Windows - thermal holes

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You want as much light as possible? Windows have a physical limit to insulation. The best r-value is only appr. 2

All or nothing

Styrostones/PIF/ICF provide you with a super insulated shell to your new property. However what should you be looking for in your windows and doors? It is only glass after all. Or is it?

As with the walls of your property, the rate of heat loss of a window or door assembly is indicated in terms of the U-factor (U-value). The lower the U-factor, the greater a window's resistance to heat flow and the better its insulating properties.


determine that you must obtain a certificate from LABC or have a FENSA Registered Company carry out any window installation or replacement. When you first apply for your planning permission the Local authority Building control will require that your project passes a SAP rating. If you have employed the services of a code assessor or architect they will ensure that your windows will meet the requisite criteria.


is the Government's Standard Assessment Procedure for Energy Rating of Dwellings. SAP is adopted by government as part of the UK national methodology for calculation of the energy performance of buildings. It is used to demonstrate compliance with building regulations for dwellings - Part L (England and Wales), Section 6 (Scotland) and Part F (Northern Ireland) - and to provide energy ratings for dwellings.