Tile 101

A Beginner’s Guide to In-Floor Heat

In-floor radiant heat is a simple, economical way to warm any floor and provide years of comfort in all climates. Achieve a warm spa-like feeling without significantly increasing your monthly bill. You can effortlessly run the system through a programmable thermostat ensuring you get the benefit of in-floor heat when you’re home while being able to save money when you’re not. Learn the basics about in-floor heat and what installation method might be right for you!

Why heated floors?

What To Consider

What do you want your in-floor heat to do for you?

The spacing of the heat cable determines the way your in-heat works and feels. Tighter spacing of the heat cable warms the floor up quickly and creates more radiant heat, while wider spacing offers a gentle warmth that can be enjoyed even with the air conditioner running at the height of summer.

2-Hub Spacing
2-3 Hub Spacing
3-Hub Spacing

What will it be installed over?

Before installing in-floor heat, it is important to understand what type of surface you will be installing it over. This can tell you how much of an affect the temperature will have on the floor and also how long it will take to warm up. In general, more insulated floors allow for a greater increase in floor temperature than floors that are less insulated.

The base can also help you decide the best wire spacing. For example, a concrete slab will hold the cold temperature and because it is so dense, will take a much longer time to heat up. In this case, you might want to lay the wires closer to help shorten the time it takes to heat up.

In above-ground applications, where there is insulated air space on wood floor sheeting, the heat will easily radiate upward. On concrete or steel, it takes a lot of energy just to warm the substrate, so installing special insulating paneling underneath the wire will prevent wasted energy heating the substrate. Thinking about the efficiency of your in-floor heat during the install dramatically increases the enjoyment—and value—of the final result.

Requirements of Installation

Know how much space you want to heat. To figure out the amount of heat wire needed, follow these simple steps:

1. Start by figuring out the square footage of the entire room.
(ie.: 8′ x 12′ = 96 sq. ft.)

2. Subtract unheated areas from the total square footage. Any areas where there is furniture (ie.: vanity) or that are unoccupied should not be heated. (ie.: If the total square footage that will be occupied by furniture is 22 sq. ft, then 96 sq. ft. – 22 sq. ft. = 74 sq. ft.)

3. Multiply the total square footage by 90%.
(ie.: 74 sq. ft. x 0.9 = 66.6 sq. ft.)

4. Round to the nearest heat cable size because you cannot cut the wire.
(ie.: 66.6 sq. ft. = 70 sq. ft.)

Choose the best way to secure the wire. Here are two of the most common methods:

Embed the wire in a membrane:
This works as both a method to secure the wire as well as acting as an uncoupling underlayment that allows you to tile immediately. It can be layered directly over the entire subfloor, making it possible to install electric heating even on tricky substrates like wood and level concrete with hairline cracks present. Once this underlayment and heating wire are in place, you’re all set to start installing your tile on top of it.

Embed the wire in self-leveling underlayment:
The heated wire is strung between and secured by straps running the length of the room. This method does not provide an underlayment for the project. This means that prior to tiling, you must cover it with at least 3/8″ of self-leveling underlayment to embed the wire and ensure that it is not damaged during the tiling process.

A thermostat to control the system.

Depending on your desired point and the capabilities you would like, there are different thermostat options. Programmable and non-programmable options are available to fit any of your needs.

Electrical considerations.

When running the heat wire, you can assume that the wire will draw 1 Amp for every 10 square feet.  So, for 120-volt circuits only up to 150 square feet is recommended to be installed per circuit. For spaces from 150-300 square feet, a single 240-volt circuit can be used, but anything larger than 300 square feet will require multiple circuits. Also, it is recommended to have a dedicated circuit for your in-floor heat due to the amount of power that it will draw. This ensures that there is no need to sacrifice warm floors for being able to use a hair dryer! As always, we recommend referring to a licensed electrician for specific questions or concerns.

Installation

Disclaimer: This is not a step-by-step guide to install in-floor heat. For specific installation recommendations, always refer to the manufacturer’s instructions or consult with a professional before installing. The following is what you can expect during installation.

1 – Measure and plan.

The spacing for the heat wire will depend on many factors including the subfloor, location, and installation method. General guidance is provided assuming there is a 3″ spacing. Areas with exterior walls or those with a greater desire for warmth may be spaced 2.5″ – 3″. Areas such as hallways, entryways, and areas with low heat loss may be spaced 3″ – 3.5″.

Always plan out the wire to ensure than there is no crossover of the wires and that there is enough wire for your project without cutting. Remember, you should never cut a wire as it will result in a system failure. Also, ensure that you mark where built-in furniture, cabinets, fixtures, or baseboards will be so you plan to install around those items.

2 – Prepare the area.

Prepare the floor by sweeping and vacuuming to remove all dust or debris while ensuring that the subfloor meets TCNA requirements. Always test the heat wire with an Ohms Meter prior to installation to ensure that it is working properly.

3 – Lay the wire.

When installing the wire, use a float to press it in to place, keeping it tight but not forcibly stretching it.

If using the membrane method, apply thinset with 1/4″ square trowel to apply the underlayment to the floor and place the wire in the grooves of the cups in the membrane.

If using the self-leveling underlayment method, secure strapping every 2′ – 3′ to the subfloor with adhesive, staples, or nails and place wiring in strapping.

Using the layout that was created during the initial planning, lay the wire to specifications. Be sure to not cut, shorten, or cross the wire. During placement, always use a current metering device. It emits an audible alarm if the wire is damaged during the installation process, and ensures a worry-free installation.

4 – Install the Sensor

Install the included floor sensor at least 11″ from the wall. This must be centered in the cable loop between two heating wires.

It is recommended to install a second back-up sensor, leaving the wires where they can be easily swapped with the first sensor. Though sensors rarely fail, placing a sensor in an alternative location can help overcome environmental factors that might go unnoticed until after installation, like where the sun comes through the window at certain times of the year or a dryer vent that creates heat near where the sensor is placed. (see image examples)

5 – Install Tile

If using the membrane method, after you place the wire and the sensor, place a layer of thinset as you install tile directly on top of the wire. No self-leveler is needed.

If using the self-leveling underlayment method, after placing the wire, pour at least 3/8″ of self-leveling underlayment to embed the wire. Allow the self-leveling underlayment to fully cure before proceeding with the tile installation. This ensures that the wire will not be damaged when the tile is installed.

Next, connect the power supply and thermostat. Be aware that state or local codes may require electrical components be installed and/or connected by an electrician.

After connecting, conduct a final resistance test to ensure that all electrical components were installed correctly.

6 – Turning on your in-floor heat.

You should wait at least 30 days after installing before turning on the floor heat. This allows the thinset, grout, or self-leveler to properly cure.

Things to remember

Securing the wire:

Once the wire is placed, use a high quality polymer-modified thinset when installing Pro-heat products. Make sure the thinset fully covers the wire when laying the tile.

The wire must be spaced properly and mechanically secured before installing tile; either in an underlayment designed for heat wire or a fully cured self-leveling underlayment bed.

Installing the wire:

The wire cannot be cut shorter to fit any area. It is better to have a smaller amount of heating wire and adjust as needed rather than having it run long. Do not cross or overlap the wire. Any modification or misuse of the heating cable will lead to system failure and ruin the investment in the heating system.

Resistance testing:

If resistance readings do not measure within guidelines at any time, do not proceed with the installation. Contact the manufacturer of your heating cables for help.

For more information on in-floor heat, your local store representative can help you every step of the way. As always, refer to the TCNA requirements and consult with a professional before installing.

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