Capturing Energy-Efficiency Opportunities in Historic HousesAuthor(s): James CavalloSource: APT Bulletin, Vol. 36, No. 4 (2005), pp. 19-23Published by: Association for Preservation Technology International (APT)Stable URL: http://www.jstor.org/stable/40003159 .Accessed: 17/08/2011 09:36

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Capturing Energy-Efficiency Opportunities in

Historic Houses

JAMES CAVALLO

Residences in Galena, Illinois,

illustrate how both monetary and

energy savings can be incorporated

into historic houses.

Successful sustainability requires an eco- system that maintains its capacity to conserve resources while accomplishing particular tasks. For instance, a popular formalization of the sustainability con- cept is an ecosystem that maintains its capacity to provide a continuing stan- dard of material and environmental well-being from one generation to the next - or, put differently, an ecosystem that provides descendants of today's population with a standard of living as high as that being enjoyed today.1 Since wasting resources today implies passing fewer material and environmental re- sources along to later generations, waste indicates a lack of sustainability. Viewed more positively, minimizing waste is an opportunity for improved well-being for both current and future generations.

Analyzing energy consumption in historic houses provides an opportunity for improved sustainability. Indeed,

Fig. 1 . The home of President Ulysses S. Grant, 500 Bouthillier Street, Galena, Illinois. All photographs

by the author.

capturing this opportunity can be an easy way to stretch tight budgets. En- ergy-efficiency upgrades can also extend the lives of building systems and main- tain a better indoor environment for historic objects.

This article discusses an approach used to examine opportunities for reduc- ing energy use without reducing the ser- vices provided at three historic proper- ties in Galena, Illinois. It presents the methods used and some results that have already been observed. The paper also discusses tools and resources, including professional home-energy raters, that are available to the historic-preservation community in the U.S.

Energy Rating and Historic Properties

In 2003 Illinois' Division of Energy, housed within the Department of Com- merce and Economic Opportunity, started working with the Illinois His- toric Preservation Agency to examine and demonstrate the applicability of the tools and methods of home-energy ratings for historic buildings. Two years earlier these tools and methods had been successfully applied to older resi- dences in Quincy, Illinois' historic com- munity along the Mississippi River. The residential-energy program manager of the Division of Energy, John Marley, was keen on exploring what energy rating could offer state-owned historic houses.

Home-energy rating is an approach to evaluating the energy efficiency of a residential building. Although largely applied to new construction and closely identified with the Environmental Pro- tection Agency's Energy Star Homes program, home-energy rating is also ap- plicable to existing housing. The tech- niques and tools of energy rating have much in common with energy auditing.

19

20 APT BULLETIN: JOURNAL OF PRESERVATION TECHNOLOGY / 36:4, 2005

Fig. 2. The Washburne House, 908 Third Street, Galena, Illinois, is approximately one-quarter mile from the Grant Home.

Fig. 3. The Callahan House, 307 Decatur Street, Galena, Illinois. The house has heating ducts located in the attic and cellar.

The key distinction is that energy ratings compare existing houses to standard prototype residences and energy audits examine the energy systems in a house as used by the current residents.

Like an auditor, a home-energy rater collects information on all energy-using or energy-losing systems through inspec- tion and testing. A score, or rating, is then developed using specialized soft- ware, such as Architectural Energy Cor- poration's REM/Rate. The score can range from 0 to 100, with 100 indicat- ing an almost "zero energy" house, meaning that the house achieves all possible energy savings given the specific house type and climate. Under this system, a residence built to the 1993 Model Energy Code will receive a score of 80, while a house of greater efficiency will receive a higher score. To qualify for the Energy Star Homes program, a residence must be rated by a certified home-energy rater and achieve a score of 86 or better. In addition to developing a rating score, the software estimates annual energy use and the cost of energy consumed for a standard family during typical local weather conditions and current fuel rates.

With existing housing the rating score is usually less important than the estimated annual cost of energy con- sumed. In the fall, winter, and spring of 2001-2002, several energy raters work- ing for Adams Electric Cooperative con- ducted home-energy ratings to assist homeowners in and around Quincy, Illinois. They worked with each owner

to identify possible energy improve- ments and then rated the houses again assuming the proposed upgrades to estimate potential energy savings. The state energy office provided an incentive for owners in the amount of a $50 per rating-point improvement. Thus, if a residence scored a 55 in its initial config- uration and could achieve a 20-point improvement by insulating the attic and walls and installing a new furnace, the owner would receive a $1,000 payment after the improvements were completed and verified. Generally the incentives covered 25 to 50 percent of the im- provement costs; it was estimated that the energy-bill savings would cover the balance within three to four years. The energy raters found that the initial rat- ings averaged 54.8, with the middle two-thirds extending from 40 to 66. The average rating-point improvement after the energy-efficiency measures were installed was 21. 9. 3

The completion of the Quincy project coincided with a serious deficit in the Illinois state budget. As a result, interest at the energy office was directed to cost-

cutting techniques in state-owned build- ings. The lessons of Quincy seemed applicable to the state-owned historic houses in Galena.

Galena is a town rich in historic buildings. Like Quincy, Galena grew up in the mid-nineteenth century. The source of its early wealth was its lead mines. From the late 1830s until the 1890s the town prospered, but its for- tunes reversed quickly at the close of the century. For much of the twentieth century the town suffered economic decline, until the late 1960s and 1970s brought a rebirth due to tourism.4

One of the principal points of interest for visitors to Galena is the home of President Ulysses S. Grant, who moved to Galena in 1860 after having retired from the army to work with his brothers in the family's leather-goods store. With the start of the Civil War, Grant re- turned to military life and achieved his legendary victories. Following the war local businessmen and Congressman Elihu Washburne purchased an Ital- ianate brick house, built in 1860, and presented it to General Grant (Fig. 1). Grant made Galena his official residence until he was elected president in 1868 and lived there intermittently until 1876. The residence remained in the Grant family until 1904, when it was given to the city of Galena. Ownership was transferred to the State of Illinois in 1931 when Galena suffered financial difficulties.5

Three state-owned houses in Galena were chosen for study: the Grant Home; the home of Congressman Washburne, built in 1843, where Grant waited one evening to hear the results of the elec- tion of 1868; and the Callahan House, built in 1891 and occupied by the Illi- nois Historic Preservation Agency (IHPA)'s office for the Galena Historic Site (Figs. 2 and 3).6

Tablei. Baseload and Space-Heating Natural-Gas Usage Prior to Energy Improvements, 2002-2003

Conditioned Space Baseload Usage Space-Heating Usage (sq. ft.) (Therms/day) (Btus/HDD/sq. ft.)

Grant Home ~

3167 .^6 16.28 Washburne House 4292 (10 14.22 Callahan House 1517 (H) ^09

Btus/HDD/sq. ft. is British thermal units per heating degree day per square foot of conditioned space.

CAPTURING ENERGY-EFFICIENCY OPPORTUNITIES IN HISTORIC HOUSES 21

Fig. 4. Adjusting the controls of a blower door

during a test at the Grant Home. A blower door creates a pressure difference across the enve-

lope of a house, thus permitting analysts to

quantify convection losses and to identify points of air infiltration.

Searching for Efficiency Opportunities

The tools and techniques of home- energy ratings were applied to the three houses so that cost-effective energy- efficiency measures could be imple- mented within the restrictions imposed by historic-preservation standards. The SHPO required that the recommenda- tions would not adversely impact the exterior appearance of the structures and that the interior spaces open for public viewing not be altered.

In looking for cost-effective opportu- nities, the analysts began by analyzing utility bills, focusing on the natural-gas use in winter to separate the gas con- sumption for space heating from that for baseload natural-gas usage, which occurs throughout the year and includes water heating and cooking (Table 1). (See the sidebar "Screening before Rat- ing" for a description of an easy-to-use method for separating natural-gas utility bills into baseload and space-heating load.) All three houses had been retro- fitted with modern forced-air furnaces and central air-conditioning previously.

Table 1 shows that the Washburne and Callahan houses had no baseload usage. The Grant Home had a water heater and a small kitchen, which also served as a staff room, resulting in a baseload usage of .56 therms per day.

Experience in the Quincy project and many private energy analyses suggested that baseload usage would typically fall in the range of .5 to 1.0 therms per day. Estimates above 1.0 therm per day sug- gest the presence of an inefficient water heater, leaking faucet, or poorly operat- ing gas appliance. The Grant Home was well below this level.

The space-heating usage shown in Table 1 suggested many opportunities to save energy on space heating at the Grant and Washburne properties. As a rule of thumb, houses with space-heat- ing usage above 10 Btus per heating de- gree day per square foot of conditioned space usually provide fertile ground for cost-effective energy savings.

To determine specific energy im- provements, each of the three properties was measured and studied for a home- energy rating. Measurements included the square footage and volume of condi- tioned space, exterior wall dimensions, and ceiling area. Because windows and doors offer less insulating value than exterior walls, analysts collected infor- mation on the sizes of the windows and exterior doors. In addition, information on the efficiencies of space-heating, air- conditioning, and water-heating systems was collected. This information was later entered into an energy-rating soft- ware tool that enabled the analysts to compute a rating score and estimate what fuel consumption and energy cost would be for a standard family during typical Galena weather with the cur- rently prevailing fuel rates (Table 2).

The Grant Home and the Callahan House had better energy-rating scores than 80 percent of the Quincy residences. The Washburne House also was above the average Quincy score. The higher

performance resulted from better heat- ing systems. The Washburne and Calla- han houses had high-efficiency furnaces, and the furnaces in the Grant Home were recent medium-efficiency systems.

Table 2 shows the results of the blower-door test, which estimates exte- rior air infiltration. The blower door consists of a metal frame that fits into a doorway, a cloth panel that seals the area around the frame, and a large ad- justable-speed fan that fits in the panel (Fig. 4). The object of the test is to create a precise pressure difference between the inside and outside of the house and to measure the resulting air infiltration. Air infiltration can account for 5 to 40 percent of space-conditioning costs.7 The infiltration results indicated high rates of air movement into all three structures.

High air infiltration can be particu- larly problematic in historic houses because it is closely linked not only to higher energy bills and reduced comfort but also to increased moisture move- ment into building systems (e.g., walls and attics) and higher indoor humidity levels during summer. Both types of moisture movement can reduce the longevity of a structure. For museums, higher air-infiltration rates can increase variations in relative humidity that can cause damage to artifacts. Air-infiltra- tion deficiencies should be identified before installing additional insulation to preclude having to remove the new insulation to reach the points of air infiltration.

While the blower door was operat- ing, the analysts identified specific sites of air infiltration. The larger air-leakage sites for the Washburne and Callahan houses were in the attic space. For the

Table 2. Blower-Door Test Results and Energy-Rating Estimates Prior to Energy Improvements.

Conditioned Blower-Door Estimated Estimated Rating Score Space Results Space-Heating Space- (sq. ft.) (CFM at 50 Pa) Usage Heating

(Therms/year) Cost ($/year)

Grant Home 3167 4565 2859 1075 70.3

Washburne 4292 7259 4820 1705 60.5 House

Callahan 1517 2370 1126 460 76.5 House

CFM at 50 Pa is the air-infiltration test results of cubic feet per minute if the air-pressure difference between the inside and outside of the house is 50 pascals.

22 APT BULLETIN: JOURNAL OF PRESERVATION TECHNOLOGY / 36:4, 2005

Table 3. Air-Infiltration Goals and Simulated Energy Savings with Proposed Improvements.

Blower-Door Estimated Space- Estimated Space- Rating Score Results Heating Usage Heating Cost (CFM at 50 Pa) (Therms/year) ($/year)

Grant Home 2739 2387 902 73.9

Washburne House 3992 3054 1105 7^7 Callahan House 1896 906 365 80.2

Grant and Washburne houses sizeable air infiltration came from the cellars. Remediation work could be implemented without affecting areas seen by the public or historically important features. Attic insulation levels were below those recommended for residential buildings located in northwestern Illinois.

The integrity of the forced-air duct systems was also investigated. A varia- tion on the standard blower-door test provides a rough estimate of air leakage to unconditioned spaces through the furnace ducts.8 This test is performed by making two blower-door estimates. The first test is done with all duct vents open as normal. The second is done after covering the vents with plastic to isolate the duct system. By subtracting the two blower-door estimates and adjusting for internal air entering the ducts, an esti- mate of how much air escapes from the ducts to unconditioned areas can be made.9 All three houses were found to have leaky duct systems. The Wash- burne and Callahan houses presented greater problems due to the fact that the ducts were located in attic areas.

Proposed Improvements and Initial Results

The software used to generate an en- ergy-rating score can also supply infor- mation to simulate and examine alter- native improvement strategies and estimate cost savings. Discussions fo- cused on three proposed improvements to the Galena houses: reducing overall air infiltration, especially air movement to attic areas in the Washburne and Callahan houses and movement to the cellars in the Grant and Washburne houses; tightening the duct systems, particularly the ducts in the attics in the Washburne and Callahan houses; and installing additional insulation in the attics after air-sealing and duct-tighten-

ing work was completed (Table 3). These measures were viewed as very unlikely to impact historic features.

A standard set of goals for reduced air infiltration have been developed by the Illinois Home Weatherization Assis- tance Program. The goals for air sealing propose reducing infiltration by 20 per- cent if the initial CFM at 50 Pa is be- tween 1560 and 2750, as is the case for the Callahan House.10 The goal for air sealing is a 40 percent reduction when the initial CFM at 50 Pa is between 4250 and 5500, as at the Grant Home. The goal is a 45 percent reduction if the initial CFM at 50 Pa is 5500 to 7500, as in the Washburne house.11 These goals were used in the simulations shown in Table 3. The simulations for Table 3 also assumed the reduction of duct leakage to 100 CFM at 25 Pa within the ducts and an increase in attic insulation to R-42. The overall estimated savings for space heating during a year with typical weather and current fuel rates would be $868 per year, or approxi- mately 26 percent.

Weatherization and insulation work was conducted at the Grant Home during the fall of 2003. The analysts returned in November 2004 and per- formed an additional blower-door test. Natural-gas bills for the winter of 2003- 2004 were also analyzed. The blower- door test showed that the weatheriza- tion work reduced air infiltration from 4565 CFM at 50 Pa to 4198 CFM at 50 Pa, an 8 percent reduction. The analysis of the natural-gas bills showed a reduc- tion in space-heat energy consumption from 16.28 Btus to 14.27 Btus per heating degree day per square foot. Those bills indicate that 470 therms of natural gas would be saved at the Grant Home during a winter with typical weather (7,376 heating degree days), which would be a 12.4 percent reduc- tion in energy consumption for space heating.

Applying Rating Methods Elsewhere

Applying the tools and techniques of home-energy rating enables owners to identify and then capture energy savings while still maintaining, if not improving, the comfort of the property. This ap- proach can be used in any state because each state has some type of home-energy rating program. The elements of the ap- proach that can be used in the context of historic houses are as follows.

First, conduct a simple screening of the utility bills for the space-heating fuel to roughly evaluate the potential for energy-efficiency improvements. If space-heating energy consumption is high relative to similar residences -

greater than 10 Btus per heating degree day per square foot, as a rule of thumb - the owner should obtain an energy analysis.

Next, be sure to conduct a blower- door test. While the blower door is operating, walk around the house to identify the locations of air infiltration for possible action. Pay particular atten- tion to air leakage to the attic or from crawl spaces and cellars. If furnace and air-conditioning ducts travel through unconditioned spaces like the attic, measure how tight or leaky those ducts are by using a duct blaster or by apply- ing the blower-door subtraction method discussed above. If possible, conduct an infrared scan while the blower door is operating to identify air movement within the walls and ceilings.

Third, capture the improvement opportunities in areas not impinging on historic features. These will likely in- clude sealing air bypasses to the attic, crawlspace, and cellar; tightening all furnace and air-conditioning ducts in unconditioned spaces; weather-stripping doors and hatches to unconditioned spaces; and adding insulation to attic areas. Always observe sound building- science practices about where to place the vapor barrier in relation to the insulation and how to provide a path to evacuate moisture that may enter the wall.

Using the tools and techniques of home-energy ratings may seem inconse- quential in terms of global sustainability. Reducing energy waste in one, two, or three historic houses will not generate a sizeable resource dividend to pass on to

CAPTURING ENERGY-EFFICIENCY OPPORTUNITIES IN HISTORIC HOUSES 23

future generations. However, the same energy-saving actions can be imple- mented more aggressively in newer residences. The many visitors passing through a historic property like the Grant Home each year present an im- portant ongoing opportunity to educate the public about sustainability. Local newspapers and other media linked the energy-conservation efforts at the three Galena houses to opportunities for energy savings in other homes. This news coverage will likely continue dur- ing the current season as homeowners are dismayed by the size of their heating bills.12

JAMES CAVALLO, PH.D., is principal at Kouba-Cavallo Associates, Inc., a consulting firm helping clients find sustainable solutions to housing, environmental, and community economic-development challenges. He is also an associate editor at Home Energy Magazine and the executive director of the Illinois Associ- ation of Energy Raters.

(Minneapolis: Energy Conservatory, 1993), 43- 44. John Krigger and Chris Dorsi, Minnesota Weatherization Field Guide (Helena, Mont.: Saturn Resource Management, 2003), 121-123.

10. A pascal is a measure of pressure. It is the pressure or stress of one Newton of force on a square meter (Pa = N/m2). Another unit of pressure measurement is an inch of water. One pascal is approximately equal to .004 inches of water. Therefore, 50 Pa is slightly more than .2 inches of water. More precisely, 1 inch of water at 60°F is 248.84 Pa.

1 1 . Illinois Home Weatherization Assistance Program: Program Year 2005 (Springfield, 111.: Illinois Department of Public Aid, 2005), 8.

12. Between 65,000 and 85,000 people visit the Grant Home each year according to Dan Trindle of the IHPA Galena Historic Site (telephone conversation on November 8, 2004).

Screening before Rating

Most property owners pause when con- fronted with the question of whether to undertake an energy audit. The stan- dard response is to wait and gather more information. One approach to gathering more information is to conduct a screen- ing of past energy bills. This can be done using a software tool such as PRISM.1 If the owner does not wish to purchase software to screen only one property, an alternative is to roughly separate energy consumption into base- load and weather-sensitive usage and compare that usage to a benchmark. Here is a simple way to employ that method for natural-gas-heated houses.

Baseload natural-gas usage can be computed by taking the lowest monthly usage in therms of natural gas for a typical month in which space heating is not used and dividing it by the number of billing days in the month. The months of June, July, or August are usually good months to choose; non-typical months would be those with unusual schedules, like holiday closings, or unusual activi- ties, such as renovation work. Baseload usage is expressed as therms per day. If usage is greater than 1 therm per day, further investigation of hot-water usage or baseload equipment and appliances is advisable.

Space-heating usage can be estimated by taking a typical midwinter month's natural-gas consumption in therms, sub- tracting the daily baseload energy usage multiplied by the number of billing days in that month, and dividing by the prod- uct of the number of heating degree days

in that month and the square feet of conditioned space. The result should be converted from therms to British ther- mal units (Btus) by multiplying by 100,000. The final estimate will be given in Btus per heating degree day per square foot. Generally, sizeable cost-effective energy improvement opportunity can be determined from an audit or an energy rating if a house consumes more than 10 Btus per heating degree day per square foot.

Most natural-gas utility companies include the therms of gas consumed on the monthly energy bill along with the number of billing days included in the month. Often heating degree days also are included on the bill, or they usually can be obtained for a nearby major city from the National Climatic Data Center (www.ncdc.noaa.gov). The square feet of conditioned space should not include unconditioned areas, such as porches or basements. If the utility estimates natu- ral-gas usage for some months, one should sum the usage and billing days for two or more months so that the calculation is based on usage from one actual meter reading to another actual reading.

1. PRISM is the best-known analysis tool for energy bills. It is available through the Prince- ton University's Center for Energy and Environ- mental Studies at http://www.princeton.edu/- marean/.

Notes

1. This definition of sustainability is given in many textbooks, such as Eban Goodstein, Economics and the Environment (Englewood Cliffs, N.J.: Prentice Hall, 1995), p. 62. Similar constructs are found in Geoffrey Heal, Nature and the Marketplace (Washington, D.C.: Island Press, 2000), 165-177.

2. A listing of certified home-energy raters can be found at www.natresnet.org, the Web site of the Residential Energy Services Network.

3. James Cavallo, "How the Good Old Days Weren't," Home Energy Magazine 19, no. 5 (2002), 16.

4. See Carl Johnson, The Building of Galena: An Architectural Legacy (Galena, 111.: Johnson Creative, 1977).

5. Jean Edward Smith, Grant (New York: Simon and Schuster, 2001), 95-103 and 419- 420. See also the Web site of the Illinois His- toric Preservation Agency, www.illinoishistory. gov/hs/Galena.htm.

6. Information on the Grant and Washburne homes is available at www.GrantHome.com.

7. John Krigger and Chris Dorsi, "Air Leak- age," in Residential Energy: Cost Savings and Comfort for Existing Buildings (Helena, Mont.: Saturn Resource Management, 2004), 73.

8. More precise estimates of air losses from ducts can be made using a specialized tool known as a Minneapolis Duct Blaster®. How-

ever, in this case precise measurement was felt to be unnecessary since the analysts could develop an appropriate recommendation based on a rough estimate.

9. "Measuring Duct Leaks," in Minneapolis Blower Door Operation Manual, Model 3