The simple answers to radiant floor heat, “To heat, or Not to Heat?” That is the question.
Radiant floor heat is one of the most energy efficient ways to heat a room and will provide energy savings for the long term. Floor heat provides the most uniform heating available today. Forced-air systems use vents to distribute warm air and the location of those vents always means the area where the vent is located, will be warmer or colder than others. Floor heat systems are warrantied for 25-30 years and they are quiet, no furnace, no air blowing dust everywhere and above all, the floor heat warms the people and objects in a room meaning everything is warm and the same temperature. With these systems, there is no thermal air circulation occurring from rising warm or hot air.
Traditional radiators or steam heat, need to be heated to 149-167 degrees F whereas, floor heating systems only need to run at 84 degrees F. Radiators heat the air nearest first which, is why rooms have cold spots with steam heat radiators. Radiators can make a room too hot as well. Radiant floor heat does not overheat and, it is much better for the air quality since it keeps the air oxygen-rich and fresh.
The average savings with floor heat is 15% and it is 25% more efficient because all the heat produced does not escape through the heating system. Virtually all the heat is retained. Installation is easy particularly, the electric systems. We could list the cons but they focus mainly on the installation costs, the time and type of heating whether it is electric or hydronic and if a retrofit or new construction. Personally, when talking about creature comfort, more energy efficient systems, the cost is always something that will run into the future, some longer than others but it is never a loss. For a typical bathroom, it will cost roughly $1.00/day to run the system.
Floor heat will keep your feet warm where forced air will not. Floor heat provides waves of infrared radiation rising from the floor and warming up the building mass and all the objects in the room. Forced air systems push the heated air out at the ceiling where it drops down as its temperature lowers so your feet will always be cold while shoulder height and above may be hot. Radiant floor heat = pure warmth maintaining our warmth at a lower temperature.
Now, we can get into flooring materials. All materials can be used with radiant floor heat, some work better than others due to the conducting properties such as, stone, concrete and ceramic tile. These materials conduct transfer and hold the heat withstanding high temperatures. Solid wood can shrink and expand with fluctuating temperatures but that is not an issue with a professional wood installer who can manage the potential movement. Vinyl and plastic have temperature limits and carpeting insulates, reducing heat flow.
Where does Radiant Barrier fit in with radiant floor heating? Radiant barrier should be used under the floor and under the radiant heat. In a hydronic floor heating system, the tubes would attach to the bottom of the subfloor. They will heat up and once hot, the heat will try to go both upwards and downwards into the space below. Since the goal is to heat the floor above the tubes, heat loss to the space below needs to be prevented. Radiant barrier will act like a mirror, it will reflect the heat trying to move downwards, up towards the floor making the radiant floor heating system much more efficient and creating some savings in the wallet as well since the heat is not getting lost below the tubes.
When adding radiant barrier over a conditioned space floor heat system, the radiant barrier should be added to the floor joists first from the basement or crawlspace side. Leave an air gap between the foil and tubing. The layering should look like this: from the floor down, the subfloor, spacers, radiant heat tubing, air gap, radiant barrier and then insulation. Here is where we take it a step further, “kick it up a notch” by not adding thermal insulation but using more layers of bubble foil to create the insulated R-value needed. The spacers under the subfloor are added for those of you who may add the thermal insulation because it could get compressed during insulation and the whole assembly move up towards the floor and that critically necessary air gap, would be gone. Of course, the finished space would have drywall or other product to keep the insulation in place and, provide an air barrier for the thermal insulation.
If you are going to install radiant floor heat, then you need to go the extra mile and add radiant barrier so you maximize efficiency and savings for the longer term.