Hi,
I'm in the process of planning a single storey extension. I want to add more window area than the permitted 25% of internal floor area. I have spoken to Buidling control and they say I can offset other areas to gain more glazing i.e add more insulation in walls, floor or ceiling. They gave me the following figures for U values, 0.35 walls, 0.25 floor, 0.25 roof, 2.2 glazing per sq m. I presume these are the min U values required for each element.
I have calculated that I need an extra 1.96 sqm glazing so after deducting the U value of the decrease wall area from the increase glazed area gave me a figure of 3.62. I then divided this figure by the internal floor area of 17.2 sqm to give a figure 0f 0.21. This is where now I came to a stall. My drawings quote the insulation for the floor of 85mm of Celotex, I am considering putting 100mm of Celotex but cannot find any information as to check if 15mm of extra celotex will increase the U value by 0.21.
If anyone has any input to whether I am on completely the wrong track it would be most appreciated.
I'm in the process of planning a single storey extension. I want to add more window area than the permitted 25% of internal floor area. I have spoken to Buidling control and they say I can offset other areas to gain more glazing i.e add more insulation in walls, floor or ceiling. They gave me the following figures for U values, 0.35 walls, 0.25 floor, 0.25 roof, 2.2 glazing per sq m. I presume these are the min U values required for each element.
I have calculated that I need an extra 1.96 sqm glazing so after deducting the U value of the decrease wall area from the increase glazed area gave me a figure of 3.62. I then divided this figure by the internal floor area of 17.2 sqm to give a figure 0f 0.21. This is where now I came to a stall. My drawings quote the insulation for the floor of 85mm of Celotex, I am considering putting 100mm of Celotex but cannot find any information as to check if 15mm of extra celotex will increase the U value by 0.21.
If anyone has any input to whether I am on completely the wrong track it would be most appreciated.