Domestic Water Heaters instead of Boilers

Who can blame a customer who is bewildered by all of the different products, techniques and choices that are available for radiant heating?

No one solution is best for everyone and Radiantec has a large selection of different products. But after many years in the business and after helping tens of thousands of customers, a few systems and products stand out.

We like simple honest value, with no gimmicks or do-dads. We think energy efficiency is very important. Systems should be simple, reliable, long lasting, and easy to repair. They should be environmentally responsible and affordable to the common man.

It should be possible to convert a system to use solar energy to the extent that it is practical.

With these values in mind, Radiantec suggests that you consider the following systems and details.

The Best Overall Heating System

Heating systems that are based upon the domestic water heater is a relatively new approach with many advantages. Systems cost about half as much as one using a typical boiler system and yet are much more efficient. They are generally made of better materials. As you may expect, these systems can be controversial among those with a vested interest in the status quo.

They are a simple, ingenious way to make radiant space heat, domestic hot water and even pick up some free cooling, all within the same unit.

Domestic hot water based systems are very safe when they are designed properly and they meet all major codes.

These systems operate at low temperature for safety and exceptional energy efficiency.

The expense of a boiler is eliminated entirely and domestic hot water heater based heating systems are compatible with a solar energy assist.

Click here for more information about radiant systems that use the domestic hot water heater as the heat source.

Domestic Hot Water Based Heating Systems are Affordable and they make the benefits of Radiant Heating available to everyone.

Exceptional Comfort, High Efficiency, and Health Benefits are now available to all and not just to the wealthy

The Best Heating Unit

The Polaris heating unit is a water heater (not a boiler) that is engineered to make space heat as well as domestic hot water. Because it is engineered to make warm water instead of boiling hot water right from the beginning, it is incredibly energy efficient and safer as well. Standby losses are nearly eliminated.

The Polaris is all stainless steel. A truly large submerged stainless steel flue extracts nearly all of the heat from the flue gas.

Even with these benefits, the Polaris costs far less than any equivalent boiler. It is a good value and a very good value to operate.

Click here for more information about the Polaris.

The Best Detail for a Joisted Floor

Heat the floor with tubing installed in the joist spaces beneath the sub floor. Use 5/8" PEX with .070 wall thickness. Space the tubing 8" apart within a 16" joist space. Use thinner gauge aluminum heat emission plates and use them everywhere if possible.

The 5/8" tubing is larger than typical 1/2" material. It puts out more heat and allows the system to operate with lower fluid temperatures for longer life and better efficiency. The larger size reduces pump work and allows longer circuits. Tubings which are larger than 5/8" may be too difficult to work with.

The aluminum plate takes heat away from the tubing and distributes it throughout the sub floor. Research shows that this detail is important. The plates support the tubing well and the improved heat transfer is significant. Thinner aluminum plates have equivalent performance as thicker plates with half the cost.

The aluminum material has a very important and often overlooked property. Aluminum radiates much less heat than other materials. This property sharply reduces heat loss in the downward direction (back loss) and has the effect of insulation. It is very important to control heat loss in the wrong direction as these losses can nullify most of the benefits of radiant heat.

Click here to read our research report about aluminum heat emissions.

The radiant thermograph (right) shows that the aluminum plates (blue) emit much less heat than the surrounding areas (red, orange) even though they are at a much higher temperature. This property means that the plates are taking the heat away from the tubing, distributing it throughout the floor, and then, making the heat go in the right direction.

Feel free to contact customer service technicians if you want more information about these details. Customers may also request a research report.

The Best Details for Slab on Grade Construction

Insulation Details

Our experience and research indicates that under slab insulation is most important at the perimeter and less important in the center of the building. Insulation should be extruded polystyrene. We know of no other acceptable material. In cold climates, it should be 2 inches thick at the perimeter and may taper off to 1 inch as it goes inward towards the center of the building. Insulation should extend 12 feet from the perimeter towards the center in cold climates but can be reduced to 6 feet in warmer climates.

Concrete reinforcement

"Rod" type reinforcement is preferred over the "mesh" type because of overall strength and workability. Put down half of the reinforcing first and set it on "chairs" or bricks. Then lay out the tubing. Then lay out the other half of the reinforcing on top of the tubing and tie everything together. It will be easier to lay out the tubing (because only half of the tubing is placed), and the tubing will be well protected by the reinforcing. The reinforcing will carry heat away from the tubing, and the reinforcing is generally well placed with half above the centerline of the slab and the other half placed a little beneath. Fiberglass reinforcing fibers are not a substitute for steel reinforcing.

Tubing Size and Spacing

If the slab is to be of any significant size, (500 square ft or larger), a larger diameter tubing is preferred (up to 7/8" diameter). A larger tube (within reason) will put out more heat, reduce pump work and enable longer circuit lengths. Tube spacing may be spaced 24" on center in very efficient and stable environments (such as basements). A 16" spacing is more typical for reasonably efficient residential construction and 12" spacing will provide a little more heat and a more rapid response time.

Detailed research (DOE) has shown that 7/8" PEX tubing with 0.70" wall thickness and a circuit length of 200 feet is about ideal. The electrical energy consumption of the pumps will be as low as possible and the flow will be just slightly turbulent. The temperature drop will be about 10 degrees F from inlet to outlet. This is ideal, but different designs can still produce satisfactory results.

Tubing layout should be a spiral or have gentle turns by another design. Very tight turns strain the material and raise pumping costs. There is no benefit to a very tight and very evenly spaced design.

Click here to learn more about the benefits of an engineered tubing.

The Best Solar Heating Systems

Solar heating is worth another look. The first generation of solar heating systems was too expensive, not efficient enough and required too many solar panels.

The next generation of solar heating systems is more efficient, more attractive and has a better payback.

There are two innovative approaches that are worth study in the continental United States.

The first, "Solar Option One", uses slab on grade construction, and the earth beneath it as a heat sink. Low operating temperatures enable high efficiency in the solar panels and the heat storage has low cost. This combination of improvements results in a much better cost benefit. DOE research supports these findings.

The other system "Solar Option Two", is an extension of successful solar domestic hot water applications. In the right place, the solar domestic water heaters have been successful as long as the work is done right and the domestic hot water production is valued (schools and churches are not appropriate, residential construction is often ideal).

The radiant heating system is designed to use the domestic water heater as the energy source and additional solar panels are provided so that some contribution to space heating or other energy needs can be made. The overall system may be limited by the ability of the house and system to store heat.

The system, either as a solar "assist" or in a building that already has its own “thermal mass” is cost effective in all areas of the Continental United States when it is planned thoughtfully.

The Best Pumping Design

Every month of the heating season, you must pay the electric company for the energy that your pumps use. It is most efficient to use a single individual pump for each heating zone. The alternative would be to use one large pump and individual zone control valves. This is a common practice, but it is not good design. The pump must be sized so it is large enough to provide adequate flow when all of the zones are calling for heat but most of the time, only one or two heating zone are calling. The pump is too large for the task resulting in a waste of electricity and unnecessary wear and strain on the system.

A zone valve costs nearly as much as a small pump so there is really no money to be saved by using them. Small pumps are mass produced and cost much less than larger pumps.

Radiantec provides adjustable three speed pumps that can be set to meet your needs with the lowest amount of electrical use possible

The Best Systems