Small is Beautiful: House Size, Resource Use, and the Environment

Since 1950, the average house size in the United States has more than doubled, even while the average family size has steadily shrunk. We’re providing more square footage per family member than ever before, and projections are that the trend will continue.

As house size increases, resource use in buildings goes up, more land is occupied, there is more impermeable surface resulting in more stormwater runoff, construction costs rise, and we use more energy. For single-family houses, small is beautiful in terms of environmental performance.

This article takes a look at some of the trends in single-family home building during the second half of the 20th century and provides recommendations for downsizing our houses to improve resource efficiency and quality.

Demographics vs. House Size

The U.S. Bureau of the Census has been collecting detailed information on household size since 1940 and tracking certain characteristics of houses since 1963. Data on houses was collected by the U.S. Department of Housing and Urban Development and a few other agencies from 1940 to 1963.

Average household size in the U.S. has dropped steadily from 3.67 members in 1940 to 2.64 in 1997. The average size of new homes increased from about 1,100 ft² (100 m²) in the 1940s and ’50s to 2,150 ft² (200 m²) in 1997. Factoring together the family size and house size statistics, we find that in 1950 we built houses with about 290 ft² (27 m²) per family member, while we’re providing more than 800 ft² (74 m²) per family member today, an increase of 2.8-fold! These trends are illustrated in the graph at left.

Other trends in single-family housing have been similar. In 1967, for example, 48% of new single-family houses had a garage for two or more cars; by 1997, that figure had jumped to 79%. In 1975, 20% of new single-family homes had 21⁄2 or more bathrooms; by 1997, 50% did. In 1975, 46% of new homes had central air conditioning; in 1997, 82% did.

Resource Consumption

Table 2. Wood Use in New Single-Family Houses, 1950-1992

It almost goes without saying that larger houses consume more resources—both resources used in construction and resources used in operation. But just how much more? The National Association of Home Builders (NAHB) provides on its Web site an estimate of the materials used in building a 2,085 ft² (194 m²) single-family home.

These materials, including roughly 13,000 board-feet of framing lumber, 6,200 ft² (576 m²) of sheathing, and 14 tons (12,670 kg) of concrete, are listed in Table 1 below.

One might expect that there would be some economy of scale as house size increases—in other words, a reduction in material use per square foot of floor area. But that’s not the case, according to Gopal Ahluwalia, the Director of Research at NAHB. While NAHB has not compiled data comparing material use as a function of house size, Ahluwalia told

EBN that he believes larger homes consume proportionally

more materials. That’s because larger houses tend to have taller ceilings and more features. He estimates that a 5,000-square-foot house built today will consume three times as much material as the 2,085-square-foot home they have modeled, even though its square footage is only 2.4 times larger.

David McKeever and Robert Phelps, of the U.S. Forest Products Laboratory, examined the use of wood products in houses from 1950 through 1992 in a paper published in the Nov.-Dec. 1994 issue of the

Forest Products Journal. Lumber, structural panel, and nonstructural panel use in new houses during this period, along with figures for total wood use calculated by

EBN from this data, are presented in Table 2 below.

As would be expected, total wood use in homes has increased steadily between 1950 and 1992, as houses got bigger. But when we examine total wood use

per unit of floor area, we find that it dropped between 1950 and 1970—perhaps due to the substitution of plywood sheathing for board sheathing and the introduction of more wood-efficient roof trusses. Then around 1970, wood use per square foot of floor area began to increase again and is up about 12% from the low point. Exactly why this is occurring is not clear; it could be the increasing use of 2x6s instead of 2x4s for wall framing, or a shift to more complex geometries.

What about energy consumption? In general, the energy efficiency of a building envelope is a function of how well insulated it is, how airtight it is, exposure of its glazed areas to solar gain, and its area. All else being equal, a house with more surface area will consume more energy for heating and cooling. Thus, a larger a house—or one that has more complex geometry—will consume more energy.

Table 3 on page 8 compares heating and cooling costs for 1,500-square-foot (139 m²) and 3,000-square-foot (279 m²) houses.

Six different houses were modeled: well-insulated versions of both houses in Boston and St. Louis, and a poorly insulated version of the small house in Boston and St. Louis. The houses all have simple geometry. Comparing the large and small versions of the houses with comparable energy features, we find that in halving the floor area of the house, heating costs are slightly more than halved, while cooling costs are reduced by about a third. When the small house is modeled with lower energy standards, its energy consumption goes up a lot compared with the energy-efficient house, but it still uses a lot less than the large house that is well insulated.

Be aware that reducing the square footage of a house does not always mean a comparable reduction in surface area. If we reduce the size of a house by breaking it into smaller, separate wings, for example, as is sometimes done in custom homes, we may not gain much in the way of energy savings compared with the large box. Along with the greater surface area increasing heat loss and unwanted heat gain, larger houses also generally require longer runs for ducting and hot water pipes. Losses in conveyance of warm air, chilled air, or hot water can be significant.

Quantity vs. Quality

With single-family houses, the notion that bigger is better has been a leading driver of the real estate industry. Large houses—“starter castles” as some pundits refer to them—are a status symbol. Even retirement homes for “empty-nesters” are usually a step up in terms of size. According to Gordon Tulley, AIA, an architect with Steven Winter Associates in Norwalk, Connecticut, “buyers today want as much space as they can afford.” This is true, he says, for virtually every segment of the home buying market.

When asked why people think they need such large houses, designer-builder John Abrams, of the South Mountain Company in Chilmark, Massachusetts (on Martha’s Vineyard), offered three possible explanations: “First, with less of a sense of community and public life in our culture, the home becomes a fortress which needs to contain everything we need, including multiple forms of entertainment, rather than basic shelter; second, the building industry has been selling ‘big is better’ and the message has been heard; and third, diminishing craft and design generosity has resulted in sterile homes—people mistakenly think that what’s missing is grandeur: more space.”

But there are signs that this status quo is being questioned today. Abrams himself says that many of his clients are not looking for

big—they’re looking for

good! And the new book

The Not So Big House, by Sarah Susanka (see review, page 15), which emphasizes a very different approach to house design—one focused on quality not quantity—is selling extremely well. According to Taunton Press, there are 70,000 copies in print, and this was Amazon.com’s best seller in the home design category during 1998! A residential architect in Minneapolis, Susanka argues for space-efficient homes with spaces that will be used. For example, she suggests eliminating the formal dining room in favor of a larger kitchen that provides both dining space and even some informal living space.

Abrams’ company has been emphasizing space-efficient houses since its launch 25 years ago. In addition to providing open-plan living/dining/kitchen areas, he suggests providing built-in furnishings and storage spaces, eliminating single-use hallways, designing multiple uses into rooms, and utilizing often-wasted attic and low-roof space. (Specific strategies for providing workable, compact living spaces are provided in the checklist on page 11.)

Legal and Regulatory Issues with Building Small

Zoning regulations, restrictive covenants and design standards for specific subdivisions, and even mortgage banking requirements can significantly limit your options in creating small, space-efficient single-family houses. Some municipalities establish strict limits on how small a house can be. Though less common than in the past (due in part to lawsuits that have challenged their constitutionality), such regulations still exist. In the suburbs around Atlanta, for example, Fulton County specifies minimum heated floor area of houses in most of its zoning districts. For single-story homes, these minimums range from 850 to 1,800 square feet (79-167 m²); for two-story homes, from 1,100 to 2,000 square feet (186 m²).

Far more common than minimum house size regulations in municipal zoning ordinances are restrictive covenants established by developers for specific subdivisions. In the La Marche Place neighborhood in the 3400-acre (1,400 ha) Wooded Hills subdivision in Little Rock, Arkansas, for example, single-level homes must be at least 2,600 square feet (242 m²) and multi-level homes at least 3,000 square feet (279 m²). In the Spring Glen subdivision in Medina County, Ohio, the minimum heated square footage of homes (exclusive of garages, finished basements, porches, etc.) ranges from 1,800 to 2,600 square feet (167-242 m²), with a provision for reducing the square footage by up to 10% if the developer deems that “the design is unusually good and is or will be compatible with other houses in the development.”

Mortgage bankers can also

in effect specify minimum house size for new homes by mandating ratios of house value to land value. Secondary mortgage markets often have a rule-of-thumb that the lot should not be worth more than 30% of the total value of the real estate. Thus, on an expensive lot, homeowners are required to build expensive homes. In the real estate appraiser’s eye, expensive generally means large. Appraisals for small houses also run into difficulty when all the houses in a particular area are very large and the appraiser can’t find small comparable houses. Real estate appraiser Linda Lloyd, of Shermans Dale, Pennsylvania, described a recent situation in which she was unable to appraise a 1,700 square foot (158 m²) home on 3 acres in an area with all houses over 2,500 square feet (232 m²). “It would absolutely not appraise,” she said. This issue does not apply at the high end of the real estate market, according to developer John Knott, where land values commonly exceed house values.

There are also examples of both zoning regulations and restrictive covenants on subdivisions that specify

maximum house size. Many municipalities effectively limit the

footprint of houses on small lots by specifying the maximum coverage of the lot. This restriction generally has more to do with stormwater management than building size, but particularly with small infill lots, it can have a big impact on house size. Cupertino, California goes much further by restricting house floor area to a maximum size of 6,500 square feet (604 m²)—less in areas of significant slope or smaller lots.

Santa Cruz County in California and several communities in the Chicago suburbs also have maximum house size regulations. Megan Lewis, of the American Planning Association, told

EBN that in the Chicago area the regulations are addressing a trend referred to as

mansionization, in which houses are often designed to fill the maximum available footprint of a lot—overwhelming the neighborhood scale.

In the environmentally focused Dewees Island subdivision in South Carolina (see

EBN

Vol. 6, No. 2), maximum house size has been established by covenant at 5,000 square feet (465 m²).

Given that this is a luxury development, with most 2-acre sites selling in the $400,000 range, but some as high as $850,000, this restriction on house size is highly unusual. So is the fact that there are no minimum floor area or footprint requirements. Developer John Knott suspects that they have lost a few sales because of these standards, but in general he thinks that property owners feel relief at the maximum size limit—they don’t have to “keep up with the Joneses.” The average-size home at Dewees is 2,600 to 2,700 square feet (242-251 m²), with the smallest just 1,200 square feet (111 m²).

Another influence on house size has long been our capital gains tax policy. Until very recently, when a family sold a home they had to buy a new home of equal or greater value within two years to avoid capital gains tax on appreciated value. That policy often resulted in people moving into larger houses, especially empty-nesters moving into an area with lower real estate values. Fortunately, that policy changed in 1998. We are no longer taxed for capital gains of $250,000 ($500,000 for a couple) on a primary residence, so the incentive for moving up into larger homes to avoid capital gains taxes is gone in most cases.

Selling the Concept

All right. Let’s say that you, as the designer or builder, are convinced that a small, resource-efficient, well-designed house makes sense for a particular client. And let’s further assume that there aren’t any regulatory or financing impediments to building a compact 1,500-square-foot (140 m²) house. How do you sell your clients on the idea?

Abrams finds that clients often come to him with a preconceived notion of how large a house they need—say 3,000 square feet (280 m²)—because a friend’s house of that size seems to have what the client wants. Abrams turns that around by taking a different approach. “We toss out the numbers, start at the beginning, and analyze our clients’ needs—what they will do in the house, how they live, and what they care about.” He then takes clients to visit houses his firm has built to show that the

quantity of space is way less important to them than the

quality of that space. “There’s nothing like experiencing a successful, finished dwelling to convey this idea,” says Abrams.

It is also possible to convince clients that, by keeping the square footage down, they can end up with a higher quality house. Rather than using up the budget to create the largest, most impressive house possible, Abrams, Susanka, and many other designers today recommend creating smaller houses with a higher level of finish quality and added amenities. “A house that favors quality of design over quantity of space satisfies people with big dreams and not so big budgets far more than a house with those characteristics in reverse,” says Susanka in

The Not So Big House. She argues that a good house designer should suggest to clients that, for a given budget, they reduce square footage to allow for high-quality detailing. Fine carpentry detailing, granite countertops, hardwood floors, labor-intensive but soulful salvage materials, and quality architecture can be far more impressive than sheer size.

In the tract home sector, we are likely a long way from having the market accept smaller for the sake of higher quality. Gordon Tulley has found that, for the tract home market, the only reason a buyer would want something smaller would be to save money. It is a very rare buyer, he laments, who wants a more modest-sized house with better detailing.

Final Thoughts

A great deal of attention is paid to material selection and energy detailing in creating green homes. We seek out recycled-content building materials, or low-embodied-energy materials, or natural materials. We use

advanced framing to reduce wood use. We design high-R-value walls and ceilings and specify performance glazings and high-efficiency equipment. But way too often we overlook a far more important consideration: size.

Consider that a 1,500-square-foot (141 m²) house with quite low energy performance standards (R-13 walls and R-19 ceilings) will still use a lot less energy for heating and cooling than a 3,000-square-foot (282 m²) house of comparable geometry with much better energy detailing (R-19 walls and R-30 ceilings), as described on page 8. Downsizing a conventionally framed house by 25% should save significantly more wood than substituting the most wood-efficient advanced framing (24”-on-center studs, single top-plates, two-stud corners, elimination of cripple studs at windows, etc.). And it is easier to reduce the embodied energy of a house by making the house smaller than by searching for low-embodied-energy materials.

Building small isn’t necessarily easy. To make small houses work, they have to be carefully designed.

Simply using off-the-shelf house designs may not adequately account for the specific needs of the family. Fortunately, there are a number of excellent resources available on compact house design, some of which include floor plans and elevations. To ensure success with small, resource-efficient homes, however, builders should involve a designer, preferably one with experience in compact house design. And both builders and designers should spend enough time with clients to adequately explain the benefits of smaller homes.

– Alex Wilson