Types of Water in Radiant Heat Systems

A radiant heat system.

Water radiant heat is becoming increasingly popular among homeowners. Water radiant heating is fairly energy efficient and can easily heat your entire house. There are a few types of water radiant heating systems.

The Closed System

This system is designed exclusively for space heating and uses either a boiler or a water heater to heat the water, which is then circulated through the in-floor tubing. This design is widely popular among homeowners and is well-accepted with building code officials.

With a closed water radiant heating system, heat is provided when the pump is turned on by a thermostat (pretty much how traditional home heating works, in that once your home gets to a certain temperature, the heat kicks on). Warm water then flows from the boiler or the water heater through the tubing in the floor until your room or home (however you have it set up) is warmed to your preferred temperature.

The only downfall of the closed system is that it does not use a heat exchanger to keep your heating needs and regular hot water needs separate. If you have a newer home, however, this shouldn't be a problem.

The Indirect Heating System

Another hugely popular and widely used water radiant system is the indirect heating system. This system uses a high-efficiency hot water heater for not only your space heating needs, but also for your domestic hot water needs as well. With an indirect system, you can keep the two systems separate with the use of a heat exchanger.

With an indirect system, when heat is needed hot water is pumped from your water heater to the heat-exchanger. Once there, the heat is transferred to the heating fluid on the other side. During this time, the heating zone pump, or pumps (depending on how large an area you have) come on and will circulate the heating fluid where it is needed.

The Open Direct Heating System

The open direct heating system is a preferred system for most residential applications. This system uses a high-efficiency hot water heater to provide hot water for both space heating and regular hot water use within a single system.

When the thermostat senses that heat is needed, it turns on the pump. Warm water is moved from the water heater, through the tubing in the floor, and then returned to the water heater.

Warm water flows out of the tank and into any fixtures. Coldwater from either your street or your well will replace the water that is used. This cold water goes through the floor on its way down to the water heater. This helps prevent the water from going stagnant within the tubes during the summer and provides your home with some free cooling.

If you want some extra-and free-cooling during the warm summer months but not in the winter, you can turn a bypass valve, and all of the cold water that the house uses goes through the floor.

The open direct heating system has significant advantages in terms of cost, fuel efficiency, simplicity, and environmental friendliness.