A heated driveway means there’s no need for a shovel, snowblower, or de-icing chemicals
SOMETIMES FALL in Atlantic Canada is so beautiful—glowing radiant and golden for weeks on end—it has the effect of putting us in a trance, where we remain in deep and blissful denial about what is to come. Although there are preparations to be made, often we fail to turn our attention to such things until we are finally slapped in the face with the cold, hard facts of winter—like the necessity of clearing snow from the driveway. Most of us, once in the thick of it, find ourselves thinking that there must be a better way to accomplish this task.
Whether we like it or not, clearing the driveway in winter is a form of self-expression. We’re out there in public, and the neighbours are watching. You have probably admired the physical endurance of die-hard shovelers, or secretly coveted one of those large and powerful snowblowers with an enclosure to protect its operator from the elements. Perhaps you have remarked on the fastidiousness of homeowners who clear the snow and then sprinkle a chemical ice-melting compound on the walks and driveway, achieving the much desired bone-dry effect.
Snow removal secrets
But there are a few homes where the driveway is always clear despite any evidence of snow removal efforts. At these places, the pavement remains bare even in the midst of a blizzard. You can be sure that these homeowners are periodically gazing out the window with a feeling of deep satisfaction, because these are people who have solved the snow clearing problem forever by installing a heated driveway.
These snow-melt systems for driveways and walkways are essentially the same as indoor radiant heated floors. Heat is supplied to the concrete slab (or for driveways, sometimes asphalt, or aggregate material under paving stones) in one of two ways: via an array of embedded cables that warm up through electrical resistance (like a large-scale version of the defroster wires in the rear window of your car); or with a hydronic system comprising loops of tubing that circulate hot water. In either case, the heat radiates upwards to bring the entire surface to the desired temperature.
Investment pays off
These technologies are widely used in commercial applications, in critical areas such as loading docks, helipads or car ramps. For a private residence it’s a big investment, but some believe the payoff is immediate when you factor in convenience, safety and peace of mind.
If you are energy-conscious as a matter of principle, or if you have devoted a certain amount of effort to heating your house more efficiently, this whole concept may strike you as wrongheaded. After all, we’re talking about a feat of engineering designed to dissipate heat into the great outdoors. But it’s important to remember that the system will only be operating occasionally. Unlike in-floor home heating, which is meant to maintain a steady temperature, driveway heating only kicks in when required.
The most basic system could be set up with a manual switch in the house, but most installers recommend electronic controls. Remote activation by phone may be a useful feature for a place like a chalet that is only used occasionally. For day-to-day use, sensors can be installed to trigger the system when precipitation is accompanied by freezing temperatures. The controller would be programmed to continue heating for a period after the precipitation ends, to ensure the driveway is fully dry.
During periods of cold, dry weather, there will be no heat demand whatsoever. Your energy consumption will depend upon the frequency and duration of freezing precipitation, so it could vary considerably from one year to the next.
The operating costs for electric snow-melt systems tend to be higher than for hydronic systems, especially in jurisdictions where power rates are high. (Prince Edward Island has the highest average rates in Canada, and Nova Scotia is not far behind.) But the equipment for an electric system is generally cheaper upfront, and the installation is relatively easy. Before the slab is poured, the cables are unrolled and suspended within the forms, putting them about two inches below the surface. Some manufacturers supply mats comprising several cables at the correct spacing, which makes the job faster. You may be able to do this part yourself, as long as you get a certified electrician to hook the system up.
The controls for an electric system are also relatively simple, with no moving parts. It’s not much more sophisticated than a giant toaster encased in pavement. But like a giant toaster, it will draw a lot of electricity when it’s turned on. Depending on the size of your driveway, your home electrical system may not have the capacity to run it. An older house with a 100-amp service may require an upgrade.
A hydronic system is more complicated. Instead of cables, flexible tubing known as PEX piping is suspended in the pavement. (Some types of tubing will not hold up to the heat and compression involved in laying asphalt, so a concrete slab is more common for hydronic installations.) The tubing has be hooked up to a pump to circulate the fluid, and it must pass through a water heating unit of some kind. Of course, water alone would freeze when the system is not operating, so it has to be mixed with glycol; this solution must be tested periodically to ensure it is still sufficiently concentrated.
If your home has hydronic heating (either radiators or in-floor), and the boiler has enough capacity, you may be able to tap into that system for the driveway snow-melt system, as if it were an additional heating zone in the house. Otherwise, a separate water heater for the driveway must be installed in the garage or the basement, fired by electricity, oil, natural gas or propane.
Technically it would be possible to tie in with a renewable power source such as solar or geothermal, but this is not a common practice, partly because a driveway snow-melt system requires high heat on demand. Warming the driveway marginally could result in a buildup of slush, which would be worse than snow. The operating temperature for hydronic systems is usually in the vicinity of 130°F or 54°C, ensuring that snow melts on contact with the pavement. In Reykjavik, Iceland, geothermal energy is used to heat some roads and sidewalks, but few other places in the world are blessed with high-temperature geothermal resources so close to the surface.
Cost estimates for driveway snow-melt systems vary widely. Some suppliers suggest electrical cables and controls can be purchased for as little as $6.50 per square foot, but it would be safer to count on spending $10 per square foot for the equipment, and the same again for professional installation. For a hydronic system, part of the cost is the water heater, and it may be a significant part if you choose a high-efficiency model to save energy over the long term. Cost comparisons should also factor in the duration of the warranty on all system components.
If a snow-melt system is installed when a new driveway is being poured, usually the bed is first insulated with about two inches of rigid foam, to reduce heat loss into the ground. But this is not absolutely necessary and some installers will retrofit an existing driveway. For electric systems, this can be done by cutting a network of channels in the pavement, laying the cable and then filling in the grooves—although having visible lines on the driveway takes some of the magic out of it. Alternatively, if it is feasible to raise the grade of the driveway, cables or piping can be laid over an existing surface and an additional layer of pavement applied on top.
Another cost-saving approach is to heat only in high priority areas, such as the walkway to the house, and tire tracks about two feet wide leading from the road to your parking places. For light snowfall this will work fine, but in the event of a big dump you may have to clear the mound of snow between the tracks. Besides that, it does not provide the uniform dry-pavement effect, which is so pleasing to the eye and so handy when you want to pad out to the car in your slippers.