With the popularity of radiant floor heat and sales rising each year more and more concrete contractors and general contractors are selling radiant floor heating systems with their projects. Radiant Floor heat creates some questions when first starting, in this article we will explain the key points of radiant floor heat and give you the confidence to start including radiant floor heat in your projects.
–by Les Graham
What are the advantages of radiant floor heat?
Slab design considerations when using radiant floor heat?
The main consideration is the use of insulation – both under the slab horizontally, and vertically installed around the perimeter. The perimeter insulation needs to have an R – value of 10. Generally, this is done with 2’’ blue or pink polystyrene. If possible, incorporate this 2’’ foam as part of the original concrete forms. This can save hand digging later, which can undermine a monolithic slab.
The thickness of the slab does not have to change because of radiant floor heat. The base you normally use underneath does not need to be changed. (Personally, I like to see a 6 mil. vapor barrier under the slab.)
Do I need to insulate under the slab?
You need to consider insulation under the slab. Heat does NOT rise, but travels in all directions – hot air rises. Generally speaking, you should always insulate a project 2000 square feet or smaller with an R-value of 5 – 10. On larger projects, consider the dampness of the soil below. If you are high and dry, you can consider zero insulation, or insulate the first 6-8 feet in from outer edge. If the water table is high in an area, then insulation under the whole area becomes necessary. Under concrete there is no benefit or need for reflective type insulation.
Where is the tubing placed in the concrete?
The tubing can go in the middle or at the bottom of the concrete. Both have advantages. When placed in the middle of the concrete, the heat is delivered a little faster, thus allowing for a slight gain in efficiency. Snowmelt systems should always be installed in the middle of the slab. When placing tubing in the middle of the concrete, keep in mind that with shops you need a minimum of 1-1/2 inches of concrete above the tubing, homes require a minimum of ¾ inch above.
The advantages of the tubing placed at the bottom of the concrete are several:
Can I place the tubing in the sand below the concrete?
Radiant floor heat installed in a County Maintenance building in Illinois.
Radiant floor works well with colored concrete. Farmers love the efficiency of radiant floor heat.
Post Frame buildings and Steel buildings are common applications for floor heat.
Notice the Pex-Al-Pex staying flat on the Styrofoam. Air test is on tubing and ready for the concrete.
Les Graham is the president and owner of Radiant Outfitters based out of New London, Minnesota. Graham has 24 years of experience in radiant floor heating and has certified with the Radiant Panel Association.
Radiant Outfitters, a wholesale distributor, offers complete design service and product, partnering with all types of contractors that install radiant floor tubing.
For more information, call 877.855.2537, or visit www.radiantoutfitters.com.