Imagine waking up in the morning to a snowfall that covers your driveway with thick and heavy snow. You need to get the shovels out or a snowblower to clear that driveway in the morning in order to get to work. Yet it is still snowing so you know when you get home from work you will need to do more of the same.
Now imagine there was a system that could be installed in your driveway that melts the snow on contact and keeps your driveway clean, clear, and safe year-round. Electric Radiant Heating Systems do just that for you. They are installed in your bedding layer or concrete for paver, concrete, and asphalt applications and are extremely efficient.
What is Electric Radiant Heating
In the past, most of the time when you say radiant heat you automatically think of glycol systems that has all the PEX tubing that is in everything and that has boilers, manifolds, and pumps. Traditionally, that’s been the way to heat up any surfaces. But over the years, electric heat has become much more efficient making it much more affordable while being easy to install. It doesn’t take a lot of scientific knowledge to be able to install it. But there are some really, really important do’s and don’ts that you need to know.
Because electric heat is more efficient, it is really an excellent way to protect investors or investment for pavers. If you are going to spend the money on pavers, you don’t want to throw salt or other harsh chemicals on that product. You really want to wait to melt the snow and not only melt it, but dry it out. And so with electric radiant heat, you can do that while also usually being much more efficient than plowing. It is also eco-friendly. You don’t have to worry about any chemicals or things leaking into the environment. You do not have to worry about using salt or magnesium or other harsh cases.
How Electric Radiant Heat Melts Snow
Now with electric heat, as opposed to other types of heat it is really designed to be embedded and melt the top two to three inches of pavers or concrete or asphalt. So insulation is really optional, you don’t necessarily have to heat the entire slab. Traditionally, if you are going to heat concrete, the rating heat goes clear down at the bottom of the slab and you put insulation under it, and you heat the slab and so you have to turn it on early, preheat the slab, and that way it melts the snow and then it will turn off eventually.
But with electric radiant heat because you are only melting the top two to three inches it is very efficient. These systems are designed to prevent snow accumulation. The reason we can do that is because they have automatically activated sensors.
Basically when it hits 39 degrees Fahrenheit, or about five degrees Celsius, the snow starts to form and the sensor senses moisture, it turns on to preheat and melts the snow as it comes down. Then it turns off when it senses no more moisture. It continues to work and dry out the moisture, so that you do not have to worry about black ice. It does not really matter how big the project is. When you decide to heat an area, you will heat the whole area.
Different Parts of Electric Radiant Heat Sytems
The main part of the electric radiant heat system are the heat mats or cables, but there are also sensors and controllers that control when the system turns on and off during a snow event.
- Heat Mat or Cable
- Installing Electric Radiant Heat for Pavers
- Installing Electric Radiant Heat for Concrete
- Installing Electric Radiant Heat for Asphalt
- Panels, Controllers, and Sensors
The most important part is the heat mat or cable. These heat mats are about 22 inches wide and they roll out like a sleeping bag. But the cable that choose to melt the snow is actually only about a quarter of an inch in diameter. It is about the size of a pencil. If you get a mat that is 22 inches wide, it is spaced apart with some spacing tape. The cable itself is four inches apart and it has a spacing tape on it to make sure that it is spaced four inches apart.
You can get it spaced three inches apart if you want a little bit hotter system. The mat is also available in cable on a spool. It is the same cable, but it is a lot easier to use for harder to fit areas like “S” curves or steps. They are all installed about the same way, but it depends on the type of medium that you are using.
Take a hardscape contractor that is doing concrete paver project. We would want to know how thick the pavers are and what the bedding layer is. These cables are designed to go right in that one inch bedding layer under the paver. You can use concrete sand or HPB / 1/4″ clean chip, but the sand pulls off the heat a little bit better.
In most cases, you can use a 37 watts system. Basically that means the cable is spaced four inches apart. If you are going to use HPB or you are going to use something other than a standard paver like a cobblestone, we would want to use a 50 watt system which means that the heat cable is spaced three inches apart so it draws a little bit more power. It costs a little more money, but it heats very well.
In paver projects after you have your base down and it is all compacted, you are getting ready to do your pavers. That is the time to install the heat cable. You want to install a half inch of sand down, the heat cable on top of the sand, another half inch on top so that that cable is totally embedded. You can screed it then you can put your paver down, compact, and then install your joint fill. The most important thing is that the cable is spaced correctly and totally embedded. We do not want any air to get to that cable at all. The air part is like our Achilles heel or kryptonite. Any air that gets to the to the cable will burn out at that point.
If you are installing the heat mat or cable in a synthetic base application using paver base panels for patios and walkways, you do not want the mat or cable sitting directly on insulation because it gets too hot and will burn out. So what you need to do is install another bedding layer on top of the paver base panels of either concrete sand or HPB / 1/4″ clean chip. In this layer, the heat mat or cable is installed in between much like how it is described above.
If you are installing concrete, we want to be about two inches below the surface of the concrete. We do not need to heat the whole slab. We just want to heat the top two or three inches, melt the snow, dry out the driveway, and then turn it off. Usually the easiest way to install the heat mat in concrete is typically when you are pouring concrete. You will use rebar or a four by four wire mesh that you just lay flat on the ground. The heat mat can then be rolled out and just zip tied to that mesh or rebar to ensure that the spacing is proper. In doing so you are still at the bottom of the slab and so you use something called chairs. They are about two inches high, but you can get them in different sizes. After you have zip tied that heat mat to the mesh or rebar, then you put in the little chair underneath, so that the cable is sitting up two inches. So it’s about right in the middle of the pour of the concrete. That way when it turns on, it takes less time to melt the snow. You really do not need insulation underneath. If you do, it just acts the way it is supposed to it will turn the heat up or it will retain heat.
The other thing about concrete you have to be careful of is that most concrete projects have some expansion joints using some sort of oil filter where the concrete project meets a foundation or sidewalk. We do not want to cross through that expansion joint with the heat cable. The oil filter will let air in and where that air comes in it could burn out the cable. Also, if the concrete shifts at that joint it could snap the cable. In this case, we would run heat mats or cable on one side of the joint and then cap the heat mats and cables on the other side of the joint.
If you are doing control joints, you just tool those in or if you saw cut them you just want to make sure you go down 3/4″ to 1″. That way they do not go down far enough to really damage the cable. You never ever want to cut the cable.
The heat mat or cable can also be installed in an asphalt application. When asphalt comes out of the plane it is about 325 or 350 degrees Fahrenheit, and so that could melt the insulation on a standard cable. You will need to choose the heat mat or cable that is made specifically for asphalt applications. They can handle up to 400 degrees Fahrenheit. They do cost a little more.
The application there is a little bit different with asphalt. You need your base lift down, a one inch or inch and a half binder, and then the next lift is the one that is really important because the heat mat goes down on top of that base lift of asphalt. It is secured in position there to make sure the spacing is correct. Then that next layer of asphalt is usually about an inch thick but has to go on by hand. You cannot drive a three axle dump truck over it or one of your boxes on top of that because you could damage the cable. So that part goes on by hand either wheelbarrows or something to that effect, rake it out, and you can tamp it using a plate compactor or you could use the thousand pound roller on that lift with the heat cable to make sure that the cable is not damaged. Once that layer hardens, then you can just do whatever you normally do using your paver, you can run your truck over it, and put an inch and a half to two inches on top of it. You can roll it at that point.
Some municipalities require that you pull an electrical permit for the install. The other part about this is that because it is electric, it uses power, and it will draw quite a bit of power. Depending on how large the project is, some projects will require that you to upgrade your electrical service in order to melt the whole area that you want to melt. Sometimes people will have to bring in another 200 AMP panel and sometimes they may have to be a little larger than that. You can make your project a little smaller, rather than heating the whole driveway, you could do tire tracks up to an apron in front of the garage, so that they would use less power and the cost would be less. On the other hand, if it is a smaller project, a lot of times you have air conditioners that will pull 40 or 50 amps that are not being used in the wintertime. You can swap those out and run a walkway or a patio without really having to do much.
There are different types of sensors that can be used, but they all work on pretty much the same principle. They activate on temperature and moisture. A controller is included with the system that controls the sensor. Then in most cases you might need a contact or relay panel to activate the system. It does not ever run right into your power panel. You want a relay panel or two depending on the size of the system to activate that system to pull the power equally across the system. Then you do not need to worry about if you use the right size breakers, you do not have to worry about blowing breakers unless something has gone wrong.
Repairing Broken Radiant Heat Cables and Mats
When the heat mat or cable comes out of the box, you should do an OHMs test on it to make sure the resistance is correct. There will be a tag on each cable that states what that resistance reading is. You should test it when it comes out of the box, you should test it when you lay it out to make sure there has been no damage, you would test it after you covered it to make sure you did not hit it with a shovel or placed a paver directly on it, and then you should test it when the electrician connects it.
If a cable is cut or snapped, we just find where the damage has been on the cable and use a splice kit. If it is a paver project, you just pull out the pavers, splice it, put the paver back. If it is concrete, you have to locate it and chip out the concrete to splice it which is more difficult and requires patching.
If you have a damaged area where that cable quits working or it burns out, usually you can turn it on and you can find it by using a thermal imaging camera. Because the rest of the system will be warm, but where it has been damaged it will not be as warm and you can see that area through the camera. And if that is the case, then it is easy to find that portion and pull it out and just patch it using a splice kit. If the cable has been totally severed it does not show up as not working as well. You will not see any heat on it. In that case, there is equipment that sends high voltage electricity back through that cable once you connect it. At that point, a soft weld is required where that break is in the copper, so that you can then put a thermal imaging camera on it and find out where the break is and then patch it from that point.
Maintaining the Electric Radiant Heat System
There is not much that needs to be done if you get the right system. The main thing would be to clean off the sensor. If there is moisture on the sensor you just wipe off with a little soap and water. You can do that once or twice or three times a year just depending to make sure the sensor is working properly so that the system is activated.
You can control the system to turn on manually instead of automated using the sensor. You can put it on standby, you can put it on reset, you can activate them through Wi-Fi using an app for your phone. If it is set to automatic, it will turn itself on and that snow be melted.
What Radiant Heat Systems Cost
A typical system will run about $10 to $11 a square foot for the material at retail price. The labor involved in installing that material would be in addition to that as well as the electrical contractor to hook the system up and any additional panels that would be needed for power. They are going to be connecting the cables into a junction box, then to the contactor relay panels, and then on to the power panel. They will also be connecting the sensor along with that. If they need to bring extra power, then they would be doing that as well.
A big question on top of that is what is the operational cost? It really depends on where you are. It will vary depending on the cost of hydro, but the average cost is usually around 16 to 18 cents per kilowatt hour. If you are going to base the operational cost on that and if you are going to take 1000 square feet it would cost about $6 to $7 an hour to melt the snow on 1000 square feet. And most snow events are four to five hours. So six times four or seven times four, you are talking probably $30 to $50 on average per event to melt the snow and dry it out. If you have 10 snow events then take it times 10 to calculate the total cost per year. Compare that to having somebody to plow, blow, or shovel the surface and it is not completely dry or free of snow like a snow melt system would be.