SunTouch® UnderFloor™ Retro Fit Heating FAQ
We recommend SunTouch UnderFloor Mats be installed in all floor areas where floor warming is desired. Where no mat is installed, the floor will be cold so don't skip any areas if possible. No Mat = No Heat
What is SunTouch UnderFloor?
SunTouch UnderFloor is a retro fit heating mat system designed to warm existing floors without having to replace the floor coverings. Simply staple UnderFloor heating mats (without disturbing your existing floors above) to each side of the floor joists. All you need is access from below via a crawl space or basement. The end result will be warm, comfortable, radiant heated floors from SunTouch.
What do you mean by Joist Spacing?
Floor Joists are the boards under your floor that are parallel from wall to wall or across beams to support the floor. 16 inch center to center (or on center) spacing is the most common with some 12 inch used.
Modern lumber is not really the dimension it says; i.e. a 2 x 8 board is really 1.5 x 7.25 inches.
SunTouch only makes UnderFloor mats for 12 and 16 inch joist spaces (bays) for the 2 most common joist spacing used in North American Construction. 16 inch refers to the actual dimension of the Orange Mesh Mat material while the Blue Foil is approximately 1.5 - 2 inches narrower than the Orange Mat so the foil can completely fit within the bay as required for the UL Listing and safety.
- 16 Inch On Center joists will have approximately 14.5 inches between them inside edge to inside edge.
- 12 inch On Center joists will have approximately 10.5 inches between them inside edge to inside edge.
Can you make custom sizes?
Unfortunately, No. We cannot make special widths or different lengths. Only the widths and the lengths listed are manufactured by SunTouch. No special orders.
How many UnderFloor Mats are needed for my Installation? Which Lengths do I choose?
To obtain accurate measurements, look under the sub floor to see where mats can be stapled. Looking carefully at each joist bay, simply measure:
- The width of each bay from the center to the center of each adjoining floor joist and also verify the space between each side to side (this should be 1.5 inch less than the on center (OC) measurement for modern 2-by lumber (2”x8”, 2”x10”, etc). Some floors mix joist spacing of 12 and 16 inches, so check each one.
- The length of open area in that bay that can receive a mat, and select the mat from the available sizes that fits each joist space. Remember that these mats cannot be cut shorter or narrower to fit, and CANNOT be cut or modified in any way to fit multiple joist bays. Do not include in these measurements areas that contain items that would obstruct installation of the mat (return air ducts, supply ducts, drain pipes, etc).
- If there is an obstruction in the middle of a bay, you could run a mat from each side of it, as long as they each fit completely within the space.
Once you have a list of your sizes, you can choose them from the available size listing on our site. See All UnderFloor mat sizes here. Or you can Email, Call or Fax us and we will be HAPPY to assist you.
Will a few mats warm other areas adjacent?
No. Wherever mats are not installed, the floor above will not be warm. The heat does not spread sideways more than a few inches. So, if you want the floor heated, cover as much as possible. Remember, more than one mat may be installed in a joist bay where there are barriers such as cross bracing. You can run mats from both edges toward the middle of appropriate lengths.
Click here to view a gallery of images showing a typical installation. Select mats for the easiest wiring possible. If all the power leads end up at one end of the room, it will be much easier to wire them together in the junction boxes. The junction box(es) must be accessible after all finishing work is completed, according to Electrical Code. Be sure to position the mats so that this is possible. You can bring several mats to each Junction Box, and then join several J-Boxes together with conduit.
How Do I choose Voltage: 120 or 240 Volt?
First, NEVER mix 120-VAC mats and controls with 240-VAC mats and controls. Observe these general voltage guide-lines:
- For areas totaling up to about 190 SqFt. (about 15 amps), use 120-VAC mats with a 120-VAC SunStat.
- For areas exceeding about 190sq.ft.and up to about 350 Sq.Ft. use 240-VAC mats with a 240-VAC FloorStat to have mats totaling 15 amps or less. Each SunStat control or SunStat Relay is limited to 15 amps max.
- Use 240-VAC mats and a 240-VAC SunStat Relay control system or a contactor system (see wiring diagrams in manual) for mats totaling more than 15 amps at 240 VAC. Regardless of the voltage requirements in a particular installation, make sure the circuit breaker can handle the load. Follow all electrical codes for determining the size of the breaker.
How Much heat does UnderFloor provide?
UnderFloor mats are Safe and UL Listed to provide 10 Watts per Sq Ft (34 BTUs/SF). How much heat reaches your floor surface depends on the flooring and R-Value of the sub floor. A typical 3/4 inch thick wood subfloor has an R-Value of only 0.9, so UnderFloor is very effective for most floors:
- Expect up to 15 º F more warmth on most floors of Tile, Wood, Stone or Laminate;
- For Carpet, expect 6-10 º F more warmth. The thickest carpet and pad allows the least heat.
Should I insulate after installing the UnderFloor mats?
Yes. Insulation is essential for the mats to perform. Batts or roll insulation is recommended.
Are SunTouch UnderFloor mats Safe for me and my family?
Yes. Safety is the most important issue - Look for a UL (Underwriters Laboratory) Listing - ALL SunTouch Floor Heat Systems have this listing. See the UL Listing You'll see Watts actually manufactures SunTouch products in the USA - unlike others who just re-package someone else's imported product, from countries like India & South Africa. Plus, all our Thermostats have been safety certified by independent testing agencies and all include GFCI protection BUILT-IN for shock protection. And, unlike our competitors, have NEVER had a safety recall for our electric floor heating products.
SunTouch UnderFloor heating mats also are the safest in regards to Electro Magnetic Field, with a virtually ZERO reading that has been INDEPENDENTLY tested and verified. Tested and found to have the LOWEST readings of any manufacturer.
We don't just SAY we have low EMF - we back it up with test results, unlike our competition. See the ZERO EMF details here
SunTouch is the only Electric Radiant Floor Heat Manufacturer who offers a solution for ALL electric radiant under floor heating projects. And, SunTouch offers an Industry Leading 25 Year Warranty on ALL products. It's even transferable!
Is UnderFloor Heating a Do It Yourself Project?
Yes! Our Under Floor Heating mats are “do-it-yourself” friendly or can be installed by a handyman or contractor. If you have access under a floor simply staple UnderFloor heating mats to the floor joists and connect the factory installed 10 ft power leads directly to the thermostat or junction boxes. Don’t forget to insulate under the mats as it is essential to performance.
Each UnderFloor heating mat is designed to be installed in only one joist bay. The heating mats cannot be cut shorter to fit a shorter joist bay or modified in any way to cross into another area. More than one mat may be installed in a joist bay where there are barriers just don’t let the mats touch or overlap.
Can I install these special UnderFloor mats on top of my sub floor in mortar?
No. This is not an approved use, is not safe and will not work. Install UnderFloor mats only in joist bays under sub floors. The blue foil is the indicator of an UnderFloor mat. Always follow the installation manual.
Can I use regular SunTouch Mats in joist bays?
No. SunTouch mats can ONLY be installed in mortar and cannot be used under the sub floor, only on top of it set in mortar.
Why should I choose to give Warm Your Floor my hard-earned money?
We love this question! Warm Your Floor is the nation's leading radiant heat, floor-warming resource. Making your floors warm and cozy is all we do. And we have the largest inventory in the U.S., from the leading manufacturers, in stock and ready for immediate delivery – 99.6% of orders ship the same day you order. We are a brick & mortar distributor with a real office, showroom and large warehouse -- packed with floor heating solutions. We are Floor Warming Experts and have been offering the best prices and service since 1999.