I have been designing radiant heating systems since 1987. It is not easy.
However, I can give you some positive direction.
First, you need a heat loss analysis for the space you want to heat. This is gained by deciding the temperature you want to maintain in the space, when you want to maintain it- e.g. all the time or just of weekends-and what your outdoor design temperature is. This should be done by a professional and is the most important part of any comfort system, be it heating, cooling, ventilation or humidity control. If you don’t have an accurate heat loss analysis you literally “don’t know what your doing”.
Once you have secured an accurate heat loss you can proceed to choose the kind of radiant panel that will best fit your application (slab-on-grade, sub-floor, sandwich, wet, dry). Floor covering can dictate both the type of radiant panel and the source of hot water. Sub-floor systems require higher water temperatures than slab systems; suspended tubes are less efficient at transferring heat than sub-floor emission plate systems, which in turn don’t have the heat potential of sandwich systems such as Warmboard or slab-on-grade installations. Don’t forget ceiling, wall and steel panels.
Next, determine the fuel source (see my factoid on ‘which home heating fuel is most cost effective’) this may be wood, electricity, natural gas, propane, oil, geo-thermal or solar. Hydronic (boiler) systems can’t be beat for efficiency when it comes to distribution systems. Hydronics allows you to change your mind or integrate more than one fuel source such as solar and natural gas.
Water heaters (tankless or otherwise) are not boilers. Small systems (under 1000 sq.ft.) can be served by a conventional water heater or one could consider the Combi1 by Bradford White, which has the capability safely heating domestic (bathing) hot water and space heating water all at once. Tankless water heaters are not designed for space heating.
Of course all-electric heating systems abound. They are capable of heating practically anything from a small bathroom (a fairly common and inexpensive installation) to an entire house, including snow melting the driveway! Naturally one has to start with the heat load and talk to an electrician or designer before ordering components. The down side to large electric radiant jobs is the common requirement to upsize the electrical service to your home, the inability to switch fuel sources and the generally high operating cost.
If electricity is your least expensive fuel at the moment, then a two-stage electric boiler (such as an Electro) is the wise choice.
A few things to consider:
Professionals do not install so-called “open” systems, wherein potable (drinking) water is commingled with space heating water. It is considered an unhealthy practice and does not (to my knowledge) meet any building code in North America. We use 1/2″ barrier PEX pipe on nearly all residential radiant jobs, protecting ferrous metal in the most common system components (pumps, expansion tanks etc.) from premature failure do to oxidation. Air is the enemy of any properly designed hydronic system, pay close attention to the close piping and install a micro-bubble air eliminator in the proper position and orientation to the pump and boiler. Common thermostats can be used with great success and outdoor reset (a common feature on Mod-Con boilers) makes any hydronic radiant panel more efficient and comfortable.
MA
