Many older homes in the U.S. still sport the old cast iron radiators of days gone by. Whether for aesthetic appeal, low operating cost, or just lack of funds to remodel, there are plenty of homeowners who continue using this method for heating their homes. But if you're considering replacing those radiators you might be wondering if you can covert the system into radiant floor heating using your existing boiler.
The short answer to that is “yes”. Read on if you want to know how.
First of all, the boiler and water system is perhaps the simplest and most efficient central heating method ever invented. In a nutshell, these systems work using a gas or oil-fired burner in the lowest level of the structure which heats water to a given temperature. The pressure in the boiler forces the hot water up into the structure's pipes and radiators all the while pushing cool water back down into the boiler. With no moving parts, no fans, and water's ability to retain heat, the system works extremely well.
Knowing this, we can now rest assured that the boiler and pipe system does not care what type of radiator heats the room as long as water flow is not impeded. Radiant floor heating is really just a smaller and more efficient upgrade of the old cast iron pieces that we're trying to replace.
In order to do this you'll first have to choose between installing tubing loops into a newly cast concrete sub-floor, or use another method where a concrete sub-floor isn't an option. Since installing radiant floor heating is complicated you'll want to use a contractor to do the work. He can tell you which installation method is best.
Next comes the calculations for flow rate, water temperature and heat loss, which all must be considered when designing the system. Once again, your contractor should be able to do this without a problem.
Finally you must decide about using a mixing valve with outdoor reset. When converting from cast iron radiators it's important to remember that your current boiler is optimized for the higher water temperatures those old radiators require. Since moving such hot water through a radiant floor is not necessary, the mixing valve solves that issue by adjusting the water temperature with cold water. An outdoor reset monitors the air temperature outside the house and adjusts water temperature accordingly.
The hardest part of converting old radiators to radiant floor is the planning and calculations. Once that phase is completed it's simply a matter of preparing the sub-floor, disconnecting the radiator, connecting the new tubing to the system, and applying the new floor. If you use a contractor with plenty of experience it should not be a difficult or time consuming process at all.