Setting Up Indoor Floor Heating For Your Home

Setting Up Indoor Floor Heating For Your Home

Floor heating can be accomplished either by circulating hot water under your floor or using an electric heating cable system. Hot water or hydronic systems are ideal for heating an entire home but not something you would consider installing yourself when renovating a room in your home. We will therefore focus this discussion on the use of electric heating cables & mats which are better suited for DIY renovations.

Electric floor heating products can be used in under virtually any flooring but are most popular under tile and stone flooring which are normally quite cold and uncomfortable to walk on. The same property that makes tiles cold is what makes them the ideal flooring for use over an in-floor heating system. Tiles are fairly good heat conductors and therefore normally draw heat away from your feet. However, when the tiles are warm they act in reverse and easily transmit the heat to your feet and make you feel warm. Floor heating can also be installed under other finish flooring such as hardwood, laminate, cork, vinyl and even carpet but won’t have quite the same dramatic effect as when used under tile or stone since these products act more like insulators and do not conduct heat as readily as their tile and stone counterparts.

When planning or considering an electric in-floor heating installation there are a number of factors to consider. Below are some of the most important and common things you will need to consider:

Electrical Considerations

Before you start dreaming about your warm floors you better make sure you can get an electrical connection first. Have an electrician come in and determine whether they can provide the room with a new or existing 120/240V circuit to where your thermostat will be located on the wall. If you are upgrading a room where electric baseboard heaters were previously installed then most of the work is already done. If you are heating a room much larger than 150 square feet then you may need a 240V circuit capable of handling twice the load of a 120V circuit.

Sizing the Heating System

Heating cables and mats come in a range of fixed sizes measured in Watts. The wattage you will need depends on how cold it gets where you live, whether the heated floor will be your primary heat source or used for floor warming only. By default 12 Watts/square foot is the norm under tile or stone flooring but can go up as high as 15W/SF when used in cold climates or rooms with little floor space to heat. You therefore need to measure the exposed floor space in the room you will be heating and multiply this area by 12-15 W/SF to get an idea of what wattage you will need and pick a size that falls within that range.

Choosing between Heating Cables or Mats

Most vendors offer a choice of heating cables or mats for floor heating installations. Mats will cost more but should be easier and less time consuming to install than loose cable. However, mats are designed to cover exact areas at specific watt densities or W/SF. Before choosing a mat you must ensure that you choose one either the same size as your heated area or slightly smaller – but never bigger. Cables on the other hand are much more flexible in that you can adapt them to fit any room by merely placing the loops closer or farther apart. Sometimes both can be used in the same room by using a mat to do the larger rectangular part of a room and then using a cable to complete it and used to fill odd shaped areas.

Sub-floor Preparation

If you’ve ever installed tiled flooring before you know that you need to strengthen the sub-floor or de-couple it before it is safe to install tile or stone. Normally this means screwing down an extra sheet of plywood over the existing subfloor so that the overall thickness is at least 1” thick or more. Alternatively, diamond lath metal mesh and mortar may be used to strengthen a floor – especially when the floor is not level or needs to be raised more than ½”. Before installing any type of floor heating system you will need to ensure that the floor is clean and secure.

Installing the Heating System

Each system on the market has different installation instructions which you must follow in order to ensure the system will perform as it was designed to, meet safety & electrical regulations and be covered under the manufacturer’s warranty. Low profile cables typically require plastic fastening strips or the use of adhesive tape to fasten them to a subfloor while some thicker heating cable types may allow you to use special staples to fasten them to wooden surfaces. The more powerful the heating cable the less cable is required to heat the floor and the farther apart the loops need to be. Sometimes it may be necessary to purchase a thicker, more powerful heating cable product which can be embedded in a thicker “dry-pack” or concrete slab installation. Most installations, however, are likely to be over an existing subfloor and can be covered in self-leveling cement or thinset mortar before flooring is laid.

Longevity Consideration

One thing most people don’t consider is how long they expect their in-floor heating investment to last. Left alone, most electric floor heating products should last as long as your home. However, their ability to survive future finish flooring changes is not likely unless special consideration is made to the heating product and installation method used. When taking-up an outdated tile floor you are almost certain to irreversibly damage any thin heating cables lying directly underneath. One alternative to traditional subfloor installation methods is to use thicker, tougher heating cables intended for interior use over subfloors and cover them with 1/8” thick diamond lath metal or plastic reinforcement mesh before embedding them in self-leveling cement. Reinforcement mesh is an accepted means of reinforcing wooden sub-floors under tile installations and should be nailed securely in place every 5-6” over the thick heating cables before embedding the whole works in at least 3/8” of self-leveling underlayment. This technique is recommended for new construction and some renovations but is not for novices.

Thermostat Installation

In-floor heating thermostats all require the installation of a small floor sensor in order to measure floor temperature. Try not to locate the probe where it may be covered by rugs, furniture or appliances since these will act as insulators and prevent the thermostat from working properly. All electric Floor heating installations are required by the electrical code to offer you protection from electrical shock in the unlikely event of a cable break. This is accomplished by using GFCI protected thermostats which automatically shut down the system if anything should go wrong. Note that the ground sheath surrounding the heating cable must be grounded in the thermostat box in order for the GFCI circuit to work properly.

Shop around for the system best suited for your renovation and make sure you follow the manufacturer’s installation instructions since not all systems are the same. Take care not to damage the heating cables before they are covered in mortar and be sure to test heating cables during installation and before finish flooring is finally installed.