Radiant heating provides a whole range of benefits. The heat produced by a radiant system is consistent and stays in the living space or work area; floors are warm enough to comfortably sit on; and furniture can be placed wherever desired without the hassle of radiators, heat vents and grills.
The air in in the space heated by a radiant system is cleaner, as dust and airborne allergens are not blown around through forced air ductwork. Allergy sufferers can breathe easier, and the temperature is consistent and controlled. Heat is generated where it is wanted. There are no drafts, or hot and cold spots. An important benefit of radiant hydronic systems is zoning control for individual areas within a house or building. Regular living or work areas can be kept warm while reducing the temperature in areas that are used infrequently. The ability to use zones to control heating creates system efficiency and can provide substantial cost savings.
A radiant heating system can be installed almost anywhere. To ensure the radiant system will perform properly and meet the needs of the client or building owner, a heating system designer will calculate the building heat loss and design the radiant system. For the heat loss calculation, the designer will need to know: the geographic location of the project; the floor plan and elevation plan for the building envelope; the R-value of wall assemblies, ceiling structure, window and door styles; and building structure – slab on grade, slab below grade, full basement floor. For the radiant system design: the effective floor area for heating; installation method; and floor covering.
Hydronic radiant heating systems are based on circulating warm water through loops of tubing (most commonly cross-linked polyethylene, also known as PEX). In determining the installation method, the highest efficiency versus the easiest installation method versus the least structural impact is taken into account. With the use of either concrete or gypsum (“wet” or “poured” system), the thermal mass of the floor will bring the most fuel efficiency and greatest comfort. While there may be slower recovery times, the high mass ensures a more even heat output, and in turn the floors retain their heat longer. The weight of the concrete may be a structural consideration. The use of concrete in commercial and industrial projects makes a wet installation method ideal.
Radiant heating is often dismissed as an option when there is a concern about the load bearing ability of the structure. However, it is still possible to have radiant heating in these circumstances, by either placing the tubing within the joist cavity (using the DryBelow/staple-up system), or between plywood strips (using the DryAbove/clip-down system) on top of the subfloor. In both systems, heat transfer plates are used to improve efficiency and distribute heat over a wider area than a narrow tube. Dry systems are often used in new residential construction or to add radiant heating to any existing construction (e.g. renovations or retrofits).
In all installation methods, spacing between radiant heating tubing has an indirect impact system performance. Tight spacing helps reduce noticeable difference between hot and cold spots and is especially suited for areas where bare foot comfort is desired, such as bathrooms, change rooms, or pool decks.
Floor coverings slow down heat transfer from tubing to the surface as they create thermal resistance to heat transfer. Some important areas to consider when selecting floor coverings include:
Carpet: Use only brand name products where the manufacturer has confirmed the suitability for floor heating. Choosing products with a minimal thermal resistance will help ensure that the radiant heating system performs optimally.
Quarry tile/Ceramic tile: All tile work should be installed according to industry standards. Expansion joints and control joints in the floor topping should continue through into the tile floor. The expansion/control joints in the tile floor need to be permanently elastic.
Vinyl/Plastic flooring: All expansion and control joints should continue through the flooring to reduce damage caused by movement of floor slab.
Hardwood flooring: Shrinkage can and will occur in most hardwood regardless of the heating system chosen. It is important to follow proper installation techniques and ensure hardwood has been properly acclimatized to the region where it is being installed. This will ensure shrinkage stays within the normal range of the product.
Advanced radiant systems incorporate a pre-engineered panel that ensures the system functions effectively, uses minimum space, and provides a clean, well-structured appearance. These pre-engineered solutions reduce design and quotation time; enforce standardized, reliable construction practices; and reduce the chance of installation and cost overruns on the job site.
Jeff Robinson, marketing and Randall Quon, communications coordinator are part of HeatLink Group Inc., a leading supplier of PEX-a plumbing, radiant heating and cooling systems, and hydronic panels for the residential and commercial building markets across North America.