SteamyTea

I have done every panel on my car, where I live is like Stapleford, it is the place that stolen cars get torched.

They should give then automatics/EVs.

Not really. All the 'solar houses' books I read 20 years ago when studying this area were all a bit flaky and 'it will be alright'. Geometry and physics is really all that is needed. And a spreadsheet.

Where is it all going, downwards?

High temperature UFH is not the best, higher losses to the ground, not so nice to walk on in bare feet.

? Slow flow rate or high flow temperature.

Yes, you are right. Anyone else got one as it would be interesting to know how good, or bad, they are.

Yes. The best correlation was with AT difference, rather than just OAT. Probably more true in places that have prolonged periods below 0°C. The problem with cramming in as much energy in as shorter time is that it requires a larger output heat source and room for the storage. This penalises smaller houses. For my climate, as I said in my analysis, ToU probably does not make much difference. Out of the 2152 hours I have had my heating on, only 676 hours were 4°C or less (31.4%). 325 hours and I did not need heating as it was over 9°C (my mean switch on temperature) that is 15% of the time. Of course, having storage heaters I don't have the luxury of stopping output fully, so the room temperature just rises a bit for a few hours. Most of those few hours, the excess heating is during the day, when it is most useful and does not cause excessive heating, My mean room temperature, when it is 4°C or below, it is 18.6°C, when it is 5°C and above, it is 20°C (which is my target temperature).

Welcome. What thickness Celotex did you fit and did you fit a vapour control layer (VCL) and what are you doing to heat the space?

Would Shelly relays suffice? If you initially want to keep the storage heaters (as you have them and you are doing other work), remote control relays should do the trick. You just reduce the hours they are running to limit the input/output. The only thing I would worry about is how well they deal with a power cut. Do they reconnect easily and reliably?

You can get them, our old mate @Jeremy Harris had one. Can't remember the make. Think it was only 2 kWp, which would me useful in my house, but for larger properties several may be needed.

Shall have a look when I get time/bored. Currently looking at the temperature and energy distributions.

With UFH it is really down to how much insulation you can get under it. I suspect that radiators are going to be your best option. But still add floor insulation if you can. If you can put up with a bit of noise, and the new room/s are not constantly used, then plinth/fan assisted radiators may be an option. They take up less space.

Should always be the first thing to do.

Worth reading as it has some notes and comments that explain a lot of it.

One way to increase the efficiency of an ASHP is to increase the size of the external heat exchanger (the radiator). Our planning system puts a limit of 0.6 m3 for a permitted development unit I think though.

That was lucky for everyone. I drive up the M5 every couple of weeks, there is a new development near Taunton, seems to be mainly detached houses. Talk about crammed in, and next to a motorway. And it seems to be on a flood plain. About 2% of the UKs land area is housing, about time we added another 1% to that. Many of the old arguments i.e. near work, transport links, schools and services are really outdated these days. Not as if householders only want to walk or travel by bicycle. My nearest town is 2.5 miles away. 40 minutes walk. Walking is not a practical solution. And the town is rubbish for shopping, but they have built a few thousand houses on the outskirts. The town has not improved, still no decent shops or restaurants.

Have you done any manual calculation that include the solar elevation and azimuth? https://www.sunearthtools.com/dp/tools/pos_sun.php

Really hard to say. A lot of the price is in the installation, i.e. scaffolding, split roof system. To give you an idea, 12 years ago, we fitted a 4 kWp system for £8k on an old, slate roofed place. Same week, we fitted a 3.5 kWp system for £5k on a bungalow. The hardware is not that expensive these days, a quick google bring up https://www.gov.uk/government/statistics/solar-pv-cost-data Seems the price, per kWp, is around £2100.

Water takes 4.2 times as much energy, per kilogram, to heat up than air. Air density is 1.25 kg/m3, water 1000 kg/m3. The Specific Heat Capacity of air is 1 kJ/kg.K, water is 4.2 kJ/kg.K. It is also heated to a higher temperature i.e. 50°C rather than 20°C, then there is the associated temperature differences. Mains water will enter the house at around 8°C this time of year, air around 5°C, though that can go lower i.e. -10°C. So the DHW will have a deltaT of 48K, the air in the house between 15K and 30K. If it is a sunny day, then there is some solar gain in the house, that contributes nothing to the domestic hot water. There is also the question of how much DHW you use, it is easy to use more than you think. The legionella cycle may also be permanently on, which makes the CoP of the heat pump effectively 1, rather than 3.5 or better. And then there is the time period. I would think it was a bit high over the last week or so, but over the year probably about right. Do you have a breakdown of the actual numbers?

As it is winter, the same questions are coming up, again, again. I decided to have a look at my temperatures to see what is happening at different times of the day, even though I don't have an ASHP, I thought it would be an interesting exercise anyway. I sample, and log, temperature data via my energy monitor (approximately every ten seconds) and via a RPI and a DS18B20 outside (every 600 seconds). For analysis purposes I take the mean temperature over each hour and use that. The standard error of the mean is smaller than the resolution of the DS18B20, so I am not worried too much about accuracy being way off. For this analysis I am using daily means taken from the hourly means, while not perfect, they are easily good enough to get a decent understanding of what is really happening. Over the last 11 months, the daily mean internal temperature has been 20.9°C (the secondary glazing fitted last year has raised my temperature about 1°C compared to previous years), the minimum has been 17°C (Jan 8 when I was away) and the maximum 25.4°C (was that heat wave, on June 24, I grew up in the tropics so don't find it excessive). This is shown, by the red line, in the chart below. The chart below shows the outside air temperature. Another way to look at this is temperature differences between the internal temperature and the external temperature, again it is the red line. You may have noticed that there are two other series on these charts. These show the temperatures between midnight (0 hour) up to 8 AM and 8 AM to midnight. Over the year the mean temperature difference has been 9.8°C, with a minimum difference of 1.1°C and a maximum difference of 19.6°C. The 0 hour up to 8 AM (near enough my E7 window) mean difference is 10.4°C, minimum of 4.5°C and maximum of 19.5°C. The non E7 times the mean temperature difference is 9.4°C, minimum of 2.4°C and maximum of 19.6°C. Now I do not know how much of a difference the coefficient of performance is affected by, at worse, a 2.1°C difference when the mean temperature is 9.4°C (E7 window), compared to 10.4°C (non E7 window). Now this year, I turned my heating off on the 1st April. Thought that would be a laugh. So below are the same charts adjusted to just my heating times. Taking just the numbers from the temperature differences, which are the important ones as they show how hard a heating system needs to work. The mean temperature difference is 13.4°C, minimum 10.2°C and maximum difference 19.6°C. During the E7 window, the mean difference is 13.5°C, minimum 9.2°C and maximum difference 19.5°C. Outside the E7 window, the mean difference is 13.4°C, minimum 9.5°C and maximum difference 19.6°C. With those differences I don't believe there is anything to worry about regarding the CoP of an ASHP. This analysis is, obviously, only for my location and my house heat loads, and I am not sure how well it would describe other locations and houses/households. One way to try and make a universal model is to look at the energy usage over the heating period (1,463 kWh) and adjust that to floor area and see how it compares. For my house (~50m2), for 90 days heating (and DHW/Cooking/Laundry/Lighting/etc) it works out at 0.325 kWh/m2, which is 13.5 W/m2. I am not sure of that is good or bad to be honest. It seems quit low to me for resistance heating. If the above is plotted, then the correlation between temperature difference and energy usage shows that for every 1°C increase (in difference), and extra 70W of power is needed. That is an extra 1.4 W/m2 or over the 90 days, 3 kWh/°C. Looking at the rest of the year, to 01/12/2023 (non heating), shows that for every extra 30 W, the temperature difference increases by 1°C. This is nonsense as it is the non heating season and the house is ventilated a lot more (windows open). What is actually happening is that the house is at a relatively stable temperature and the OAT is varying. What needs to be done here it the 36 W/°C (from the trend line function calculation) needs to be subtracted from the 70 W/°C trend line in the above chart. This leaves 34 W/°C needed to heat the house. As a power per square meter number that is 0.7 W/°C, which is very little. The important point there is that my house is thermally stable, even though it is a timber frame. It can 'store' enough thermal energy for short term OAT variations (just as well as Cornwall has extremely variable weather). I am not sure if any of the above is going to be of use to anyone else, but the main point is that for a few quid, basic temperature and energy monitoring can show a lot of useful information when deciding to change a heating system. There is enough information on here to build your own monitors and it amazes me the amount of people that don't monitor and spend a couple of hours analysing the data.

Have you ever looked into the costs of running it? A diesel CHP unit that also runs a small HP could be an interesting option. Diesel, at the pumps is about 15p/kWh at the moment.

Not a bad idea to post up. While you may never recover the capital cost, long term, you may be doing the right thing. Hard to tell where energy prices are going, I suspect that there will be a convergence between natural gas and electricity prices in the medium term. If you really are only using 5 kWh/day during the heating season, and say 2 of them are for showering, then you may be better off fitting PV and heating a water cylinder. That would get the gas cost down to zero for DHW. But when I think about it, if it is really 5 kWh/day in total, then a heat pump and PV is really the say to go. You would only be importing energy for a couple of months a year.

Do you know how many litres of kerosene you use each day? Know that, and the local weather, you can get a good idea what size you need. Is your hot water stored in a cylinder? What size oil burner do you currently have?