Last Updated: Jan 16, 2021
As part of my LEED for Homes From the Editor series, I have introduced a “LEED for Homes 101” and provided an in-depth guide on the first of eight categories, why Location & Transportation and matter. The second LEED category, Sustainable Sites, is about making more sustainable choices for landscaping and hardscaping—the areas around the house. Hardscaping means the areas around your house that are hard—like driveways, patios, and roofs.
This section allows you to earn up to seven points out of 100, making it the least important of all the LEED for Homes categories. So why discuss it? Homebuilders and designers often ignore the site and focus on the house—which is a mistake. Your house sits on a piece of property, and how you manage that property can have a big impact on the comfort, beauty, operating costs, and maintenance requirements of your own home. Site elements can also dramatically affect your home’s impact on the health of your surrounding waters, soil, and air.
The Sustainable Sites category is divided into five sections: two prerequisites and three credits to address these important elements. (And as I’ve argued in the past, all homebuilders should take all the LEED prerequisites and do them as a matter of course.)
Have you ever seen a house under construction and blankets over part of the earth and silt fences around the edges? This may not mean it’s a LEED project, as it has become standard practice (or best practice) for builders to do this. Why? To protect topsoil from eroding and prevent air pollution from blowing dust around the site. If you are building new, find the exact LEED language of this prerequisite and show it to your contractor—if it’s not yet building code in your area, it should be.
This may seem like an obvious requirement, but it needs to be called out. Not everyone realizes what types of plant species are invasive, and that can be a problem. The US Forest Service defines invasive plant species as a “species that is non-native (or alien) to the ecosystem and whose introduction causes or is likely to cause economic or environmental harm or harm to human health.” They can be aggressive and smother surrounding vegetation, so it’s best to get rid of them as soon as possible.
The types of invasive plant species vary by region, so you’ll want to refer to the U.S. Department of Agriculture’s GRIN Taxonomy for Plants database, the National Association of Exotic Pest Plant Councils, or another state or local list. Common examples of invasive species include the Norway Maple, Japanese honeysuckle, and English ivy.
Some areas actually require you to go beyond not introducing invasive species and might require removing existing plants—such as buckthorn—so check your local building code. Also, note that just because a plant is not native does not mean it is invasive.
Have you ever noticed that the city is hotter during the summer than the suburbs, which are hotter than the countryside? Have you ever wondered why? It’s called the urban heat island effect, and it has a tremendous impact: according to the US EPA, “heat islands can affect communities by increasing summertime peak energy demand, air conditioning costs, air pollution and greenhouse gas emissions, heat-related illness and mortality, and water quality.”
How does this happen? It’s not just due to the additional cars heating the outside. Asphalt, concrete, dark roofs, and other hardscapes all contribute to the heat island effect. All of these built materials absorb the sun’s heat and slowly release it back into the air. The more air conditioning is used, the more hot air is blown back outside—causing it to be even hotter. The simple fact exacerbates the problem that these human-made materials have replaced trees and plants, which, due to their ability to evapo-transpirate, allows them to help cool the area (think about running barefoot on the driveway in the summer and saving your feet by running into the grass—it is naturally cooler).
So, as we think about how we build or renovate our homes or upgrade our landscapes, it’s important to consider how much dark hardscape will be on the site—because both you and your air conditioner will be happier during the hot summer months. On a bigger scale, your community will benefit.
The LEED for Homes rating system rewards projects that mitigate the heat island effect for at least 50 percent (one point) or 75 percent (two points) of the hardscape and roof on your property. How would you do this? Two options:
By simply planting trees to shade your hardscape, you will be doing yourself a favor. The exact calculation requires that at least 50% of your hardscape will be shaded by a tree, after ten years of growth, at noon during the summer solstice—usually between June 20 and June 22 in the northern hemisphere (see Rise’s article on natural shading strategies or the Passive Haus method of calculating shading for more information).
This can be accomplished in multiple ways. Pavers, driveways, and roof shingles do not have to be dark. For example, roof material can be ENERGY STAR® qualified, meaning it is more reflective than absorptive, so it remains cooler underneath the sun. The US Department of Energy actually offers a free roof-savings calculator to help you figure it out. A green roof will also qualify to reduce the heat island effect, among many other benefits of a green roof.
For patios and driveways, you can use open pavers, engineered grass pavers, and/or paving materials with a solar reflectance (SR) of at least 0.28 (see the USGBC’s definition of the SR Index). Translated, your pavers might be light gray or light brown, not dark gray or dark brown—which means no additional cost, and it will be much more comfortable underfoot!
The building community has been calling for a paradigm shift: instead of building to try to get water off your property, the entire community benefits when homeowners manage stormwater on their property site. Think about it: as the residential streets grow, and everyone designs their homes to get the water to flow off their property, the water has to go somewhere—and it usually ends up overwhelming the city’s storm sewer system, causing all kinds of problems and often contaminating local water resources. This home in Minneapolis, for example, manages 100 percent of its own stormwater and even absorbs some of its neighbors’.
To accomplish this LEED credit, you need to think about where all the water goes once it hits your roof and your outdoor patio and driveway. To keep the water on-site, you can install a vegetated (green) roof, permeable pavers, and/or water collection features such as cisterns or rain barrels. Vegetated swales and rain gardens also work to keep rainwater on your property and allow you to introduce plant species you may not have considered.
The points add up by calculating your site's total permeable area as a percentage of the total lot area. It’s one point for 50 percent, two points for 65 percent, and all three points for over 80 percent of your site being permeable. In a nutshell, the more plantings, the better!
We don’t want pests in our homes, nor do we want to expose our families to dangerous pesticides. This credit, worth two points, lays out 11 building strategies that can make a difference in preventing pests from getting in your house in the first place. Taken verbatim from the LEED reference guide, here is what the experts have deemed as best practices—most of which would not add any cost:
The purpose of these From the Editor columns is to help homeowners become aware of more sustainable home building practices. We recognize that not all homeowners will be able—or want—to go through the LEED certification process. But the body of knowledge, heavily studied and researched by experts in the field, is quite worthy of emulating. Many strategies do not cost more—they only require awareness of the impact our choices have. And while only new homes and complete remodels are eligible for LEED certification, many prerequisites and credits can be applied to minor home improvement projects.
So don’t worry about getting everything right. Educating yourself on the most important components of a more sustainable house is the first step—and it’s okay to take baby steps—toward a home that is more comfortable, durable, healthy, and costs less to operate. Next month, we’ll tackle Water Efficiency!