary dep
24、ending on region, in Chicago basements are the predominant foundation, in Phoenix, its slab on grade. Beyond the foundation differences, all homes share the following characteristics: 2,500 sq ft, two-story, vented attic, three bed, two bath, and 15% finished floor area (FFA) glazing area. With the
25、city and home types selected, it was then time to design the homes for maximum cost-effective energy efficiency. The complexities involved with modeling building energy efficiency and identifying appropriate costs (both labor and material) will not be documented in detail. Rather, the general approa
26、ch is discussed below. There are two main programs which were used to model the energy consumption and savings of the proposed homes. EnergyGauge USA, developed and supported by the Florida Solar Energy Center (FSEC), was the primary building energy simulation tool used for analysis. To supplement a
27、nd validate the EnergyGauge USA analysis, The Building Energy Optimization Program (BEopt) was used. BEopt, developed and supported by the National Renewable Energy Laboratory (NREL) for Building America teams, is specifically designed to find optimal residential building designs along the path to Z
28、ero Net Energy. Reliable cost information is difficult to find, and once identified has a short “shelf life.” As a general rule, the author has developed a hierarchy of cost information sources. 2011 ASHRAE 3411. Actual builder costs or subcontractor/distributor bids 2. Representative builder (size
29、and region) costs or subcontractor/distributor bids 3. National distributors or contractors price estimates or bids 4. National database information (e.g. RS Means) Cost information was generated assuming the builder had some familiarity with high performance building. Perhaps the builder had been c
30、onstructing ENERGY STAR homes, and then constructed a BA prototype home before building a small 20 to 100 home community at proposed savings level. This cost methodology was selected to represent a production builders entrance and commitment to high performance home construction, typically a prerequ
31、isite for success. Building America uses national source to site multipliers; 3.365 for electricity and 1.092 for gas. Thus, every kWh of electricity consumed at the site is multiplied by 3.365 to account for the total primary energy required to power the end use equipment. HIGH PERFORMANCE HOMES Fo
32、r our selected climate zones and cities, we will focus on two savings levels; 30% and 70% whole house savings. Given the hundreds of combinations and savings levels, these two levels were selected to represent the baseline high performance home (30%) and the most aggressive high performance home (70
33、%) possible using todays technologies and no on-site electricity generation1Figure 1 shows the summary least cost analysis for each climate zone and city selected. For comparison, a selling price of $250,000 was used for each home. However, all other variables are local, including utility rates, cli
34、mate, and efficiency measure and installation costs. Despite regional differences, dominated by heating and cooling loads, the least cost point for most climates was at 30%. However, as demonstrated in Chicago, the climates with higher heating loads require more expensive efficiency measures to reac
35、h further savings. So the investment to reach 50%, 60%, or 70% was incrementally more than in the cooling dominated climates of Phoenix, Atlanta, and Houston. . Given space limitations, Chicago will be used as the example city to demonstrate the analysis results. $22,000$22,200$22,400$22,600$22,800$
36、23,000$23,200$23,400$23,600$23,800$24,0000% 10% 20% 30% 40% 50% 60% 70% 80%Annual CostMortgageSHGC) 0.39/0.32 0.35/0.51 0.18/0.30HVAC SYSTEM:A/C: SEER 10 14 18Furnace (AFUE) Gas- 0.78 Gas- 0.92 Gas- 0.96Duct Insulation R- 3.3: Inside Conditioned Space R- 0- Inside Conditioned Space R- 0- Inside Cond
37、itioned SpaceVerified Duct Leakage 3% 5% 2%Ventilation No No ERV 72%WATER HEATING:Energy Factor Gas- 0.54 Gas- 0.62 Gas - 0.92 Tankless + Solar Flat PlatLIGHTING:% High Efficacy 14% 50% 100%MAJOR APPLIANCES:Refrigerator, Dish/Clothes Washer Standard Base ENERGY STAR Best in Class ENERGY STARClothes
38、Dryer Gas/Standard Gas/Auto Terminate Gas/Auto TerminateRange Gas Gas Gas PLUG LOADS- MELs:Real-time electricity feedback system and manual switches for entertainment center and home office NO NO YESChicago: 2-Story - Basement - Vented Attic - 2,500 sq ft - 3 bed - 2 bath - 15% Glazing FFA0501001502
39、00250300350Benchmark 30% Home 70% HomeMBtu/yrChicago High Performance HomesSource Energy Use AppliancesHot WaterHeating Cooling Lights Energy Savings from Benchmark: 67%Figure 2 Chicago High Performance Homes- Source Energy Use 2011 ASHRAE 343Figure 2 graphically shows the energy savings for each Ch
40、icago home from the BA Benchmark. As the graph shows, most of the energy consumption, and energy savings, are found in the space heating end use area. The 70% home demonstrates the importance of appliance energy use. Although major appliance energy use is reduced, it is not reduced at the rate of ot
41、her end use segments. Plug loads, included in appliances, are reduced through occupant feedback and controls, but also at a reduced rate compared to other segments. Figure 3 shows the source energy use distributed between electricity and gas between the three designs. The important take-away from th
42、is graph is that the natural gas use is reduced by 73% in the 70% home, whereas electricity use is down by only 51%. 050100150200250300350400Benchmark 30% Home 70% HomeMBtu/yrChicago High Performance HomesSource Energy: Gas vs. ElectricElectricNatural GasGas Savings from Benchmark: 73%Electric Savin
43、gs from Benchmark: 51%Figure 3 Chicago High Performance Homes- Source Energy Use: Gas vs. Electric Table 2 shows summary source energy, carbon emission, incremental cost, and cash flow analysis for each Chicago home, including an all electric case. The net annual cash flow to the consumer is estimat
44、ed to be $537.53/yr for the 30% home. This positive cash flow demonstrates the appropriateness of design and logic for investing in home energy efficiency. For the 70% home, the net cash flow to the consumer is negative, meaning the efficiency improvements will not pay for themselves. It is importan
45、t to remember that there are benefits beyond utility bill cost savings from improving the efficiency of a home, such as; comfort, health, moisture control, durability and higher resale value. Table 2. Chicago High Performance Homes- All Homes Chicago HomesSource Energy Use (MBtu/yr)Source Energy Sav
46、ingsTotal ThermsTherm SavingsCarbon Emissions (lbs/yr)Carbon SavingsIncremental CostCa sh Flow ($/yr)Chicago Benchmark368 NA 1943 0% 47,892 0% $0.00 $0.00Chicago 30% Home242 29.7% 1261 35% 33,771 29% $5,216.55 $537.53Chicago 70% Home121 67.1% 517 73% 16,999 65% $32,969.59 -$369.17Chicago 70% Home- A
47、ll Electric148 59.8% 0 100% 21,494 55% $32,859.59 -$612.89The last row in Table 2 shows the results of an analysis which looked at all electric equipment, instead of gas and electric. The results show a clear bias toward the gas/electric home, where the source energy savings are higher, carbon emiss
48、ions are lower, and cash flow is improved compared to the all electric home. The efficiency features are comparable to the gas home for the electric case using a 18 SEER, 9.2 HSPF electric heat pump, a .98 EF electric tankless water heater with solar water preheat, induction cook top and an electric
49、 dryer with a moisture sensor and auto terminate function. 344 ASHRAE TransactionsHigh Performance Homes Summary The Chicago analysis, in addition to Phoenix, Atlanta and Houston (not displayed), suggests that homes approaching 50% energy savings are cost effective and technically possible. In all cases, thermal loads were best addressed, while plug loads remain a concern. In the Chicago 70% design, the electric savings was roughly 50% from the Benchmark while the natural gas savings was 75%. Most of the natural gas savings came from space heating, but impr
