Timber frames vary significantly depending on species, thickness, and construction method. Our calculator accounts for these variables to produce accurate, real-world U-values that generic calculators cannot replicate.

You do not need to be a member of our website to make use of our calculator. It is open to use by anyone. You can use it as often or as little as you want. From one window to a thousand. Contact us for discounted rates where several windows are involved.

Our U Value Calculator will provide you with a calculation that is performed in accordance with the U-Value equation provided in European Standard EN ISO 10077 part 1 Thermal performance of windows, doors and shutters. This is the industry-recognised methodology for windows and doors Our results will provide an accurate u-value that should be suitable for Building Control submissions.

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A U-value certificate provides formal evidence of thermal performance, required for Building Control, SAP calculations, bespoke windows, or when requested by architects or inspectors. Indicative results may be sufficient for design, but final approval often requires a certified calculation.

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On submitting the required details to us and on receipt of the necessary payment, we will calculate your U-value and send you a certificate with a unique serial number for that window or door. You can then use that certificate to demonstrate compliance with Building Regulations (depending on the U-values that were obtained).