U-value Calculations
U-values measure how effective a thermal element is when taking into account the materials used and the lower the U-value the more efficient the element is as an insulator and the better and thicker the insulation, the lower the U value will be.
A U-value calculation is used to demonstrate the thermal properties of built-up elements such as an external wall, exposed floor or a roof and they are used in SAP energy calculations to determine how much insulation needs to be used for a particular construction element and with a U-value, the lower the value the less heat that will be lost through the construction element.
The Building Regulations have minimum target U-values but meeting these target u-values does not always guarantee compliance as there are other minimum requirements to consider such as the efficiency of a heating system and more complex calculations taking into account a Target Emissions Rate (TER) and Target Fabric Energy Efficiency Rate (TFEE) that must be achieved.
How are U-values calculated?
Each material layer is included within the calculation and then variables such as bridging factors (timber, wall ties, etc.), element thickness and each material's 'conductivity' is included.There are practical and cost implications to each U-value calculation as the following issues should be considered:
- Materials used should be considerate to design and clients budget
- Better use of High Performance insulation materials will generally translate into a better U-value.
- Thermal Bridging should be carefully considered as continuity of insulation will provide improvement in insulation performance.
- By using EAC South West you will benefit from clear advice on solutions available that are cost-effective to your project.
Adjustments to thermal elements are made for openings (doors, skylights and windows) by inputting the dimensions the U-values.
U-values for windows will usually be supplied by the manufacturer, but SAP does allow for a default entry if not available. The U values are for the window as a whole (frame and glass).
SAP and U-values
The dimensions of thermal elements are necessary to accurately assess the areas of each heat loss element and this is detail is entered into the SAP design model along with the U-values calculated. Adjustments to thermal elements are made for openings (doors, skylights and windows).
U-values for windows will usually be supplied by the manufacturer but SAP does allow for a default entry if not available.
We can make a Building Regulation application on your behalf
We will take time to understand what you want and then deliver what is required for Building Regulation compliance.