Window performance explained

Windows have to tick a lot of boxes to make them fit for purpose.  

When comparing technical parameters, the basic point to remember is that there’s a big difference in performance between the glass on its own and the overall window with frame. It’s usually the frame, especially where it meets the glass, that is the weak link. 

Most window companies now quote overall U-values for units in frames (not a mid-unit value, which is better). Always make sure you are comparing performance like with like. 


Written by Astrid Madsen

Astrid Madsen is the editor of the SelfBuild magazine. She previously held the same role in an Irish trade publication, before that she worked at the National Standards Authority of Ireland. She graduated with a BA in Urban Studies from Columbia University in New York and holds an MBA from the Instituto de Estudios Bursatiles in Madrid. France of origin, she now lives in Portarlington, County Laois, where she's taken on the task of renovating a listed building! Email

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