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Navigating and Complying with Building Regulations: Windows and Doors: V2 Existing Dwellings

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In our previous blog we discussed the different ways of ensuring you comply with the building regulations in England on new homes, this second volume looks at the building regulations that apply when replacing windows and doors in existing homes.

Now most will think that if you are just replacing windows in your own home building regulations don’t apply, but they do. Since April 2002, it has been necessary to prove that any replacement glazing improves the performance of existing homes in an effort to achieve the national energy targets and this meant that the window basically should have a u value of no more than 2.0W/m²K but since the introduction of the new regulations in 2010 the window should achieve a u value of no more than 1.6W/m2K

Let’s start with an overview of the current building regulations that apply to replacement windows and doors.

The Window and Door Regs

Approved Document L1B – Conservation of fuel & power in existing dwellings

Approved Document K 2013 – Protection from falling collision and impact.

Approved Document B1 – Fire Safety

Replacement Window Checklist

  1. The replacement scheme has not commenced and before works start I will give a minimum 48hrs notice to the council.
  2. The replacement will achieve a U-value of 1.6w/m²k or WER Band C for windows, or 1.8w/m²k for doors.
  3. All frames will be suitably draught-sealed and where ever possible insulated cavity closers will be provided.
  4. Glazing within critical locations will be replaced with appropriate safety glass.
  5. Existing measures for background and natural and mechanical ventilation will be retained.
  6. Where no ventilation openings exist – opening lights will be provided as follows: Habitable rooms – 5000mm2 equivalent area / Kitchens / utility rooms /bathrooms (with or without w.c.) – 2500mm2 equivalent area.
  7. Existing measures for means of escape from relevant rooms will be retained (changes to the existing window pattern may affect means of escape). This means that the clean opening sizes of the opening lights must not be any less than the ones being replaced. However, you might want to consider bringing the new windows up to the current standards (where possible)
  8. If rooms where window/door replacement is to be undertaken contain open flued appliances the adequacy of combustion air supply will be checked by a suitably qualified person
  9. If necessary, a suitable means of support will be provided above the replacement window / door.
  10. Where the dwelling has existing easily accessible thresholds and entrance doors these will be maintained.

Primarily there are 2 routes of compliance with Part L1B of the building regulations:

U-Value: Part L1B of the building regs is for replacement dwellings and currently states that a window to be compliant has to be a U-Value of 1.6 or better and this is fundamentally what requires compliance with during a window replacement situation.

WER: The WER calculations are based on various factors (including U-Value) and give a more complex picture of a windows overall energy performance (see attached method of calculation) and are now also accepted as a route of compliance with Part L1B of the building regs when the window achieves a “C” rating or better (i.e. “C” is equivalent to the minimum 1.6 U-Value requirement).

The U-Value, although used as part of the WER calculation, can be different from one spec to another on the same product but as this is not the only criteria that is used it means that a window can have the same WER as another even if the U-Value is different. See information shown under “U-Values” on this link – http://www.energysavingtrust.org.uk/home-energy-efficiency/energy-efficient-windows

The ratings we provide on our paperwork are for guidance purposes based upon the product performance calculations that make up the WER and are a simulated calculation method.

When selling property, surveyors will ask for evidence that replacement glazing installed after April 2002 complies with the new Building Regulations. There are two ways to prove compliance:-

  1. a certificate showing that the work has been done by an installer who is registered under the Fenestration Self-Assessment Scheme by Fensa Ltd, or a Person registered by BM Trada Certification Limited, the British Standards Institution or CERTASS Limited or Network VEKA Limited.or
  2. a certificate from the local authority saying that the installation has approval under the Building Regulations.

DIY projects or installations by non-registered firms need Council approval under the Building Regulations and ultimately this may be your responsibility. Therefore be sure to ask whether an installer is able to self-certify. If not, either they, or you, will need to make an application to the Council for approval under the Building Regulations and pay the current Building Regulation charge payment.

How can i check my windows and doors comply?

Well you could spend hours and hours reading the approve documents but in my experience that will just leave you more confused; even with 13 years of experience reading and interpreting Building Regulations; British Standards and Test Reports I struggle to interpret what they actually mean.

My advice; leave it to the experts.  Ask your supplier to prove compliance.

What Bereco do to ensure you comply?

We train our staff to quote to ensure you comply and offer advice and guidance if we see a problem.

We test, with UKAS certified body Bluesky.

We show u values; certificate numbers and air flow on our quotes. By declaring the total EA on our quotes and order document we help you ensure you achieve the levels required to ensure compliance.

In order to prove fully and without doubt that our wooden windows are fully compliant with Part K we have undertaken the testing of our sash window to the British Standard BS6180.

Our Contemporary Lipped Casement has a Uw range of 1.2 – 1.4 W/m2K which means that it performs 40% better than the requirement set out in Building Regulation L1B.

Although there is no requirement to air test an existing building, or to achieve any air permeability figure, unlike new builds, reasonable provision would be to ensure the design allows for a continuity of the thermal insulation for the new elements. Our casement windows are tested to perform against winds of 136mph and tested to withstand driving rain at 55mph.


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