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Use a Water Heater to Make Radiant Heat
Instead of a Boiler

Many people use a water heater instead of a boiler because it COSTS LESS. Certainly, cost is important, but there are many other important factors as well. A high quality water heater is more energy efficient and friendlier to the environment. Quality water heaters will be made of stainless steel for many years of trouble free service. It is important to note that the same cannot be said for cheap, low end water heaters.

Radiant heat runs on warm water.  Boilers are engineered to make very hot water for radiators.  Many cannot run well at lowered temperatures and require expensive additional components so that they can provide lower temperature water without damage.  Many boilers are subject to “cold shocking” damage when a lot of room temperature water comes back upon start up unless more expensive controls are added.

But water heaters are engineered from the beginning to operate at lower temperatures.  Lower temperatures are good for efficiency.  Modern water heaters can condense the flue gasses right down to water in a simple non mechanical way because of their low operating temperature.  Boilers are made to boil and they do not condense as well as a unit that is engineered to operate at low temperatures.

Illustration of a Water Heater


A water heater should not be used as a cheap shortcut.  Radiantec only recommends water heaters if they will be high efficiency units with long lasting materials and if they will be powerful enough for the job.

The Polaris Water Heater is one such example.  It is all stainless steel, 95% efficient and powerful enough to provide both space heat and domestic hot water at the same time.

At Radiantec, we look for units that have a large submerged flue and units that vent with plastic pipe.  In that case, almost all of the heat goes into the heating system and little heat is lost up the chimney.  The exhaust is so cool that it cannot melt plastic.

An additional benefit is that no chimney is needed at all with plastic vents.  Direct venting is possible with high efficiency units, and this saves money.

"My Plumber friend believes in a hot water boiler, but we used the Polaris water heater and our system works perfectly. Oh yes, we installed it ourselves." -Rick, MA


Whenever you burn a hydrocarbon like gas or oil, you get heat (which is what you want) plus carbon dioxide and water in the form of steam.  You also get nitric oxide and sulfur dioxide. 

Carbon dioxide, nitric oxide and sulfur dioxide are pollutants that are doing serious harm to the environment in the form of global warming and acid rain.  Air pollution also causes thousand of deaths and disabilities every year from asthma, emphysema and other conditions.

IF YOU CONDENSE THE STEAM IN THE EXHAUST DOWN TO WATER, YOU CAN PICK UP ANOTHER 10% IN EFFICIENCY. Significant amounts of the pollutants will dissolve in the water and they go harmlessly down the drain instead of polluting the air.

But most boilers and water heaters are not efficient enough to condense the flue gasses down to water. This limited efficiency is intentional.  Most boilers and water heaters would rust out or otherwise corrode if condensation occurred within them.

For reasons of long term cost, energy efficiency and respect for our environment, Radiantec Company recommends the use of condensing water heaters.

Click here to learn about the environmental benefits of Radiantec systems.
Click here for more information about the need for energy conservation and environmental protection.


We must note here that "innovation is not always welcomed by those with special interests in the status quo". You must consider the source when you evaluate comments from those who profit from the sale of boilers. The use of water heaters in radiant heating applications is accepted by all major codes and is simply a better way to do the job. Click here for more information about Radiantec systems and code compliance.

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