Online Celotex U-Value Calculator

Online Celotex U-Value Calculator

Calculating u values can be a complicated process.

There are many factors to consider when calculating the U-value for a building envelope. It can be difficult to find the right information, and it can be time-consuming, too.

Celotex has created a calculator that simplifies this process and makes it easy to calculate your U-value.

Celotex U-value calculator is an online tool that allows you to input the dimensions of your building and the type of insulation you are using. It will then calculate the U-value for you. You'll also see what Celotex products are available in that area, so you can find out more about these insulation products too.

 Click here to use the tool, or keep reading to find out more.

U-Value Calculator

U-values provide essential information for any thermal design or building projects, allowing engineers and architects to calculate the optimal balance of insulation and windows for a given space. U-Values, measure the rate at which heat flows through a material, based on its structure and composition, with the lower number representing higher levels of insulation efficiency. 

 For example, the u value calculator might indicate that a roof or a wall constructed from a single block of 8-inch thick concrete will score better in terms of heat flow relative to a steel frame ceiling with light clay tiles. With many different materials available to build, it is important to take u-values into account when planning construction projects, as they provide vital information on which materials offer optimal thermal performance.

 The Celotex range of PIR insulation boards from Insulation4Less provides cost-effective thermal insulation solutions that fully meet current legislation requirements, including Part L and BREEAM as well as the demands of building professionals, specifiers, and users.

Insulation4less and Celotex have come together to help assist customers with Celotex's new U-value calculator. Insulation4less is one of Celotex's biggest online suppliers of the full Celotex product range and has the largest Celotex catalogue over all other online suppliers.

What are the U-values for insulation materials?

Insulation is an effective way to improve building energy efficiency and maintain comfortable temperatures. Different insulation materials have different U-values, which indicate their thermal performance; the lower the U-value, the better the thermal performance. For example, Celotex wool insulation offers a particularly good level of thermal performance at 0.038 W/mK.

There are u-value calculators available online to help you with your calculations for roofs, walls, and ceilings, as well as light steel construction framing and precast block set for insulation of a building. Having detailed information from u-value calculations can save you time and money when looking for the best materials and solutions to meet your needs.

What are the units for U-Values calculation?

Calculating u value of a structure is an important step for many industries, such as architecture and construction. The u-value (W/m²K) is calculated by measuring the rate of heat flow in watts per square metre per degree Celsius (˚C or K). Technical U Value Calculators are available online to calculate u-values for different materials, such as wood, which require more technical data to be entered, including the thickness in mm of multiple layers across different areas of the structure. An accurate u-value calculation is necessary to maximize energy efficiency, and can also help reduce costs. It can therefore be useful to put in the time to use the u-value calculation you have derived with or consult a professional u-value calculator.

What technical U-Values do you need for Building Regulations?

In 2022, the UK building regulations were updated to include revised minimum U values for new builds and renovations.

These updates are designed to improve the energy efficiency of buildings and reduce their carbon footprint.

According to the updated Part L documents, the minimum U values for new builds will be as follows:

  • Roofs: 0.11 W/m²K
  • Walls: 0.18 W/m²K
  • Floors: 0.13 W/m²K

For new elements in existing dwellings, the minimum U values will be:

  • Roofs: 0.15 W/m²K
  • Walls: 0.18 W/m²K
  • Floors: 0.18 W/m²K

For existing elements in existing dwellings, the limiting U values will be:

  • Roofs: 0.16 W/m²K
  • Walls: 0.30 W/m²K
  • Floors: 0.25 W/m²K

It is important for builders and contractors to be aware of these updated U values and ensure that they are met in order to comply with building regulations for insulation. Improving the U values of a building can result in energy savings, improved comfort, and a lower carbon footprint.

The table below outlines the required u-values according to Approved Document Part L – Dwellings – England:

Criteria Approved Document Part L, Conservation of Fuel and Power, Volume 1: Dwellings,, 2021 Edition - England Passivhaus EnerPHit Requirement
Table 1.1 - Summary of notional dwelling specification for new dwelling Table 4.2- Limiting U-values for new Fabric elements in existing dwellings Table 4.3 - Limiting U- values for existing elements in existing dwellings
Roof(Including flat roof) 0.11 W/m2K 0.15 W/m2K 0.35 W/m2K / 0.16 W/m2K 0.08 -0.15 W/m2K 0.12 W/m2K
Wall (Including dormer cheeks) 0.18 W/m2K 0.18 W/m2K - - -
Wall - cavity insulation - - 0.7 W/m2K / 0.55 W/m2K 0.08 - 0.15 W/m2K 0.15 W/m2K
Wall - internal or external insulation - - 0.7 W/m2K / 0.3 W/m2K 0.08 - 0.15 W/m2K 0.15 W/m2K
Party wall 0.0 W/m2K - - 0 -
Floor+ 0.13 W/m2K 0.18 W/m2K 0.7 W/m2K / 0.25 W/m2K 0.08 - 0.15 W/m2K 0.15 W/m2K
Window 1.2 W/m2K 1.4 W/m2K * - 0.8 W/m2K <=0.85 W/m2K
Rooflight 1.2 W/m2K - 1.7 W/m2K 2.2 W/m2K - - -
Doors with >60% of internal face glazed See window requirements 1.4 W/m2K ** - - -
Other doors 1.0 W/m2K 1.4 W/m2K * - - -
  * or Window Energy ration Band B minimum
  ** or Window Energy ration Band C minimum
  * refer to floors adjacent to soil and unheated basements, not internal floors

U-value requirement External Walls 0.18 W/m²K

U-value requirement Party Walls 0.0 W/m²K

U-value requirement Floor 0.13 W/m²K

U-value requirement Roof 0.11 W/m²K

U-value requirement Windows (whole window U-value) 1.2 W/m²K

For further help or advice on U-Value calculations for your projects or more information about our products, please contact our expert team on 020 3582 6399 or talk to us via Live Chat.

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