I am looking at replacing old sash windows with uPVC windows. Is this a good idea for a four-bedroom house?

Some say sash windows have advantages, but most say go with uPVC. Perhaps a wooden double glazed replacement is the answer. Anyhow, I hope someone can shed light.

Thanks, being in Leicester means I dont see that much inspiring me outside of the grove where I live. anyway, I found these ones for the benefit of others in the area. Having spoken to a rep, and getting thumbs up from a friend, think I will remove the sashes myself, and then get these guys to do the uPVC. Hope I can get it done by summer.



Windows are very religious and debate inspiring. Identifying top goals will help in selection and maximizing ROI.

FWIW: uPVC and vinyl are synonyms in North America.

Energy Efficiency

  • Maximizing u-factor depends on the heating/cooling zone you are in. .35 might be good for a northern climate, while overkill for a southern one
  • SHGC (Solar Heat Gain Coefficient) is more important in a southern area.
  • Air Leakage
  • Condensation reisitance


  • Durablity factors are hard to estimate accurately, but price is usually some indication of quality
  • Fit and finish Construction materials used have an effect on appearance as well as durability. Maintenance requirements and paint-ability are factors
  • Resale issues

You can get uPVC sash windows now that look very much like the traditional wooden sash windows they replace. They run on springs rather than pulleys and weights and can be tilted inwards to allow for easier cleaning of the outside. So you get the benefits of both having a sash window and one that's low maintenance.

They are a little bit more expensive than a casement window - but cheaper than a wooden sash window (I know because we've just replaced some of ours).

In general it's better to put in windows that look like the existing ones for a couple of reasons:

  1. If you can't replace all of the windows in one go then the house will still have a consistent look to it.
  2. You'll match your neighbours - something that might be an issue when you come to sell.
  3. If you live in a conservation area there may well be planning restrictions that mean you have to keep the same appearance at least to the front of your house. This isn't the same as "listing" where you have to keep the house "as is" so you should be able to fit uPVC if you want.

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