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SECTION 3

INSULATING TECHNIQUES

Topping

In a building that is to have tubing installed above the wood sub floor with a concrete topping poured over top of the tubes will require insulation to be placed under the sub floor between the floor joists. The amount of insulation will vary depending on the resistance of the floor coverings above the tubing. For a more accurate amount of the insulation needed contact R.D.S. Ltd.

One of the big advantages of floor radiant heat is the ability to zone it. Proper insulation of a floor heating system ensures that you will not have unwanted heat radiating down below to other living areas with their own heat requirements. The amount of insulation needed is far less than that needed to do a floor that is installed below the sub floor. The usual required amount in a topping situation is a friction fit bat of R8.

Floor Joists

An essential part of each installation is insulating underneath the floor with a foil faced insulation product. A foil placed on top of fibreglass batt is the most common choice. The foil must be installed facing up towards the heat tubing. You should leave a minimum of a l" air space between the foil and the underneath surface of the floor heat tubing. The foil serves to reflect the radiant energy back up through the floor. The R-Value of the insulating material may vary according to the climate and the BTU/sq. ft. heat load on the floor and if the heated space is over a heated area or an unheated area.

The trimmer header around the outside of the building that the joists are nailed to is an area that requires very careful attention to proper sealing and insulating of this area. The space between the floor joist at the exterior of the building needs to be caulked with sealant around the cracks where the floor sheeting meets the trimmer joist.

Then an R20 insulation should be placed in this space to stop the cold from entering the air space we are heating with the floor heat tubing. After the trimmer space is insulated then a space should be left free of insulation then the joist space can be insulated, like described above.

At the opposite end of the joist the insulation that is below the floor heat tubing must seal the space where the tubing comes down to meet the header. This is to ensure that the air space above the foil is a closed in container capable of heating up to close to the same temp as the water in the tubing. The more the joist space is closed in by vapour barrier or drywall the better the heat system will perform.

This type of installation requires hotter water than a slab installation. Depending on the heat loss of your structure and your floor coverings you should expect to provide at least 150 deg F temperature water to the supply manifolds. This will normally be sufficient to maintain an 85 deg F temperature at the surface of your floor, or the required temperature needed to heat the space. We do not suggest this type of installation in areas with large expanses of glass, or where the floor covering may be plush carpets with thick padding. As a rule of thumb, you should use some supplementary heat anywhere your installing contractor expects that the heat loss may exceed 32 BTU'S per square foot per hour.

Basements

In any basement slab heat job the least that should be done is a vapour barrier placed below the concrete slab. This is to ensure that moisture is not drawn into the building by the heated slab. It is a good practice to insulate below all concrete slabs, this will quicken the heat response time and prevent heat from being lost below the slab. In jobs where the basement is very dry soil then the need to insulate is not as great, and in some situations the cost of the insulation would not even pay for itself. The insulation needed under a basement is a ridged foam insulation that is not capable of absorbing any moisture. The thickness of the insulation should be a minimum of 1.5", this will not break very easily, and provide enough insulating value. A better way of insulating under the basement slab is to use 6" of an insulating gravel called granulite. This product is installed the same as backfill and provides the same insulation value of 2" of SM board insulation. Any insulation that is to be used under the basement floor is to be installed over the prepared compacted base, then on top of the insulation is placed the floor heat tubing, then on top of that the reinforcing is put down and concrete is poured over the tubing. The tubing can be installed above the reinforcing and tied down to the steel or mesh, this would be done in all slabs thicker than 5" thick.

Slab on Grade

The slab on grade installation will require that the perimeter of the slab be insulated to stop the migration of heat to the exterior of the building. The interior space may require insulation depending on the soil conditions, and in any situation that you are not sure of the soil then insulation should be recommended as a safety precaution. The times that insulation is a must is when there is very moist soil conditions or a soil condition that will soak up a lot of heat. The grade beam or the footing should have insulation installed all the way around the building, by either putting the insulation on the inside of the footing or around the outside of the building. This is to insulate the heated slab from the footing or grade beam to stop the transfer of heat to the outside of the building. There are many ways to insulate the slab on grade installation so either refer to the enclosed diagrams or consult with R.D.S. Ltd. to confirm the proper way to insulate the project in question.

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