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A_L last won the day on October 12 2017

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  1. To confirm we are using the same terminology, a pre-heater heats incoming air and the vast majority of this energy is transferred to the outgoing air in the heat exchanger. (Another way of looking at it is, the incoming air is heated to be warmer than the outgoing air to prevent it cooling the outgoing air, at least at the 'outside end' of the heat exchanger) The purpose of this is to prevent ice forming in the heat exchanger passages as a result of water vapour in the outgoing air condensing and then being cooled by below 0°C air in the incoming side. There is an alternative to this strategy. Replacing the standard heat exchanger with an enthalpy heat exchanger will prevent the water in the outgoing air freezing, until the perhaps falls as low as at least -8°C, see bottom of this link :- https://www.paulheatrecovery.co.uk/components/moisture-heat-exchanger/ It achieves this by transferring water vapour from the outgoing air to the incoming air, preventing condensing/freezing in the outgoing air.
  2. At the simplest it is the time taken for energy at the outside of a wall to transfer through to the inside. https://www.concretecentre.com/Publications-Software/Design-tools-and-software/Dynamic-Thermal-Properties-Calculator-(1).aspx from the middle of the link :-
  3. Assuming this is a modern condensing gas boiler turn the flow temperature down to a maximum off 60°C so that the return condenses the flue gases, which occurs at about 57°C. This gives 10-15% more heat from the same amount of gas.
  4. It does look OK but I would prefer the Intello on the warm side of the 50mm PIR layer, much bigger difference between actual and saturated vapour pressures. Are not 25 x 50mm battens inadequate without fixing to something else?
  5. Why? Table 2 (page16) of Part L1B says 0.28 for new thermal elements in an extension https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/697629/L1B_secure-1.pdf The Thermalite/Plasterboard option is 0.24
  6. Traditionally in Scotland six inch wide planks were nailed to rafters as 'sarking' this increased the strength of the roof in our weather conditions and slates (not tiles) would be directly fixed to them. My theory is that it is a 'sop' included to get building regs approval and has little strengthening effect (as evidenced by its fragility).
  7. hello and welcome, (note my location) italics and bold my edit, did you mean 'around'? 😁
  8. do you actually mean a sewage treatment plant (STP)? like https://premiertechaqua.co.uk/products/wastewater/conder-asp-sewage-treatment-plant.aspx
  9. Hideous extensions. 'outstanding architectural merit'? - pah!!!!!!!!!!!!!!
  10. Only if you intended to use 70mm or less of PIR and you use silver/graphite EPS beads.
  11. First hello and welcome, Here is a possible 'off the wall' solution. Seal wet suit neoprene to the inside of the toilet cistern. It does not have to be a perfect seal, a small amount of water getting between the neoprene and the cistern should be O.K. The neoprene insulates the cistern from the mass of water preventing it cooling the air below its dewpoint, preventing the formation of condensation. A small amount of water getting between the neoprene and cistern will heat up quickly and any slight condensation should evaporate before it forms large enough droplets to run down the cistern. An alternative would be to pre-heat the water entering the cistern😁
  12. Looks like 0.15W/m2..K, Part L1A (Wales) https://www.labc.co.uk/professionals/building-regulations-guidance-documents/approved-documents-and-technical-guidance-wales/wales-approved-document-l-conservation-fuel-and-power Table 1 bottom of page 18
  13. Celotex has a thermal conductivity of 0.022W/m2.K and the usual open cell Icynene has a thermal conductivity of 0.039W/m2.K. This means that 100mm of Celotex has the same insulating effect as 177mm of Icynene.
  14. 1) Can you detail how the electrical demand is made up? For an ordinary off-grid house it is unusually high. IMHO you are going to need at least two days worth of batteries. Also remember that electricity consumed for appliances then turns up as a 'casual' heat gain within the heated volume. 2) Is the heat loss rate really an instantaneous 15-20kW? or do you actually mean 15-20kWh per day, in which case it would be covered by the casual gain referred to earlier. If the former can you describe the property? Insulation and draught-proofing would seem to be called for. 3) I would meet the DHW by using a small dedicated ASHP along with Waste Water Heat Recovery (WWHR) if your space heating demand is actually 15-20kWh per day. If your heat demand is 15-20kW then DHW would be heated as a by-product of the space heating solution. 4) Electricity to be provided by Hydro/PV with an air cooled backup generator (Lister)
  15. The bottom of the footing should be at least 450emm deep to prevent frost heave. Bottom of Page 37 here https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/429060/BR_PDF_AD_A_2013.pdf