Underfloor heating, whether electric or hot water-based, is rapidly becoming the preferred heating solution in UK homes—and it's clear why. First, since heat naturally rises, having the heating system beneath the floor is more efficient than positioning it against a wall or under a window. Second, underfloor heating is more cost-effective than radiators, an important advantage for homeowners concerned about long-term energy expenses.
In this guide, we'll explore how to reduce your energy bills by efficiently controlling the temperature of your underfloor heating. Achieving maximum energy efficiency requires understanding the full benefits of advanced temperature control systems, including the latest thermostats.
Understanding Underfloor Heating Heat Output
A key consideration for those considering underfloor heating is optimizing its temperature output. Calculating the heat output for underfloor heating, measured in British Thermal Units (BTUs), is similar to the process used for radiators, which is based on room area. However, underfloor heating can significantly increase heat output by insulating the area directly beneath the system. Insulation is crucial for minimizing running costs and maximizing heat output. Additionally, the type of floor surface covering can influence heat output, but let's first delve into the details of calculating floor size.
Calculating Floor Size
To determine floor size, measure and multiply the length and width of the floor space. For instance, a 20' x 15' (6.1 meters x 4.6 meters) room. However, not all of this area may require heating. In a typical bathroom, for example, spaces occupied by the toilet, bath, and hand basin don't need heating. Measure these non-heated areas and subtract them from the total to get the effective heated floor space.
Choosing the Right System
The size and shape of the floor often influence whether you opt for electric mats, flexible electric cables, or a wet installation. An electric underfloor heating (UFH) system is usually the best choice for smaller rooms because it’s easier to install and heats up faster. Additionally, electric systems are ideal for existing properties since they cause less disruption during installation.
By carefully considering these factors, you can ensure an efficient and effective underfloor heating system that keeps your home warm and your energy bills low.
What Temperature Should Underfloor Heating Be Set At?
The optimal temperature for underfloor heating in any room depends entirely on your personal preferences. With an underfloor heating system and thermostats, you have full control over the desired warmth of your floor. Most people find an ideal floor surface temperature to be between 23°C and 27°C. Whether you choose a wet or dry underfloor heating system, your thermostat allows you to make instant adjustments to suit your needs. The only factor that may affect the actual floor temperature is the type of floor covering, as most coverings have a maximum heat output limit.
Vinyl Floor Underfloor Heating Temperature
Vinyl, linoleum, and laminate are all compatible with both electric and water-based underfloor heating systems. However, it is crucial to ensure that the surface temperature does not exceed 27°C. Ideally, the subfloor should be concrete, solid screed, or a wooden floor covered with 18mm Weather and Boil Proof (WBP) plywood.
Wooden 18mm floorboards or chipboard can also be suitable if they are covered with 12mm WBP plywood or ProWarm™ tile backer boards. For vinyl sheets or tiles, there are two electric underfloor heating options: the loose cable system and 100W – 200W mats.
Tile Floor Underfloor Heating Temperature
Tile and stone floors can be heated to 29°C and, due to their high thermal conductivity, they retain heat longer than most other floor coverings. For new builds and renovations, tile and stone are the most efficient long-term options, working well with both electric and hot water underfloor heating systems.
Floor tiles such as ceramic, porcelain, terracotta, and slate all have excellent heat retention properties. These surfaces remain warm long after the heating system has been turned down, maintaining a comfortable temperature for longer periods.
The size and shape of the floor often determine whether to choose electric mats, flexible electric cables, or a wet installation. An electric underfloor heating (UFH) system is typically the best choice for smaller rooms because it is easier to install and heats up more quickly. Additionally, electric systems are ideal for existing properties, as they cause less disruption during installation.
Carpet Floor Underfloor Heating Temperature
Carpets naturally provide warmth, but their material, along with the underlay and foam backing, does not conduct heat very effectively. While it is possible to install underfloor heating under carpets, thick carpets can act as insulators, reducing the system's efficiency. To optimize heat transfer, it is recommended to use hessian-backed carpets, as they offer the least resistance to heat.
For best results, choose carpets and underlay with a combined rating of 2.5 tog or lower. Higher ratings may impact the performance of the underfloor heating system. The maximum temperature for carpeted flooring should be 27°C.
Wood Floor Underfloor Heating Temperature
Natural wood is a popular choice for flooring and works well with both wet and dry underfloor heating systems. However, not all types of wood are suitable due to their tendency to expand and contract with temperature changes, which can lead to warping. To avoid this, it’s best to choose engineered hardwood or laminate flooring.
Wood flooring should not be exposed to temperatures exceeding 27°C, and the entire surface must be heated evenly. Additionally, it is highly recommended to install a vapor barrier beneath the wood flooring to protect it.
Thermostat Selection and Air Temperature
Controlling the temperature of your underfloor heating is crucial for maximizing warmth while minimizing costs. Once you've determined your preferred underfloor temperature, setting your thermostat is straightforward. ProWarm™ thermostats are an excellent choice, offering options like programmable models and smart WiFi thermostats.
While thermostats measure floor temperature, adding an air temperature sensor to your room can provide an extra level of assurance that the overall room temperature is optimal.
Floor Insulation and Heat Output
Proper floor insulation is essential for an effective underfloor heating system, as heat can escape downward as well as rise. Without adequate insulation, valuable heat may be wasted below the floor. To prevent heat loss, install the appropriate insulation, which may include a combination of insulation boards and edge insulation.
A well-insulated system increases heat output and operates more efficiently, resulting in significant savings on heating costs.
Optimal Temperature Settings for Underfloor Heating
Determining the ideal temperature for your underfloor heating depends on several factors, including floor covering type, heating system type, room size, and personal preference. Electric systems can achieve higher temperatures compared to hydronic (wet) systems, but generally, a thermostat setting between 21°C and 25°C works well for both types.
To reach these temperatures, the heat output from the system will need to be approximately double the desired temperature.
Ideal Floor Temperature
The ideal floor temperature is one that feels comfortable to you. On average, this is around 25°C. For smaller rooms, such as kitchens or bathrooms, a slightly lower temperature may be sufficient, while frequently used areas like lounges might benefit from higher settings.
To avoid wasting heat, installing a thermostat in each room, similar to radiator controls, is highly recommended. This allows for precise temperature management and helps reduce running costs.
Heating Up Time for Underfloor Systems
Electric underfloor heating systems typically reach maximum heat output within 30-60 minutes. In contrast, water-based systems take longer, usually about 2-3 hours, as heat needs to penetrate the screed covering the pipes. However, wet systems are more economical to operate and retain heat longer even after being turned off.
To accommodate the warming-up time, consider using a smart thermostat that can be controlled remotely via your phone. This allows you to preheat the system before you arrive home.
Maximum Temperature for Underfloor Heating
The maximum temperature for underfloor heating is influenced by the type of floor covering. Stone, ceramic, terracotta, porcelain, and slate can be safely heated up to 29°C, while carpets, wood, and vinyl should be limited to 27°C.
The flow temperatures needed to achieve the desired room temperature typically range from 35°C to 55°C, depending on whether the system is wet or dry and the type of floor covering used.
Choosing the Right Underfloor Heating System
There are two main types of underfloor heating systems: electric and wet. Electric systems, which use heat mats or flexible cables, are best suited for retrofitting existing rooms with minimal disruption. These systems are generally easier and cheaper to install but can be more expensive to run.
Wet systems, which involve installing pipes through which hot water circulates, are ideal for new builds, extensions, and major renovations. These systems are compatible with existing condensing boilers or heat pumps and are more cost-effective in the long run.