Electric in-floor systems are similar to other fuel types of in-floor systems, up to the point of heating the floor. While other systems produce heat on demand (e.g., with an oil boiler or electric cable - www.britech.ca), electric thermal storage in-floor systems use electric heat sources and the thermal storage capacity of the concrete floor itself. Because of this, there are some considerations to be taken when designing the system.
Because each installation is different, Nova Scotia Power cannot provide specific design and/or installation instructions beyond the equipment used to control the time of day the system is in operation. However, in talking with our customers and their contractors, we have identified some practices that contribute to higher-quality installations. Please consult a qualified industry source for more detailed information and specific installation details.
Our customers have told us that:
- A 4" slab with a minimum of 2" of rigid insulation underneath offers best thermal retention.
- At a minimum, the basement (or slab, if no basement) must be thermally heated. Upper levels can be heated with in-floor as long as an overpour of 1½“ concrete is used. Occasionally, our customers have had comfort issues with this method, depending on the openness of the floor plan, the insulation levels in the home (e.g., less than R2000) and the amount of solar gain (i.e., sun exposure) of the home. A better option for the main/upper levels can sometimes be thermal storage heaters. Tubes or cables running through the floor joists or stapled under the subfloor have not been successful, due to their high heat loss and limited thermal capacity.
- In general, the better insulated the home (i.e., the lower the heat loss), the more successful the installation. Because the system cannot inject heat on demand, the heat loss should be calculated for each home and the appropriate capacity built in to the home’s heating and installation design.
- Often, our customers have found that systems using an outside temperature sensor cause some under-heating of the slab. If the temperature falls quickly, the system may not have stored enough heat.
- For in-floor hydronic systems, two 40 or 60 gallon domestic water heaters suited for space heating tied in parallel, with element sizes ranging from 4.5 kW to 6 kW, are often adequate. For larger homes, our customers have found that electric boilers or instantaneous water heaters can offer quicker recovery. Also, a mixing valve that combines cool water with water from the heater/boiler should be installed in order to supply input temperature ranging from 90° F - 110° F.