Can you have grilles between the glass with the new H1 changes?
The H1 changes set out minimum thermal performance criteria and allow specific combinations of window options that meet those. For example, when a R-Value of 0.46 is required, a minimum of double glazing with Low-E and thermally broken aluminium frames is required just to meet that performance requirement. Adding grilles between the glass lowers the R-Value of the window a little (2-4%) so the minimum aluminium window no longer meets the requirement of 0.46. A higher grade of Low-E or even triple glazing may be required to meet the R-Value of 0.46 with grilles.
However, our double glazed uPVC window doesn’t just barely meet the 0.46 R-Value criteria, it far surpasses it. Our standard windows start at an R-Value of 0.65. Therefore if adding grilles between the glass, our slightly lower R-Value is still very much above the minimum 0.46 R-Value requirement.
It is perfectly fine to have grilles between the glass with uPVC windows.