Best Under Slab Insulation For Radiant Heat

Determining how much insulation.

Best under slab insulation for radiant heat.

Without a thermal break between the slab and the ground heat will sink into the ground under the slab resulting in longer warm up time higher energy costs and overall poor performance of the system. Below grade under slab system with foamular extruded polystyrene rigid board insulation and radiant heating. The insulation phase is crucial for a radiant floor. Any cooler surface in contact with the slab will try to steal its heat.

In warm climates a minimum of r 5 is recommended below the slab. Slabs that include embedded hydronic tubing for radiant heat always need a continuous layer of horizontal insulation under the entire slab. Insulation under the slab can reduce temperature swings in the heated space and respond quicker to new changes in thermostat settings. Remember that your slab will be about 75 degrees f.

R 10 in cold climates. A continuous layer of horizontal insulation reduces heat loss in the winter and it reduces condensation of humid air on the slab during the summer. Get all the construction documentation you ll need in a single click. Mainly heated slabs radiate outward rather than downward so insulation on the edges of the slab is most important.

A john siegenthaler a consulting engineer who specializes in hydronic heating system design responds. Also make sure that you insulate the slab edge as that s where the heat loss from a slab is greatest. This reason by itself can justify the use of under slab insulation. Downward heat loss from a radiant slab should not exceed 10 percent of upward heat output a ratio derived from european installation standards for floor heating systems it s possible to calculate the r value needed to meet.

Q how much insulation is necessary under a typical radiant slab. The rpa guidelines provide a simple formula for calculating the r value for heated slab insulation. Insulationstop is the best source for top quality products at the best price. Some people use twice the r value at the slab edge as they do under the slab.

Insulation is of crucial importance to a radiant heated slab with pex.