Green Building Bible, Fourth Edition |
![]() |
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment. PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book. |
Vanilla 1.0.3 is a product of Lussumo. More Information: Documentation, Community Support.
Posted By: WillInAberdeenThe green line (boiler temperature? can't quite read) …Sorry, the forum software squished my graph and doesn't let you click for a larger view. I tried posting it as SVG (1/10th the file size) in the hope that that would be scaleable but nope, it wasn't having it.
…the boiler is firing for maybe a quarter of the time at ~55degC when the heating is on,Yes, 30.6% from 14:00 to 23:00.
* There are actually several Texp(-t/k) terms going on for heat loss from air to fabric and from fabric to ambient and soil, some of those k will be much longer than the experiment, so the apparent steady state temperature will be warmer than ambient.Indeed, taking the outdoor temperature, particularly one a distance a way, is dubious for all sorts of reasons. However, when I was away for a few days in October 2018 the house [¹] settled around 13.3°C when Wick was showing 11°C. Again, in early November 2019 I was away for a few days and the house settled to 11.2°C when Wick was showing 9°C so I think I can reasonably assume Wick + 2.2°C for the steady state approached in a day or two.
** We can see Dyce airport, but our temperature is distinctly colder than theirs in winter, they are closer to the sea. The nearby village is in a frost hollow and is colder still.
Posted By: Ed DaviesSorry, the forum software squished my graph and doesn't let you click for a larger view. I tried posting it as SVG (1/10th the file size) in the hope that that would be scaleable but nope, it wasn't having it.
Posted By: RobLThe usual boiler control of air-temperature hysteresis may get very confused when heating a very large thermal mass - say floor screed. There is generally 1 dominant low low frequency timeconstant in a stable heating system…There's a chap on another forum who has a high-mass Passivhaus with a cooling time constant of the order of many days; it drops about 1°C per day when the heating is off even in the coldest weather. He heats it with wet UFH which is in turn heated via direct electric heating (Willis heaters) run off overnight tariff electricity.
Posted By: Ed DaviesThe control system is some JavaScript running under Node-RED which looks at the air temperature at the end of the day (and, perhaps, the amount the temperature has dropped during the day, I can't remember) and uses that to tweak the amount the heating is run the following night, increasing or decreasing the run-length by a smallish increment (half an hour?) so the overall “time constant†of the heating controls operates over a period of a week or more. That seems to work well in the UK climate.
Posted By: revorMy build is not PH but used the principles of one and last year the heating requirement was about that for a PH. I am on bottled gas thermal store and solar thermal. The gas not very green but make up for it elsewhere. Heating the house with electric hot water at night tariff appeals to me but using the immersion in the TS would not be enough
Posted By: revorSo how do you use it to heat a house UFH even a passive house. … so are these Willis heaters ganged in multiples?.Yes, IIRC he has two so that'd be 6 kW total output I think.
Posted By: WillInAberdeenI'm struggling too, to make sums work for retrofitting PV. PV is more cost effective in large scale solar farms, they can install in bulk with ideal orientation and slope and no scaffolding or shading. I sometimes wonder if domestic PV is going the same way as domestic wind turbines (anyone installed one of those recently?)
If it feels the right thing to do, people can use their PV kitty to buy a share of a solar farm company.
Posted By: revorSome 340sq M. Would have built smaller but were not allowed to knock down the original old stone building so built around it. Thought PH limit was 15 kw/sqM.
My logic was in gas, was given the amount of insulation I have, the thermal mass and solar gain gas would be the most cost effective option. We top up with a wood burner in the lounge in winter so consumption is a bit more Kwh than a PH but of the gas we did use, a lot was consumed commissioning the UFH and conditioning the screed before tiling. So this coming winter will be the first proper test. Hot water has been on solar thermal since end of February apart from 1 hr boiler use In March to top up the hot water. Bathing is via electric shower at moment as bathrooms not complete. Typically consume 6 to 7 kw per day for everything electric and a proposed solar pv and batteries should mean that grid usage will be much reduced, but this project is not very cost effective unless electricity prices rise to compensate but seems the right thing to do.
Posted By: revorTypically consume 6 to 7 kw per daykWh per day.
Posted By: WillInAberdeenAt current dividend rates it pays back straight away, rather than waiting 20years for rooftop PV to finish paying off its cost.Err, don't they both pay back as you go along, one as a dividend and one as reduced electricity bills/some sort of feed-in compensation? The difference is you can sell shares easier so your money isn't tied up in the same way.
Posted By: revorThe logic of batteries is that you can opt for a cheaper tariff by not using electric at peak times 4pm to 7pm. You use the battery that has been charged up during the day (hopefully). Then at night 1am to 4am you can top up your battery with off peak electric about 5p kwh.