Energy Ratings – The Facts

Energy ratings take into account solar gain when calculating the energy efficiency of the window. Glass has been developed that has a high solar factor which increases solar gain to achieve the top ‘A’ rating. However the extra UV light and heat gain may cause householders problems in summer.

Practically all of the ‘A’ rated windows available use glass that has a High Solar factor. The energy label will show the solar factor. If it is 0.41 it will not have high solar factor glass.

Customers should consider carefully the following points:

1.            The solar gain will not be achieved on North facing
               windows

2.            On South and West facing windows the extra UV light
               will increase the possibility of discolouration of fabrics
               and furniture

3.            The extra heat gained in summer may make rooms
               uncomfortably hot especially conservatories and large
               South or West facing windows

4.            The heat loss in winter will still be the same as a
               ‘B’ or ‘C’ rated window.

It may be that in many cases the ‘A’ rated window is not the best buy. If an ‘A’ rated window is required then the Timberlook ‘A’ Rated window is the most efficient on the market because it is made without using high solar factor glass.

The reason the ‘A’ rating can be achieved without using high solar factor glass is the PVC-u frame is better insulated and better designed than other PVC-u frames which were designed many years ago. An ‘A’ rated window with high solar factor glass will lose in winter up to 15% more heat than a Timberlook ‘A’ rated window.

Timberlook windows are also available with Tripleshield Double Glazing which has a ‘U’ value of 1.2 and a similar heat loss to an “A” rated window made using high solar factor glass. Tripleshield Double Glazing does not have the heat gain of high solar glass.

In conservatories and large south or west facing windows consideration should be given to using Staycool Glass which will reduce the temperature of a glass roof conservatory on hot summer days by 20°F when compared to Pilkington K and Antisun Glass. Staycool glass offers the best protection against UV light with the roof glass providing 94% protection and the vertical glazing nearly 30% more protection than standard glass.

In addition the ‘U’ value is 1.0 which means Staycool Glass is also very efficient at reducing heat loss in winter in conservatories and rooms with Patio or Bi-Fold Doors. The ‘U’ value is a better measure of heat loss for large glass areas than energy ratings which are calculated on windows less than 2 sq meters which have a high frame to glass ratio.