Chendy

... for background... I'm massively constrained with ceiling height and lining up with existing door thresholds - its an ex council flat. So want to calculate everything and trade off against these two other considerations.

Hello, I am completely new to the building control process, stumbling my way through, any help very appreciated... I have a maisonette flat situated on the ground and first floors of a 4 storey residential block. The block is a reinforced concrete frame construction. All floors are reinforced concrete slab, with uninsulated screed over the slab. I want to remove the existing screed. Replacing with floor insulation, then a finished concrete floor containing underflooring pipes. I understand from LB1 the new floor should ideally meet a U-value of 0.25 W/m²K, "feasibility" aside. Q1.A How to calculate the U-value of the ground floor? Is this a correct approach? https://warmafloor.co.uk/support-centre/u-values/ is a guide to calculation of the U-Value of the uninsulated floor. based on The IP 3/90 formula is U = 0.05 + 1.65(P/A) – 0.6(P/A)² Where: U = U-Value of the uninsulated floor (W/m²K). P = Length of the exposed perimeter (m). A = Area of the floor (m²) https://insulation-uk.com/member/u-value-calc is an example of a insulation manufacturer provided calculator I have cross compared and they line-up close enough. Q2.A How to calculate the U-value of the first floors within the same dwelling? I haven't been able to find any guides how to do this Whilst it seems a U-value of 0.25 W/m²K still applies, I would assume that first floors within the same property would require less insulation?? the heat only really escapes from thermal bridging of the floor with the wall, heat wasted downstairs is in the same property?? and/or the room below can be assumed to also be heated or normal room temperature, so there won't be such a large temperature difference, so less insulation is needed?? http://files.nu-heat.co.uk/core/media/media.nl?id=237176&c=472052&h=f809f347f001eb168007&_xt=.pdf this datasheet from a underfloor heating company states "In ground floors the insulation beneath the screed should be 70mm ‘Celotex’ or equivalent, or conform to Part L of the Building Regulations; whichever is greater. In upper floors insulation should be to a minimum of 30mm ‘Celotex’ or equivalent to prevent downward heat transmission" Q2.B can anybody link to a formula or calculator to use? Q2.C or is the calculation just the combined U values of the concrete slab + floor insulation? any help very appreciated : )

Thanks @SteamyTea I checked L1B, and that's what I found too. 1. Is this the correct value irrespective of whether underfloor heating is to be installed? 2. Is it still 0.25W.m-2.K-1 for upgrading intermedia floors of existing buildings? If so, seems strange, as like you point out, there is less heat loss, and much of the 'loss' will be into the room below. Thanks

I have got off the phone from Kingspan who thought but couldn't confirm that the U-Value is 0.25 W/m²K for floors, irrespective of whether there is underfloor heating or not. Is this true?

Hello, Does anybody know the U-Value required when retrofitting / renovating underfloor heating? There seems to be plenty of resources talking about new builds but finding it hard to find any definitive information for retrofit. For my specific property, I have a ground and first floor. Both having a concrete slab floor with screed over it. I will remove the screed, then add insulation, then UFH pipes, then concrete poured over. Trying to work out how much insulation I need. I'm assuming less required for the first floor. Once I determine the maximum U-value permissible for building regulations, I can use various services such as this U-Value calculator to work out how much of what insulation I need. Any help appreciated!