The Support We Get

The Support We Get

Basic U-Values

Basic U-value calculations using ECWINS Software

Obtaining a precise U-value can be prohibitively expensive for smaller manufacturers.  The BWF is able to offer members a basic U-value calculation to enable them to obtain the figure they need to comply with Building Regulations and the Construction Products Regulation (CE Marking) at a highly reduced cost.

What will I get from BWF?

We are able to carry out a basic U-value calculation based on Part 1 of the standard “BS EN ISO 10077 Thermal performance of windows, doors and shutters.  Calculation of thermal transmittance. General” using the ECWINS software tool, which is only available through the BWF and only to BWF members.

Whether or not the window or doorset itself complies with the requirements of Building Regulations depends on the U-value it actually achieves. The BWF technical team can advise you on how to comply with the requirements of Part L. You submit the relevant data forms for the window or doorset to us.  We will liaise with you if necessary to check aspects of this data and then calculate the U-value using the ECWINS software, and issue you with a certificate in accordance with that standard, which can be used as formal support when you supply U-value information to potential customers or Building Control Bodies (BCB).

A U-value calculated by this method will be sufficient to satisfy the requirements of Building Regulations and/or CE Marking declarations (see below), but is not as precise as a full U-value simulation.  It cannot be used as the basis for obtaining a full BFRC Window Energy Rating (WER), nor could it be submitted as if it were a WER.  A U-value for an energy rating needs to be simulated to Part 2 of BS EN ISO 10077.  The BWF offers other Toolkit + packages which can help you obtain full U-value simulations or Window Energy Ratings.

For all windows for which we have calculated the U-Value, we will register the window design with us if you wish to provide U-values to clients in the future. This is particularly useful if you later want to change the design or specification, for example, the timber species, section size, glazing unit or other data and require a new calculation to be performed.  We will maintain the database of windows registered with us, and make it available to FENSA and other inspection bodies.

Can I use this on my Declaration of Performance for CE Marking?

U-values are considered ‘essential characteristics’ for the sake of CE Marking, and will need to be included as part of your Declaration of Performance (DoP).

If you are a micro-enterprise* this can be calculated using any available calculation tool that follows ISO 10077-1 or -2.  In the case of all other windows and doors manufacturers a certificate will need to be accredited via a notified body. BWF will be able to provide U-values calculations through a notified body upon request. For further information, please contact our technical helpline.

*A micro-enterprise is defined as an enterprise which employs fewer than 10 persons and whose annual turnover and/or annual balance sheet total does not exceed EUR 2 million.

What is involved?

The basic U-value service is for BWF Members only. If you are a member, then you can log in and visit to our windows publications section where can then choose the appropriate form to download and complete from:
Flush and stormproof casement windows
Vertical sliding sash windows - spiral balance and weights & pulleys



Both casement and sliding sash windows will be modelled on the BR 443 standard design. In the case of dwellings, the BR 443 model window will represent all the windows using a standard window 1.48 m high by 1.23 m wide, with a central vertical divider, and one opening light and one fixed, or directly glazed, light.

We are also able to carry out U-value calculations for doors, which you can find in the same location
TYPE 1 UNGLAZED DOORSET
TYPE 2 PARTIALLY GLAZED DOORSET
TYPE 3 FULLY GLAZED DOORSET 2xGG
TYPE 4 FULLY GLAZED DOORSET Pattern 10
TYPE 5 FRAMED, LEDGED AND BRACED DOUBLE BOARDED DOORSET
TYPE 6 FULLY GLAZED FRENCH DOORS


DOWNLOAD OUR BASIC U-VALUE APPLICATION AND DATA FORMS NOW

Please ensure you provide all the relevant data requested, details of a technical contact within your company, read the terms & conditions, and sign the declaration. Calculations will only be produced once payment has been received in full.

Once you have completed your form, please email it to: bwf@bwf.org.uk. You can ring the technical team on 0844 209 2610  to discuss your application.

We will calculate the U-value. We then send you a certificate for that window and you can use that certificate to demonstrate compliance with Building Regulations depending on the U-values obtained.