- The Driveway – Your Big Green Welcome Mat
Congratulations on your decision to build the most energy efficient house you can dream up; with indoor air quality as good as living in a bubble; gorgeous plumbing fixtures that conserve water, wood from sustainably managed forests and you’re even planning to catch rain and irrigate with it. This is going to be one very green house. Just one more thing - - what are you doing about the welcome mat? You know, the driveway.
The driveway can be a polluter. In keeping with your dedication to building a green home, the driveway should be permeable. A permeable surface allows water to sink into the ground or into the landscape giving it a chance to return to our underground water supply instead of flowing over pavement taking pollutants like oil and gasoline into the drain and eventually out to larger the watershed and larger waterways. A driveway that reduces this runoff is working for the environment
A few decades ago, crushed stone and hard sand driveways were the norm in the Tri-State area. They were permeable and allowed water to sink into the ground naturally. Over the years we’ve moved away from shell driveways for aesthetic reasons (the appearance is rough along the edges and often requires, heaven forbid, mowing!) A loose pebble drive is also permeable, but some don’t like loose pebbles because of the crunching sound when cars drive on them. It’s a noisy driveway, and specially in the winter season with all the snow, it will not be possible to shovel the snow withou moving pebles. That will result in work for spring fixing up the pebbles on driveway.
Concrete driveways gained favor for their neat appearance and convenient hard surface. Asphalt is often used for longer driveways because it costs less than concrete, but neither are permeable. Rainwater hitting concrete or asphalt runs off into ditches or drains carrying pollutants with it.
Today we have permeable pavement options that are aesthetically pleasing, low maintenance and better for the environment.
Porous concrete allows water to seep into the pavement and percolate into the ground. The concrete itself becomes a storm water retention system. A good example can be found at Villanova University where a central mall walkway on the campus is actually a porous concrete retention system. The Florida panhandle community of Watercolor used porous concrete for walkways and some streets.
Matt Ross, President of Eco Smart, Inc., a green construction materials supplier that operates in partnership with the Florida House Institute in Sarasota explains, “The concrete mixture contains an additive which creates capillaries within the concrete, tiny tunnels where water can accumulate while gradually trickling into the ground. The product looks like regular concrete.”
Although, material for the product is widely available and is attractive, popularity of porous concrete has not grown significantly. This is due to lack of knowledge of its existence and the fact that fewer contractors know how to install it. Special training is required for proper installation. Price ranges from $8 to $9 per square foot more than conventional concreteI.
Rubber. Fairly new on the market is a recycled rubber poured-in-place pavement product. The main ingredient is truck tires that are chopped, colored, and bound with proprietary ingredients. The finished product comes in many colors and provides the same storm retention qualities as porous concrete. The cost runs around $10 per square foot installed.
Paver stone. While porous concrete does provide good permeability, and rubber seems like a cushy new alternative, paver stones or bricks are the most popular permeable driveway, but not necessarily because of the permeability factor. Many of us don’t ponder permeability. We like pavers because they are attractive - a high profile welcome mat.
Pavers are a concrete product first introduced in the Netherlands after World War II out of the need for time saving construction materials to replace roadways destroyed during the war. In the 1970s, paver technology came to North America, first to Canada, later to the U.S.
Pavers are versatile in style, size and color. The cost varies greatly, from $8 to $20 per square foot. They can be installed over a concrete or masonry sand base, but only when the stones are installed on a sand or fine gravel base do they allow storm water to infiltrate the ground. As long as there is space between stones and the stones are placed on sand, there is a measure of permeability; however, the most environmentally friendly are those spaced farther apart with turf or gravel in between the stones.
Your green house is going to be great. Congratulations on your good decisions. For all the neighbors and strangers who drive by your green welcome mat, the driveway may be all they’ll ever know about you. You’re the neighbor with green curb appeal.
• A quart of oil can contaminate 250,000 gallons of water. A pint can make an acre-sized oil slick.