Radiant Floor Heating Concrete Slab Insulation

This is about installing hydronic radiant floor heating in a slab floor system.

Radiant floor heating concrete slab insulation.

While it was done as a new house was being built in my last house i poured a concrete floor on top of a wood framed floor system and could have put radiant heat in that as well. The insulation phase is crucial for a radiant floor. Radiant heat insulation is installed to prevent heat loss from a pex radiant floor heating system most commonly pex embedded in concrete slab or stapled underneath the plywood subfloor. When the thermal mass of the concrete is heated the warm slab acts as a radiator distributing even heat throughout the structure.

If your slab is heated it s a good idea to increase the r value of the vertical and the horizontal insulation to at least r 20. Need insulation for under concrete slabs slabs with radiant heat. Mainly heated slabs radiate outward rather than downward so insulation on the edges of the slab is most important. Our photo above shows a well designed insulated radiant heated concrete slab with an insulated foundation perimeter being installed in two harbors minnesota in 2007.

Different insulation types help to minimize heat loss from convection air circulation conduction direct contact or radiation energy waves modes of heat transfer. Our photo above on this page shows that tubing was in some sections more than 18 deep and adjacent to a large area where sub slab insulation was simply omitted by the contractor. Slabs that include embedded hydronic tubing for radiant heat always need a continuous layer of horizontal insulation under the entire slab. It s possible to calculate the r value needed to meet this goal while accounting for such factors as floor coverings soil temperature and required upward.

How much insulation is necessary under a typical radiant slab. The system works via pex pipe a small pump a water heater and a thermostat. Insulationstop is the best source for top quality products at the best price. Radiant floor heating concrete slab insulation cerazorb is a 3 16 inch 5 mm thin synthetic cork underlayment that is highly recommended when installing a floor heating system over an existing concrete slab or under tile and stone.

Radiant tubing was at the bottom of the slab in this area more than seven inches down in the concrete and set atop the foam sub slab insulation. In a heated floor slab heat losses into the ground and outward through the edges of the slab and foundation wall are quite significant. The picture above shows a concrete floor we re about to pour with radiant heating tubes installed. Any cooler surface in contact with the slab will try to steal its heat.

John siegenthaler a consulting engineer who specializes in hydronic heating system design responds.