Energy Vol. 16. No. 8, pp. lllY-1123, 101 Printed in Great Britain. All rights rewrved

0360~5442/Yl $3.00 + 0.00 Copyright @ 1991 Pergamon Press plc

SAVINGS FROM ENERGY-EFFICIENT INDUSTRIALIZED HOUSING FOR THE U.S.

E. TASDEMIRO~LU, S. CHANDRA,~ and S. MOALLA

Florida Solar Energy Center, 300 State Road 401, Cape Canaveral, FL32920, U.S.A.

(Received 20 October 195X))

Abstract-Yearly and cumulative energy savings in industrialized housing projects are estimated for the period 1995-2030. The sensitivity analysis is based on experimental results and existing market conditions. The cumulative savings in 2030 will be about 12 exajoules (EJ) if the necessary steps toward housing industrialization are taken.

INTRODUCTION

A multi-year research program to improve the energy efficiency in industrial housing has been conjointly conducted by the Florida Solar Energy Center and the Center for Housing Innovation, University of Oregon, since 1988.‘%’ The project is funded by the U.S. Department of Energy, the States of Oregon and Florida, and by industry. The goal of this research project is to develop new knowledge and technology that will produce energy-efficient, affordable, and marketable industrialized housing: housing 25% more energy efficient than the strictest U.S. residential codes require, yet less costly than current homes.

Preliminary findings of the project prove that an energy-efficient industrialized house may save about one-quarter of the energy consumed for domestic hot water heating (DHW) and space heating and cooling (SPHC).3.4 The objective of this paper is to highlight the energy savings in the U.S. residential sector which can thus be achieved.

ASSUMPTIONS

This assessment is based on results obtained from the first phase of the industrialized housing project and existing market conditions. Our goals and constraints are the following:

(i) The results of our investigations are expected to start impacting housing by 1995, after a 5-yr period of R&D. In view of rapidly increasing visibility of the project in the industrialized housing industry, it is expected that the industry will incorporate some of our results in 5 yr.

(ii) The energy consumption of typical base-case houses will remain constant over the forecasting horizon of 1995-2030. The base-case house is here defined as the reference house unit with 193 gigajoules (GJ) of yearly energy consumption. Two trends support this observation: (a) the average house size is getting larger and (b) the use of central air conditioning and electric appliances is rapidly increasing, offsetting the benefits from reduced but unproved efficiences in space heating and water heating. A U.S. Department of Energy report states that the end-use GJ/household-yr consumptions for 1987 and 1984 are 107 and 112, respectively.’ The numbers, excluding appliance energy use, are 81 and 86 GJ/household- yr. respectively, and support the second assumption.

(iii) Through industry-supported sales, design, manufacturing, and testing, the project will save 25% of the DHW and SPHC energy use of the typical base-case house. Experimental work by the Florida Solar Energy Center supports this estimate: an average 20% of heating and cooling costs can be saved, if the return-side and supply-side leaks in the air-distribution system are eliminated.4 Several other design alternatives to improve the insulation and to

tTo whom all correspondence should be addressed.

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1120 E. TASDEMIRO~LU et al

decrease energy consumption have also been successfully tested.3 These are in the areas of roof radiant energy control, roof ventilation, and floor and wall systems.

(iv) The net new addition to housing stock (completions minus demolitions) per year will be 1 million houses per year during the estimating horizon. In view of uncertainties in housing starts, this number appears to be a reasonable assumption. From past years, it is difficult to estimate the number of new houses added to the total stock each year.6

(v) The project will impact 50% of the net new addition to the housing stock at the end of 1995. According to Automated Builder, industralized housing accounted for nearly 50% of all housing in the U.S. in 1989 and its share is steadily increasing.’ Industralized housing has a large potential to affect the rapidly increasing remodelling market. In many areas of the country, many desirable lots have increased in market value so much that old existing houses are being 90% or more demolished and rebuilt. This phenomenon has already happened in the urban housing market in Japan: industrialized housing has a large market share as the desired infill/remodelling housing is built rapidly with minimal disruption to existing neighborhoods. This process is likely to occur here, and we have guessed its effect by selecting a high (50%) penetration factor.

CALCULATION PROCEDURE

A simple computer program was developed to calculate yearly and cumulative energy savings from the project during the period 1995-2030. Currently, the residential energy consumption is about 17.94EJ, and there are roughly 93 million homes in 1990.6 The source-energy consumption (EC) is 0.193 EJ/million houses. The fraction of household energy used for DHW and SPHC (EP) is 76.4%; the number of total housing stock in 1995 (TH) is 98 million; the percentage of energy saving due to the project (SF) is 25%; the numbers of new houses added to the stock per year (HA) are 1 million; the penetration factor of industrialized housing into the market (PF) is 0.50; and the number of years after 1995 when the defined savings need to be calculated (N) is 35 yr (see Table 1).

The yearly total energy consumption (YT) for DHW and SPHC for the new added base case houses is

YT=EPxECxHA=O.l47EJ.

The yearly total energy consumption for DHW and SPHC for newly added houses, considering the industrialized housing penetration (YTI) and new technology resulting from the project (SF), is

YTI=YTx(l-PFxSF)=O.l29EJ.

Table 1. Main parameters and their assigned values.

Parameter 1 Assigned value

Energy consumption per house,EC 193 GJ/yr

Fraction of household energy use for space and water heating,EP 76.4%

Number of total housing stock in 1995,TH 98 million

New houses added to the stock per year,HA 1 million

Percentage of energy savings due to the project,SF 25%

Penetration factor of industrialized housing into the market,PF 0.50

Number of years through which the savings were calculated,N 35 years

Energy savings from industrialized U.S. housing 1121

The yearly savings in the year 2030 are

YES = N x (YT - YTI) = 0.645 EJ.

The cumulative energy consumptions for the base-case houses in 2030 will be

CYT=ECxEPxTH+YTx 5 [N-(J-1)]=107.345EJ. J=2

The cumulative energy consumption in 2030, considering the estimated industrialized housing penetration, will be

CYTI = EC x EP x TH + YTI x 5 [A’ - (J - l)] = 95.733 EJ. .I=2

Cumulative savings from the project are

CS=CYT-CYTI=11.612EJ.

EVALUATION OF THE RESULTS

The results clearly show that cumulative savings may reach 11.612 EJ in 2030, constituting about 11% of the cumulative residential energy consumption in that year. Variations of cumulative energy consumptions and savings during the projection period are shown in Fig. 1. The yearly residential energy consumption per house will drop from 193 in 1990 to 187 GJ in

2030. The results are highly sensitive to the values associated with three parameters: number of

new houses added to the total stock each year, energy-saving fraction achievable in an industrialized house, and the penetration factor of industrialized housing into the market. Cumulative energy savings are presented for a wide range of these parameters in Figs. 2-4 and demonstrate a likely linear relation between the cumulative savings in 2030 and the values of the three parameters. For instance, each quarter-million increase of new homes approximately corresponds to 3 EJ of cumulative energy savings (Fig. 2). In Figs. 3 and 4, a 10% increase in

energy savings in industrialized houses, or a 20% increase in the penetration rate of industrialized housing, will lead to 4.5 EJ of cumulative energy savings in 2030.

0 Bosecose consumplions [1 Modified consumptions b Cumulative sovings

New houses= 1 Million/y Penetration foctor=0.50 Enerav sovinas=0.25

3 0

1995 2000 2005 2010 2015 2020 2025 2030 PROJECTION YEARS

Fig. 1. Variations of cumulative energy consumptions and savings during the projection period.

1122

New houses Penetration foctor=0.50 /5 (Million/y)

6- f3 0.75 A 1.00 d 1.25 0 1.50 x 1.75 t 2.00

Energy sovings=0.25

~

19.95 2000 2605 2010 2015 2020 2025 2030 PROJECTION YEARS

Fig. 2. Variations of cumulative energy savings for different values of new houses added to the total stock each year during the projection period.

Our results are comparable with those of a recent study on maximum potential energy savings in which the authors conclude that the residential sector has the potential to save between 27 and 45% of the year 2000 base-case electrical energy.* Assuming the same number applies to the total (i.e., electric and gas) residential energy use, we estimate potential savings between 4.52 and 8.02 EJ, if the 18 EJ of energy used in residences remains about the same in the year 2000.

As the population grows and people stay in their homes longer, the desire for retrofitting and upgrading the homes can also be satisfied by industrialized housing. Industrialized housing can deliver packaged solutions to remodelling needs which require less time and minimize site work, especially in urban infill situations.

Energy savings 0 rl 0.15 A 0.20 t 0.25

New houses= 1 Million/y Penetration factor-O.50

I

s 0

1995 2000 2005 2010 2015 2020 2025 2030 PROJECTION YEARS

Fig. 3. Variations of cumulative energy savings for different values of the energy-saving ratio during the projection period.

Energy savings from industrialized U.S. housing I123

Penetration factor

0 0.30

New

Enel

0

1995 2000 2005 2010 2015 2020 2025 2030 PROJECTION YEARS

Fig. 4. Variations of cumulative energy savings for different values of the penetration factor during the projection period.

Acknowledgements-This research was sponsored by the U.S. Department of Energy, Office of Buildings and Community Systems, and administered by the DOE San Francisco Operating Office. We gratefully acknowledge additional support provided by AFM (R-Control), American Ingenuity, GE Plastics, Fleetwood Industries, DOW Chemical Co., the States of Florida and Oregon, and the Fulbright Commission. We appreciate the cheerful assistance provided by S. Blum in manuscript preparation.

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REFERENCES

S. Chandra and G. Z. Brown, “Multi-year Research Plan Energy-E~cient Industrialized Housing Program,” Research Report, Center for Housing Innovation, University of Oregon, Eugene, OR and Florida Solar Energy Center, Cape Canaveral, FL (1989). S. Chandra and G. Z. Brown, “Energy Efficient Industrialized Housing Program,” FY89 Task Report, Center for Housing Innovation, University of Oregon, Eugene, OR and Florida Solar Energy Center, Cape Canaveral, FL (1989). S. Chandra, “Energy Efficiency in Industrialized Housing An Assessment and Recommendations for the 21st Century,” presented at the ACEEE 1990 Summer Study, Pacific Grove, CA (26 August- 1 September 1990). J. B. Cummings, “Central Air Conditioner .Impact Upon Infiltration Rates in Florida Homes,” Research Report, FSEC-PF-158-89, Florida Solar Energy Center, Cape Canaveral, FL (1089). U.S. Department Of Energy, EIA, “Household Energy Consumption and Expenditures 1987,” DOE/EIA-0321 (87)/l, Washington, DC (October 1989). U.S. Department Of Commerce, “Statistical Abstract of the United States,” 109th edn, Bureau of the Census, Washington, DC (1989). Anonymous, ‘LPanelizers/Pre-Cutters Build 47825 Units Worth $2.17 Billion,” A~fu~ated ~u~ider 7, 29 (June 1990). Barakat and Chamberlain Inc., “Efficient Electricity Use: Estimates of Maximum Energy Savings,” EPRI CU-6746, Project 2788 Final Report, Oakland, CA (March 1990).