Building regulations for underfloor heating 

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building regulation for underfloor heating

According to the Business, Energy, and Industrial Strategy Department, powering and heating buildings take up about 40 percent of the total energy consumption in the United Kingdom. The residential sector accounts for about 15% of the total energy usage. Therefore, it’s important to change how new buildings, homes, and renovations are heated in an attempt to reduce carbon emissions. In addition, this calls for the implementation of the building regulation changes before the introduction of Future Home Standards in 2025. 

So, when installing an underfloor heating system in your home, it’s important to ensure that your work adheres to the relevant rules and regulations. A good example of these regulations that apply to underfloor heating is Part L of the building regulations. 

In this article, I’ll show you some crucial details about Part L building regulations you should know about as you prepare to install the best underfloor heating system in your home! 

Part L building regulations for underfloor heating

Introduced in 2010, Part L of the building regulations provides a framework to conserve power and fuel in both new and existing buildings in Wales and England. It’s an outcome of the government’s commitment to increasing the energy efficiency of buildings by reducing solar gain and heat loss. In addition, it covers the installation of energy-efficient fixed building services like underfloor heating, while providing adequate information to the homeowners to maintain the property and its services. 

Part L building regulations do not specifically relate to UFH systems. Instead, it relates to the flooring insulation of the building. Nonetheless, these regulations require a significant level of insulation beneath an underfloor heating system to minimize downward heat loss. 

To be precise, they demand that floors on new homes should have a U-value of less than 0.25w/ m2K. In addition, these homes should have a guidance note indicating that the value was less than 0.15w/m2K during the installation of the underfloor heating (UFH) system. U-value measures the amount of heat loss from a building, such that the lower the U-value, the less the heat loss. 

U-Value and Building Regulations for Underfloor Heating 

As already mentioned, floor insulation is required below all UFH systems to prevent downward heat transmission. In addition, the building regulations propose the need for a better-insulated structure and a reduction in the building heating requirements. 

Initially, building regulations required U-value for floors to be less than 0.45w/m2K. However, recent changes to these regulations now require the floor’s U-Value to be less than 0.25w/m2K. 

To calculate the ground floor U-value, you can use the formula provided in CIBSE Guide A3, although it’s very complicated. 

Alternatively, you can use the simplified formula described in BRE Information Paper IP 3/90 to calculate the U-Value of an uninsulated floor. Interestingly, you can use this simplified method for all kinds of ground floors, including suspended timber, ground bearing, and suspended concrete floors. Plus, it’s relatively easy to use for both rectangular and irregularly -shaped floors. 

How to calculate the U-value of an uninsulated floor using IP 3/90 formula 

U-Value of Uninsulated floor (U) = 0.05 + 1.65 (Length of exposed Perimeter(P)/ Floor Area(A) – 0.6 (Length of exposed Perimeter(P)/ Floor Area(A)2

U= 0.05 + 1.65 (P/A)-0.6(P/A)

Using this formula, you’ll get the following U-values for different Perimeter to Area (P/A) ratios; 

Perimeter to Area (P/A) ratio = 0.1, 0.1253, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7

U-Value for Uninsulated floor = 0.21, 0.25, 0.36, 0.5, 0.63, 0.73, 0.83, 0.92

As you can see, only floors with a perimeter-to-area ratio of less than 0.1253 will meet the new building regulation requirements (0.25w/m2K) without additional floor insulation. 

You can also use the above figures to determine the effective thermal resistance of an uninsulated floor. The floor’s thermal resistance is the reciprocal of its U-Value (m2K/W). This will show you that you need to increase the thermal resistance of uninsulated floors to at least 4 m2K/w by adding insulation to meet the new Building regulations. In addition, knowing the thermal resistance will help you to determine the required insulation thickness depending on the thermal conductivity of the material. 

How to ensure your underfloor heating complies with the recent building regulation changes 

The Part L building regulation changes require homes to reduce the carbon emissions of their current energy requirements by 31%. However, this is a temporary step towards a 75 percent reduction in CO2 emissions by 2025. 

Conforming to the new building regulations for underfloor heating is an effective way to minimize carbon emissions. According to the Future Home Standard (FHS), expected to be implemented in 2025, new homes should produce about 75% fewer carbon emissions. The new building regulations affecting part L are part of the government policy to meet the Future Homes Standard. This will play a crucial role in helping the government achieve its commitment to tackling climate. 

The 2022 changes to Part L building regulations demand that heating systems in new-build properties have a maximum flow temperature of 55 deg C. 

In addition, the government recommends the adoption of heat pumps as the primary heating technology in new-build homes. Heat pumps can be used to heat water for hydronic underfloor heating systems as they operate at lower temperatures of 35-55 deg C. In comparison, gas boilers with radiators operate at temperatures of around 80 deg C. 

Moving on, there is also a requirement for zones and automated control devices. On the bright side, you can operate an underfloor heating system in separate zones controlled by smart home thermostats. This allows you to only heat occupied spaces and heat different rooms in your homes to varying temperatures. 

Even better, UFH systems are cheaper to run, which reduces your energy bills by about 15 – 40%. Not to forget that the pipework for hydronic underfloor heating systems usually last longer than typical conventions. More importantly, underfloor heating is an excellent option for heating homes with people suffering from allergies. That is because there is less movement of airborne particles compared to other options like forced air heating. 

Do I need planning permission for underfloor heating? 

If you’re installing an underfloor heating system in an existing property, you don’t need planning permission. However, if you’re building a conservatory or an extension, you’ll certainly need planning permission from the relevant authorities. Luckily, you will not need separate planning permission since the heating system will be part of the overall construction plans. 


In general, if your home is compliant with part L building regulations, the underfloor heating system will satisfy regulations. Thankfully, these building regulations for underfloor heating offer flexibility in meeting the net-zero targets. Moreover, there is already a wide range of renewable energy sources available. 

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