Steve Andrews is a residential energy consultant and freelance writer, based in Denver, Colorado.

Bigelow Homes (Palatine, Illinois) established a reputation for affordable energy-efficient housing during the mid-1980s. The foundation for this success lies in Perry Bigelow's ability to design both neighborhoods and floor plans that appeal to buyers, while maintaining an appreciation for building engineering, attention to small building detail, and a commitment to housing affordability, energy conservation, and resource sustainability.

The guaranteed annual heating bill provided with every home has gained Bigelow notoriety--plus a host of awards--from Professional Builder magazine's Special Achievement Award to the only twice-named Chicago Sun-Times Builder-of-the-Year. The guarantee also spurs potential buyers to stop by his model homes to see what the gimmick is.

Guaranteed Annual Heating Bills

While a number of contractors, especially those in the Pacific Northwest, include good energy packages in their new construction, builders typically cringe at the thought of guaranteeing the upside of their buyers' heating bills. Most see it as a potential liability headache. You can guarantee the house, they say, but you can't guarantee the homeowner.

From the 1978 Twin Rivers report to utility data studies of more recent times, the skeptics have a point: In relatively cold climates, energy use for space heating can vary by a factor of two or more among families living in identical homes. Given the huge lifestyle variables--thermostat setpoints, ages of occupants, personal values, comfort requirements, and more--builders often ask: Why doesn't Bigelow lose his shirt on that offer? Most don't realize that if you build in enough efficiency, even a large variation in an otherwise low heating bill still leads to a relatively low bill. Furthermore, the variations may be smaller in more-efficient homes.

When Bigelow began his guaranteed heating bill campaign back in the mid-1980s, he started with a $100 per year threshhold for homes heated with natural gas. There was some incredulity among buyers; a common response was "that's $100 per month, right?" To get an early read on how the bills were totaling--and to obtain some documentation for marketing purposes--he sponsored heating-bill contests: the lowest annual heating bills won prizes, from a free dinner on the town to an all-expenses-paid weekend. One time the winner had a $24 per year heating bill while the disappointed runner-up came in with $26.

Although a lot of space heating bills averaged $130 to $140 per year, most homeowners were so pleased that only $470 was paid out in claims. However, since the average heating bill was slightly higher than expected, Bigelow shifted his guarantee up to $200 annually in the late 1980s. Since that time, he hasn't had to pay out a dime in claims.

How it works

Bigelow uses a simple subtraction method--subtracting 12 times the average summer load from the annual gas bill--to determine the customer's annual space-heating bill. If the homeowner uses gas just for water heating, Bigelow may simply subtract one therm per day, the amount that Northern Illinois Gas says the average family uses to heat water.

The guarantee's wording doesn't hide any fine print or loopholes (see Figure 1). All Bigelow asks is that "Purchaser agrees to manage the home efficiently." For a three-year period of time, the company will pay any amount which the calculation method shows in excess of $200 per heating season.

Every year two or three households call to have their bill examined for possibly exceeding the guarantee. In every case, the homeowners have merely forgotten to subtract their hot water usage from their annual gas bill. Once this is brought to their attention, they are satisfied.

Marketing hook.

Bigelow insists that energy efficiency is not what sells homes. He does not emphasize the construction techniques or the energy features to his sales staff; he doesn't want them dwelling on this angle, because saying where you put what type of caulk or insulation isn't what generally motivates a buyer to buy. What the heating-bill guarantee does do is generate traffic.

"The guaranteed bill is the value that sets us apart," says Bigelow. "Home shoppers who notice the guarantee in our ads say `I can't afford to not go look at what that guy is doing.' If they come, and they like what they see, they buy. If they like what they see, our guarantee and the benefits from our energy package give them rational reasons to make their emotional buying decision."

Bigelow still sponsors annual heating-bill contests, largely for their marketing benefit--participating homebuyers provide him with heating bills he can post on the wall as evidence of the company's success. During the winter of 1992-93, eight people submitted their heating bills for the contest. The winner came in at $62 for the winter, with an average of $85 for all eight.

An Evolution

Bigelow established his initial market niche by building with an environmentally sound site design, focusing on tree preservation when building on heavily wooded lots. During the early 1980s, he added energy conscious design to the mix, balanced between an improved insulated shell and passive solar features. Sunrooms were particularly popular.

Most of Bigelow's early sales were to upper-end custom clients, people who could afford to pay relatively high energy bills even if they preferred not to. Then one day, a utility company representative, touring a glamorous home, issued Bigelow a challenge: Could he build homes this efficient for lower-income buyers--people squeezed between mortgage payments and high heating bills.

Bigelow took the challenge seriously. He targeted more entry-level housing, added the annual heating-bill guarantee, de-emphasized passive solar, and fine-tuned his conservation features. The production side of his company--the largest of three parts--now builds about 100 townhomes (at 1,000-1,800 ft²) a year, priced between $100,000 and $125,000. He still builds some custom homes in the $300,000 to $500,000 range. His latest efforts--two types of in-fill inner city housing in beleaguered neighborhoods being reclaimed from drug dealers--represent a dramatic departure for any production builder (see "Efficiency for those Who Really Need Low Energy Bills" below).

Current Building System

With Bigelow's approach to energy efficiency, the only constant is change. He used to install a twin set of single-glazed, metal-framed windows with movable insulation between them, but that's gone. He used to install a heat-recovery ventilator, but no longer. Listed below are the key components of his insulated building shell:

Framing:

With 226-inch studs, Bigelow makes selective use of Optimized Value Engineering (OVE) techniques: 24-inch on-center framing, single top plates, 2-stud corners, and so forth. This reduces lumber consumption, increases the percentage of wall area filled with insulation and costs Bigelow no more than the standard 16-inch on-center (with 224s) framing method, while meeting all structural code requirements.

Insulation

Metal corner bracing allows for a one-inch layer of polyisocyanurate foam sheathing over the entire building, which is finished with vinyl siding. When combined with unfaced 6-inch fiberglass batts, the wall system rates R-25. Both the attic and the floor over the garage are insulated to R-38.

Windows

Vinyl windows with low-E coating and argon gas-filled airspace are installed.

Foundations

R-13 interior batts are used in the foundations. For inner-city homes, a frost-protected shallow foundation design dramatically reduces hauling of excavated dirt and debris from these rebuild sites, along with backfill hauling, and dumping fees. The crawlspace foundation is a heavily reinforced, 12215-inch concrete-grade beam combination wall and footing, with rigid foam on the exterior allowing a shallow (less expensive) footing. Total construction savings are typically $6,000 to $10,000 per site.

Lighting

This package includes kitchen, hall and bath fluorescent fixtures. Exterior lights on photocells are also fluorescent.

Tested Tightness

Bigelow has featured tight construction for a decade. Without it, the guaranteed heating bill wouldn't be possible. As with most production builders, Bigelow's homes are built by subcontractors whose work is overseen by job superintendents working directly for his firm. Construction adhesives such as Liquid Nails used by subcontractors at the rim joists and to adhere floors to floor joists during the framing process, provide some tightness. But since air sealing requires a systems awareness and multiple steps, the bulk of that job rests in the hands of one on-staff specialist and a laborer. For the last five years, Nolan Swift has done all of Bigelow's air sealing. Swift is Bigelow's only permanent field employee, apart from supervisors. Bigelow sees the tightness job as too critical to leave in the hands of subcontractors.

For an average townhome, Swift spends 25-30 hours applying three different types of sealing products. He attaches a sticky-backed Swiss foam gasketing product (BG32, from Resource Conservation Technologies) against some studs or plates--a modification of the Airtight Drywall System. For example, all top plates on upper floors are gasketed before drywalling, in order to prevent air leakage into the attic. This process consumes roughly 350 linear feet of gasketing.

Then Swift uses approximately two 16-ounce cans of Hilti foam per unit, sealing all electrical and plumbing penetrations plus the heating distribution system. In a number of locations, siliconized latex (AC20 from Pecora) goes in more effectively and less expensively than foam caulk; Swift orders it in 5-gallon buckets and applies it with a pump gun.

Some sealing details stand out. For example, when a bathtub is to be installed against an exterior wall, Bigelow installs a layer of full height Durarock (by U.S. Gypsum). Once taped, covered with joint compound, and sealed to the floor, this detail prevents warm moist air from leaking into the wall behind the bathtub, a problem that often leads to tile damage in bathrooms. A second example: since vinyl windows are attached from the outside and come without deep jambs, the drywallers use gasketed corner bead around all the windows where the drywall wraps to the window; after trim, the wooden sill is caulked to the window and adjacent drywall.

In order to obtain feedback on the houses, Bigelow schedules a third party--usually his insulator--to randomly blower-door test as many homes as possible in a day. Last year, instead of scheduling his insulator for one day, Bigelow substituted with the two-day tests by Joe Lstiburek and Gary Nelson.

Simple Ventilation

In place of his earlier heat-recovery ventilators, Bigelow installs a simple and less expensive exhaust-only system. A quiet Kanalflakht fan, mounted in the attic, exhausts about 80 cubic feet per minute (CFM) of air from the bathroom. In order to guarantee buyers some background ventilation, the fan runs continuously; the only switch is located in the attic, which inhibits homeowners from turning it off.

What about possible problems with radon and backdrafting of combustion appliances? Bigelow is not concerned about the slight negative pressure caused by an exhaust-only fan. Since he builds his townhomes over garages, with crawlspaces or slab-on-grade foundations, few units have much connection with the soil. Thus in most cases, operation of the homes in a slight negative pressure mode does not pose a radon problem. All space- and water-heating appliances are direct-vent, sealed-combustion models. The only remaining issue is kitchen ventilation; like many production builders, Bigelow uses a non-venting charcoal filter range hood--a less-than-ideal strategy.

Scaling-down the

HVAC/Distribution System

Three aspects of each townhome's heating system stand out: reliance on a gas-fired combo heater, the lack of conventional ductwork in the heat distribution system, and Bigelow's ability to save money on this part of his package (see Table 1).

Although Chicago's relatively cold climate (6,125 annual heating degree-days) can be harsh, all space heating in these homes is supplied by the water heater. Eliminating the need to hook up a separate furnace saves $150 per townhome, which covers the cost of installing a higher-efficiency water heater. Two additional bonuses are achieved with this approach: when used as a space heater, the water heater's life expectancy increases somewhat, and when it comes time for replacement, replacing a water heater is less expensive than replacing a furnace. Bigelow locates the sealed-combustion 40,000-50,000 Btu water heater against an outside wall for easy direct venting of the appliance. Hot water circulates to the water-to-air heat exchanger in an Apollo air-handler unit (combo heater), located in the dropped ceiling of the centrally located main floor powder room or utility room.

Bigelow's low heating loads allow him to use a small air-handler blower (600-1000 CFM) to circulate heated air. Metal ductwork has been eliminated in favor of a dropped soffit/plenum and floor distribution system. Air moves through selected floor joist spaces that are sealed from adjacent floor spaces with caulk, foam, and blocking. Warm air enters each room through holes cut in the second story floor or first level's ceiling for registers; a piece of caulked blocking is placed to deflect heat from the floor space into the room.

Given Chicago's summertime humidity and its 923 cooling degree-days, more than half of Bigelow's buyers have air conditioning installed when they buy their homes. However, their system size typically rates at 1.5 tons, shaving a full ton of capacity (and demand) compared to normal sizing for similar conventionally built homes.

A Rigorous Two-Day Exam

A year ago, Bigelow invited building researchers Joe Lstiburek of Building Science Corporation in Boston, and Gary Nelson of The Energy Conservatory in Minneapolis, to test, probe, and pry into his townhomes. They spent two days making visual inspections and testing both finished and in-progress homes for tightness, duct leakage, and potential moisture. Bigelow and eight to ten of his staff (plus the author) followed the testing process.

Blower-door tests confirmed the tightness of the homes. Of the three-bedroom, 1500-ft² units tested, the tightest came in at 650 CFM of leakage (at 50 Pa of air pressure). In a summary communication, Lstiburek wrote the following:

After inspecting hundreds of houses in all regions of North America (constructed by all the major builders), the units I inspected and tested which were built by your company are the first production houses tested in North America which both meet and exceed (to a surprising margin) ASHRAE Standard 62-1989--Ventilation for Acceptable Indoor Air Quality--and the air leakage standard of the Swedish National Building Code (3 air changes per hour at 50 Pascals). Furthermore, none of the units exceeded the pressurization/depressurization limit of 5 Pascals of the National Building Code of Canada.

Bigelow's distribution system seemed considerably tighter than the average production builder's home. Nelson found that the amounts of house leakage linked to the distribution system ranged from about 120 CFM--an acceptable figure--to a less-than-desirable 300 CFM. He suggested a bit more duct sealing, which Swift has partially incorporated in his air sealing work. Both Lstiburek and Nelson appreciated the ventilation system's simplicity, though Lstiburek thought 80 CFM of constant ventilation might be a little high.

The Bottom Line

Bigelow builds homes which, in another three to five decades, should definitely not be candidates for the weatherization services provided by many readers of Home Energy.

Many builders who have heard about Bigelow are interested in borrowing a bit here and a bit there from what he does but this casual approach may not work effectively. For example, a builder might not be able to heat a home with a combo heater in a cold climate like Chicago's without significantly reducing the heating load through insulation, tightness, and good windows. Builders wanting to learn from Bigelow's success will have to take a systems approach and do their homework. n

Portions of this article first appeared in The Space Heating Technology Atlas, published by E SOURCE in September 1993. E SOURCE is a subscription service providing information on energy-efficient technologies. The complete 362-page Atlas is available to non-members for $1,500. (Contact: E SOURCE, 1033 Walnut St., Boulder, CO 80302 Tel:(303)440-8500.

Figure 1. Bigelow's "energy cost warranty" provides potential buyers with a big reason to buy a Bigelow home. While energy use is only one factor in construction, the attention to detail and innovative building techniques used to achieve such low energy use are additional incentives. Courtesy of The Bigelow Group Inc.

Sections of west-side Chicago fit the description of a wasteland: shells of houses gutted by fire and waiting for demolition, neighbored by empty lots which once held stately masonry homes but now hold abandoned shells of cars. More than 35,000 such lots exist in the city. Some of the ruins shelter the comings and goings of drug dealers.

On the boundary of these areas, embattled residents--rallying around strong churches--struggle to hold off the advancing decay. Under very difficult circumstances, the churches help people "take back" blocks from the dealers. In locations such as these, Bigelow is working on two types of housing that should make a small contribution toward reclaiming the neighborhoods.

For moderate income buyers, Bigelow offers what he calls "provider housing." On lots donated by the city of Chicago, he is building two-story duplexes, priced at roughly $75,000 per 1,200-to-1,600 ft2 unit. With a $15,000 interest-free forgivable second mortgage held by federal agencies, the cost to the buyer drops to $60,000.

Energy packages include nearly all the features described in the main article. In addition, all light fixtures are fluorescent. Bigelow reports that the shallow foundation concept used in these homes required years of effort to gain approval from code officials. The payoff is worth it; each home will save roughly $6,000, primarily through dramatic reductions in the debris and soil removal from the site. Dow Chemical is monitoring temperatures above and below grade at the first site.

Bigelow plans to build roughly 160 more provider units. Local churches serve as critical joint-venture partners in all three neighborhoods where Bigelow operates; in fact, they market the projects and qualify the buyers.

For low-income buyers, Bigelow and the churches are offering owner-built opportunities that he calls "supporter housing." The first units, underway last fall, were designed and are being built by the eventual occupants, with initial design concept and site supervision by Bigelow. To make the construction process simpler, yet still very energy efficient, Bigelow and the occupants selected R-Forms (Palm Beach Gardens, Florida)--a foam-form foundation system that will also be used above grade. With a great deal of sweat equity invested by each future homeowner, plus an investment in a limited amount of skilled workers, the finished costs should run approximately $25 per ft².

With the financial backing and moral support of local churches, the owner-builders began planning the project three years ago. A major hitch was the loss of their initial piece of land which extended the process by a full 18 months. The first stage--eight two-story townhomes plus a community building--will fit on a 1252125 foot lot.

In an unusual move, the initial owner-builders decided to eliminate any financial gains from their own labor by putting a cap on appreciation (a cost-of-living adjustment). Their goal was to create a permanently affordable housing opportunity. The second generation of buyers will have to invest an equal number of sweat-equity hours in the community.

In an equally unusual move, Bigelow himself and two of his staff are participating as initial owner-builders. Once the first eight-unit project is completed, he intends to provide the framework for the process and supporter-housing system to builders in other areas, who in turn would adapt it to their area on a pro-bono basis.

Among the many societal motivations Bigelow expresses for working in the inner city is the issue of sustainable development. "One of the telling statistics about greater Chicago is that our population over the last 20 years increased by a total of about 10%; during that time, the land area occupied by development has doubled. For the last 40 years, what we have done is destroy dense neighborhoods and built sprawling ones. Almost none of the massive infrastructure that has been built in the last 40 years needed to be built. Patterns of ten to 20 dwelling units per acre have been replaced with three dwelling units per acre. Knowing what we know now, no development of one to three dwelling units per acre is going to be sustainable. The density patterns of the last 20 years are simply not sustainable."

                                                  Bigelow system
                                         (compared to standard practice)
Building component                         Added cost     Cost savings
Framing: from 2x4 to 2x6                       ---             ---    
Insulation                                  $500-$600          ---    
Ductwork eliminated                            ---           $1,000    
Combo high-efficiency 
water/space heater                             ---             ---    
Air conditioner                                ---           $80-$100    
Low-E gas-filled windows                    $200-$300          ---    
Tightness                                     $500             ---    
Foundation system*                             ---             ---    
Fluorescent lights                            $200        
Totals                                    $1,600-$1,800      $1,100    

Total increase over conventional construction: $500-$700
* On inner-city homes, Bigelow estimates he saves $6,000-$10,000 by
using a shallow foundation system.

As part of a study assessing the performance of recently built low-energy houses in North America, "Buildings Energy-Use Compilation and Analysis: A. New Residences, or BECA-A," Lawrence Berkeley Laboratory (LBL) is studying Bigelow Homes. A statistical sampling is underway of units built between 1987 and 1992 that are occupied by their original owners. Occupants complete a detailed questionnaire about their house, their use of it, their satisfaction with it, and why they purchased it. Occupants also release their gas and electric utility billing histories to the researchers.The utility bills are used with analytical tools such as PRISM to normalize the houses' performance for temperature. The questionnaires not only provide demographic data but also allow researchers to normalize for variations in the number of occupants and for long vacations. The results of this study will be provided to Bigelow Homes, but will not be tied directly to the company when presented in the BECA-A report (the brand names have been removed to protect the innocent!). Other builders of energy efficient homes who would like their product to be studied and included in BECA-A should contact LBL's Barbara Litt: Tel:(510) 486-5159.

Figure 2. Section of the construction techniques used on a Bigelow home.

"Combo heaters," also known as dual-integrated appliances, integrate water and space heating. The water heater operates like a conventional water heater but it is also used as the home's heating source (see "Once Heated, Twice Used," HE July/Aug '92, p.14). Hot water is pumped from the water heater to a water-to-air heat exchanger inside a pre-plumbed, pre-wired air handling cabinet. When the thermostat "calls for heat," it activates the blower and pump. It forces air across the hot water radiator and circulates the warm air. If the water heater is set at 120deg.-140deg.F, air supplied by the blower will run about 15-20 degrees cooler (105deg.-120deg.). Where cooling is required, air handers can be supplied with a cooling coil powered by a standard electric air conditioning compressor. Besides offering greater energy efficiency, combo heaters increase the life expectancy of the water heater because of increased circulation of sediment that would otherwise settle in the bottom of the tank.

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