Highly glazed or Over glazed extensions pass Building Regulations
100 % pass and up to 100 % glass!
Sun-rooms Orangeries glass rooms etc
An over- glazed extension is an extension with substantial amounts of glazing - where the amount of glass exceeds 25% of the floor area - after taking into account windows and doors openings which were formerly exposed but are no longer so. In this case the extension is no longer compliant on an individual element basis. However the extension can pass L1B regulations using one of the alternative methods.
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.
An over glaxed 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
Yourself or the architect sends us your construction plans
We Arrange and appointment and 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 complare the heating requirements to see if there is an 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 are provided :The report contains
Cover / Index
Letter of recommdation 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.
At least 2 copies of the report are provided properly spiral bound.
Our typical cost for this service is : Call now for a competitive quote
We have a 100 % record in getting these applications approved
Telephone : Martin Gill on 01634 799115 for advice or to book and apointment
We are members of the NHER approved scheme and our calculatons are fully acceptable to building control.
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.