This article will take an in-depth look at radiant heaters.
The article will bring more detail on topics such as:
This section will explore the principles of radiant heaters, including their operational mechanisms and design features.
Radiant heaters are devices that produce heat internally and then emit it to nearby surfaces and individuals. A common example of this is the sun. On a sunny day, the warmth we feel on our skin comes from the infrared radiation emitted by the sun.
Infrared heating operates by using electromagnetic waves to deliver energy directly to the object being warmed, bypassing the air in between. This form of heating emits energy in the range of 0.7 to 6 microns (µ). To maximize efficiency, specific wavelengths are chosen based on the target object, thereby reducing overall energy consumption.
Unlike conventional heaters that warm the surrounding air, a radiant heater directly transfers heat to people and objects in its vicinity. As a result, it avoids the dry air often produced by convection heaters.
Radiant heaters produce heat through internal processes and transfer it via electromagnetic waves. When these waves encounter an object or person, they are converted into heat. The radiant heat travels through the air with minimal loss and only warms surfaces such as floors, walls, or bodies upon contact. Just as clothes absorb sunlight, objects in a room absorb this radiant energy and help warm the space.
Radiant heaters can provide warmth without needing direct contact with the heat source (for example, one can feel the warmth of the sun without touching it). This feature is particularly useful in industrial settings where avoiding direct contact with heated objects or preventing contamination is important. In contrast, conduction and convection transfer heat through molecular movement from areas of higher to lower temperature.
Radiant heaters transfer thermal energy through electromagnetic waves, eliminating the need for a heat transfer medium. The amount of heat emitted by a surface increases significantly with temperature. For instance, if the temperature of the heat source is doubled, the radiated heat emitted can increase by approximately 16 times. When standing within the radiant heat field, a person experiences direct warmth from the source.
Even in cooler air temperatures, the absorbed radiant heat provides a comfortable feeling. This principle of infrared radiation is effectively applied in commercial products like tube space heaters and radiant heaters. Infrared radiant heaters operate as decentralized systems, converting energy into heat with minimal loss, unlike central heating systems.
The main components of radiant heaters are:
A radiant heating system looks the same as a boiler, at its core. It makes use of heated water as its source of warmth. As with a boiler, it consists of a tank where either the ejection of gas occurs or electric heating elements raise the water temperature, and then a pump is used to circulate the water through the closed system.
These pipes, embedded in the floorboards, carry water from the tank and raise the floor temperature through the heat they emit. This setup effectively turns the pipes into a heat source beneath the floor. Typically, PEX tubing is used for these pipes, which can be installed within a concrete slab, on top of a subfloor, or beneath a subfloor.
Usually, the installation of this component is done between the in-floor pipes and the water tank to help in the regulation of the distribution of the water. The complexity of the manifold is dependent on how many areas of a home have in-floor pipes.
When designing a radiant heating system, the following factors should be taken into account:
Radiant heaters embedded in the floor utilize the floor itself to heat the space above by warming the floor until its heat output compensates for the heat lost from the building. To determine the necessary floor temperature, it is crucial to calculate the building’s heat loss. Based on this, the type of radiant system, tube spacing, and fluid temperatures can be selected for optimal efficiency.
This step involves calculating the heat loss per square foot of the building. For example, if the inside temperature is 65 degrees Fahrenheit and the outside temperature is -10 degrees Fahrenheit, the heat loss is 22.5 BTUs/hr. per square foot (calculated as temperature difference x heat loss) (30 BTUs/hr. per square foot per degree Fahrenheit x 75 degrees Fahrenheit).
For instance, a floor temperature of 80 degrees Fahrenheit can provide 27 BTUs/hr. This should suffice for a well-insulated system even in sub-zero temperatures. Most residential and many commercial buildings meet this standard today. To size the heating source, multiply the heat loss per square foot by the total area in square feet to determine the required heater or boiler output.
This involves estimating the heat that can be delivered from the floor. Achieving outputs above 45 BTUs per hour generally requires floor temperatures exceeding 90 degrees Fahrenheit. If higher outputs are needed, consider using additional heating sources and implementing energy conservation measures. Radiant ceiling or wall heaters can also provide extra comfort.
If there is uncertainty about whether the radiant floor will produce sufficient heat, consider the following:
Floor temperatures should not exceed 80 degrees Fahrenheit during normal operation and should never surpass 85 degrees Fahrenheit.
Proper tube spacing ensures even heating within the desired fluid temperature range. For example, a tube diameter of 1/2 inch typically corresponds to a spacing of 8-12 inches.
To find the total length of tubing needed, multiply the floor area in square feet by the multiplier for the chosen tube spacing. For a tubing spacing of 16 inches, this multiplier is 0.75.
It is important to avoid circuits that are either too short or too long. Tubing should allow water to flow and transfer heat effectively. If the tubing is too long, water may lose excessive heat before reaching the end, resulting in reduced heating efficiency and potential underperformance. This issue can be mitigated by increasing the fluid velocity with a more powerful pump.
Excessive pump work and electricity usage can become impractical if the water flow becomes too turbulent, which may even cause erosion corrosion in extreme cases. Conversely, very short circuits may result in laminar flow, reducing heat exchange efficiency and potentially trapping air bubbles, which can obstruct flow. Ideally, the fluid should exit the tube within 10-15 degrees of its entry temperature, moving with a slight turbulence for effective heating.
Various types of radiant heaters are available, including:
This type of radiant heating system makes use of electric coils that are capable of producing heat as electricity passes through them. These metal coils are able to resist electricity. When electricity passes through the coil, the resistance emanates heat. Polymer sheets are wrapped around these coils so that they can act as insulation. They can heat the wall of the ceiling or floor, as mentioned earlier, depending on their location.
This method is commonly used for floor heating and is known for its low maintenance needs and long lifespan compared to other systems. However, operating these systems can be costly due to rising electricity prices.
They tend to be more energy-efficient in smaller areas such as driveways or bathrooms.
These radiant heating systems utilize a boiler to circulate heated water through a network of pipes installed throughout the house or floor. They can also be fitted in ceilings and walls. Although their operational costs are generally lower than those of electric heating systems, there is a risk of pipes bursting or leaking.
Hydronic radiant heating systems are the most energy-efficient and cost-effective option for heating an entire house.
These radiant heating systems use heated air to transfer warmth. Out of the three standard heating methods, they are the least efficient due to air's limited ability to carry and retain heat. This inefficiency is exacerbated in older homes, which may have more air leaks or cracks that allow heat to escape.
Examples of radiant heating systems include:
These radiant heating systems utilize infrared radiation to directly warm objects and people in a space. This approach is more comfortable and efficient compared to air-based heating systems, as it provides consistent warmth from the ground up, minimizing cold spots and drafts.
The principle of radiant floor heating involves radiating thermal energy from the floor surface, similar to how heat from a stove burner can be felt from a distance. This system does not warm the air directly but instead makes people and objects in the room feel warmer.
Radiant floor heating systems are categorized into two types: wet and dry installations. It is important to note that this classification does not refer to the heat transfer medium itself; the terms "dry" and "wet" do not relate to electrical resistance or hydronic piping.
This is the oldest type of radiant floor heating installation. It tends to be more costly compared to dry installations because it involves embedding mats, electrical cables, or hydronic tubing within a concrete slab, whether thick or thin. Although it takes longer for the system to heat the floor and room air, the substantial thermal mass of the concrete retains heat for several hours after the system is turned off.
This type of radiant floor heating is easier to set up, less costly, and more convenient. Mats, heating cables, or tubing are installed in an air pocket beneath the floor rather than being embedded in concrete. As a result, heating is achieved more quickly compared to wet installations. However, this setup requires operating at higher temperatures since it is not integrated into the flooring material.
The types of radiant floor heating systems are:
These are the earliest types of radiant heaters. Air heaters are somewhat less efficient compared to other types and are thus less common. Instead of directly pumping air beneath the floor, heated air is circulated through a network of tubes, similar to how water is distributed.
The key difference is that air is lightweight and can be moved more easily through the tubes, which can make the system faster. In this setup, a heater pushes air through tubes or ducts installed in the floor rather than through vents. Although this system can be challenging to make energy-efficient, it generally requires less space because the heaters and ducts are embedded in the floor, eliminating the need for a large furnace or boiler.
It is crucial to ensure that the system is properly sealed and installed, typically using a wet installation method. Heaters can be placed in accessible locations and are housed in boxes within the concrete, making repairs and maintenance simpler if needed. Air-heated floor systems can be used in various building types and with different floor materials such as engineered hardwood, hardwood, tile, laminate, stone, linoleum, vinyl, and concrete.
Their installation can be made either in a suspended floor system or in a structural slab on grade. When the installation is done in a slab, the ground is covered with a layer of polystyrene installation after leveling the ground. This is then used in the holding of the furnace piping, boxes, and ductwork, which are held in place by means of a level of mesh.
Concrete is then poured over the installation as usual to create the slab. Curing begins after three days, with the entire process taking approximately three weeks. While retrofitting is possible, it still requires poured concrete and wet installation; dry installations may not be feasible with this system.
In electric radiant floor heating systems, cables or wires—and sometimes mats in smaller areas—are installed beneath the flooring using either dry or wet methods. These wires connect directly to the home's electrical system, and a thermostat is used to control the floor's temperature.
The system comprises several key components: heating elements (wires or mats), in-floor sensors, and a thermostat. For smaller spaces, mats with embedded wires are placed in a thin layer of mortar, cut to fit the specific area. In larger areas, wires are typically spaced about 3 inches apart and also embedded in a thin mortar layer.
A type of heat-conducting plastic is used to transfer heat from the cables to the floor above. Electric radiant floor heating systems heat up more quickly since the cables produce warmth immediately, unlike systems that require water or air to be heated first before being circulated. These systems can be installed under any flooring type without raising the floor level significantly due to their thin cables.
While both the installation and operation of electric radiant heaters are more expensive, they offer faster installation and less disruption, particularly in small areas like bathrooms. They are often used as a supplementary heat source.
Hydronic radiant floor heating systems utilize hot water to heat a building and are the most efficient among the three types. These systems feature a hot water heater or boiler that heats the water, which then circulates through a network of PEX tubes installed beneath the floor using either dry or wet methods. The hot water moving through these tubes warms the floor above. The system operates in a closed loop, allowing water to circulate continuously. This type of radiant heating can be installed beneath any flooring type and is highly efficient, consuming up to 30% less energy compared to traditional forced-air furnaces, which can significantly reduce energy bills. It also offers various installation options, making it suitable for retrofitting.
The performance of radiant floor heating is greatly affected by the choice of flooring material. Thermally conductive materials can improve efficiency, while insulating materials can hinder it. This does not mean insulation should be avoided entirely, but it should not be placed where it can obstruct heat transfer between the radiant system and the indoor environment. Ceramic tile is one of the most effective materials due to its thermal conductivity and high heat storage capacity. In contrast, materials like vinyl and linoleum offer excessive insulation, reducing system efficiency. Wood floors can conduct heat well, but laminated wood is preferred over solid wood, which can dry out and contract more easily.
Radiant heating systems are not limited to floors; they can also be installed in walls and ceilings. Floor-based radiant heating is often the most effective because it ensures even heat distribution throughout the space.
Radiant panels can be mounted on walls to heat smaller rooms, but they are generally less effective than floor or ceiling installations due to difficulty in covering large areas. On the other hand, radiant ceiling heating systems can be more efficient than floor systems since they only heat the air, not the floor itself. This method can provide a very comfortable environment without disrupting existing flooring.
These radiant heaters are a recent addition to the market and provide several benefits. One major advantage is their slim profile, which does not occupy floor space. They offer a more even distribution of heat from head to toe. In terms of safety, these heaters are also a better choice for homes with small children and pets.
In this type of radiant heating system, the radiant heat panels are installed in the ceiling. These panels then radiate heat downward to warm objects and people below. When the radiant ceiling is heated just a few degrees above the surrounding surfaces, it promptly emits infrared heat in all directions.
These radiations directly warm any object or surface in the vicinity, whether they are above or below the panels.
These radiant heaters are generally smaller than wall-mounted models and offer the advantage of easy mobility between rooms. This flexibility is particularly useful when heating needs to be directed to various locations. They are also well-suited for providing heat in very small spaces.
This chapter will explore the uses and advantages of radiant heaters.
Radiant floor heating systems provide several advantages. Since they don’t warm the air, the temperature in the room remains more consistent from the floor to the ceiling, eliminating cold spots on the ground. This leads to increased comfort and often reduces energy consumption, thereby lowering heating costs. They are compatible with a wide range of flooring types, preserving the aesthetic of a home. Additionally, because these systems do not rely on air ducts, they minimize the circulation of allergens. Operating radiant floor heating systems is straightforward and efficient.
Hydronic radiant floor heating systems offer even heat distribution throughout a building at a lower cost, making them ideal for larger businesses and facilities that own their premises. These systems provide comfort for both employees and customers, eliminating cold or hot spots in retail environments.
Electric radiant floor heating systems are highly adaptable, supporting both wet and dry installations and various retrofits. They are quick to install and can be used almost immediately, making them suitable for large buildings with multiple offices that need individual temperature control.
Free-standing radiant heaters are portable and can be easily relocated to different areas as needed.
Despite some drawbacks, the advantages of radiant heaters significantly outweigh their disadvantages.
Radiant heaters operate most effectively when placed close to the objects or people they need to warm. Whether the room is open or closed is less important, as the focus is on directly heating individuals or items rather than the surrounding air.
Since radiant heaters do not use blown air, they avoid creating drafts, which can be particularly beneficial for individuals with asthma, allergies, or other respiratory issues. They are well-suited for rooms that have specific functions, are smaller in size, or are infrequently used, such as bathrooms and bedrooms.
Radiant heaters are also a great energy-efficient option for spaces like garages, basements, storage sheds, workshops, and patios that require temperature regulation.
Radiant heaters are systems used to warm objects or people directly within space. They generate heat internally and do not require an air medium to transmit the heat. They do not warm the surrounding air but target the object or person. There are different types of radiant heaters available including air, electronic and water radiant heating systems. Each radiant heating system offers its own unique benefits. Therefore it is wise to consider the specifications of the type of radiant heater before selecting one. Some are more suitable in small areas whereas some are more suitable for large areas. Radiant heaters can be installed beneath the floor, on the walls or in the ceiling. There are also free standing radiant heaters offering the main benefit of being easily moved from one point to the other. Radiant heaters have a wide range of applications as mentioned before.
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