Greening Main Street Buildings

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In the late 14th century, England's King Richard II commissioned a new building, College Hall(1), at Oxford University. The carpenters who built College Hall knew that the massive oak beams spanning the great hall's ceiling would probably need to be replaced in a few hundred years, so next to the building, they planted a row of oak seedlings from the trees they used for the beams. Sure enough, the beams needed to be replaced about 300 years later, and the new carpenters had mature oaks right there, ready to be milled and turned into new beams.

Empire
Historic Main Street buildings, unlike most modern commercial structures, were built of durable materials such as stone, brick, and dense heartwood and designed to last for decades.

Now, that's thinking ahead. And, for centuries – millennia, actually – that's the kind of planning that went into most major building development projects. Materials were simply too expensive to waste. So was energy, so buildings were designed with conservation in mind – conserving heat in cool weather, cool air in warm weather, and even collecting rainwater to use for building functions.

But, somehow, things got off track, and during the second half of the 20th century, the energy efficiency of buildings and community development practices in the United States plummeted. According to the U.S. Energy Information Administration's most recent "Commercial Buildings Energy Consumption Survey," the energy efficiency of commercial buildings declined dramatically between 1945 and 2000. And the situation is worse in this country than in most other Western nations: in the United States, buildings are responsible for 40 percent of all carbon emissions, compared with only 25 to 30 percent in the European Union(2).

What went wrong? Many factors contributed to the decline of energy efficiency in commercial buildings, from the passage of the Interstate Highway Act to the advent of air conditioning. But the good news is that, after decades of neglecting the energy-conserving features of older commercial buildings, communities throughout the nation have a new appreciation for the environmentally friendly features of older buildings.

Older main street buildings are ideal models of sustainability. There is simply no method of construction that is more environmentally responsible than rehabilitating an old building.

Among the typical environmentally friendly features of main street commercial buildings:

Shared party walls: Traditional main street storefront buildings are narrow and deep – 20 to30 feet wide by 100 to 150 feet deep – with shared side walls. For a 20-by-100-foot building on the interior of a block, 83 percent of the building's wall surface is shared with other buildings. The shared walls conserve heat, limiting the amount of wall surface experiencing significant heat loss to less than 20 percent.

Thick masonry walls: Solid masonry walls store heat and cooled air very efficiently, helping regulate the temperature inside the building.

Operable awnings: Awnings that can be rolled down when the weather is hot can reduce heat gain by more than 65 percent, and rolling up the awnings when it's cold outside increases heat gain inside the building.

Operable
An example of operable windows on a historic building in South Boston, Va.

Credit: The Clue Group, LLC

Operable windows: Windows that open, as opposed to windows with fixed frames, help circulate air and regulate interior temperatures. For example, opening the top sash of a typical double-hung window on the sunny side of a room permits hot air near the ceiling to escape; opening the bottom sash of a double-hung window on the shady side of the room lets in cooler air.

Operable shutters: Just as awnings help regulate temperature gain through storefront windows, operable shutters on upper-floor windows keep rooms cool during hot weather by shading out the sun while still permitting ventilation.

Reflective ceilings: Shiny ceilings painted a light color, such as white or silver, reflect light back into the building, reducing or even eliminating the need for artificial lighting during the day.

Transom windows: Transom windows help magnify light shining into the building, providing more ground-floor ambient light while intensifying heat in the area immediately behind the storefront window.

Skylights: Like transom windows, skylights boost the amount of natural light in the building, thereby minimizing the need for artificial lighting.

Tall ceilings and ceiling fans: Hot air rises naturally. Tall ceilings in commercial buildings help keep the lower six feet or so of air space cool in warm weather, while ceiling fans circulate the air above, moderating temperatures in the store.

Passive solar: As sunlight shines through storefront and transom windows, the masonry flooring inside the storefront window absorbs heat, radiating it back into the ground-floor space when the temperature cools.

Water tanks: Roof-mounted water tanks collect rain water; and gravity, rather than a pump, delivers it to toilets and for other secondary uses inside the building.

Recessed
Example of a recessed entryway - a characteristic common to many traditional commercial buildings that helps prevent hot or cold air from rushing inside when a door is opened.

Credit: The Clue Group LLC

Recessed entryways: Recessed entryways help prevent hot or cold air from rushing into the store when the front door is opened.

Atriums: Whether protected by a skylight window or open to the sky, an atrium illuminates the interiors of multi-floor buildings, lighting all the rooms and hallways facing it.

Embodied energy: The energy it took to manufacture the materials used in buildings, transport them to the construction site, and construct the building has already been spent and is embodied in the building itself.

Materials created locally: Historically, most main street building materials were purchased from local or regional sources, rather than being shipped in from long distances.

Walkability: Probably one of the most environmentally friendly characteristics of older and historic main streets is that they are walkable.

Durability: Unlike most of today's commercial buildings, whose lifespans are driven largely by taxable depreciation schedules, older main street buildings were built to last for decades, if not centuries, with durable materials like stone, brick, copper, and dense heartwood.

The list of the energy-saving characteristics of traditional main street commercial buildings could go on and on. But, unfortunately, the list of ways that property owners have mutilated main street buildings over the years, inadvertently eroding their green characteristics, is equally long. Among the more common energy-inefficient remuddlings:

  • Enclosing upper-floor windows or replacing them with new ones. Some seem to think that replacing the upper-floor windows in a historic commercial building is an energy-wise improvement. The R-value of a double-glazed window, however, is only nominally better than that of a single-glazed window; and the historic window's heartwood frame will last decades longer than its replacement. It is usually more environmentally responsible, and less expensive, to simply repair the original window, seal any gaps or cracks around the molding to prevent air infiltration, and install an interior storm window.
  • Installing suspended ceilings. Suspended acoustical tile ceilings erase several green characteristics of traditional main street commercial buildings – particularly in ground-floor storefront spaces. By lowering the ceiling height, they disrupt vertical air circulation. By blocking the transom window and covering up the bright, shiny original ceiling, they significantly cut the flow of natural light into the building.
  • Enclosing storefront windows. Some businesses – especially professional offices and bars, it seems – have a tendency to reduce the size of their storefront windows by partially enclosing them. This disrupts the passive solar benefits of large storefront windows and, incidentally, disrupts the visual rhythm of the overall streetscape.
  • Replacing functional awnings with fixed awnings. It seems as though awnings are now frequently used as business signs, rather than for the energy-conserving purposes – allowing or preventing heat gain – for which they were originally intended.
  • Removing rooftop water tanks. Unfortunately, rooftop water tanks are only a distant memory on most main streets now; but, by collecting rainwater and using it to fill toilet tanks, they helped manage the district's storm water, reduced demand for treated water, and saved property owners money.

How to Make Main Street Buildings Greener

At its simplest level, making main street buildings more environmentally friendly involves just two things: using less energy and using fewer materials. Using less energy means consuming less energy, primarily through passive methods such as using natural sunlight and heat gain or generating more "green" energy, or both.

Here are some major actions that can make main street buildings greener:

Undo inappropriate alterations.

The first step in(re)greening main street buildings is simply to undo the alterations that have, over the years, reduced their energy- efficiency. In a few instances, the alterations may be so extensive that undoing them would be prohibitively costly. But, in most cases, the alterations are relatively simple, and it is usually possible to reverse them for a few thousand dollars or less: removing a suspended ceiling, for example, uncovering transom windows, or restoring a storefront window.

Seal air leaks.

Air leaks are one of the biggest energy-related problems in older commercial buildings. By most estimates, leaks around storefront and upper-floor windows through ducts and vents and around doors can waste 20 to 50 percent of the energy spent on heating and cooling commercial buildings.

Sealing air leaks in a main street commercial building is similar to sealing air leaks in a house. Make sure the weatherstripping around doors and windows is tight and that any cracks or gaps around doors and windows are caulked. Use duct insulation to wrap heating and cooling ducts. If the building has a basement or crawlspace,
be sure it is adequately insulated. If the building has a wood frame, make sure the external walls have adequate insulation in the cavities between the exterior siding and interior wall finish.

Certain types of blow-in insulation, such as rock wool, cellulose, and fiberglass, are environmentally friendly and can be installed without removing the interior sheetrock, plaster/lathe, or other interior wall finish. Be sure, however, that the insulation contractor checks the wiring in the walls first to make sure it can be encapsulated; some older types of wiring, such as "knob and tube" wiring can become a fire hazard if encapsulated with insulation.

Older masonry – stone, brick, concrete block, etc. – absorbs moisture from outside air and must be able to "breathe" to let moisture evaporate. Hire a contractor who has worked on older and historic buildings and understands how to install insulation and seal windows and doors in a manner that won't trap moisture inside walls or allow it to condense on wall or trim surfaces.

Repair or replace inefficient heating and cooling units.

According to the U.S. Department of Energy's Energy Efficiency and Renewable Energy (EERE) program, heating, ventilation, and air conditioning (HVAC) consume 40 to 60 percent of all energy used in commercial buildings and houses in the United States. According to the U.S. Environmental Protection Agency (EPA), cooling interior spaces alone accounts for 15 percent of all the electricity used in commercial buildings across the nation, second only to lighting. Of all the ways in which the energy efficiency of main street buildings can be improved, HVAC is without a doubt the most significant.

There is no single solution for all main street buildings. The best HVAC system for a particular building will depend on its size and materials, its orientation, the local climate, and the availability of nearby energy resources, among other factors. The good news is that more options for making main street buildings' HVAC systems energy- and cost-efficient are available now than at any point in history. Among some of the newer options:

High-efficiency, gas-fired rooftop units: By combining the condenser, compressor, and evaporator in a single unit and by using pulse combustion, these units control temperature better than older gas-fired rooftop HVAC units. Some newer units also modulate air flow, preventing the energy loss that results when an HVAC unit cycles on and off frequently.

Boilers: Many mid-size and larger commercial buildings employ boilers to heat interior spaces by using natural gas, oil, or coal to generate steam or hot water. New, energy-efficient boilers tend to be smaller, which enables a building owner to use several small boilers to heat different parts of the building to different temperatures, depending on building use. Also, boilers that use solar energy and biomass energy are now appearing on the market.

Generate on-site energy.

The range of options available for generating on-site electricity has expanded dramatically in the past few years. For older and historic main street buildings that have roofs with access to direct sunlight, roof-mounted photovoltaic solar panels that convert sunlight into electricity are becoming a practical option. Solar panels can provide part or all of the electricity required to operate a main street building, depending on how much sunlight the building receives and how much electricity it consumes.

What size solar panel does your building need?

A typical solar panel using crystalline silicon wafers generates approximately 70 milliwatts(3) per square inch per hour. If direct sunlight strikes the panel for, say, four hours per day, it would generate 280 milliwatts daily (70 milliwatts times four hours). In reality, it would probably generate more than that on sunny days, because it would receive partial sunlight for part of the day; but on cloudy days, it would generate less energy — so, let's assume that 280 milliwatts per day is a daily average.

Next, let's say you plan to use solar energy to power some of the building's electrical appliances and light fixtures, and that these appliances and fixtures need 1,000 watts of power. You would need 24,000 watt-hours per day (1,000 watts times 24 hours per day). Thus, you would need 85,000 square inches of solar panels (24,000 watt-hours times 280 milliwatts of solar electricity generated per square inch), or about 590 square feet (85,000 square inches divided by 144 square inches per square foot).

Solar panels work through a chemical reaction triggered when sunlight hits a silicon wafer treated with phosphorus and boron. Each treated wafer is a solar cell; cells are joined together to form modules; and modules are connected to one another to form arrays. An array plus the other components needed to turn the solar energy into a usable form comprise a solar panel. Energy from a solar panel can be fed directly into a building's electrical panel for immediate use or can be stored in batteries for later use, or both.

During the early decades of solar energy use, wafers used crystalline silicon. Unfortunately, there is a finite supply of crystalline silicon in the world, it's relatively expensive, it's somewhat bulky, and it only passes along about 15 or 20 percent of the energy it harnesses. Today, several new advances offer solutions to these problems – using copper indium gallium selenide (CIGS, for short) instead of silicon, for example – and increased demand is gradually driving down prices.

Some historic preservationists worry that solar panels will spoil the appearance of a historic building. This is usually a greater concern with residential buildings than main street buildings; on a typical commercial building with a low parapet wall at the front roofline, the parapet may be tall enough to conceal the solar panels and thus minimize their impact on the design integrity of the building. For buildings with pitched roofs, solar shingles – thin-film solar panels that look like somewhat shiny asphalt shingles – might be the solution.

No other mechanism for generating on-site energy offers as much promise for main street buildings as solar energy – yet. Roof-mounted wind turbines can vibrate so much that they jar loose masonry and mortar, which makes them a poor choice for older and historic buildings. But researchers are constantly experimenting with new forms of energy generation, from harnessing the energy created when someone uses a revolving door to converting the heat absorbed by masonry surfaces into electricity.

Improve window efficiency.

For years, the windows of older and historic main street buildings have been closed in, punched out, and narrowed down by building owners who think that doing so will make the building more energy efficient. But, while it might be tempting to replace old windows with newer, double-glazed windows, window glass is not a major source of heat loss.

Studies by the Rocky Mountain Institute(4), the Vermont Energy Investment Corporation(5), and others have demonstrated that the energy savings that might be gained by replacing historic windows with new double-glazed windows is inconsequential. Glass, whether single-or double-pane, is a poor insulator. The environmental costs of manufacturing new windows and sending old ones to the landfill are far greater than the benefits to be gained in energy savings. Window efficiency can be improved, though. Be sure the weatherstripping on operable windows, usually those on upper floors, is tight and that any gaps or cracks around windows are securely caulked. Building owners can install interior storm windows, if desired, by attaching them to the interior window casing with magnets or brackets.

Obtain building materials locally.

A few years ago, contractors removed the stucco-like cladding that had covered a historic commercial building in downtown Dubuque, Iowa. Underneath, they found several cast-iron columns framing the storefront, all in good condition. Like most cast-iron columns made in the early 20th century, the name and location of the foundry where they were manufactured was stamped near the base: they had been made right there in Dubuque. At the time they were made, it was commonplace for building materials to come from manufacturers within the community or the region. Today, unfortunately, building materials are usually trucked in from many miles away. Buying materials locally or regionally cuts down on the amount of gasoline needed to transport materials and, ultimately, on costs.

Improve interior and exterior lighting. Compact fluorescent light bulbs have been commercially available for years now, and their cost and energy savings are well known. Other choices are on the horizon as well; LED light bulbs, in particular, could surpass compact fluorescents in light quality, bulb longevity, and cost efficiency. Until now, LED lighting has not been bright enough to replace traditional incandescent bulbs for interior lighting, but a few manufacturers are now producing LEDs powerful enough not only for interior use but also for streetlights.

There are many other things building owners can do to improve the energy efficiency of a main street building's lighting. Installing timers and occupancy sensors can ensure that lights are turned on only when needed. Removing the covering from a transom window and putting it back in use will dramatically boost interior lighting. Be sure the ceiling is painted a light color – better yet, with a glossy finish – to maximize natural light transmission.

Install green roofs.

Technologically, a green roof is pretty simple – it's basically just an engineered layer of vegetation on top of a building – but it helps the environment in two major ways: it improves air quality by absorbing carbon and releasing oxygen; and it absorbs rainwater, reducing runoff into the municipal storm water system. A typical green roof also has key benefits for the building. For instance, it helps prevent heat loss when it's cold outside, and it helps keep the building cool when the weather is hot, both of which lower utility costs. And, by protecting the roof surface from harsh sunlight, a green roof lasts longer than a conventional membrane or built-up roof, thereby reducing replacement costs.

There are two ways to install a green roof on a main street building: it can be integral to the roof structure itself, or it can consist simply of shallow planting boxes placed on top of the roof.

Green roofs that are integral to the roof structure can be extensive, which means that the growing medium is relatively shallow, that it is used primarily to insulate the building, and that the roof isn't usually employed as an outdoor room; or intensive, meaning that the growing medium is relatively thick, the roof can incorporate large plants, and the roof functions as an outdoor room. Green roofs that aren't integral to the roof structure but consist of planting boxes are generally referred to as roof gardens.

In either case, the rectangular, gently sloping roofs of most main street buildings are ideal candidates for "greening."

When a green roof is part of the roof structure, it includes an edge-to-edge membrane, similar to the rubbery membrane many main street commercial buildings already have, topped by a layer of rigid insulation; a planting tray; a growing medium, such as gravel, a shallow layer of soil or engineered soil, or a hybrid mixture; and a layer of vegetation. Sedum is the plant favored by most green roof engineers; rugged and durable, with a low profile, it absorbs an enormous amount of water. There are over a thousand varieties of sedum. Some work better than others in certain climates; but, for every climate, there are several varieties of sedum that will thrive.

Given that conventional membrane or built-up roofs have useful lives of only about 15 to 20 years, odds are that, every year, at least a few roofs in your district will need to be replaced. The cost of an integral, extensive green roof is only slightly greater than the cost of a conventional roof; so, within a few years, many of your district's buildings could be sporting new, green rooftops.

What Your Organization Can Do

Make your planning and zoning policies green friendly. Check your community's planning and zoning policies to see if they encourage full use of existing buildings before constructing new ones. Letting buildings sit vacant while new ones are developed is a waste of resources and poor environmental policy. Encourage civic leaders to provide incentives for reusing existing buildings and disincentives for constructing new ones if vacant buildings are available. Conduct a roof survey. Look out the windows of the tallest building in your district and note which buildings have flat roofs and which roofs look as if they may need to be repaired or replaced sometime soon. Talk with property owners about the benefits of green roofs and about how, when it is time to replace the roofs of their buildings, they could install a green roof.

Encourage property owners to promote the energy efficiency of their buildings. A growing number of business owners are looking for locations that offer sustainable features; in many instances, they are willing to pay a little extra for them, particularly if energy-saving features will reduce their operating costs.

Offer energy audits for property owners. A number of organizations and government agencies offer energy audits for little or no cost. Check with your regional office of the U.S. Department of Energy for referrals to organizations that conduct energy audits in your area, then ask one or more of those organizations to offer audits to district building owners.

Inform property owners about state and federal incentives. For commercial buildings, the federal government offers tax deductions of up to $1.80 per square foot for improvements that save at least half of the energy needed to heat and cool the building. To qualify, improvements must meet ASHRAE(6) Standard 90.1-2001(7), which spells out the minimum requirements to design and construct energy-efficient buildings.

The federal government also offers tax deductions of up to $0.60 per square foot for qualifying improvements in each of three categories: the building envelope, lighting, and heating/cooling systems. Considering the savings that a main street property owner is likely to realize in energy bills after improving the energy efficiency of a commercial building, the federal tax credits make most improvements a financial no-brainer.

Federal tax credits are also available for owners of residential property. For instance, someone who owns an upper-floor condominium in a main street building or a house in a residential neighborhood adjacent to a main street district may be eligible for tax credits if he or she makes energy-conserving and/or energy-generating improvements. The recently enacted American Recovery and Reinvestment Act – the federal stimulus package – has extended the timeline for residential property owners to earn and claim these tax credits and has raised the dollar caps for eligible expenditures(8).

Residential property owners can now claim hefty tax credits –30 percent of eligible expenses, in most cases – for making energy-conservation improvements, such as adding insulation, installing green roofs, or improving energy generation, by installing solar panels, for example. Moreover, these are income tax credits, meaning that every dollar spent on upgrades, up to the cap, reduces a dollar of tax liability, not tax deductions, which reduce the amount of income on which taxes are calculated. Include information on state and federal incentives in your newsletter, on your website, and on your  meeting agendas; and make sure your district's property owners, area architects, and building contractors know about these incentives.

Create local incentives for environmentally sustainable upgrades. City governments and nonprofit organizations can put local incentives in place to encourage property owners to make their buildings more environmentally sustainable. These incentives range from grants to local property tax abatement. Dubuque, Iowa, for example, is creating an Energy Efficiency Zone that offers property owners an array of financing and incentives, including energy design grants, technical assistance, low-interest financing through an Energy Revolving Loan Fund, and access to case studies.

When designing your incentives program, focus particular attention on main street building projects that might not be covered by other incentives. For example, federal tax credits focus slightly more attention on active technology – installing solar panels, for example – than on passive technology, such as reopening transom windows or removing suspended ceilings. Concentrate on developing incentives that directly address some of the unique needs and opportunities of main street buildings.

Also, consider providing a sequence of incentives over the course of several years. Begin with incentives to stimulate quick, low-cost upgrades, such as providing free or heavily discounted programmable thermostats or lighting controllers; and gradually move up to incentives for more extensive upgrades or improvements, such as matching grants for green roofs or solar water heaters.

There are a number of possible funding sources for incentives, such as Community Development Block Grants, grants from utility companies and foundations, municipal general funds, and cash grants or gifts in-kind from manufacturers of green building materials. Talk with local and state officials, utility company representatives, bankers, and foundation representatives about potential sources of funding for incentives. In many cases, a small amount of money may encourage property owners to make upgrades. The goal of any incentive program should be to establish momentum for improvements, not to provide ongoing financing for them.

Ensure the availability of adequate capital to finance energy-efficiency upgrades and improvements. Some banks have been reluctant to loan money – or as much money as is needed – for green building projects because they aren't familiar with the technology, resulting in either a capital shortage or tighter  underwriting criteria. Talk with area bankers about the economic benefits of improving the energy efficiency of main street buildings and encourage them to provide lending incentives that support green upgrades. A bank might reduce the amount of replacement reserves it requires a building owner or developer to set aside in the budget if he or she agrees to use materials with a longer life-cycle. Another possibility is for the bank to provide a greater percentage of a project's financing if the owner or developer can demonstrate that the project's energy-efficient features will reduce annual operating expenses by a certain amount.

Sponsor an energy fair. Offer workshops on energy-efficient commercial and residential building improvements and showcase regional suppliers of green building materials, energy systems, and related goods and services.

Provide how-to information in your program's newsletter. Include brief how-to articles on ways to improve the energy efficiency of main street buildings.

Promote the cost savings associated with environmentally sustainable improvements and construction. Enough "green" rehabs and new construction projects have taken place over the past few years to provide significant evidence that environmentally sustainable improvements almost always produce economic benefits as well. A green roof, for example, not only helps main street property owners and their tenants save money on heating and cooling; it also helps the municipality reduce storm water runoff and, by doing so, reduces maintenance costs.

Make policy changes to encourage full use of existing buildings before developing new ones. For civic leaders, the single most important action is to commit to reusing existing commercial buildings before permitting or encouraging the construction of new ones. In many ways, it seems self-evident that developing new commercial buildings when the community has vacant buildings waiting to be used is a waste of materials, energy, and money. But, for several reasons, communities have been slow to act on this key policy. Among the hurdles:

Logistics:

In many, if not most, communities, adopting a policy of fully using existing commercial buildings before building new ones requires changes to zoning laws and the revision of planning documents and permitting processes. And many local planning commissions work primarily by reacting to proposals submitted by developers and property owners, rather than by implementing new policies.

Lack of knowledge:

Many people simply don't know about the harmful environmental impacts of sprawl development or the environmental benefits of rehabbing and keeping existing buildings in active use. In particular, few people are aware of the phenomenal amount of energy embodied in existing buildings – the amount of energy it took to manufacture the materials, transport them to the building site, and construct the building. Nor do they realize how much energy and materials are wasted by demolition and new construction.

Information about "embodied energy" has been around for decades. Thirty years ago, for example, the federal Advisory Council on Historic Preservation commissioned a study to examine how much energy historic buildings embodied. The study found that the amount of energy embodied in one square foot of a traditional building equals approximately 16,000 British Thermal Units (BTUs).

In other words, the amount of energy required to manufacture eight bricks, haul them to a construction site, and place them in a wall is equal to the amount of energy in a gallon of gasoline(9). Consequently, the energy embodied in the bricks alone in a typical three-story, 20-x-100-foot main street storefront building is roughly equal to the amount of energy embodied in 3,900 gallons of gasoline – enough to keep the average American driving for more than eight years – or to the amount of energy saved by recycling 1.3 million aluminum cans.

LEED:

The U.S. Green Building Council, a national nonprofit organization, encourages sustainable design and development through a point-based certification program called Leadership in Energy and Environmental Design – LEED, for short. The council awards LEED certification in four categories – Certified, Silver, Gold, and Platinum – depending on how many points a project achieves. LEED is only one of many certification programs for sustainable design that have cropped up in the past decade, but it is without doubt the best known and most popular in the United States. It's so popular that a rapidly growing number of local and state governments encourage or even mandate that new building construction and rehabilitation projects comply with LEED standards. The federal government is on the LEED bandwagon, also, with most federal agencies now committed to seeking LEED certification for their building development projects.

But LEED has its critics, including some historic preservationists, who point out that LEED awards more points for new construction than for building rehabilitations. Until relatively recently, for example, the program awarded only three points (out of a total of 69 possible points) for certification of new construction and major rehabilitation of commercial buildings if they reused 95 percent of a building's walls, floors, and roof and 50 percent of its interior walls. In several recent speeches and in a 2007 video interview now available on YouTube.com(10), historic preservation economist Donovan Rypkema blasts LEED for its bias toward new construction, calling the acronym "Lunatic Environmentalists Enthusiastically Demolishing."

Fortunately, through the efforts of the National Trust for Historic Preservation and other preservation organizations that have been working closely with the U.S. Green Building Council, LEED has recently modified its project evaluation criteria. It is now awarding more points for adaptive use and adding new categories through which projects can seek certification, including LEED-EB for existing buildings, and LEED-ND for neighborhood development(11). (For more information on LEED-ND, see "From Main Street to Green Street: LEED Certification for Sustainable Neighborhoods," on page 14.)

While LEED is becoming a more preservation-friendly rating system, some significant issues still need to be ironed out to make historic preservation and green development mesh together better. In particular, LEED does not yet fully recognize the greater life spans of historic buildings compared with most new buildings, or their many "passive" energy-conserving features.

Footnotes:

  1. College Hall's biggest room - the great hall - is likely to look familiar to many people. It's been digitally restyled to be the dining hall at Hogworths Academy in the Harry Potter movie series.
  2. Gordon Gill, "Designing Sustainable Buildings." Urban Land. June 2007.
  3. A milliwatt is one one-thousandth of a watt.
  4. http://planetgreen.discovery.com/home-garden/energy-efficiency-where-to-sta.html
  5. http://www.homeenergy.org/archive/hem.dis.anl.gov/eehem/97/970908.html
  6. The American Society of Heating, Refrigerating and Air-Conditioning Engineers. For the full text of ASHRAE Standard 90.1-2001, see http://xp20.ashrae.org/frame.asp?standards/std90.html.
  7. ASHRAE Standard 90.1-2001 has recently been replaced by ASHRAE Standard 90.1-2004, "Energy Standard for Buildings Except Low-Rise Residential Buildings" – so, in other words, the phrase "New Buildings" has been replaced with "Buildings," a change that will presumably make this standard friendlier to existing commercial buildings.
  8. For more information on the tax credits, see http://www.energystar.gov/index.cfm?c=products.pr_tax_credits#s8 and http://www.efficientbuildings.org/.
  9. According to a May 27, 2006 article in the New York Times, "How Many Miles to the Bushel?," the average American uses 464 gallons of gasoline annually.
  10. http://www.youtube.com/watch?v=SzIy5Wm4ujI
  11. For a concise summary of some of the historic preservation-friendly changes in the LEED rating system, see "How Changes to LEED Will Benefit Existing and Historic Buildings," by National Trust architect Barbara Campagna, on the website of the American Institute for Architects: http://www.aia.org/practicing/groups/kc/AIAS076321.