tonybythesea

I can now share some heat loss calcs - document attached. It gives two options as to level of insulation; we are currently thinking of the lower level. The usage pattern for our studio building will be almost entirely daytime use and with periods of many days together with nobody there. The nature of that use means we will be going for a very durable washable floor surface but not ceramic tiles. Vinyl or vinyl tiles most likely as of now. Therefore I don't think we can expect the floor to hold a lot of heat and may just need to accept we put the energy in often at peak tariff times. Careful management and control systems presumably can make all the difference to eventual bills. Revised Heat Load Calculations 11 10 19.xlsx

Help! I thought Mr Boltzman would make an appearance son and that by then you'd have lost me. ? Just so you know, the explanation offered by Warmfloor of why their resistance heating can be more cost-effective than other electric UFH is as follows. "The reason why cable systems require more W/m² to operate is that a very small diameter cable only heats 2% of the floor so has to reach a very high temperature in order to pass heat across a 50mm space. Step Warmfloor heats more than 60% of the floor so needs less energy to heat a much much larger area and does not need to reach such a high temperature to do so. It heats the whole floor at an even temperature with no hot or cold spots." Does this relate to Ed Davies' comment: "If the amount of insulation above the element (wire, foil or pipe) is increased then the element will need to be hotter which will increase the losses downwards unless the insulation below is also increased to compensate but, as @JSHarris points out, with sensible amounts of insulation below this loss will be relatively small anyway. It's just possible that a low-voltage element which can be very close to the surface could make significant savings compared with elements buried a bit deeper but only if the insulation below is completely inadequate. I suspect their figures are done on the assumption of no insulation below the elements. If so, that's a cheat IMNSHO." I'm intending to post the heat loss calcs and other dimensions of our building FYI later today but my wonderful day job needs me too!

I appreciate you guys responding so promptly. When I asked for more detail from the UK distributor of Step Warmfloor (American) this is part of what I received: "For 1 Kw of electricity the area heated and cost would be as follows For 230/240V products 100W/m² 1000 = 10.m²/unit price 100 150W/m² mat 1000 = 6.7m²/unit price 150 200W/m²mat 1000 = 5.0m²/unit price 200 Consider now Step Warmfloor. In order to provide the same room temperature and 28°C at floor level Step Warmfloor requires only 54.3W/m² Therefore for 1 Kw of electricity the area heated and cost would be as follows 24W Element 1000 = 18.4m²/unit price 54.3 Therefore to summarise for 1Kw of electricity a 230/240V system would heat an area of only 10.2m² using 100W/m², 6.7m² using 150W/m² and only 5.0m² using 200W/m² Whereas Step Warmfloor heats an area of 18.4m². Therefore Step Warmfloor heats an area of between 2-3 times larger with the same 1Kw of Electricity. ... As regards to cost it is easy to see that Step Warmfloor costs 2.75 less to run than the 150W/m² product and 3.68 times less to run than the 200W/m² product." I am suspecting that the assertion that I've put in bold italics is the crucial bit I'm being asked to take on trust. I realise this is only a comparison with more usual forms of electric UFH, not with wet systems.

Does anybody have useful experience of 'warmfloor' underfloor heating: carbon-enriched semi-conductive polymer mats with copper elements down each side? It claims to be adequate for complete room heating (not just taking the chill off e.g. small bathroom floors). And to do this using far less electricity than other electric UFH systems for the same achieved room temperatures. I gather the technology was first developed in Norway for things like warming car seats. Two brothers who developed it seem then to have fallen out so that they now run two competing businesses offering this, one based in Norway, one in the US. Both have distributors in UK. Another version of a similar technology (as far as I can see) is sold as Ecofilm. I'm considering using this in a newbuild, so could equally go for a wet system. I know that is generally more economical to run. Gas is not an option, so in this case for a wet system we'd be using either an electric boiler or ASHP. But we have plenty of PV to effectively reduce running costs for any electric system. A dry system would have its attractions. Warmfloor being low voltage can be run directly from the PV when the sun shines, or uses a transformer when run on the mains. And if warmfloor lives up to its publicity we'd get satisfactory heating and there'd be no boilers to replace, no annual servicing, no danger of leaks etc. Unlike other electric UFH it is apparently suitable under any floor covering, not a danger to timber etc. NB our design already includes good insulation values and MVHR so a high proportion of heat 'lost' in transformers should still be put to use. Problem is, although I can get assurances (and some figures) from the people dealing in warmfloor, I've failed to find anything online that gives solid independent evidence that I won't end up with rooms that don't get warm enough in winter. I've had some positive feedback, I should say, from past clients whose contacts one of the warmfloor distributors gave me.

Thanks for your welcome. I'll post shortly on the UFH subforum. I'd read the whole long saga of Nexgen discussion with Clive Osborne, Steamy, and notice he's never come back (has he?) with test results. Also Nexgen seems to have disappeared so links previously given don't work. Hmmm... Where are we? West Dorset, between Bridport and Abbotsbury.

Hi everybody. The charity I work for (and on whose land I live) has done a lot of self-build in the past (e.g. 5 bedroom chalet-style house done as self build training project in 1996, 'solar' building c. 2010 that included cob, rammed earth and straw bale). Now I'm steering (with 4 others) a project to build a multi-purpose studio with kitchen, toilets, store and lobby. We did demolition (of previous 'classroom' type building) and site prep ourselves. Photo shows me removing old ceiling insulation and a million dead flies! But we are working with contractors from here on in. We aim for a building that will be carbon neutral in operation over the course of a year. We are in a brilliant location for PV on the south coast (and already have PV arrays producing more than 10,000kW a year) but this building will also be on grid so we can export what we don't use and draw energy on dark winter days. My current puzzle that brings me back to Buildhub (which I've often read with interest) is about options for heating. Specifically confused about innovative low voltage electric UFH which might suit our particular conditions well. Which sub-forum do you recommend for posting a query on this please? Thanks, Tony.