How to Read a Water Temperature Guide for Radiant Heating

Mon, 08/27/2012 - 08:21

When it comes to specialized industries, it can often be hard for outsiders to understand what exactly is happening. Each industry has its own way of doing things, its own lingo, its own nuances. Terminology used in the tech industry (SaaS, iOS, Ice Cream Sandwich, MySQL, UI/UX) is very different from that used in the Radiant Heating industry (Parasitic Loss, Passive Solar, R-Value, STC and IIC ratings).

As such, when people outside the industry need to learn about radiant technology, there can often be a communication gap.

One example of this is the dreaded “Water Temperature Chart.” Every radiant heating product has one, but to the untrained eye, these charts make little sense. Even to the trained eye, it’s designed poorly (at best). And yet, these charts can be found everywhere and are a standard throughout the industry.

But how do you read it?

The numbers along the bottom of the chart are water temperatures – 80º F on the left, 180º on the right. Along the left side we see the “Required BTU/h/ft2” This stands for Required BTU (British Thermal Unit) per hour per square foot. A BTU is a standard measurement of energy derived from heat. Specifically, 1 BTU is the amount of energy needed to raise 1 pound of water 1 degree Fahrenheit. The more BTUs you get from a small area, in this case a square foot, the more efficiently that energy is being used (when compared to other radiant panels’ BTU outputs).

Now, how does BTU translate into a real understandable number for most people? Well, there’s a simple equation for that. We base this equation on two factors: surface temperature and air temperature.

Our chart assumes a room temperature of 70ºF. If you measured the temperature of the flooring (say it was 75ºF), you would subtract the room temperature and multiple by 2.

So the equation is: “Surface Temp” minus “Air Temp” times 2 = BTUs

In the example above: 75–70=5. 5x2=10 BTUs

If the floor temperature was 80ºF: 80-70=10. 10x2=20 BTUs

Now, the green lines running through the grid represent different types of flooring. Each type of flooring has a different R-Value. The R-Value refers to “Thermal Resistance”. It essentially means how much heat can a material absorb before it starts emitting it again. A thick wool carpet might have an R-Value of 3 while a hardwood floor would have an R-Value of 1. You’ll want to check your manufacturer’s specs to see what the exact R-Value is of their product. Many of these values can also be found in our Installation Manual.

By following the green line, you can find out the necessary water temperatures to achieve the perfect temperature for your home.

If you installed hardwood (R=1.0) over Warmboard, and you wanted to keep your home cozy with 75º floors, you would need to run 85º water through your tubing. Or, if you had a nice thick carpet (R=3.0), and you wanted 80º floors you would need to run water at just over 140º.

Warmboard is among the most energy efficient radiant heating products on the market. The conductivity in our aluminum panel allows the heat to transfer more quickly and efficiently, and because of that, Warmboard can get your home much more comfortable while using lower water temperatures. This saves energy and saves you money month after month.

If you have any further questions about this chart or Warmboard in general, feel free to contact us or write a response below and we’ll be happy to help.


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