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Ages ago I wrote a spreadsheet for doing what-if comparisons to see whether it was better to invest in more insulation in the walls, roof, floor, fit better windows and doors, or fit a better MVHR system. Others have found it useful and I've been reminded that I've not re-posted it over here, so here's the latest version. It should be self-explanatory, you fill in the cells with your wall, roof/ceiling and floor areas, add the areas of each door and window, put in the U values for each and, if you can, get hold of the met data from the met office for your area (the data in there is for West Wiltshire, right on the border with Dorset). This isn't a thorough modelling tool, it just looks at heat loss fairly accurately but doesn't take into account heat gains, although there is a crude way of doing that by drawing a line across the seasonal plot at the point where you don't use heating and you can very roughly assume that anything above that line will be heating. Please feel free to ask any questions, but bear in mind I wrote it back when I was designing our house and haven't used it for a couple of years. so I may be a bit rusty. Heat loss calculator - Master.xls [edited to add latest version of the spreadsheet]
So we had our first meeting with the designer last week and when I asked about the u-value for the walls he said he had calculated it to .22 with a 125mm thick full fill mineral wool, block inner and outer, render finish, plastered inner walls. I stated I wanted it to be lower and asked about the advantages of using a foil faced eps. He then said if we used a foil faced then we need to leave a gap i.e. not full full?? Is this right? For example, using the Concrete Block Association Website u-value calculator a medium density block inner, plaster finish, brick outer with 150mm foil faced full fill cavity gives a figure of .15 which is more like the figure I was hoping for. Just found his comment about the gap was a little strange as it contradicts all my research, but he has me thinking I've missed something now? I was just curios to anyone's thoughts on the point to see if they had heard similar?
Hello Members, this is my first post and I'd like to say that I really appreciate Jeremy's Heat Loss Calculator, which took one day to complete (yesterday). The compact one-page format with 'what-if' ability is very, very useful. Thank you Jeremy. These are my current considerations and I'd appreciate any comments and/or advice from members Regards, Hugh