SteamyTea Posted August 22 Share Posted August 22 1 hour ago, Sparrowhawk said: the promise of gas burned heating the radiators not just going out the flue this winter Just about 10p and hour, when on full chat, going up the flue now. Link to comment Share on other sites More sharing options...
G and J Posted August 22 Author Share Posted August 22 Fab discussion. Very illuminating. But I still don’t know how to calculate total heat demand. 😞 Link to comment Share on other sites More sharing options...
JohnMo Posted August 22 Share Posted August 22 4 minutes ago, G and J said: Fab discussion. Very illuminating. But I still don’t know how to calculate total heat demand. 😞 Why not, you have all the tools. Your coldest temperature, and the heat loss at that temperature, you told us earlier 2.5kW @ -10. If that temperature over 24 hrs that's 2.5x24 and is 60kWh of heat required. Link to comment Share on other sites More sharing options...
G and J Posted August 22 Author Share Posted August 22 31 minutes ago, JohnMo said: Why not, you have all the tools. Your coldest temperature, and the heat loss at that temperature, you told us earlier 2.5kW @ -10. If that temperature over 24 hrs that's 2.5x24 and is 60kWh of heat required. I thought my heat load as measured at -10c and with 148m2 of floor is 2500/148=16.9W/m2 which is not so good compared to the PH target of less than 10W/m2. I was also hoping to be able to calculate what I think is called total heat demand which is measured in kWh per m2 per annum. Maybe I need to raid me piggy bank to buy a PHPP license to find out, but as it’s only of passing interest I was hoping there would be a way of deriving a credible estimate. Link to comment Share on other sites More sharing options...
MikeSharp01 Posted August 23 Share Posted August 23 7 hours ago, G and J said: I was also hoping to be able to calculate what I think is called total heat demand which is measured in kWh per m2 per annum. Maybe I need to raid me piggy bank to buy a PHPP license to find out, but as it’s only of passing interest I was hoping there would be a way of deriving a credible estimate. I found this relatively straightforward guide to the difference between heating demand and heating load. https://sustainableengineering.co.nz/qa-with-jason-explain-heating-load-vs-demand/ there is also a discussion here http://public.wookware.org/gbf/newforum/commentsbb9a.html?DiscussionID=13647 on GBF looking at the same issue. Essentially the two values don't have a direct relationship, and you need to know that the Passive House Planning Package (PHPP) & passive house concept generally, has this concept of treated floor area (TFA) which differs from the more traditional floor area - but not significantly for most designs, in ours TFA is 139, and actual is around 150, this is used in PHPP for calculating both Heat Load and Heat Demand but that is where the similarity between the two ends. Heating load is: the number of Watts you need to pour into the house across each square meter of the building's TFA to keep it at set point temperature at the coldest point of the year (it has no time dimension so its an instantaneous thing). In our case this is 8.268W/m2 according the our version of PHPP. Given we have 139m2 of TFA we have therefore need a heating plant capable of delivering: 139 x 8.268 = 1149W or 1.149kW (Which on reflection is bonkers small but that is what PHPP says it is) and as you cannot get a ASHP below 4kW that is the size we we will need. Actuallly in our case, assuming we could get the flow temperature above 42oC space heating via a heat battery in the MVHR would be enough in our case but we have UFH in the slab anyway and will use that. Heating demand is: the total amount of energy required to keep the house at the set point temperature across the whole year, based upon: the average outside air temperature (OAT) each day / week / month (monthly and annual for PHPP) the amount of gains & losses from things like Solar gains (N/S/E/W + Horizontal / Ground) and internal heat gains (people / things / operations - EG Washing up & running the fridge and your mega sound system!) Here is what that looks like for our build in our version of PHPP : So we have will use 1465 kWh/a which comes out at 10.512 kWh(m2a) using the monthly method on our 139m2 TFA given a coefficient of performance (COP) of 3 we will need to pour 488kWh of electricity into our ASHP to keep the house at set point (without cooling - cos PHPP says it won't be a problem, even if I think it will) at 30p a kWh that comes out at £146 pa. Does that clear up the differences for you? 4 1 Link to comment Share on other sites More sharing options...
G and J Posted August 23 Author Share Posted August 23 Very interesting and useful stuff @MikeSharp01, thank you. I’d grasped the principles of load vs demand but it’s details like TFA and perhaps a rough and ready calc method I was seeking to get a feel for how far short of passive we will end up being. ’Near passive’ is a term used on here but I am interested in quantifying how near. Maybe I’d be better of not knowing and staying deluded lol Link to comment Share on other sites More sharing options...
G and J Posted August 23 Author Share Posted August 23 I guess I want the formula behind the annual heating demand row in your spreadsheet. Link to comment Share on other sites More sharing options...
MikeSharp01 Posted August 23 Share Posted August 23 38 minutes ago, G and J said: I guess I want the formula behind the annual heating demand row in your spreadsheet. Can't tell you what that is because the sheet is locked and its on a hidden row, however by unpacking it (pasting the formulas from the hidden rows into another sheet) I can see it takes more factors into account, there are intermediate rows, than are in the table shown above - so I guess its complicated but it must just, in the end, be some function of the values shown. Link to comment Share on other sites More sharing options...
marshian Posted August 23 Share Posted August 23 10 hours ago, G and J said: Fab discussion. Very illuminating. But I still don’t know how to calculate total heat demand. 😞 Sorry for threadjack - it happens it's not meant to Sign up here https://heat-engineer.com/home Pay £12 and use their online tool - all you need to know is house dimensions and u values for the fabric of the building It will give you your heat loss at pre-determined external temp and annual energy demand 2 1 Link to comment Share on other sites More sharing options...
MikeSharp01 Posted August 23 Share Posted August 23 24 minutes ago, marshian said: up here https://heat-engineer.com/home Pay £12 and use their onlin Just ran the free version and it gets close to the PHPP outcome. Link to comment Share on other sites More sharing options...
G and J Posted August 23 Author Share Posted August 23 26 minutes ago, marshian said: Sorry for threadjack Don’t be. I’ve probably learnt more on here from diversions than direct responses - it’s the lifeblood of a forum methinks. 27 minutes ago, marshian said: Sign up here https://heat-engineer.com/home Pay £12 and use their online tool - all you need to know is house dimensions and u values for the fabric of the building It will give you your heat loss at pre-determined external temp and annual energy demand Fab. Do you happen to know if the results are comparable with PHPP? If not then I need to be careful how excited or depressed I get! Link to comment Share on other sites More sharing options...
G and J Posted August 23 Author Share Posted August 23 1 minute ago, MikeSharp01 said: Just ran the free version and it gets close to the PHPP outcome. As if by magic, the answer appears….. Link to comment Share on other sites More sharing options...
marshian Posted August 23 Share Posted August 23 23 minutes ago, G and J said: Don’t be. I’ve probably learnt more on here from diversions than direct responses - it’s the lifeblood of a forum methinks. Fab. Do you happen to know if the results are comparable with PHPP? If not then I need to be careful how excited or depressed I get! No idea but once I'd got the basics right and refined the ACH to a more sensible level it was pretty damn close in terms of heat loss - Annual usage was probably a little higher than actual but I did make a couple of errors - one room somehow I screwed up the wall heights and it's heat loss was huge compared to the adjacent room. My only advice is check and check again until you are 300% happy with everything before generating the final report. I didn't know there was a free version but I was very happy with the detail provided from the paid version - it produced a 25 page report broken down in sections covering lots of aspects. Link to comment Share on other sites More sharing options...
Nick Laslett Posted August 23 Share Posted August 23 The Heat Geek tool is also free to use. No idea what it is like. https://heatpunk.co.uk Link to comment Share on other sites More sharing options...
billt Posted August 23 Share Posted August 23 The heatpunk tool seems to be provided by Midsummer Wholesale. AFAIKS there's no relationship with Heat Geek. The Heatpunk tool was very good when I used it. They seem to have introduced a subscription version, I don't know if that has resulted in reduced utility in the free version. Link to comment Share on other sites More sharing options...
Alan Ambrose Posted August 24 Share Posted August 24 @G and J btw this is what PHPP figures out for climate for East Anglia - average monthly min/max air/ground temperature is: 4.8/17.3C & 9.4/16.9C Link to comment Share on other sites More sharing options...
G and J Posted August 24 Author Share Posted August 24 1 minute ago, Alan Ambrose said: @G and J btw this is what PHPP figures out for climate for East Anglia - average monthly min/max air/ground temperature is: 4.8/17.3C & 9.4/16.9C So the lowest external temperature is 4.8C so if I plug that into Jeremy’s spreadsheet my heat load is nicely less than 10W/m2 so I’m building a passive house after all. Good job. Where do I hang my certificate? 😉 Link to comment Share on other sites More sharing options...
Alan Ambrose Posted August 24 Share Posted August 24 Ummm, in the toilet with the others Link to comment Share on other sites More sharing options...
SteamyTea Posted August 24 Share Posted August 24 7 minutes ago, G and J said: lowest external temperature is 4.8C Seems high? Where did you get the data from? This is mean minimum temperature from the CET data set. The annual mean may well be around 6°C, but that includes all months, not just the winter. Just taking temperatures equal to and below 0°C, it happens 16% of the time, so 1400 hours a year. Link to comment Share on other sites More sharing options...
Alan Ambrose Posted August 24 Share Posted August 24 (edited) >>> Where did you get the data from? Well the black-box PHPP dataset for East Anglia. I believe this is daily temperature averaged over the month - not sure how many years or what period that's averaged over. I must admit, I've taken it as read, there's a bit more info here: https://www.passivhaustrust.org.uk/guidance_detail.php?gId=27 This is what it gives for Exeter btw: Ah, I think I get the problem - 6.3C is (apparently) the lowest monthly average temperature i.e. the average temperature of the coldest month (presumably averaged over an unknown number of years). That's good for an overall heat calc. It tells you how much heat you'll need on average for January, say. It isn't the average minimum temperature by month i.e. how low it generally gets in January. That gives you a better idea of, say, what your max heating load is and therefore boiler size. Here's some other random weather site's (weatherspark's) data for Hemsby, unknown source, model and averaging dates. It comes up with 5C rather than 6.3. Edited August 24 by Alan Ambrose Link to comment Share on other sites More sharing options...
Alan Ambrose Posted August 24 Share Posted August 24 @G and J FYI I see weatherspark has data for Woodbridge https://weatherspark.com/y/147921/Average-Weather-at-Woodbridge-Royal-Air-Force-Base-United-Kingdom-Year-Round No idea if the data is good or not. Link to comment Share on other sites More sharing options...
marshian Posted August 24 Share Posted August 24 44 minutes ago, Alan Ambrose said: @G and J FYI I see weatherspark has data for Woodbridge https://weatherspark.com/y/147921/Average-Weather-at-Woodbridge-Royal-Air-Force-Base-United-Kingdom-Year-Round No idea if the data is good or not. Stick your postcode in here https://www.degreedays.net/?gad_source=1&gclid=EAIaIQobChMIsoL13PmohAMVG7CDBx27swedEAAYASAAEgJ_bPD_BwE Will find the nearest weather station to you and if you want you can download the temps by hour for up to 36 months or HDD data as a value by day Excellent data resource for me as I have 3 weather stations within 10 miles of me The HDD data I find really useful to compare if improvements (Boiler/insulation etc) are working or not - my base line target is 3.7 kWh per HDD - if I use more than then I've left a door open or I've got my boiler set up wrong!!! Link to comment Share on other sites More sharing options...
JohnMo Posted August 24 Share Posted August 24 4 hours ago, G and J said: So the lowest external temperature is 4.8C so if I plug that into Jeremy’s spreadsheet my heat load is nicely less than 10W/m2 so I’m building a passive house after all. Good job. Where do I hang my certificate? 😉 So East Anglia doesn't get frosts or snow anymore - me thinks a bit of rubbish in and rubbish output. Computer says... Norwich had down to -5 in Dec and January last winter and sub zero every other winter month. Now add some common sense, average temperature is pretty meaningless for heating design, we also had an average of 4 degs for Dec, but a week where the temps dropped to -9 and barely got above -3, we had the same in Nov and January and March. You design for the likely lowest temp, not the temp that gives you the answer you want to hear. Link to comment Share on other sites More sharing options...
G and J Posted August 24 Author Share Posted August 24 Well, whatever I calculate my ASHP will be a bit too big and when I light the fire none of the calcs will even start to be relevant… And so from my point of view I’m not sure I care what figure I should use in Jeremy’s spreadsheet as long as it gives me an approximate answer to the ‘how close am I really’ to passive house standard. Maybe I shouldn’t worry. Maybe it’s better to travel in hope…. Link to comment Share on other sites More sharing options...
SteamyTea Posted August 24 Share Posted August 24 Here is some Lowestoft Met office Data. https://www.metoffice.gov.uk/pub/data/weather/uk/climate/stationdata/lowestoftdata.txt Lowestoft / Lowestoft Monckton Ave from Sept 2007 Location 654300E 294600N 25m amsl to July 2007 & from Sept 2007 653000E 293800N, Lat 52.483 Lon 1.727, 18m amsl Estimated data is marked with a * after the value. Missing data (more than 2 days missing in month) is marked by ---. Sunshine data taken from an automatic Kipp & Zonen sensor marked with a #, otherwise sunshine data taken from a Campbell Stokes recorder. Edited to remove the data - which ruined the scrolling - the data is available at the link above. Link to comment Share on other sites More sharing options...
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