Glass extensions - Unseparated conservatories

I seem to be getting a reputaton for getting these through building control Part L1B
The person wants an extension to their home usually the living area in the back garden with a substantial amount of glass - only this is not separated from the rest of the dwelling.
In part L the normal amount of glazing allowed is only 25 % of the extension floor area - plus any windows or doors covered up. if the amount exceeds this then Building control ask for energy SAP calculations. The first stage of the process is to identify the shape and size of the extension and the calculate the U values of the surfaces. Then using a weighted U value calculation to see if the heat loss from the extra glass can be offest by increasing the U values elsewhere in the extension fabric. Usually without exception it can not. At this stage I also check the U values against the limits in the tables in L1B. The next stage of the process is to model the rest of the occupants home using SAP.

Being the accurate person that I am I try to get an accurate model as possible and this requires a lot of data - sometimes a visit . Once the SAP model of the whole house is complete I identify improvements that can be made somewhere else in the home so that the additional heat loss identified elsewhere is offset.

Finally the most important stage the report- this takes lot of time to produce as I want it to be very clearly crafted - a compelling case that Building control should pass this design - no tricks no gimmicks - clear evidence. None of the cases that I have presnted have been rejected.