AliG

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AliG last won the day on October 10 2018

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  1. I just meant don't compromise your house for the sake of two similar houses, decide yours first which you seem to have done. If you want 1200sq feet, and you have permission for 3000 in 1 house, I would be looking to build a second house at 1800sq feet to maximise your retirement pot. Start there and see what the planners say. If you cannot get permission for two houses, build one sell it and buy yourself something the size you want with the profits is probably your second choice. There is probably a point where planning for two becomes so difficult, time consuming and costly that this might be the better option. As for planning - We bought one house to knock down and spoke to the planning department about replacing it with two. They were quite against this as it "changed the spacial aspect of the area" If you ask me you can only see this from Google Maps, but they were pretty firm on this. We ended up building one house the same size as the two houses mooted previously and they had no issue at all. Is there some kind of character appraisal for the area that deals with this kind of matter? Or is there some kind of greenbelt development guidance that he council uses? Often you can refer to this if it helps your case. I think the argument that two houses will make a greenbelt site seem more built up than one is not unreasonable and you need a way around this. Building a big extension or a big rebuild is still not two houses. My suggestion/question is could the site be split leaving the current building in place. If it can I would apply to split the plot and build a second house. If you get permission for that you can then apply to demolish and rebuild the original building. If this is possible it might be an easier route.
  2. I totally see where you are coming from @Big Jimbo. Money can't buy you time with your family. That's why once I thought about it, I came down on simply decide what house you want for yourself. It seems like you can build whatever you want for your self and you may or may not be able to build another house too. Don't start from the position of wanting to build two similar houses as that may not be best for you. Best for you is living in a house that suits you, near to your family. So I would design that and if that allows for another house to be built then that's good, but I would make a decision for you and your family first and then see what possibilities you have after that.
  3. A lot depends on whether you want to do what is best for the community or best for yourself. As others have said, efficiency won't make much difference to planners. I doubt they really understand it anyway, you could probably build something quite standard and flummox them like volume builders. They can also definitely argue that two houses appear larger than one also, there will be more driveway space, patios etc as well as the larger amount of house. What you are suggesting is commendable, two modest houses are more sustainable than one large house. Although in truth the planners could free up land to build houses if they want to, so I don't know that it is your responsibility. Just to note the economics - Say houses in the area sell for £500 a square foot, could be up to £700 depending on the area from a quick Google. You already own the land. Assuming a generous build cost of £200 a square foot then you are going to make £300 per square built. Thus if you build a 3000 square foot house you will make £600,000 profit, it to fit two houses on you downsize them as suggested so that you build 2x 1250sq foot houses, you are going to only make £500,000. So your community spirit could cost you a lot of money. If your planning consultant can get 3000 square foot across two houses in then they will cost slightly more to build maybe than one house but the economics will be OK. You might also consider what kind of house is most appropriate for the area. If it is out on its own it may be that one large house is more what is expected and may even sell for a premium. It also depends on if you want to keep or sell a house, cashflow etc. Having thought about it, I think what you do is decide what house you want for yourself, a very personal decision. It may be that you want something small, it may be that once you start planning you end up at 2500sq feet. Once you have decided that see if you can build something else with what is left over out of 3000 square feet.
  4. This is one of the best designs that I have seen posted on here with very few issues. Most issues are interior layout which is not a planning issue. The only exterior/planning issue. I would consider swapping the WC and the hall cupboard around so the WC can be larger and have a small window to the side. It also looks like the stairs will encroach on the head height where it currently is. Seems a shame in such a nice spacious house to have a compromised WC, a room which many visitors will use over time. If you are planning a gas or solid fuel fire it is not going to be easy to get a flue/chimney out from the current position. The longer it is the more expensive it is and you could also need unsightly inspection hatches. The kitchen layout may not be finalised, but I wouldn't want the freezer in the utility room and I would consider putting the hob on the island so that if you are cooking you are looking into the room not at the wall. I would consider accessing the playroom off the hall as you already have a very large open space there, but it depends how you want to use the space and the age of your sons. Making it easier to close it off may be better as they get older. I think the master en suite could be better arranged, unless there is a view out of the window the bath might be better on one of the sides. At the moment the entrance between the sink and shower is a little tight at only around 70cm. But the interior arrangement does not affect planning. It seems a shame to have an ensuite reserved for occasional guests and not your own family, I would give one child the en suite and the other child has sole use of the bathroom, so everyone has their own space. Neither having an en suite might be fairer, but I would guess they would prefer having their own spaces.
  5. I think the trouble is that you are amortising various close to fixed costs across a very small building. Bringing in the services will cost the same whether it is 50 or 100square metres. A consumer unit and boiler will cost the same. A kitchen and bathroom may be slightly smaller but will cost the same. These will really boost the cost per sq metre. One thing to consider is do you need gas in the annex, work with gas piping, boilers etc is all regulated and extremely expensive. Why not just put in electric radiators and an electric water heater. I would guess that this will save £3000ish. There are too many sockets and LED lights, each will cost around £60. 50sq metres is basically a 1 bedroom apartment and does not need so many fittings. Can you make it more open plan, this will save on stud work, woodwork fittings etc.
  6. It may be that the builder changing the “curve” was increasing the flow temperature. Hwating on all day wouldn’t affect the temperature but it does have to run for a while to get up to temperature. I’d also get checking for air leaks. I keep finding new little ones in my place. It’s also worth monitoring electricity usage more closely for a little while. I would expect you to use about 20% more when the temperature is freezing than when it is 7C. Checking it daily for a while will give you a better idea of what is driving consumption.
  7. Thanks @JSHarris. That is pretty consistent with my guesstimates. I was looking for about around 37 W/m Sq to get 100kWh per day output running for 17 hours a day. This would be the maximum output of the system and then if less is needed the thermostats should kick in and switch it off. This is confirmed by your spreadsheet as requiring a flow temperature just below 25C. I reckon that would keep the house at 21C down to about -5C outside. To be more accurate I would need the area of floor with UFH in it, I only know that the total floor area is 230sq m and that downstairs is larger than upstairs so I have taken a guess at 160 sq metres of UFH. Using the table I attached, to get 37W/m would need 39C flow with 200mm pipe spacing and 37C flow with 100mm spacing, roughly 38C with 150mm spacing. I don't know the spacing figure. The key figure is 100kWh per day of maximum output. You can then work back from the length of time the heating is switched on, UFH heated area and pipe spacing to get the flow temperature. I have ignored the issue of no heating upstairs. It may be that you require putting out more heating than the calculations suggest to heat upstairs also. TBH with your insulation levels I suspect you will need extra heating upstairs sometimes, but let's see what happens when you have enough heat downstairs to heat the whole house. I have one unheated room that is open to a heated room below and it tends to sit at around 19c with the UFH running hard in the lower room. Partly this is due to it being almost 3x the size of the heated area in the room below. @Jude1234 mentioned that it seemed better recently. At 7C outside the required heat output is closer to 60kWh per day which is 22W/m of output. 32W flow is going to give 18-21w/m of output. Along with incidental gains the system could keep the house warm at 7C outside temperature. This actually explains why turning the heating up should not use much more electricity. You had enough heat output for temperatures down to about 7C, but it would not be enough below this. You would only use more electricity if the outside temperature falls below this level. I had just left our heating running until the last few weeks when the temperature finally got below 0. Now I have been fine tuning it as the high temperatures we had were not putting enough pressure on the system to know how well it was running. I had one manifold set at 32C, somewhat lower than the others. It would heat the room but was taking 6 hours to raise the temperature 1C, not helped by the wooden floor in the room. We have a gas boiler and don't run the heating all the time so I turned up the flow temperature. to the high 30s. I have also found a draught into the room that has to be fixed. You can fine tune these numbers with the correct inputs. Basically then turn the flow temperature up to the calculated temperature and see what happens. You can fine tune it up or down a little from there. But don't turn it down until you have a cold snap and know it can cope. You will use a little more electricity as the COP will be worse at a higher flow temperature, but I think the first thing is to make sure you can be comfortable in your house. Then you can work on fixing air leaks to get you heating use down. I suspect that you could also help by turning the MVHR down to the minimum level as you have lots of air coming in anyway. Again you would have to see how that works out. If you could halve your air leakage you could turn the flow temperature back down by around 4C. Someone could maybe help me with this one. The ACH from a blower test is much higher than real life air changes per hour. I am guessing that from your test plus running the MVHR you are maybe sitting at 2 changes per hour and could get this down to one if you fix all the obvious leaks. My guess is that your SAP calculation was done using a figure of one and the UFH was set up based on this too low figure.
  8. I found this table that gives the heat output depending on your flow temperature and the distance between the UFH pipes, your flow temperature is lower than the lowest quoted figure. https://www.tradingdepot.co.uk/info/plumbing/polypipe/underfloor-heating-heat-output-tables/ The formula to calculate heat output is here, it depends on the temperature differential between the floor and the room. http://heating.danfoss.com/pcmpdf/handbook_planning_vgctc202.pdf At a rough guess you are putting out only 20-25W/Sq Metre. Assuming that you have 160 square metres of heated floor, your heat output is between 3 and 4 kW per hour. With your heating on 9 hours per day, you would get around 30-35 kWh of output. Admittedly you should also be using a lot less electricity than you are using if this is the case also. This is not enough to heat your house according to the SAP calculation and according to figures I input into the heat loss calculator. The SAP calculation is 12000kWh per year, I suspect it may be 14000kWh with higher air leakage. Assuming 6 months of heating, that is around 70kWh a day and probably up to 100kWh when it is cold outside. You would need to run the heating 24 hours a day to get close to this output. You also need to be able to overcome the heat loss at any one time which is likely much higher than your current output. My guess is that running the heating from 430am to 930pm each day with a flow temperature of around 38C would be needed to heat your house when it is below 0, that would put out up to around 100kWh a day. If it was warner outside the thermostats would kick in and you would use less electricity. I am making an enormous number of assumptions here on floor coverings, area of UFH, pipe spacing etc. Turning the temperature down to 16C is too low as a set back number, 21C during the day and 18C at night might be better. The weird thing is that running the heating this much should use no more electricity than you are using at the moment. There could be some weird inefficiency coming in that I am missing or it is something else that is affecting your consumption. Your insulation figures aren't that great nowadays, particularly the downstairs and window figures. Still though it is probably the air leakage that you can reduce. Halving the air leakage would cut your electricity usage by around 20% I would guess.
  9. You are right Paul. I pointed out that it may be better depending on the COP at different temperatures to run the ASHP longer with a lower flow temperature. ASHP works best in a well insulated house where the required flow temperature is low and you can run it for long periods at a high COP. If we knew the flow temperature here it would help. The interaction of the COP at different output temperatures would tell you what the optimum way to run the system is. This is why it probably also works best with UFH which reacts much more slowly than radiators. It is not clear if the system has been set up with this in mind here or set up like someone would set up a boiler and radiators to come on just before needed. It might be that in fact the ASHP is being asked to provide a high flow temperature for short periods which would not be the best thing to do at all. The problem at the moment is it seems that the heat losses are higher than the output of the ASHP. You cannot optimise it at the moment. We don't know if it is already running at a high flow temperature or running at a low one that can be raised and we do not know if it actually can heat the house when it is below zero outside. @Jude1234 if you have any information on this it would be useful. Normally there is a gauge on the manifold that shows the flow temperature. How have you had the heating set?
  10. In my old place the builder added an extra 200mm to a wall in the garage for pipework. I had to consistently park within 0 and 100mm of the wall. It was surprisingly easy judging it by the height of the lights on the wall, although sometimes when I got out I had misjusdged it and had to get back in and inch forward.
  11. Good point @Ferdinand, I hadn't noticed the length. Might be worth putting the door to one side as you won't be able to store anything at the back and get around the car once it is in the garage. I hope 5m is the internal length, again a sectional door can be closer to the external face which helps, you could build a sneaky frame that juts out for some extra space.
  12. I think 2.5m is the minimum sensible size. You don't have to go to a range Rover to be enormously wide, a Ford Mondeo for example is 2058mm including mirrors. As you start to feel nervous about putting the car in you stop using the space. If you can go wider I would, 2.6-2.8m would be good. Also it depends on the kind of door, up and over door frames cut into the usable width, sectional do not. The opening on an up and over door is roughly 100mm narrower than the door size.
  13. I went back and checked my calculations from earlier and noticed that I had multiplied by the COP twice. Errors like that creep in when I sneak in an answer whilst working. OK - 1300kWh per month. You have to remember that you don't have any gas. I don't know the exact circumstances in your house so will be guessing a little. I am also using a COP of 3.5 for the ASHP. According to the manufacturers specs, the COP is anywhere between 3 at 2C outside heating water to 55C and 4.7 at 7C outside heating water to 55C. If you only heat water to 35C the COP rises, but I do not know where it is set. Spec below http://www.mastertherm.eu/wp-content/uploads/2019/01/BAxxI.pdf Electricity for lights, cooking etc. Assuming that the average family uses around £500 of electricity a year for these, that is around 300kWh per month(at 14p per kWh). Maybe slightly more in the winter. Adding in UFH pumps and MVHR, this may rise to 400kWh per month. Hot water, apparently the average household uses about 120l per day. Assuming a 50C temperature increase, this would require 7kWh per day. Allowing for heat losses, let's call it 15kWh per day, allowing for a COP of 3.5, this is 130kWh per month at the heat pump. So very roughly 500kWh of your demand is for general electricity and hot water at a COP of 3.5. Thus you are using 800kWh at the ASHP to heat the house. At a COP of 3.5 this is around 2800kWh of heat demand. As I mentioned earlier, I use around 250kWh of gas a day for heating excluding hot water. You are using around 90kWh per day. My house is well but not super insulated and I am still working on closing up all the leaks. You are using around 1.6x as much energy per square metre for heating. Not great but not disastrous. However my house is not cold when I use this much energy. There are really two problems - Are you using too much energy and why is it cold and they are interlinked. I have looked at the heat pump specs, but maybe someone who knows them better could look. 9kW is the output, it seems it would use around 3.5kW of electricity at this level, which is not the same as the COP, but I may be misreading the spec. You are using around 27kWh a day for heating, this suggests that the ASHP is running around 7-8 hours a day for heating. It should be able to put out more than enough energy to heat your house in almost any circumstance, although this would mean running it longer and using more energy. You mentioned earlier that you are home 6.30-8 and 5-10.30. Is this when you are running the heating/ASHP? UFH has slow heat up times. Depending on your flow temperature, thickness of your slab etc you might need the heating to come on 1-3 hours before you want it to be warm. Some UFH thermostats like Heatmiser try to allow for this, but otherwise you have to figure it out yourself. I would expect you to have to set the heating to be on at 5am to be warm at 630am and then again at 3.30ish in the afternoon. Does the house feel cold when you come home, but warm up by 7pm? The advice to run the heating 24hours a day is not quite right, normally what you do is set it back 2 or 3 degrees when not using it and set the heating times earlier than when you actually want it to be warm. Roughly in your case I would set it to 21C from 5-7am and again from 3.30-9pm then 18C the rest of the time. Indeed the COP of your heat pump is much better when the water is less hot, so it may be better to run the heating for longer periods with a lower flow temperature. But this won't work at the moment as your heat losses are too high. I suspect that your pump is not running long enough and driving a high enough flow temperature in the UFH to warm up your house. You can certainly make it warmer and warmer at the right times, but this might drive your electricity bill up by another third. And so where using too much energy and it being cold become interlinked is the air leakage or insulation problems. 9kW should be more than enough energy to heat your house and keep it cosy. But if you have a lot of draughts then there will be periods where the house leaks heat faster than you can heat it up. In extremis the house could lose heat faster than you can actually get it out of the slab and it will be cold.. You can compensate by running the UFH longer and with a higher flow temperature but will use more electricity to do so. You need to reduce the house's heating requirements to what is expected. My guess is that if you fix any obvious leaks and insulation problems you can keep the house warm using the current amount of electricity, but maybe not use less electricity. You are going to use around 4-5000 kWh per year for heating, this is the peak now and 6000 kWh for everything else. Around £1500 a year for all energy use wouldn't be a bad figure if it was actually comfortable in your house.
  14. Was the blower test done with the MVHR running? There was another thread about that. At 5.25 you could probably just turn the MVHR off and would be ventilated by draughts. Do you have a fire or stove that is not sealed with a twin wall flue? That would be another source of a leak. Another thing I found in old houses was take off the plinths on the kitchen and look for holes, also under the sink. As no one can see it they just hack holes in the walls for pipes and cables and don't fill them in.
  15. AliG

    The air above your plot belongs to...

    Don't tell my wife about ostrich feather lined drawers! Joking aside, I don't like to spend too much money on furniture, the vast vats majority of my spending is in the fabric of the building. These super expensive developments are interesting. I remember looking at the numbers when the Candy Brothers built One Hyde Park in London which was similarly expensive. My guess was that around half the cost of these super high end properties is to fit them out to your own specification on the interior. Then every time they are sold the new buyer spends another fortune replacing the decor. Hence the resale value is often way below the new price. Decor is a very fast depreciating asset, I am always surprised by the premium people will pay for a nicely decorated house. Apparently I own the air above my house and the land down to the earth's core, but I cannot stop anyone using the air and don't own the mineral rights which are separate and largely belong to the government. So I own these things, but not really. https://www.balfour-manson.co.uk/news-plus-events/comments/2013/12/private-airspace-is-your-garden-privacy-under-threat/