ChrisDL

Good to know it is accurate - and I am confident my inputs are right. But as stated it worries me how the 'professionals' can be so wrong. I was looking at about 10-12kW. Samsung 12kW comes to mind... not sure if they are any good. Would you have a recommendation for a cylinder size? We are a family of four (might grow to five one day) but we are likely to have guests over, hence I have based my DHW requirements for 6 at 75l each. Which will mean I need to be able to store at minimum of 450l. Then there is the requirement for underfloor heating. I keep leaning towards a thermal store, out of a odd desire plumb in a back boiler wood burner and not waste any heat. But UVC's seem to be championed on the forums so recommendations on sizing / buffer required would be great.

Yes they do - I have struggled across the board to find reassurance from a lot of companies that they know what they are looking at - but to be this far apart on the calculations has me worried I have it wrong. Well it is Mean minimum OAT - Devon doesn't get many sub-zero days. I have already included DHW (over compensated this one) If I drop the outside temperature to -3 and remove all solar gain we calculate a hourly heat requirement of 7.88 kWh. Without any solar the Oil will be running anyway as we will be conserving battery power for electrical amenities.

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

Afternoon everyone, I have been dipping into the BuildHub Forums for quite a while and found it a great resource. Now though I think I am at the point in our build to ask for some direct opinions and ideas. Briefly: We are building a new home based around a class Q barn conversion. Currently we are up to DPC and having to make some decisions which I could do with some help with. My main consideration at this point is heating. We will in all likelihood be Off-Grid for electricity purposes relying on a very large PV, batteries and back up generator, possibly a wind turbine if I can find a reasonably sized and cost effective option. The result of this decision is that we can not rely solely on electricity for heating purposes. We do intend to fit a GSHP or ASHP (I have been around and around in forums on the merits of GSHP vs ASHP and believe I have settled for ASHP) to utilise the electricity generated from PV if the batteries are full. We will have to rely on more 'traditional' heating methods during the winter. Whether that be oil or gas. However we have also planned to install a wood burner and I thought it may merit being a boiler stove so we can dump the heat generated into a store to be used more purposefully in DWH and the UFH - this will mean installing a Thermalstore rather than a UVC. My question is: Is it worth bothering with a wood stove boiler and the thermal store? My plumber has advised that the wood stove will burn less cleanly until the return temperature is up to about 40 °C (however I don't see this being a massive problem since the store should never be starting from cold unless we have completely run out of alternative sources) Thermalstore vs UVC, seems to be a lot of opinions on this. Simplicity vs efficiency - common conception is that the thermalstore will leak more heat than a UVC - (recommendations on the highest insulated and performing ones welcome) Safety - Wood stove will need a pump to return the heated water - if this fails we don't want superheated water spraying over us. For all the aforementioned considerations, even if overcome or positive, to save a few £100 a year on heating oil or gas are we overcomplicating the system when a UVC connected to a oil/gas boiler and ASHP will suffice? I should mention that our objective is not going to be shovelling wood into the stove all day to offset the use of oil/gas. We will light it when it is cold/coldish/ and we want the atmosphere of a fire. I have been told by many overheating with a wood burner is likely to be our biggest worry, hence another reason to fit the stove boiler so the majority of the heat is absorbed into the water rather than towards the room. Any thoughts and opinions very welcome, Thank you Chris