ENERGY CODES IN COUNTRIES WITH MILD CLIMATES HIGH POTENTIAL FOR INTERNATIONAL ENERGY SAVINGS

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1 ENERGY CODES IN COUNTRIES WITH MILD CLIMATES HIGH POTENTIAL FOR INTERNATIONAL ENERGY SAVINGS Jeffrey S. Tiller Nathan Culver Robin Delarm Neri Department of Technology and Environmental Design Appalachian State University Katherine Harper Hall Boone, NC Li-Ming Wu Ching Yun University Zhong-Li, Taiwan Benjamin Sanchez Universidad de las Americas Puebla Cholula, MX ABSTRACT Implementation of energy codes in many countries has been slow to occur, particularly codes that save as much energy as the International Energy Conservation. Appalachian State University has been working with faculty members in Mexico, Taiwan, and other countries to (1) assess current energy codes and typical local construction methods, (2) do computer modeling on the most cost effective energy efficiency and renewable energy measures, (3) make recommendations for improved energy codes. In areas such as central Mexico, winters are mild, but often cool. Many buildings rely on electrical resistance heating during cooler weather. In countries such as Taiwan, the weather throughout the year is quite warm, and the number of buildings with air conditioning systems is increasing. International energy use will continue to climb as residents of these countries seek to improve the comfort of their homes by installing heating and/or cooling systems. The article will show the preliminary results of analysis of energy efficiency improvements that generate cost effective energy savings. 1. INTRODUCTION There are a host of countries that have developed energy codes that are either well below the International Energy Conservation (IECC) in terms of efficiency requirements, relatively unenforced, or both. The climates investigated during this study range from hot summers to mild winters and summers. For example, consider Mexico, where climates range quite severely. Cities at lower elevations, such as Veracruz, with over 5,000 Cooling Degree Days (degrees F), have high demands for cooling in buildings with air conditioning. Cities on the high central plateau with elevations in the 5,500 to 7,000 range, such as Mexico City, Guadalajara, Puebla, Queretaro, and Oaxaca, have a combined population of well over 10 million. Buildings in these areas have low demand for both heating and air conditioning. However, many dwellings employ electric resistance heating in the winter and have no insulation and single-paned windows. The Mexican economy is expanding, and as a consequence, these regions are experiencing new construction in both commercial and residential sectors. 1

2 Taiwan s tropical climate mirrors that of southeast Asia and much of Micronesia. Summers are hot and winters warm. Air conditioning is relatively new to many buildings in the country, but expanding rapidly in both new and existing buildings. Figure 1 shows Heating and Cooling Degree Day values, for these regions. The chart also shows that some U.S. climates, such as San Diego and Los Angeles have similar annual climates in terms of degree days as central Mexico. Honolulu s degree day values resemble those in Taiwan. In terms of climate zones used by the International Energy Conservation (IECC) to classify areas, many of the cities in central Mexico would be in Climate Zone 3, while those in Taiwan would be in Climate Zone Analytical Approach The authors used the approach below in the course of the study thus far: 1. Identify the key provisions of local energy codes 2. Determine level of enforcement of local energy codes and characterize current local construction practices Fig. 1: Heating and Cooling Degree Days 3. Identify the key provisions of the IECC 2012 energy code 4. Select typical buildings for each country to model for energy performance 5. Conduct energy modeling for at least three cases to find the energy performance for buildings that incorporate: o Current local construction practices o Relevant provisions of local energy codes o Key provisions of IECC 2012 o Suggested revisions based on typical construction in the area and measures to reduce energy used for hot water In regard to the relevancy of the provisions, the energy code may have requirements for components not common in the locality, such as central, ducted HVAC systems. The initial energy model used by the authors was REMRate. Follow-up analysis will be performed using Ecotec and Energy Typical Building Models The authors are aware of current construction practices in each of the localities. The buildings modeled in the study are as follows: Medium-sized residence 100 m 2 (1,004 sq ft) Multi-story 2,025 m 2 (20,250 sq ft) with 18 units San Diego, CA Los Angeles, CA Mexico City, Mexico San Luis Potosi, Guanjuato, Mexico Tampico, Mexico Mazatlan, Mexico Veracruz, Mexico Toluca, Mexico Honolulu, HI Kaohsiung, Taiwan Taipei, Taiwan Cooling Degree Days Heating Degree Days CURRENT ENERGY CODES 2.1 México Energy Mexico s energy code for building envelopes has evolved from the 2001 energy code to the current 2009 code. The 2001 code used typical temperature differences in different climate zones to determine conduction heat losses and the amount of solar radiation based on window characteristics and overhang design. A series of tables determined the overall heat gain of the building under investigation and showed the required insulation and window efficiency requirements. The new Mexican energy code for residential building envelopes is quite prescriptive. Table 1 summarizes the envelope values that it requires. There are three sets of values minimum code, comfort ( habitability ) code, and energy saving code. 2

3 TABLE 1: THERMAL RESISTANCE VALUES IN THE 2009 MEXICO ENERGY CODE FOR RESIDENCES (Watts/ m2-k (Btuh/ft2-F) Feature Roofs Walls Crawl Spaces Ceilings Climate Zones 3A, 3B, 4A, 4B, Option 1 2 and 3C and 4C Minimum 1.4 (8) 1.4 (8) 1.4 (8) 1.4 (8) Comfort 2.1 (12) 2.1 (12) 2.3 (13) 2.65 (15) Energy- Saving 2.65 (15) 2.65 (15) 2.6 (16) 3.2 (18) Minimum 1 (5.7) 1 (5.7) 1 (5.7) 1 (5.7) Comfort 1.1 (6.0) 1.1 (6.0) 1.23 (7) 1.8 (10) Energy- Saving 1.4 (8) 1.4 (8) 1.8 (10) 2.1 (12) Minimum N/A 0.7 (4) 0.9 (5) 1.1 (6) Comfort N/A 1.1 (6) 1.4 (8) 1.8 (10) Energy- Saving N/A 1.2 (7) 1.6 (9) 1.9 (11) The Climate Zones in the code appear to coincide with the IECC s zones. Example cities and their climate zones are as follows: Climate Zone 1: Acapulco, Puerto Vallarta, Veracruz Climate Zone 2: Nuevo Laredo, Hermosillo, Guadalajara Climate Zone 3A: México City, Guanajuato, Puebla, Jalapa Climate Zone 3B: Chihuahua, Tijuana Climate Zone 3C: Ensenada, Orizaba Climate Zone 4A: Toluca Climate Zone 4B: Pachuca Climate Zone 4C: Zacatecas The code has envelope values, but no requirements for window U-value or Solar Heat Gain Coefficients. 2.2 Taiwan Energy : The energy code in Taiwan has also evolved to include a set of prescriptive requirements. It sets envelope efficiency values for residences, along with maximum lighting power allowances in watts per square meter. Values for residential envelopes are shown in Table 2. The wall U-factors are for the entire exterior wall surface, including windows and doors. Table 3 shows the required wall U-factors for walls based on % of window area. It also contains U-factors for a wide variety of wall types that are common in Taiwan. As TABLE 2: REQUIRED ENVELOPE MEASURES FOR TAIWAN S ENERGY CODE Location Wall Roof Skylight Window Regulation Uaw<3.5 W/( m2 K) Uar<1.0 W/( m2 K) U-factor -- n/a; Solar Heat Gain Coefficient <= 0.35 U-factor -- n/a; Solar Heat Gain Coefficient <= 23 W/m 2 the window area increases, given that the wall insulating value is greater than the window insulating value, the wall U-factor will have to decrease to make up for the poor insulating value of the typical singlepaned windows. Even after factoring in the U-value of single paned windows, uninsulated concrete block walls only fail the code if the window area is in the range of 40% or greater. Concrete walls do not pass in any case unless they are insulated. TABLE 3: CALCULATED ENVELOPE REQUIREMENTS FOR TAIWAN S ENERGY CODE U-factors SI (Watts/ US (Btuh/ ft 2 - m 2 -K) F) Taiwan Energy : Max U-value for Opaque Wall 0% single-paned glass % single-paned glass % single-paned glass % single-paned glass % single-paned glass Comparative Wall Insulation Values 8" block no insulation = " block integral insulation " block no insulation +R " block no insulation +R " block no insulation +R " block integral insulation +R " block integral insulation +R " block integral insulation +R " thick solid concrete wall Above with R-4 insulation

4 In the case of roofs in Taiwan s residential buildings, concrete slabs are one of the most common construction methods. They are required to be 1.0 W/ m2 -K (0.55 Btuh/ft 2 -F) or less. Uninsulated concrete roofs have U-values of over 10 W/ m2 -K (5.5 Btuh/ft 2 -F). Just the addition of 5 cm (2 in) of expanded polystyrene foam would lower the U-values to 0.68 W/ m2 -K (0.12 Btuh/ft 2 -F), which would bring the roof system into compliance. 2.3 International Energy Conservation (IECC) The IECC contains envelope U-factors for a variety of climate zones. Taiwan would be located in Climate Zone 1 and much of central Mexico in Climate Zone 3. The current IECC insulation requirements for new homes are as follows: TABLE 4: 2012 IECC RESIDENTIAL INSULATION AND WINDOW VALUES Zone 1 Zone 3 R-values for Walls and Ceilings Walls Wood-framed walls 2.29 (13) 2.29 (13) Mass walls (insulation on exterior) 0.53 (3) 1.41 (8) Ceilings Framed 5.28 (30) 6.69 (38) Windows U-values NR 0.06 (0.35) SHGC The IECC values are substantially greater than those for the Mexican and Taiwanese energy codes. However, the construction style for residences is much different in the United States than in most other countries. Typically, the U.S. uses wood-framed attics, while other countries use concrete slabs. The IECC residential code does not contain values for concrete slab roofs. The IECC has R-value requirements for roof deck insulation for high rise residential construction in the commercial energy code. R-3.5 (Watts/ m 2 -K) (R-20 in Btu/ sq ft-f) insulation is required on such roofs in Climate Zones 1, 2 and RESULTS OF ENERGY MODELING The preliminary analysis for this article used REMRate software. Follow-up analysis will compare the results using other energy modeling software. Tables 5, 6 and 7 on the following page show the results which are described below. 3.1 Single-Family Home in Central Mexico The results for the approximately 100 m 2 (1,004 sq ft) single family home are presented in Table 5. The table contains a major assumption that the home is actually heated and cooled to typical comfort levels of 70 degrees in winter and 76 degrees in summer. Many homes are not currently heated or cooled, so the results can also infer the degree of comfort that the insulation values would provide the lower the heating and cooling energy use, the better the comfort in the absence of HVAC systems. The heating system is assumed to be electric resistance heat, which is commonly used via space heaters. The table shows that by following the current Mexican energy code for ceilings and walls, energy consumption for heating, cooling, and water heating would decline by about 6% compared to a home with no insulation in the walls or ceilings. However, the IECC values would drop energy consumption by 43%. Noting that the IECC residential ceiling values assume a framed ceiling structure and do not account for the mass of a concrete roof, the authors looked at another package of measures R-2.8 (R-16) concrete roof, R- 0.7 (R-4) concrete walls (insulated on the exterior), and the same windows as required by the IECC U-2 (U-0.35) and SHGC This package (labeled D in Table 5), shows 39% savings in energy use. A substantial benefit of either package C or D is the reduction in cooling load. The IECC (package C) reduced the load by 55%, while package D shows a 49% reduction. In case the window industry in Mexico is not prepared for double-paned, low-e windows, package E considers single-paned windows with low SHGC of This set of measures shows a reduction of 54% in energy usage, a similar reduction 4

5 in costs, and a 25% decline in cooling load. Note that the heating energy savings are based on electric resistance heating in the residences. A final package, labeled F in Table 5, addresses the proportionately high use of water heating in buildings in these climate zones. If the building is being heated and cooled by a mechanical system, water heating represents 23% of the energy use for heating, cooling, and hot water in the uninsulated building. As efficiency measures are added, the percentage of the total that is consumed for hot water purposes climbs to 52% in the IECC case. Package F includes the same insulation values for concrete roofs and walls as Package E, as well as single-paned windows with SHGC of 0.25 and either solar water heating or heat pump water heaters. The total reduction in energy use is higher than the IECC would provide, totaling 54%. The total energy savings for the package is $620 per year (assuming full heating and cooling). Preliminary cost estimates for the measures are as follows: Roof -- for 4 inches of foam and coating $1,000 Walls -- for 1 inch of foam and parging $1,200 Windows -- for low transmittance coating $200 Water Heater for solar water heater $1,000 (currently $500 units are available in Mexico) Total Estimated Cost -- $3,900 The additional costs would show 5 to 6-year payback, which is generally considered excellent. However, many prospective homeowners in Mexico would have financial problems affording the additional expenses. The higher cost is primarily driven by the need for additional coatings over insulation (such as parging and the roof coating) and solar water heating rather than just the cost of the insulation and window measures themselves. The authors will continue to refine the cost estimates to be as accurate as possible. 3.2 Multi-Family Home in Central Mexico The results for the 2,025 m 2 (20,250 sq ft) multifamily building with 18 units are presented in Table 6. The assumptions and packages are the same as for the single-family case. In the case of the multi-family structure, the Mexican energy code saves 6% and the 2012 IECC saves 43%. The revised packages with less insulation than required by the IECC, but with solid concrete roofs and walls, saves 39% with double-paned, low-e windows and 35% with single-paned windows, both assuming Solar Heat Gain Coefficients of The final package, using a heat pump water heater or solar thermal water heating system, combined with the other features reduces energy bills from the uninsulated case a total of 54% The total cost savings is in the range of $6,000 assuming full heating and cooling of the 18 units. The installed cost for the additional measures for Package F is projected to be $32,523, which would provide a payback period of a little over 5 years. 3.3 Multi-Family Building in Taiwan Single-family, detached housing is not common in Taiwan. The authors analyzed the multi-family building with differing efficiency features. The results are shown in Table 7. The building constructed to meet the Taiwan energy code saves about 21% on energy bills compared to an uninsulated building. The air conditioning load is reduced by 36%. The IECC provisions would save substantially more 38% on energy use and 59% on air conditioning sizing. Note that reducing the insulation values below the IECC requirements in package D does not affect the energy savings substantially. The building would save 34% on energy (only a 4% reduction from the IECC) and 49% on air conditioning sizing. With the domestic hot water efficiency measure in package E, the savings are greater than the IECC alone would provide. Dollar savings on energy range from $2,400 per year for the Taiwanese energy code (assuming that windows shift from SHGC of 0.85 to 0.60) to $4,400 per year for the IECC to $5,900 for package E, which includes revised insulation values, the same windows as required for Zone 1 IECC, and high efficiency or solar water heating. 5

6 TABLE 5: ENERGY USE AND SAVINGS FOR A SINGLE-FAMILY HOME IN CENTRAL MEXICO A. No insulation B. Mexico Energy C. IECC Zone 3 D. Revised case 1 (concrete roof) E. Package D + SP F. Package E + Solar Windows SHGC 0.25 DHW or HPWH Walls R-0 Conc R-0.7 (R-4) Conc R-2.3 (R-13) R-0.7 (R-4) Conc R-0.7 (R-4) Conc R-0.7 (R-4) Conc Roof R-0 Conc R-1.14 (R-6.5) Conc R-6.7 (R-38) R-2.8 (R-16) R-2.8 (R-16) R-2.8 (R-16) Window U U-5.1 (U-0.9) U-5.1 (U-0.9) U-2 (U-0.35) U-2 (U-0.35) U-5.1 (U-0.9) U-5.1 (U-0.9) Window SHGC Energy Consumption -- kwh (MMBtu) ` Heating 9056 (30.9) 8118 (27.7) 2403 (8.2) 3224 (11) 4220 (14.4) 4220 (14.4) Cooling 1143 (3.9) 1026 (3.5) 498 (1.7) 498 (1.7) 410 (1.4) 410 (1.4) Water Heating 3136 (10.7) 3136 (10.7) 3136 (10.7) 3136 (10.7) 3136 (10.7) 1568 (5.35) Total -- kwh (MMBtu) (45.5) (41.9) 6038 (20.6) 6858 (23.4) 7767 (26.5) 6199 (21.15) % Savings Cost 1,133 1, % Savings A/C Load -- W (MBtuh) 4191 (14.3) 3781 (12.9) 2462 (8.4) 2931 (10) 3136 (10.7) 3136 (10.7) % Savings TABLE 6: ENERGY USE AND SAVINGS FOR A MULTI-FAMILY BUILDING IN CENTRAL MEXICO Energy Consumption -- kwh (MMBtu) A. No insulation B. Mexico Energy C. IECC Zone 3 D. Revised case 1 (concrete roof + single-paned windows w/ SHGC 0.25) E. Package D + Solar DHW or HPWH Heating (209.2) (91.9) 0 (0) (102.4) (101.3) Cooling (71.8) (62.4) (38) (37) (37) Water Heating (194.5) (194.5) (194.5) (194.5) (109.2) Total -- kwh (MMBtu) (475.5) (348.8) (232.5) (333.9) (247.5) % Savings 27% 51% 30% 48% Cost 11,846 8,689 5,792 8,318 6,166 % Savings 27% 51% 30% 48% A/C Load -- W (MBtuh) (257.4) (181.8) (137) (138.3) (138.3) % Savings 29% 47% 46% 46% TABLE 7: ENERGY CONSUMPTION AND SAVINGS FOR A MULTI-FAMILY BUILDING IN TAIWAN Building Feature A. No insulation B. Taiwan Energy C. IECC Zone 1 D. Revised case 1 (concrete roof + single-paned windows w/ SHGC 0.25) E. Package D + Solar DHW or HPWH Walls R-0 Conc R-0.7 (R-4) Conc R-2.3 (R-13) R-0.7 (R-4) Conc R-0.7 (R-4) Conc Roof R-0 Conc R-1.14 (R-6.5) Conc R-5.3 (R-30) R-2.8 (R-16) R-2.8 (R-16) Window U U-5.1 (U-0.9) U-5.1 (U-0.9) U-5.1 (U-0.9) U-5.1 (U-0.9) U-5.1 (U-0.9) Window SHGC Energy Consumption -- kwh (MMBtu) Heating Cooling (311.1) (213.9) (133.8) (154.1) (154.1) Water Heating (152.9) (152.9) (152.9) (152.9) (72) Total -- kwh (MMBtu) (464) (366.8) (286.7) (307) (226.1) % Savings 21% 38% 34% 51% Cost 11,559 9,138 7,142 7,648 5,633 % Savings 21% 38% 34% 51% A/C Load -- W (MBtuh) (331.1) (213) (135) (169.4) (169.4) % Savings 36% 59% 49% 49% 6

7 4. CONCLUSIONS The study on International Energy s has thus far shown that current codes in countries such as Mexico and Taiwan provide moderate levels of savings. The 2012 IECC values would in general save substantially more. A revised set of measures that include lower insulating values for concrete roofs and walls than the 2012 IECC, the same window SHGC as the IECC, and domestic water heating requirements for high efficiency or solar water heating would provide the most savings. The availability of less expensive equipment in these countries, combined with generally mild climates having small probabilities of freezing, make high efficiency water heating using solar thermal systems or heat pump water heaters technical attractive. The analysis does not address the question of energy code enforcement. Thus far, contacts in both countries have mixed opinions on the degree of enforcement, which is obviously a key factor to obtain the projected savings. The authors will continue to assess this issue. With expanding populations in countries such as Mexico and Taiwan, adopting higher efficiency energy codes should be a strong priority. The resulting energy savings would provide benefits to building occupants, local businesses, manufacturers, the nations economies, and the global environment. Conditioning Engineers. Washington, DC and Atlanta, GA. July, (4) 2009 ASHRAE Handbook of Fundamentals. American Society of Heating, Refrigeration, and Air Conditioning Engineers. Washington, DC and Atlanta, GA (5) Eficiencia energética en edificaciones, envolvente de edificios no residenciales. Dario Official. April 25, Downloaded on February 28, 2012 from es/localcontent/1002/1/images/nom-008-ener pdf. (6) Translation of Taiwanese National Energy. By Dr. Li-Ming Wu. Ching Yun University. Personal Communication. March 10, (7) Yang, Kuan-Hsiung. Review on Building Energy Conservation Strategies and Recent Research Programs in Taiwan. Downloaded on February 27, 2012 from tcworkshop/pdf/24.pdf. 5. REFERENCES (1) Atlas Climático Digital de México Downloaded on March 9, 2012 from atmosfera.unam.mx/acdm./ (2) NMX-C-460-ONNCCE-2009 Industria de la Construcción Aislamiento Térmico Valor R para las Envolventes de Vivienda por Zone Térmica para la Republica Mexicana Especificaciones y Verificación. Asociación de Empresas para el Ahorro de la Energía en la Edificación A.C. January, (3) 2012 International Energy Conservation and ANSI/ASHRAE/IES Standard : Energy Standard for Buildings Except Low-Rise Residential Buildings. International s Council and American Society of Heating, Refrigeration, and Air 7