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Evening, I have been looking, sourcing and trying to design a heating system for our barn conversion. I initially contacted several reputable GSHP/ASHP suppliers and they have come back with system designs with pumps in the region of 25kW to 30kW. Granted our property is quite large but I have been suspicious over their assumptions and calculations as none of them asked me any detailed questions about our build materials etc. Before just slinging something in I have consequently made the effort to use @Jeremy Harris Heat Loss Calculator, whilst at it I also used @Lilly_Pines Solar Gain Calculator. At the worst in January I have calculated a hourly requirement of 4.41 kWh if we exclude any solar gain it is 5.82 kWh. Now I can't understand why I would need a 30kWh capable pump? Either my calculations are too good to be true and the building will never perform so well in real life/a input mistake has been made... or the suppliers are massively overcompensating. Or am I missing something else? The next issue is (whether the above is right or wrong) is installing a system that can run on ASHP and another heat source. We are off-grid - so no choice but to use another source of heat. Probably oil for ease of use. However I am seriously considering using a boimass boiler or woodburner with back boiler, this would have to be connected up to a thermal store which from most forum posts is unpopular compared to UVC. (Why is that?) I have provided monthly solar generation from a 33kW Solar PV array as per https://re.jrc.ec.europa.eu/pvg_tools/en/tools.html I assume it is accurate enough - it is suggesting a PV generation in winter which is 19% of summer output which I have seen bounded around. If my calculations are correct I have expanded Jeremy's spread sheet to estimate oil usage and it is relatively negligible so burning wood seems unnecessary unless my calculations are all wrong... I have attached my spreadsheet for those interested/willing to have a look - I have noticed @SteamyTea is pretty good at crunching the numbers. Appreciate anyone's thoughts and opinions on the matter. Edit: this is a continuation of thoughts from a post a few months ago - appreciate the responses from everyone there but realised I lacked useful detail and my own calculations. Heat loss calculator - My Barn.xlsx

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 : )

Is there a way to verify or get some reassurance about U-Values quoted by suppliers? Thanks Andy

We can view plans in three dimensions, model buildings in hyperspace and take virtual tours. Yet we continue to calculate heat losses in one dimension. As insulation gets better the proportion of heat lost through thermal bridging increases, no one cares much.