Replacement Windows Building Regulations

The Facts:

1. Replacement windows must meet minimum insulation levels
2. The lower the 'U' value, the more effective the insulation
3. Proof of compliance will be needed if you sell your home

Everywhere you look there are exhortations to save energy and many aspects of our lives are now governed by strict regulations to make sure we 'do our bit' for the environment. Replacement double glazing windows are no exception.

This means that anyone installing replacement double glazing windows must ensure that they meet the minimum levels of insulation stipulated in the relevant building regulations.  Insulation levels are measured as U values - the lower the U value, the more effective the insulation.

So, while the downside of the legislation is the fact that we no longer have complete freedom of choice when it comes to replacement windows, the upside is that the regulations ensure that our windows are more energy efficient which cuts our heating bills!

The regular type of double glazing that has been the norm in recent years - consisting of two pieces of glass separated by a spacer bar - is now unlikely to measure up to these new building regulations. In fact, in order to attain the mandatory level of insulation it will be necessary to use some type of low emissivity (low E) glass - something like Pilkington K, although there are a number of other brands. In addition, the sealed, double glazed window units may have to be filled with gas, probably argon.

The growth of the replacement window industry has resulted in an impossible burden being placed on building control officials. So, when it was recognised that the building inspectors would be unable to keep up with the high level of activity, a self-assessment scheme was devised to manage the many thousands of window installations that are subject to building regulations. In practice this means that it is not always necessary for a building control officer to inspect every installation or for companies to make separate building regulations applications. 

Any contractor who is registered with the FENSA (Fenestration Self-Assessment) self-certification scheme is authorised to carry out double glazing installations in accordance with relevant regulations and without inspection by the local authority. However, the contractor is obliged to inform FENSA when the installation has been completed and finished double glazing installations are subject to random inspections.

Bear in mind, though, that if the contractor you are using is not registered with FENSA - or if you are carrying out the work yourself - then you will need to arrange for building regulations approval. The building inspector will need confirmation that you have met a range of strict criteria. In this instance you will be responsible for paying for the building regulations application so it is wise to check in advance with your local council to ascertain the cost. Approval times vary according to the local authority so it makes sense to apply early to minimise delays in beginning the work.

Note: At the initial planning stage it is important to check with your local authority whether or not planning permission or conservation area consent is required.

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