Loft floor insulation

[sully872000]

I am doing a loft conversion and the architect plans say 100mm wool insulation in between 200mm high floor joists., which I have done. The building inspector came around to check and said you need another 100mm insulation. Is he taking the ****? What I want to know is Why did the council approve the architect plans which stated 100mm insulation? Any suggestions welcome.

 

[jeds]

?? ask the building inspector why and under what regulation he is asking for that? 100mm is normal and plenty and meets regulations.

 

[sully872000]

?? ask the building inspector why and under what regulation he is asking for that? 100mm is normal and plenty and meets regulations.

He said the joists are 200mm and the 100mm currently I have put in is for sound only and not enough.

 

[Nakajo]

In what sense did the Council "approve the architect plans"?

 

[noseall]

I am doing a loft conversion and the architect plans say 100mm wool insulation in between 200mm high floor joists., which I have done. The building inspector came around to check and said you need another 100mm insulation. Is he taking the ****? What I want to know is Why did the council approve the architect plans which stated 100mm insulation? Any suggestions welcome.

Under what guidance is the BCO asking for another 100mm?

 

[wessex101]

He said the joists are 200mm and the 100mm currently I have put in is for sound only and not enough.

That would suggest that part of the floor requires the full depth of thermal insulation. Does the thermal envelope follow the roof slope all the way down to the roof eaves or does it come down the ashlar walls with eaves storage areas uninsulated?

 

[sully872000]

That would suggest that part of the floor requires the full depth of thermal insulation. Does the thermal envelope follow the roof slope all the way down to the roof eaves or does it come down the ashlar walls with eaves storage areas uninsulated?

It is insulated down the ashlar walls and the floor insulated to the end of the eaves.

 

[jeds]

Regulations require a 100mm layer of mineral wool for acoustic purposes. The only place a floor requires more than 100mm of mineral is where the floor is also thermally insulated but, in that case, 200mm of mineral insulation is not sufficient.

I don't quite get your description in post #7; is this a floor between habitable rooms or not?

 

[sully872000]

Regulations require a 100mm layer of mineral wool for acoustic purposes. The only place a floor requires more than 100mm of mineral is where the floor is also thermally insulated but, in that case, 200mm of mineral insulation is not sufficient.

I don't quite get your description in post #7; is this a floor between habitable rooms or not?

The Floor is above habitable rooms

 

[jeds]

There you go then, BCO is talking out of the wrong orifice. Ask him which regulation he is basing his request on?

 

[wessex101]

It is insulated down the ashlar walls and the floor insulated to the end of the eaves.

That makes sense then, the floor between the ashlar wall and roof eaves needs to be insulated to achieve the require U-value. The thing that doesn't make sense is the BCO asking for 200mm of insulation. Even assuming we are dealing with the pre-June 2022 U-values you would need 270mm thickness of insulation.
I suggest you go back to your "architect" and ask them what is required if it is not clearly shown on the drawings.

 

[jeds]

The Floor is above habitable rooms

OK, 'floor is above habitable rooms'. But is it a floor wholly between rooms or is there any element of roof above or any part where the floor relates directly to external roof?