SteamyTea Posted December 8, 2020 Share Posted December 8, 2020 @PeterStarck Exactly, and as temperature differences increases, the energy usage goes up exponentially, confusing things even more. One of the reasons that just my space heating load is tiny. Take today, the sun is flooding in, washing on the line and I am sanding woodwork. All very comfortable. But if I had to tumble the washing, and was sitting down in the gloom, my energy usage would go up. 1 Link to comment Share on other sites More sharing options...
Ferdinand Posted December 8, 2020 Share Posted December 8, 2020 15 hours ago, SteamyTea said: I do. Weigh the amount of timber you put in, and every 15 minutes, note the rise in air temperature. Work out the mass of air in the room, then calculate. And while you are at it, count the number of 'rings' on each log, work out the mean, and compare the number of years it takes to grow, compared to the number of minutes it takes to burn. Alernatively, do it like an O level student - put it in a double walled calorimeter and measure the temperature change in the water. Link to comment Share on other sites More sharing options...
Thedreamer Posted December 8, 2020 Share Posted December 8, 2020 3 hours ago, PeterStarck said: Do these calculations actually mean much when interior and exterior temperatures aren't known nor is exposure of the building known. Wouldn't the number of occupants affect the energy use. I would have thought the number of variables is too high to make these figures useful. I would use a lot more energy heating my house if I lived up near @ProDave for example. When I ran PHPP, designing my house, I found heating it to 20 degrees would use 12kWh/m2/a and heating it to 23 degrees would use 20kWh/m2/a. There's also no mention of whether all a house is heated to the same temperature all the time, or whether when at work the heating is off. Not really knocking it but take it all with a pinch of salt. I agree with this, to many variables. Similar to cost per meter squared threads. All self builds are unique. I don't suppose anybody would compare a self builder in South East of UK with one in the South of France. Different conditions, different approaches. Your point about temperature is interesting, I would imagine all newish self build on here should be able to get to between 18-19 degrees without any heating. 1 Link to comment Share on other sites More sharing options...
Gone West Posted December 8, 2020 Share Posted December 8, 2020 2 hours ago, Thedreamer said: Your point about temperature is interesting, I would imagine all newish self build on here should be able to get to between 18-19 degrees without any heating. I would think the number of occupants and length of occupancy would have an effect on that. Also the residual heat from appliances, computers etc may be enough with the occupants to maintain lower temperatures. I've found windwash and therefore microclimate to be a significant factor as well. Houses in large builtup areas would benefit from shielding in winter but lose out in summer. Link to comment Share on other sites More sharing options...
joe90 Posted December 8, 2020 Share Posted December 8, 2020 6 hours ago, PeterStarck said: Do these calculations actually mean much well our Jeremy did all his calculations (not like me) and because of his micro climate he found after that he needs more cooling than heating which was a surprise. I did no calculations, loads of insulation, guessed at the heat load (pinched Jeremy’s ) and all I know is ours is cheap to run and comfortable all year. P.S. I was told that our conservatory, facing South would overheat the house and it has not, it’s a great space which we use a lot, most of the year. Link to comment Share on other sites More sharing options...
Ferdinand Posted December 8, 2020 Share Posted December 8, 2020 3 hours ago, Thedreamer said: I agree with this, to many variables. Similar to cost per meter squared threads. All self builds are unique. I don't suppose anybody would compare a self builder in South East of UK with one in the South of France. Different conditions, different approaches. Your point about temperature is interesting, I would imagine all newish self build on here should be able to get to between 18-19 degrees without any heating. The one in the South of France is probably more relaxed... 1 Link to comment Share on other sites More sharing options...
Oz07 Posted December 8, 2020 Author Share Posted December 8, 2020 There are a lot of variables but it's interesting to give a picture of how good peoples houses perform. I'd be pretty chuffed if I was getting some of the low figures quoted here. Also it's taught me something doesn't seem quite right with my place be interesting to alter this ventilation and teaches me to try something new next time. Graphite beads would be my weapon of choice going on declans experience. 1 Link to comment Share on other sites More sharing options...
Declan52 Posted December 8, 2020 Share Posted December 8, 2020 12 minutes ago, Oz07 said: There are a lot of variables but it's interesting to give a picture of how good peoples houses perform. I'd be pretty chuffed if I was getting some of the low figures quoted here. Also it's taught me something doesn't seem quite right with my place be interesting to alter this ventilation and teaches me to try something new next time. Graphite beads would be my weapon of choice going on declans experience. It's not just one thing that has the desired effect. You have to pay attention to every single detail. It doesn't really matter if it's timber frame, ICF or trad if it ain't right it won't work they way you want it to. Going round sealing every conduit, socket, switch, light fitting, taping the edges of doors and windows etc all just keep a tiny bit of heat in. Add all these steps up though and they make the difference. 3 Link to comment Share on other sites More sharing options...
Oz07 Posted December 8, 2020 Author Share Posted December 8, 2020 That almost offends me! I got an air test of just over one so think I did pretty well in terms of detailing a traditional build! I've got 200mm eps ground bearing slab, which I was hoping would be better than previous 150mm pir over b&b due to Warmer ground temp 150mm cavity filled with dritherm 34 350mm earthwool in loft All parge coated with airtight membrane linking down to parge coat and suspended ceiling void for services. Anyway it's all knowledge I'll know what to focus on next time! 1 Link to comment Share on other sites More sharing options...
MikeGrahamT21 Posted December 8, 2020 Share Posted December 8, 2020 I plan to have an air test one day when I’ve finished keep building extensions, I dread to think the result, but I try as best as I can to seal everything up and use membranes and tapes where necessary, I just keep thinking as long as my annual consumption of gas keeps dropping, whilst also adding more floor area, that’s got to be a good thing! Having completed around 40% of the total floor area this year I can certainly tell a massive difference, but know I still have a long way to go yet. Keeps me busy ? 2 Link to comment Share on other sites More sharing options...
MikeGrahamT21 Posted December 9, 2020 Share Posted December 9, 2020 10 hours ago, MikeGrahamT21 said: I plan to have an air test one day when I’ve finished keep building extensions, I dread to think the result, but I try as best as I can to seal everything up and use membranes and tapes where necessary, I just keep thinking as long as my annual consumption of gas keeps dropping, whilst also adding more floor area, that’s got to be a good thing! Having completed around 40% of the total floor area this year I can certainly tell a massive difference, but know I still have a long way to go yet. Keeps me busy ? Well it seems to be working so far: (for those who don't show signatures) Gas (CH only) - 5679kWh (December 2020) Gas (DHW only) - approx 840kWh Electric - 1420kWh (November 2020) Solar - 16 Panel, 4kWp - 3355kWh (2019) Water - 38m3/a or 104L/person/day Heated Floor Area - 62m2 Space Heating Requirement - Approx 92kWh/m2/a In the last 2 months my EAC has dropped nearly 1000kWh, now approaching 90kWh/m2/a Link to comment Share on other sites More sharing options...
john0wingnut Posted January 7, 2021 Share Posted January 7, 2021 Very interesting thread. We have a 1950s bungalow that was heavily renovated / extended in 2017. Walls are twin leaf block with 110mm full fill cavity. Upvc double glazing and 300mm fibre insulation in the loft. floor is beam and block, 100mm PIR then UFH 65mm slab. We have ASHP as no gas, Solar thermal, 7kw PV and a Powerwall. No consideration was given to airtightness etc and having got interested in sorting the place out further and frequenting the forum, there are many loose ends to tie up in terms of making the building more airtight. eg current windows are poorly installed, I’ve found a cavity without a closer in it and we have sun tunnels without there sealing closures currently as they were taken off to paint and then we’re never found, and those things haemorrhage heat to the roof, as when it’s frosty the section of roof with these is always clear, with the rest covered in frost. Have also taken a leaf out of @AliG book and going round finding all sorts of holes and drafts around stack pipes and water pipes etc. Needless to say I will be sorting all this out. Anyway back to energy usage: Tesla Powerwall is telling me we have used 13,168kwh in 2020. Of this approx 3000kwh relates to our two electric cars for the year at about 60kwh per week. Background electricity in the house is about 0.3kwh which is 2500kwh per year and I would estimate another 1000kwh for cooking per year as we have induction hob and electric ovens used at least twice a day, along with the microwave etc So that leaves 6668kwh for DHW and heating. 180m2 floor space = 37kwh/m2. I’ll round it up to 40 :). We generated 6845kwh via PV and imported 9084kwh from the grid, so we have utilised about 4100kwh of solar and exported the rest. Once out first floor extension gets done, and I replace all windows and doors with Aluclad 3G, we should in theory see that figure drop further. I know it’s a crude calculation but I’m quite please with that. 1 Link to comment Share on other sites More sharing options...
SteamyTea Posted January 7, 2021 Share Posted January 7, 2021 15 minutes ago, john0wingnut said: Background electricity in the house is about 0.3kwh which is 2500kwh per year ? Link to comment Share on other sites More sharing options...
john0wingnut Posted January 7, 2021 Share Posted January 7, 2021 58 minutes ago, SteamyTea said: ? All the other stuff that’s generally on. You get nice graphs out of the Tesla App, and other than when the ASHP is on on cooking appliances which cause large spikes, it hovers between 200-300w Link to comment Share on other sites More sharing options...
SteamyTea Posted January 8, 2021 Share Posted January 8, 2021 8 hours ago, john0wingnut said: All the other stuff that’s generally on. So that will be ~0.3 kW (not kwh, or Kwh, kWH, kW/h) Link to comment Share on other sites More sharing options...
john0wingnut Posted January 8, 2021 Share Posted January 8, 2021 3 hours ago, SteamyTea said: So that will be ~0.3 kW (not kwh, or Kwh, kWH, kW/h) Very true. 0.3Kw. It was late at night Link to comment Share on other sites More sharing options...
SteamyTea Posted January 8, 2021 Share Posted January 8, 2021 18 minutes ago, john0wingnut said: 0.3Kw or 0.3 kW even Link to comment Share on other sites More sharing options...
john0wingnut Posted January 8, 2021 Share Posted January 8, 2021 4 hours ago, SteamyTea said: or 0.3 kW even Its Friday ? Link to comment Share on other sites More sharing options...
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