Highly Glazed Extension – Orangery – Glass Extension
Modern glass extensions are fast becoming the ultimate in glass design and make a very desirable addition to your home – however these require additional proof of compliance to part L of the building regulations – we can get approval with the minimal amount of fuss and often with no change to the design. We guarantee that the final design proposal will be acceptable to building control – otherwise we will refund our fee in full .
We have a 100% record in getting highly glazed or over glazed extensions applications approved through Building Regulations. 100% pass and up to 100% glass! We ensure that your dream extension complies with building regulations Part L. We supply an extensive report with a letter of recommendation to building control and full supporting calculations.
Telephone Martin Gill on 01634 799115 for free advice or to book an appointment
What is an over glazed extension?
An over- glazed extension is an extension with substantial amounts of glazing – where the amount of glass exceeds 25% of the floor area – these are sometimes refered to as orangeries . In this case the extension or orangery is no longer compliant on an individual element basis. However the extension can pass L1B regulations using one of the alternative methods. In these cases building control ask for SAP calculations to prove compliance.
Over glazed extensions could include sun-rooms, orangeries, glass rooms etc.
Do not confuse this with the definition of a conservatory – a conservatory in L1B is outside the main insulated walls of your dwelling and is separated by outside quality doors and not heated by the main heating system.
Methods of compliance
An over glazed extension is typically an extension to a ground floor room, or a new ground floor room with lots of glass often with bi-fold doors leading to the garden or with additional roof windows. The same minimum standards of construction and services apply as to the current L1B regulations – however the additional heat loss from the extra glass need to be taken into account. There are two alternative methods of compliance in L1B However both require an expert assessor to interpret correctly.
It is sometimes possble to increase the insulation of other elements in the extension – but this is not often sucessful because the heat loss from windows is much larger than for other elements.
We nearly always use the whole house offset method of compliance : where the extra heat loss is offset by improvements elsewhere in your home. Although this is more complicated the outcome is much better and is nearly allways compliant.
This method incorporates solar gain from additional glazing so the additional heat loss is reduced – sometimes there is no additional heat loss calculated or the additional loss is insignificant.
Compensatory measures are often already incorporated into the home improvement or can easily be done so without incurring a major cost. Perhaps you are changing the boiler / improving the windows / or can add additional insulation on your loft? We will find a method of compliance most suited to your needs.
What is required?
- You or the architect sends us your construction plans
- We arrange an appointment to survey your home and discuss options (approx 2 hours)
- We prepare a SAP model of your home with the new extension
- We also prepare a SAP model of your home with a compliant extension (less glass)
- We compare the heating requirements to see if there is additional loss
- If there is additional loss we incorporate some improvements to compensate
- We write up a report with full suporting documentation
At least 2 copies of a bound report can be provided. However often we create the report as a PDF and distibute this by email. The report typically contains:
- Cover / Index
- Letter of recommendation to building control
- Key results and conclusions
- A compliance matrix to L1B
- At least 2 full SAP calculations
- U value calulations
- Any other supporting documentation and calculations.
Our typical cost for this service is competitive : Call now for a competitive quote. We are members of the NHER approved scheme and our calculations are fully acceptable to building control.
A word of caution
Finally a word of caution. The more glass you put into an over-glazed extension the more the temperature will fluctuate.
Although we could probably gain approval for a 100 % glass box extension – you should be aware of some potential problems that could otherwise spoil the gain , and incorporate solutions to these into your design , even though there is no direct requirement in L1B to do so.
If the sun shines through the glass, overheating can cause serious problems especially for southerly facing glazing. This should be addressed by passive shading and adequate ventilation ventilation. Cold spots and draughts can also be problematic in winter because of additional cooling from the glass. Cold glass surfaces can also cause condensation problems – particularly if there is cooking in the same open space. If you solve these issues then you will gain maximum enjoyment from your new glazed area.