Homes constitute the largest number of historic properties in the United States. The actual number of older residential properties listed in or eligible for listing in the National Register of Historic Places is in the millions. A 1997 study by the U.S. Energy Administration estimated that 18.1 million residential units were constructed in the country before 1939. Retaining and reinvesting in these properties would provide a significant environmental savings over demolishing and replacing them. And over the next decades, a much greater impact can be made on reducing greenhouse gas emissions through renovation rather than new construction.
Yet virtually all green rating systems, and particularly those for housing, were developed for new construction, and green rating systems typically undervalue the reuse of buildings verses other actions. For anyone pursuing only selective improvements over the course of time, which is the typical approach to historic preservation, the green rating system will not produce a meaningful score.
This analysis looks at current green rating systems for houses, and identifies some of the strategies owners of older homes can use to pursue energy efficiency and sustainability goals. To inform preservation advocates and those developing green rating systems, it also notes how rating systems could be changed to better recognize the benefits of preservation-based decisions.
Green Design Versus Sustainability
The popular marketplace has gone green. Individual consumers are presented with choices about what products and services to consume based upon some environmental benefit that may or may not be obvious to them. Green certification organizations now exist for many different products and services, to give consumers a factual basis for weighing the relative merits of competing claims of environmental benefit. The U.S. Green Building Council (USGBC) has emerged as the American system to authenticate green building practices, primarily for the commercial and institutional markets.
While the marketplace is green, the broader scientific term that quantifies the whole approach to human development is “sustainability.” In theory, a sustainable society only uses up resources at a rate that is equal to their regeneration. The most obvious and important area of concern in sustainability debates involves nonrenewable fossil fuels, primarily oil, gas, and coal. The fact that these are finite resources isn’t in debate. The amount of these resources needed to fuel the world economy is in debate, but there is pretty much a consensus that fossil fuels are going to be largely depleted during the 21st century. The push for renewable fuels has already begun. Fossil fuel depletion and the need to make buildings energy efficient have emerged as the primary concern in virtually all green rating systems. Energy efficiency is also part of the urban planning agenda, as higher density is seen as a factor that will lead to a more walkable community, where the car is less needed for daily life. The creation of green building rating tools is collectively moving us toward more sustainable practices, but even the best of these are interim tools that will continue to evolve during this century.
Green Home Rating Systems
There are now more than 25 different green home rating systems in North America and England. Some of these have been around for almost three decades. (Energy efficiency rating systems in Austin, Tex., and Boulder, Colo., appear to be the oldest.) These rating systems were written to guide new construction, but are slowly morphing to include renovation.
Of note, the Build It Green “Green Point Rated” system is one of the few that has developed a system specifically for residential renovation. While it is not a residential rating system, the Green Globes “guidelines for the continual improvement of existing buildings” is probably the most logical green policy for owners of historic properties because it (unlike most other green rating systems) encourages ongoing maintenance. The U.S. Green Building Council has developed its ReGreen system for residential properties not as a rating tool (with the usual checklists) but rather as a guideline for green building practices as applied to a variety of common renovation projects.
Green rating systems have now evolved to the point that a consensus is emerging on the categories of environmental benefits that should be measured. Virtually all of the green rating systems break down into five categories: site/location, energy, water, resources, indoor air quality, and other (house size, management practices, innovation, and the use of green certified services). While there is a general consensus on which environmental impacts need to be measured, there is no agreement on the relative weights of the various categories.
Owners of historic homes may not be able to apply for a green rating score, but they can use the green rating systems to evaluate their dwellings and to guide efforts to maintain and improve them.
Historic homes often occupy sites that have many desirable “green” characteristics in terms of urban planning and site development. Most of America’s residential historic districts are in 19th- and early 20th-century subdivisions that already meet the desirable density measures. These early subdivisions are close to public transit, major services, and important institutions such as schools. Green rating systems use proximity to these features to measure the “greenness” of a location. The new planning tool in www.walkscore.com is an excellent measure of the site location characteristics that are typical of those used in green rating systems. Property owners can use Walkscore to get a sense of the “greenness” of their home’s location.
Missing from virtually all green rating systems is any effort to identify proximity to cultural resources. Of the major green home rating systems examined, only Boulder’s Green Points Guideline acknowledges the historic status of a neighborhood. While these rating systems identify flood plains and prime farmland as two categories that need to be avoided for green development, they fail to identify the benefits of proximity to historic and cultural resources. This would be appropriate to add to green rating systems.
One other rating tool is worth noting. The Build It Green rating system awards higher points for sites that have an older platting. This gives preference to homes located in older neighborhoods rather than ones requiring all new infrastructure, which are more likely to be “sprawl” sites. From a preservation and urban development perspective, it would be good to expand this idea, with the most points given for development in long-established areas and the fewest (or even negative) points for locations that are all-new “edge” sites. This kind of weighting would encourage more urban redevelopment and would complement the proximity-based measures in the current criteria.
In most green rating systems, the greatest number of points can be earned for improving energy efficiency. For owners of historic homes, this is a critical task, but also one that can be accomplished in incremental steps.
The process begins with evaluating the current operating energy performance of a residence. This is fairly simple to do, but does require some record keeping and coordination with utility companies. Most homeowners should be able to do it themselves. It is as simple as adding up the total amount of “metered” energy you used in any give year and dividing it by the gross habitable space. (Older basements are generally not included, as they don’t count as habitable space in modern real estate calculations.) The use of professional energy raters is another option for homeowners. Your local preservation commission should be able to identify energy raters who are familiar with historic properties.
Once the energy baseline is established, the best practices for increasing energy efficiency can be examined. There are a variety of benchmark standards, but the nationally applicable one is that of the Home Energy Yardstick which is a part of the Energy Star system (www.energystar.gov).
Energy efficiency gains can made in several categories: operational changes (which can often be accomplished at no and low cost), building envelope improvements (adding insulation and sealing), and upgrades of equipment and appliances (which can be expensive and so are usually undertaken when equipment needs to be replaced, not just to improve energy efficiency). Any major improvement in total energy efficiency will require a combination of operation, envelope, and equipment changes to achieve significant results. Because air infiltration in older buildings is a huge source of energy loss, one should invest first in sealing the building from leaks.
Only after maximum efficiency has been achieved in these three areas (operation, envelope, and equipment changes) should the homeowner consider investing in expensive on-site energy systems, such as solar electric cells or small-scale wind generators.
“Invest in ‘negawatts’ first” should be the mantra of all home efficiency projects. One common complaint about green rating systems is their emphasis on using new energy equipment over the more tried-and-true solutions of efficiency. “Gizmo green” appeals to our love of technology and marketplace solutions, but misses the most important environmental principle of “reduce.”
The best way to measure an energy saving investment is that of payback, i.e., how many years does it take to pay for an energy improvement with the savings. For example, replacement windows typically have a very long payback period, whereas caulking and storm windows have a much shorter payback period. Numerous websites provide statistical averages for improvement paybacks, but they are based upon assumptions about the current performance. One useful website is the energy efficient rehab advisor.
Homeowners undertaking major renovations, particularly those that involve insulation and moisture control, face a particular challenge. The jury is still out on the best preservation practices for achieving ultrahigh building envelope energy savings for walls. Adding extra insulation in the attic has one of the best energy paybacks and little potential for negative impacts on the building. When adding insulation into walls,
there is also a need to manage the moisture transfer, which is generally not possible without some removal of historic materials. Whether it is better to locate the moisture barrier on the inside or the outside depends upon the region of the country and its cold or warm climate. It is the combination of insulation, surface materials, and moisture barriers that will achieve the desired energy performance and durability that represent best green practices.
Water efficiency is a growing environmental concern, particularly in western states. The use of more-efficient plumbing fixtures and appliances is a common green strategy. Site water management is particularly important in older neighborhoods, which frequently have combined sanitary and storm sewers. By installing an exterior water collection system the homeowner can use the collected water for irrigation and car cleaning, for example, and avoid the use of potable water. The irony is that the typical turn-of-the-20th-century house had an outdoor water-collection system, known as the cistern, but building codes in the latter 20th century frequently required these to be filled in. Now we recommend that this idea be revived, with the use of a surface-mounted rain barrel. The use of native plantings and ground covers that do not require much irrigation (and reduce lawn mowing) are also preferable green treatments for the site.
This is one category where owners of historic homes have an under-recognized advantage over those doing new construction. By starting with an existing building and maintaining most of what you have, you may make virtually no new demands for major resources. If the overall goal of green behavior is to keep us from collectively over-consuming the world’s resources and leaving too little for future generations, rewarding this seems like a no brainer. Unfortunately, you wouldn’t come to that conclusion if you looked at a typical green rating system. Only a few points are given for building reuse. Far more points are awarded for using materials deemed “environmentally preferable” because of how they are made, where they come from, or based upon complicated secondary rating systems that measure embodied energy, emissions produced, or recycled content.
For all of the collective wisdom applied to being green, this is one of the most frustrating aspects of the rating systems. They are simply based on the “assumption of consumption” rather than directing anyone to consider whole building reuse. The only residential green rating system that speaks directly to this is the English BREEAM Ecohomes system, which states, “any existing element in the building that is reused in-situ will automatically get an A rating, as the environmental impact of replacing that element is far greater than reusing the element already in place.” I like to call this “common sense green.”
Green building rating systems promote efficient use of new materials and are highly prescriptive about minimizing construction waste. Unfortunately, the rating systems generally treat teardowns as a waste management issue rather than a waste avoidance issue. As long as a certain percentage of the existing demolition waste is managed so that sending it to the landfill is avoided, the rating system pretty much ignores the idea that the existing building had a viable future. The practice of tearing down viable housing to replace it with green certified housing is alive and well, and commonly reported in green building news. The underlying message is that we can somehow or other consume our way to sustainability. More advanced Life Cycle Analysis (LCA) systems are needed to combat this notion, as well as more examples of historic renovations that achieve high green ratings.
There is another possibility for green building rating systems within the category of Resources. What if the entire point value for Resources was awarded to building reuse, with negative points calculated on the amount of the building that was demolished? Instead of a system that rewarded the purchase of new, albeit “green,” materials, this system would automatically give a positive rating to total material reuse. If part of the building was demolished, a proportionate number of points would be subtracted under the Resources category. There is even the possibility that new points could be added for new green material choices, just as would be done for any other new building. All the other categories of green building rating systems would remain the same. This revision would basically give building reuse a much higher proportion of the total rating system points, which would put reuse in its proper place as the first green strategy.
Indoor Air Quality
All homes should provide a healthy and comfortable living environment. For owners of historic homes, addressing issues of indoor air quality presents several challenges, some more easy to mitigate than others. Lead paint and asbestos are present in many historic homes. Radon is another environmental air quality concern. While older homes tend to leak air more, which hurts their energy efficiency, this can also help dissipate indoor contaminants.
The fireplace—that ubiquitous symbol of domesticity—has now come under attack in green building practices. Typically an old fireplace wastes far more energy than it produces, as well as adversely affecting indoor air quality. Some rating systems actually prohibit them, while others require them to be constructed with elaborate venting and combustion air standards. Needless to say, the historic ideal of a welcoming blaze in the fireplace and the modern energy concern about its wastefulness is a real collision of values. Our ancestors were aware of this. Open fireplaces were rarely used for heat in most homes once the metal stove came into widespread use. The “parlor stove,” as it was called, was the preferred method of heating homes, even when it sat in front of the fireplace with the flue connected to the wall above.
The catch-all category of “other” covers lots of different items, including the rather self serving one of rewarding the use of green rated professionals, and the wide open one of “innovation.” One significant item in this category is house size. This factor fits in several different categories, but I want to single it out because it is so critical and reflects an inherent philosophical debate in the whole metric of green. One school of thought is that size doesn’t matter as long as everything used in a building follows a green protocol and sustainability goals. Others disagree with this, and see size as critical to the equation of measuring best green practices. A compromise of sorts has been reached in the various systems that basically penalize increased building size by requiring more stringent measures for other items such as energy efficiency or renewable energy. In the opinion of this author, the compromises are rather weak, based upon the recent certification of the 7,000-square-foot “eco home” on a large suburban lot.
The development and use of green building rating systems is going be a part of the future, and we in the historic preservation community need to find our common ground with green building proponents. As the principal advocates for cultural continuity, preservationists have a unique perspective and important role to play in developing the best green building practices. Because renovations to existing buildings will offer far more opportunities for reducing greenhouse gas emissions than new construction will, the common missions of historic preservation and green building need to evolve quickly—which will be no easy task.
Just to put some perspective to this, it took a hundred years to go from the first building codes to having rehab-based building codes. The first green building rating systems are just one generation old, and we have to get it right in the next generation if we are going to have meaningful impact on a global scale.
But even as green building rating systems continue to improve, with our help and input, we have an opportunity right now to show homeowners how to take wisdom from them to guide them in the stewardship and enjoyment of their historic buildings.
Energy Efficient Rehab Websites
Green Rating Systems for Homes
Provides links to many different kinds of green rating systems for products as well as buildings. www.allgreenratings.com
- BREEAM Ecohomes (England)
A version of BREEAM for homes. It provides an authoritative rating system for new, converted, or renovated homes, and covers houses, flats, and apartments.
- Build It Green (Northern California)
- Green-Point Rated for Existing Buildings Checklist
- Built Green (Seattle)
- Remodeler Checklist
- City of Chicago: Green Homes
Programs and checklists for new and renovated single-family homes and apartment buildings
- Green Building and Green Points Guideline (Boulder, Colo.)
Guidelines for new buildings and major renovation.
Boulder Green Building Program
- Green Points Guideline
- U.S. Green Building Council
LEED for Homes (New and Major Renovation)
- REGREEN—Home Renovation Guidelines