Whole Window u-value calculator
Conforms to Part 1 of BS EN ISO 10077
We provide a service for anyone who is required to supply information about u-values to building control. We do not just supply a u-value taken from the centre point of the glass or the centre of a window panel. This is a whole window u-value calculator giving the combined u value of the glazing, the frame and the spacer.
No restriction on manufacturer
Our calculator does not restrict you to using products from any one manufacturer. We can calculate the u value of single, double or triple glazed windows built with softwood, hardwood, accoya and even composite frames.
We can calculate the overall u-value where other types of frame are used if you can provide the u-value of the components of that frame.
No Membership or Registration Required
We do not require you to sign up for any sort of membership to use our uvalue calculator. It costs just £35 for a calculation and for that we will send you a three page pdf certificate (usually the same day) based upon the information that you submitted.
Why you require U Values - An explanation
From 1st October 2010, window manufacturers needed to show that their windows complied with the energy efficiency requirements in the latest 2010 revision of Part L of the Building Regulations and the Approved Documents L1A (new dwellings) and L1B (existing dwellings).
Obtaining a precise u-value for a manufactured window can be extremely expensive, especially for smaller manufacturers or architects with bespoke designs.
Architects increasingly ask for the thermal transmittance values of windows, so that they can calculate the SAP ratings of the buildings where the windows are to be fitted. Clients require that value for completion certificates. You need to comply with Part 1 of BS EN ISO 10077 for building regulation approval. Our U-Value Calculator provides this information at a very reasonable cost.
Whole Window U Values - How to achieve a low u-value
What affects the uvalue of a door or window ? Heat loss through the timber sections, through the glass units and through the junction of the glass and the timber (i.e. the spacer bar).
The choice of wood you use for the frame and the thickness of that frame is important for achieving a low uvalue. The type of wood, Hardwood, Softwood or Accoya determines the thermal conductivity. The thermal conductivity is then used with the thickness of the frame to determine the uvalue of the frame. Accoya is the best followed by Softwood and then Hardwood. A thicker frame has a lower u-value than a thin one.
For double or triple glazed units it is generally true that the higher the ratio of glass to frame means the lower the u-value. To achieve a low u-value it is best to use glass units with a low uvalue. We hold u-values for some units but details should be readily available from your glass manufacturer.
The Spacer Bar
Heat loss via the spacer bar can have a significant impact on the overall u-value of the window. The lower the psi value of the spacer bar, the lower the u-value of the window. The standard aluminium spacer is not the best way to achieve a low u-value and more efficient bars known as warm-edge spacers such as the swiss spacer or thermobar are available.
Simple 3 Step Process
You Submit the Details
Our process starts with you sending us the details:
- You send the dimensions
- You pay the required fee - £35
We Calculate the u-value
We calculate the u-value:
- Hardwood, Softwood, or Accoya
- Double or Triple Glazing
- Conforms to Part 1 EN ISO 10077
We Send you a certificate
We send you a pdf certificate showing the u-value:
- Details the calculation carried out
- Specifies the u-value
- Has a unique certificate number