Words like “sustainable” and “responsible” continue to grow in importance with today’s consumers as we collectively become more conscientious about how our actions affect the world around us and the legacy we leave behind. However, we still wish to enjoy our time on this planet.
Enter the permeable paver. Permeable pavers give homeowners the opportunity to create eye-catching, livable outdoor spaces that actually improve the environment and allow us to leave the world better and more beautiful than we found it.
The technology is ingeniously simple. Permeable pavers are laid on multiple layers of crushed stone, and the joints between each paver are filled with smaller aggregate. This design allows water to instantly drain through the joints and percolate through the layers of aggregate below, where any impurities are trapped before water seeps into the ground and returns to local waterways. To create the ultimate sustainable patio, driveway or walkway, the system can be designed to collect and recycle rainwater for irrigation and other purposes.
And here’s the best part…in many states and municipalities with water conservation and stormwater management initiatives, there are often grants or tax incentives available for installing permeable pavers or a water harvesting system, which makes the idea of installing a permeable patio, walkway or driveway all the more attractive.
In colder climates, it’s not uncommon for driveways, walkways or patios to be installed with either a heated pavement system or a permeable pavement system to help control ice buildup. This homeowner, however, chose to combine the two systems into one to create the ultimate ice-management pavement system.
Benefits of a Combined Heated/Permeable Pavement System
With a heated pavement system, snow and ice melt immediately to prevent accumulation, but if the surface is not graded properly, or if the pavement settles or degrades over time, there can be pooling or other issues. In comparison, a permeable system allows melting snow to drain into the joints and down into the subsurface rather than remaining on the surface and refreezing into ice. Typically, a plow clears the bulk of the snow, ice melt is applied, and the water goes away. However, with a combined heated permeable pavement system, no plowing or ice melt is needed. All snow or freezing rain that hits the surface melts and drains immediately. Plus, concrete pavers are more durable than poured concrete or asphalt, ensuring increased longevity of a properly working system. After two winters, the homeowners report that the system is performing beautifully, with no water or snow accumulation whatsoever.
How Does It Work?
Heating cables are laid out in the bedding layer, beneath the pavers. Two heat/moisture sensors, each about the size of a tennis ball, are installed in the pavement to automatically turn the heating cables on when there is both precipitation and a below-freezing temperature. When the system is on, it takes a lot of electricity to heat the 4,300 SF drive and walkway, necessitating the addition of a 400-amp pedestal to operate the system. However, because the sensors require both moisture and freezing temperatures, the system is rarely on.
Installing the System
Although, the system was planned to include only 18” of excavation, abnormal site conditions required 36” of excavation. A variable base of aggregate was then installed – 27” of #2 stone, 4” of #57, and 2” of #9. A heating cable was installed within the #9 stone layer. In order to maximize the amount of heat transferred from the heating cable to the pavers, the stone separating the cable and pavers needs as much contact with both as possible. Crushed stone with fines transfers the most heat, but doesn’t drain, so it isn’t used in a permeable installation. Instead, the heating cable manufacturer, Warmzone Radiant, recommended smaller drainage stone (#9) because it has more contact with the cable and transfers more heat than larger stone. A layer of sand was then installed over the aggregate to create a cushion between the heating cable and the pavers. This was done to prevent potential paver movement from wearing through the cable’s protective coating over time, which could short out the entire system. The crew also took extra care during the handling and installation of the cable to safeguard the protective coating and ensure long-term functionality of the system.
2014 HNA Project Award Winner – Residential Concrete Permeable Pavers
Design/build Contractor: Grindstone Hardscapes, Josh & Kristen Graczyk, Owners
Location: Grand Island, Nebraska
The use of permeable pavers in driveway construction is growing exponentially across the country, particularly in areas with water use restrictions or strict stormwater management guidelines. Not only do permeable pavers boost your curb appeal, they also positively impact the environment by decreasing stormwater runoff and improving the water quality of local waterways.
How, you ask? It’s ingeniously simple, actually. Permeable pavers are installed over a gradient bed of aggregate, with tiny aggregate filling the joints between each paver. As rainwater falls onto the pavers (or drains onto the pavers from another surface), the water percolates through the paver joints and down through the base materials below. There, the water is filtered by the aggregates, removing a number of pollutants before the water makes it’s way into the groundwater supply or returns to local waterways. The rising trend is to incorporate an underground cistern with a pump under the paver system so that the filtered water can be captured and recycled. A number of states and municipalities offer grants or tax incentives for these types of rainwater harvesting systems. The recycled water can be used for irrigation, water features, or other greywater uses.
Constructing a driveway with permeable pavers can also provide a number of other solutions for homeowners. For example, for steep driveways, permeable paver construction is safer during rainy weather conditions than traditional impervious surfaces, such as concrete or asphalt, because rain can permeate through pavers instead of pooling on the surface, thus improving traction.
In areas prone to heavy snow, a heating system can also be installed under the sand base of the pavers so that snow or icy rain immediately melts and drains away, eliminating snow shoveling or ice accumulation. The sand acts as a buffer between the pavers and the coils, preventing damage from any shifting caused by automotive traffic.