Radiant Heat Calculator

Radiant Heat Calculator

Radiant Heat Calculator

How do you calculate radiant heating?

To calculate radiant heating, determine the heat loss using factors like outdoor temperature and insulation. Calculate the radiant heat gain by considering surface area, desired temperature, and specific heat capacity. Select an appropriate heating system, determine the surface temperature, size the system based on heat loss/gain, and consider control options for zoning and regulation.


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  1. Determine the heat loss: To calculate the heat loss, you need to consider factors such as the outdoor temperature, insulation levels, and air infiltration rates. You can use heat loss formulas or software programs specifically designed for this purpose. The heat loss calculation will provide you with the amount of heat energy needed to maintain the desired indoor temperature.
  2. Calculate the radiant heat gain: Radiant heating systems work by emitting heat from a heated surface, such as a floor or wall. The radiant heat gain calculation involves determining the amount of heat energy required to raise the temperature of the objects and surfaces in the room to the desired level. Factors to consider include the surface area of the objects, the desired temperature, and the material’s specific heat capacity.
  3. Select the appropriate radiant heating system: There are different types of radiant heating systems, such as hydronic (using hot water), electric, or air-based systems. Choose the system that best suits your needs and matches the calculated heat loss and heat gain values.
  4. Determine the heating surface temperature: The surface temperature of the heating system, such as the floor or wall, should be selected based on factors such as comfort requirements, floor covering materials, and the desired heat output. The surface temperature should be high enough to provide sufficient heat but not excessive to cause discomfort or damage to the materials.
  5. Size the heating system: Based on the calculated heat loss and heat gain values, you can determine the appropriate size and capacity of the radiant heating system. This includes factors such as the number of heating elements, pipe sizes (for hydronic systems), or electric heating panels required to achieve the desired heating output.
  6. Consider control options: Radiant heating systems can benefit from zoning and temperature control features. Zoning allows different areas or rooms to have separate controls, optimizing energy efficiency. Consider incorporating thermostats, timers, and temperature sensors to regulate the system effectively.

It’s important to note that these steps provide a general overview of the radiant heating calculation process. For more accurate and detailed calculations, it is recommended to consult a professional engineer or HVAC specialist who can take into account specific factors of your building and heating requirements.

How do you calculate BTU for radiant floor heating?

To calculate BTU for radiant floor heating, multiply the heat transfer rate (BTU/h/ft²) by the total square footage of the area. For example, if the heat transfer rate is 25 BTU/h/ft² and the total square footage is 500 ft², the BTU requirement would be 12,500 BTU/h. Consult a professional for accurate sizing and specific considerations.


To calculate the BTU (British Thermal Unit) requirement for radiant floor heating, follow these steps:

  1. Determine the heat loss: Calculate the heat loss for the room or area where the radiant floor heating will be installed. Consider factors such as the room dimensions, insulation levels, outdoor temperature, and desired indoor temperature. Use a heat loss calculation method or consult a professional to obtain accurate values.
  2. Determine the heat transfer rate: The heat transfer rate is the amount of heat energy required to raise the temperature of a given area. For radiant floor heating, this value is typically expressed in BTUs per hour per square foot (BTU/h/ft²). The heat transfer rate varies based on factors like floor covering materials and the desired temperature rise.
  3. Calculate the BTU requirement: Multiply the heat transfer rate (BTU/h/ft²) by the total square footage of the area to be heated. This will give you the total BTU requirement for the radiant floor heating system.
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For example, if the heat transfer rate is 25 BTU/h/ft² and the total square footage of the area is 500 ft², the BTU requirement would be:

BTU requirement = Heat transfer rate (BTU/h/ft²) x Total square footage (ft²) BTU requirement = 25 BTU/h/ft² x 500 ft² BTU requirement = 12,500 BTU/h

Keep in mind that this calculation provides an estimate and it’s advisable to consult with a professional to ensure accurate sizing and to consider other factors specific to your installation, such as insulation, building orientation, and climate conditions.

How many BTU per square foot for radiant heat?


The recommended range for BTU per square foot for radiant heat varies depending on several factors, including the climate, insulation levels, ceiling height, and the desired indoor temperature. As a general guideline, the typical range for BTU per square foot for radiant heat is between 20 BTU/h/ft² and 40 BTU/h/ft².

Here’s a breakdown of the recommended BTU per square foot range based on different factors:

  1. Climate: In colder climates, with harsher winters, you might need a higher BTU per square foot range, typically around 30 BTU/h/ft² to 40 BTU/h/ft². In milder climates, the range may be around 20 BTU/h/ft² to 30 BTU/h/ft².
  2. Insulation: Well-insulated buildings tend to have lower heat loss, allowing for a lower BTU per square foot range. If your building has excellent insulation, the range might be around 20 BTU/h/ft² to 30 BTU/h/ft². However, if insulation levels are lower, the range may need to be higher, closer to 30 BTU/h/ft² to 40 BTU/h/ft².
  3. Ceiling Height: Buildings with higher ceilings require more energy to heat. If you have taller ceilings, you may need to consider the higher end of the BTU per square foot range.
  4. Desired Indoor Temperature: If you prefer a higher indoor temperature, you might need to increase the BTU per square foot range slightly.

Remember that these ranges are general guidelines, and it’s essential to consult with a professional HVAC specialist or engineer who can assess your specific building’s requirements and factors to determine the most appropriate BTU per square foot range for your radiant heat system.

What should radiant heat be set at?


The optimal temperature setting for a radiant heating system can vary depending on personal preferences, comfort levels, and the specific requirements of the building. However, a common recommended temperature range for radiant heat is between 68°F (20°C) and 72°F (22°C).

Radiant heating systems work by warming the surfaces and objects in a room, providing a comfortable and consistent heat. Unlike forced-air systems, which heat the air, radiant heat provides a more even distribution of warmth and can feel comfortable at slightly lower temperature settings.

It’s important to consider individual comfort preferences, the insulation level of the building, and the presence of other heating sources when determining the temperature setting. Some people may prefer a slightly higher or lower temperature depending on their sensitivity to cold or warm conditions.

Additionally, programmable thermostats or smart heating controls can be utilized to adjust the temperature based on occupancy patterns or time of day, allowing for energy-efficient operation while maintaining comfort.

Ultimately, it’s recommended to experiment with different temperature settings and make adjustments based on personal comfort and energy efficiency goals.

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How many square feet will a 1500 watt radiant heater heat?


The square footage that a 1500-watt radiant heater can effectively heat depends on several factors, including insulation levels, room layout, ceiling height, and temperature differentials. However, as a rough estimate, a 1500-watt radiant heater can typically heat an area of around 150 to 200 square feet.

To calculate an approximate coverage area for a radiant heater, you can use the following guideline:

Coverage Area (in square feet) = Total Wattage of Heater / Wattage per Square Foot

In this case, the wattage per square foot can vary depending on factors such as insulation and climate, but a commonly used value is 10 watts per square foot. Using this guideline, for a 1500-watt radiant heater:

Coverage Area = 1500 watts / 10 watts per square foot Coverage Area ≈ 150 square feet

Keep in mind that this is a general estimation, and actual heating coverage can vary based on the factors mentioned earlier. It is always recommended to consult the manufacturer’s specifications and guidelines for the specific radiant heater model you are considering to ensure proper sizing for your intended space.

How many gallons per minute for radiant heat?

The gallons per minute (GPM) requirement for radiant heat systems depends on factors such as the size of the system, the type of heating medium (water or other fluids), the desired flow rate, and the specific design parameters. To determine the GPM for a radiant heat system, you need to consider the following:

  1. Heat load: Calculate the heat load or BTU requirement for the space you are heating. This calculation takes into account factors such as room size, insulation, and desired temperature.
  2. Temperature differential: Determine the desired temperature difference between the supply and return water in the radiant heat system. This temperature differential helps determine the heat transfer rate.
  3. Flow rate: Calculate the flow rate required to meet the heat load. This depends on factors such as the heat transfer medium (water or fluid), pipe size, system design, and temperature differential.

Typically, flow rates for radiant heat systems can range from around 0.5 GPM to 2 GPM per circuit, depending on the specific design and heat load requirements. However, it’s crucial to consult the manufacturer’s guidelines or work with a professional engineer or HVAC specialist to determine the appropriate flow rate for your specific system.

Keep in mind that the GPM requirement can vary depending on factors such as the type of radiant system (hydronic, electric, etc.), the number and length of circuits, and the specific design parameters. It is best to consult a professional who can assess your specific system requirements and provide accurate calculations for your radiant heat system.

How many square feet will 35000 BTU heat?

The approximate square footage that a 35,000 BTU (British Thermal Unit) heater can heat depends on several factors such as insulation, ceiling height, climate, and desired temperature. As a rough estimate, a 35,000 BTU heater can typically heat an area of around 800 to 1,200 square feet.

How much area will 12000 BTU heat?

The approximate square footage that a 12,000 BTU (British Thermal Unit) heater can heat depends on several factors such as insulation, ceiling height, climate, and desired temperature. As a rough estimate, a 12,000 BTU heater can typically heat an area of around 350 to 500 square feet. However, it’s important to note that these estimates can vary based on specific conditions and it’s always advisable to consult with a professional for accurate sizing for your particular heating needs.

How do you calculate underfloor heating?

To calculate underfloor heating, determine the heat loss of the room, calculate the heat transfer rate for the floor surface, and determine the required heating element wattage based on the floor area. Generally, underfloor heating systems range from 10 to 20 watts per square foot. Consult a professional for accurate calculations and specific considerations.

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What is the rule of thumb for BTU per square foot?

As a rule of thumb, the recommended range for BTU (British Thermal Unit) per square foot varies depending on factors such as climate, insulation levels, ceiling height, and desired indoor temperature. A commonly used guideline is to allocate around 20 to 40 BTU per square foot for heating purposes.

Here’s a breakdown of the rule of thumb for BTU per square foot:

  1. Colder climates with harsh winters and/or less insulation might require a higher BTU per square foot allocation, typically around 30 to 40 BTU/sq ft.
  2. Milder climates or well-insulated buildings may require a lower BTU per square foot allocation, usually around 20 to 30 BTU/sq ft.
  3. Ceiling height can influence heat distribution and may require adjustments to the BTU per square foot allocation. Taller ceilings might need a higher BTU per square foot allocation.
  4. The desired indoor temperature also affects the BTU per square foot guideline. If you prefer a warmer indoor temperature, you might need to allocate a higher BTU per square foot.

It’s important to note that these ranges serve as rough guidelines and can vary based on specific circumstances. Factors such as window quality, air infiltration rates, and additional heat sources should be considered. Consulting with a professional HVAC specialist or engineer is recommended to determine the most appropriate BTU per square foot allocation for your specific situation.

How many BTU do I need to heat 2000 square feet?


To determine the BTU (British Thermal Unit) requirement for heating a 2000-square-foot space, you need to consider several factors such as the climate, insulation levels, ceiling height, and desired indoor temperature. As a rough estimate, you can use a guideline of around 25 to 35 BTU per square foot.

Using the lower end of the range (25 BTU/sq ft):

BTU requirement = Area (in square feet) x BTU per square foot BTU requirement = 2000 sq ft x 25 BTU/sq ft BTU requirement = 50,000 BTU

Using the higher end of the range (35 BTU/sq ft):

BTU requirement = 2000 sq ft x 35 BTU/sq ft BTU requirement = 70,000 BTU

Therefore, the approximate BTU requirement to heat a 2000-square-foot space would be between 50,000 BTU and 70,000 BTU. It’s important to note that these are general estimates, and it’s advisable to consult with a professional HVAC specialist or engineer to accurately determine the BTU requirement based on your specific climate, insulation, and other factors.

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