TerryE

@worldwidewebs, Yup Heavy duty polythene is only 250 micron.

We have a stone skin and our Internorm doors and windows close the gap between the skin and the frame by sitting some 45mm forward of the timber frame's Panelvent outer skin. We had the dual challenges of how to maintain a slip layer between the outer stone reveals and the frames, and how to protect the frames over the couple of months when the frame was being erected. Our solution was simple and proved to work brilliantly. We simply covered all of the doors and windows with heavy duty polythene and stabled this back to the boxing frames which help the doors and windows at this 45mm stand-off. In the case of the front door, we then cut a hole in this about 100mm smaller on the three sides and wrapped the polythene around and into the frame; we then covered the front door with polythene. (Ditto the back door so we could use it when needed). The outer surface of the polythene got absolutely filthy. When the stonework was all done, I carefully cut around each frame where the stone pointing met the frame and removed the sheet leaving a clean and unmarked window/door and a polythene slip layer between each frame and the mortar.

I know its not an immediate solution, but you can't beat a nice spiny rose, or other bushing plants such as Pyracantha. Nature is nature.

+1 on Declan's suggestion. We also made up a double ramp covered in an old piece of carpet and 2 U sections lined with Hassian as uprights and an L section insert for the door head. If we had workers carrying stuff in and out, then these were used to cover the frame and act as protection against anything banging into our Internorm frame. Also have a lockable shed or container onsite for storage, and set a policy that the house isn't to be used as storeroom for outside tools and equipment. So only stuff that needs to go in and out goes in and out.

@gravelid, I have a passive design house that has been pressure tested and certified to 0.6 ACH equivalent, and to be honest my statements are coloured by that. With this type of house, if you look at the temperature profile through the external walls (see my modelling Modelling Thermal Lag post), then the walls are within ½°C of the room ambient. So the room, the slab, the walls are all within a few degree of each other and there are no material drafts other than the MVHR. In a more conventional house built with minimum compliance to the 2013 BRegs then heat losses though the walls might 5-10× greater, permeability maybe 20-50× greater, etc. and lots of temperature gradients. Here you ware going to have a lot more air circulation and convection and in this case I would agree with SteamyTea's comment that convection, etc. will be dominant.

Nick, the SB equation is physics. OK, you need to plug in the numbers and factors for surface reflectivity, roughness, etc, but we had a natural slate floor which will give as close to the theoretical figure of 5.7 W/m²K as you can get by plugging these in. The 7 W/m²K overall figure for output of a surface with no convection is quoted in multiple sources including BRE, so the difference, which amounts to 22%, is the conductive element. I would therefore challenge this statement and suggest that the opposite is the true: radiation swamps conduction -- at least in this scenario. However there are scenarios where this dominance can flip, as in the case of sunlight falling onto a floor which I mentioned earlier, where we can easily get an area of a few m² which is tens of degrees hotter than the room air and this will set up a strong convective transfer of heat into the room. Still give me another year and I will have hard data by instrumenting my house which will confirm this or refute it. Jeff's comment supports my analysis, I think.

@SteamyTea, Nick, thanks for the response. I miss having JSH around for this type of dialogue but you will keep me on track Yes for a point radiant source, but no for a semi infinite one. See Olbers' paradox. Consider a six sided box (sometimes called a room) with 5 sides at 20°C and one side at 23°C (the floor). Consider a small area on the floor. It is radiating according to Stefan–Boltzmann law and is receiving heat from the walls and ceiling ditto. There is an inverse r² effect between the emiting and receiving surfaces, and well as the incident angle, but this needs to be integrated over the entire floor to calculate the actual radiant energy and v.v for transfer of radiant energy from the other surfaces to the floor So the major heat transfer is actually directly from the floor to the walls and ceiling. If the room was a vacuum then the heat transfer would be entirely directly from the slab to the other surfaces, and mainly to the ceiling which faces it. The ceiling and internal walls would tend to respond quicker than external walls because of their lower thermal capacity, but once there was a small imbalance start would also start to flow from the other internal walls to the external walls, and the bulk of the heat would soon be being transferred to the external walls and feed the external heat loss through the external walls to maintain the overall house equilibrium. Now add back the air. Temperature differences of a few °C are not enough to initiate convective flow so any transfer of heat to the room air will by conduction. As I said in my first comment, this is relatively modest. The BRE fiddle factors indicate that this will be maybe 20% of the radiant component for small temperature differences. So any net rise in room air temperature will be nothing like 3°C. Sun shining in through a window and onto the floor is a different matter as this will create a localised hot area that will set up a strong convective circulation in the room and rapidly warm the room air.

We haven't used a letter box (in our front door) for over ten years. What we have is a post box next to the door. People lift the lid and can drop letters and small parcels in. Works a treat. I will be doing the same in the new house, the only tweak I'd make would be to have a small flag rocker on the lid which tips upright if the lid is opened. That way we can see if the box has been opened without opening the front door.

Here are the original eBuild comments: Crofter, 09 Mar 2015 12:04 AM That is so brilliantly simple that I may have to copy it! ProDave, 09 Mar 2015 09:44 AM I used a laser line level for mine. Best done on a dull day or at dusk. It can be surprising just how much what looks like a fairly flat piece of land actually slopes by. TerryE, 09 Mar 2015 10:36 AM I have an indoor laser level but it would be a bit of a dog using it outside: I would need to do it late dusk to get any range and doing this on a 5m survey grid is a lot of points. I have a decent professional Bosch laser measure which I use for distance work, ridge heights, etc. Using a laser level is also a two man job, really. At least with the water level technique you can easily do it on your own if you don't mind a lot of walking to-and-fro. In my case, I had a strong preference for the one-man option, because this sort of job is a tedious "grit your teeth and get on with it" one, and doing the whole site took a long time. Taking twice as long on my own involved a lot less ear ache than enlisting my helper who doesn't suffer this sort of chore gladly Crofter, 09 Mar 2015 12:38 PM That sounds rather familiar! I do have a dumpy level and staff, which we have used for the basic initial site survey, but I'm hard pressed to get SWMBO to cooperate much beyond that. So off to make up a water level... wmacleod, 09 Mar 2015 03:55 PM The water level is ideal for transferring levels round corners, through doorways etc. The laser level everywhere else for sheer speed and ease of use - although a receiver and a staff are essential for getting heights transferred quickly and easily. No messing around waiting for dusk, struggling to see lines. Use it during concrete found pours, slab pours, wall heads etc. recoveringacademic, 09 Mar 2015 05:00 PM My dad taught me exactly the same skill when I was about 10 (1963). He was also an ex-RE (RSM). I suspect he just needed a theodolite carrier, and knew that I needed a bit of push to see the relevance of maths. He made me do masses of level calculations, all by steam, and gradually allowed me to use logarithms. Since then, and to this day, I've never ever used a set of log tables again. The most fun, though, was sorting out levels the way the Egyptians did. And since he was the bridging engineer for the M5 (Strensham to Bromsgrove) there were miles and miles of spare hose lying around. Imagine the fun of picking some random spot on the empty motorway carriageway and seeing if I could work out how much higher/lower another equally random spot was. Wish I had thought of using an expansion/ inspection chamber and a ruler to get a really accurate measure. For our build, it's the link between GPS, Google Earth Projections and CAD design drawings which made me decide that the topographical survey was worth it (£540 inc VAT). And avoiding the horrors that basic errors on my part would cause. Density gradients for example - hadn't heard of that in this context until I read your blog entry. How did you establish a datum from which other professionals can measure? oz07, 09 Mar 2015 08:27 PM Self levelling Optical pentax here. No batteries to run out, no working in the dark, no need to understand science and water! slidersx200, 09 Mar 2015 10:56 PM Our topographical survey was about £250 I think and luckily, not only did the guy record the whole field we have built in, which saved the cost of a second survey when we moved the site to the other end, but he also surveyed the land we have at the other side of the road in case there is ever an opportunity for development there too in the future. The Roads Service could make the existing survey obsolete though if the planned improvement scheme gets a green light as they will be changing levels and moving boundaries along the road. TerryE, 10 Mar 2015 05:44 PM Thanks for the feedback guys. I agree that my method is a bit of a hack but it had three advantages: I could to it myself on my own It cost nothing It was accurate to a few mm. The alternatives used by others were: To commission a topo survey £250-530 (probably nearer the lower end since my plot is smaller than Ian's). To use a dumpy level @£200 ish or £65 to hire (or equivalent). I think that I'll live with my solution, but to Ian's point about a datum from which other professionals can measure, well, I can paint an X on my patio outside the kitchen door on my existing farmhouse. It's set in mortar on 10cm of compacted sub base; it's been there for 15 years and won't be going anywhere whilst we still own the house. Crofter, 13 Mar 2015 11:54 PM Thanks to a lovely still day here, I was able to do some surveying singlehanded. I was setting up profiles so simply replaced SWMBO with a bungee, and bungeed the staff to the profile post. Wouldn't work on a windy day... SWMBO seemed surprisingly happy with this arrangement. TerryE, 14 Mar 2015 01:51 AM Hi, glad to see that this is working for you. Rereading my last comment, it came across as too negative to everyone else's input. Sorry for this guys. There's a trade-off to be made here on speed / flexibility / cost, etc. I am retired so my time is free -- so long as I enjoy or at least take satisfaction in what I am doing. If I was working and my time was a constrained commodity then I'd have either gone the subcontract to specialist route or bought myself a dumpy level. But the reason for this post was that the water level method works and is amazingly accurate. It can just be a bit time consuming. The model that I described here was my V2 approach. Using the two transparent read-out tubes each against a long rule with a decent mm scale makes things a lot easier. As does having a stable reference base (my heavy wooden chair with the readout clamped to it). Black masking tape and clamps are an alternative to bungees. The design for my stand for the moveable post could be improved -- the light aluminium ladder fell over a couple of times. However, making up a couple of wooden bung pegs to close the tube ends when repositioning stops unnecessary water slop -- albeit at the cost of an extra to-and-fro walk to take them out and let the levels settle before taking the reading. I also had a couple of peg sets with 5m of string between them so that I could quickly walk a grid to take level and transcribe them onto my plan. Yes, it's a bit clunky but I don't think that a dumpy would be accurate to 1-2mm over 30-40m and this approach is. TerryE, 04 Apr 2015 12:05 PM OK, OK, I have given in and just bought a CST Berger 24X Dumpy level on eBay "as new" for £174 inc free delivery. Why? I've just had to check something for the 3rd time. The water level method is accurate but setting it up and taking measurements just takes too long. It struck me that getting the levels just right is a potential issue on our build, so the investment in a Dumpy was a sound one. Hopefully I will be able to sell it "very good condition; used on one project; one owner for ~£100" in a year's time. The time savings and extra mm accuracy of going to an equivalent laser system didn't seem worth the significant extra costs. Still doing the water levels was fun. TerryE, 14 Apr 2015 12:55 PM We had got our AT to double check my water level readings for the key measurements that we put on our application to clear preconditions, and tweaked them accordingly so that he could put his name to them. We used his Dumpy to do this, and seeing how easy was this to do was what tipped the decision for me. I've had a play with our Dumpy and it's brilliant even though it is a two man operation. You can get readings to a few mm with a 24x Dumpy if it has been correctly levelled. In our case when I rechecked a few of our TAs readings across the site, making sure my level bubble was spot on, I realised that his Dumpy baseplate must have been off level very slightly, and this caused about a 2-3cm gradient error across the 50m of the site in our submitted plan. Not enough to worry about.

Original comments from eBuild: recoveringacademic, 24 Feb 2015 08:34 PM I've come to love Newts. Not all newts get pissed - not a lot of people know that. bitpipe, 24 Feb 2015 09:40 PM Great news Terry. I just submitted the paperwork for our 14 planning conditions a few were quite detailed (illustrating compliance to Lifetime Homes standard etc) and we also have the dreaded archaeological condition due to a neolithic arrow head having been found 500m away in the 1850s. We've negotiated a watching brief which hopefully wont come to that much. ProDave, 24 Feb 2015 09:43 PM Well done. Now the planning conditions, then the building warrant........ You are not in a hurry to start are you? (4 months and waiting for my building warrant. zzzzzzzzzzzzz) bitpipe, 25 Feb 2015 02:46 PM Our LA commits to respond to conditions submissions within 10 working days with a final decision in 20 if they are acceptable. Collecting some of the supporting documentation has taken the time. TerryE, 25 Feb 2015 03:16 PM My issue isn't so much with the LPA, but with the ancillary bodies. For example the highways engineer. She had no SLA. In one case I sent her an email telling what I was proposing and asked her to get back to me if she had a problem. I followed up with another email 7 weeks later as I said I would, and then rang her after a few days. She said that she hadn't got around to reading my email. Fair enough, I thought: it's only been a couple of days -- until she started to object to points I'd made and I realise that she'd only just opened the one dated two months earlier !! In this case the LPA archaeologist has said that she got a 4 weeks backlog to specify what she wants so this sets back my selecting the archaeological consultant and preparing my "agree archaeological survey plan" precondition for start of work.

No comments from anyone else (maybe as a refection on my decision to post this on New Year's Eve!) apart from my own footnote on 28 Jan 2015 02:29 PM: As a codicil to this, a friend who is an electronics engineer came for a visit and we got around to chatting about my new house plans and how the Active slab will work. His reaction was: it can't possibly work because of the layering effect of air above the slab, "heat rises in air". A couple of points to emphasise again: The 7 W/m² figure is nothing to do with the air in the room. It's a net radiance; it would be the same figure even if the room was in a vacuum. Yes, the air column will tend to be stable is the floor is colder than the air above it. The physics of convention and its onset is complicated, but the headline you can pretty much ignore any convection effects if the slab is only a couple of degrees warmer than the air mass. This isn't the case for conventional UFH, but this is the case for an active slab.

Comments from the original eBuild post: joe90, 16 Dec 2014 01:26 PM I too am following this thread with enthusiasm and have been to Jeremy's and was very very impressed with the whole build. My planned build may have a bigger overheat problem than most because of a South facing sun space across the whole back of the house but my thoughts are that this overheat will occur when the PV is producing the most so the cost of running a Heat pump to cool should not be a problem!!!. Also I am planning shades to reduce summer heat but can enjoy the sun through the rest of the year. I also am convinced that the sunspace could be a source of pre heated air for the MVHR during the shoulder or heating months. Jeremy's brilliant find was the electric in line water heater to raise water already warmed to the required usable temp for DHW, Well done JSH. notnickclegg, 16 Dec 2014 06:06 PM "I also am convinced that the sunspace could be a source of pre heated air for the MVHR during the shoulder or heating months." I looked into this a year or so ago. I seem to recall that preheating air going in the MVHR unit has surprisingly little impact on its efficiency, because you reduce the temperature difference that drives the heat transfer. Jack TerryE, 16 Dec 2014 06:40 PM Joe90, if you are talking about putting your inlet to your MVHR on within your sunspace, you have to think about the cons as well as the pros. The whole idea of the MVHR is to recover the exhaust heat into the input stream. As Nick says, additional preheating will have little benefit, but what it might mean is that you will nearly always have heated input air and this will in practice mean that you will lose the ability to use the "summer" bypass mode to dump heat. The amounts of heat that you need to add to a near PassivHaus are trivial to achieve with an active slab. IMO, mitigating excess solar gain is a more difficult issue to master. jsharris, 16 Dec 2014 08:44 PM One thing I can report very positively on is that an exhaust air driven air-to-air heat pump is a LOT more efficient thanan outside ASHP. The give away is that the EAHP in our MVHR never needs to use power by reverse cycling to defrost. I can hear when it defrosts, as the condensate pipe is a vertical drop length of 32mm waste pipe at the back of our airing cupboard, so the drops of water when it stops and defrosts are easily heard. Looking at the temperatures within the unit when this happens shows that it just switches the heat pump off and allows the slightly warmer air from the MVHR heat exchanger to defrost the evaporator. This seems very effective and has no impact on the overall COP, which seems to be well over 4 all the time (and up to 5 or 6 at times). Clearly such a system is only able to supply a small amount of heat, and in our case I'm using it to provide fine trim adjustments, so it rarely has to deliver more than a few hundred watts around the whole house. It does this very quietly and efficiently, more efficiently than the ASHP that's mounted outside, that struggles to deliver more than about 40 deg C at the output. I regularly see temperatures of around 45 deg C at the MVHR internal output (lower at the duct outlets) when it's trimming the house temperature in very cold weather. My inclination is to rely less on the UFH for the main heating system, and just use that to provide the background, very stable, low level heating, as required, and use the MVHR EAHP to do the fine trimming of house temperature, as it has a faster response time and seems to be more efficient. I think the secret to efficiency is keeping the heat pumps very lightly loaded, so each is only required to produce a modest temperature increase. joe90, 16 Dec 2014 09:23 PM Point taken chaps!, my plans are a long way off but this is all good food for thought. When the plans get nearer to completion I will have actual figures to play with. TerryE, 17 Dec 2014 01:05 AM Jeremy, I find your last comment a little ironic. The thoughts that you lay out in it were pretty much my initial conclusions at the time when I first joined the forum and why I was going for a Genvex with no UFH in the slab. We've almost swapped positions!! You have persuaded me that your active slab system is the way to go, and at the same time you have decided that the Genvex should take point. Even so at 20,000 ft, I think that we are saying the same thing: the τ of the active slab is just far too long for it to be usable for fine control. The tactical difference between the two schemes is that the Genvex embeds an ASHP and can be used for +/- fine control, but that the MVHR "summer bypass" function can only be used for - fine control so the slab needs to be trimmed slightly on the high side so that a - control can work over the required range. I can always adopt the fallback that Neil suggested in one post: keep a little fan heater in the living room just in case we do something daft like leave the front door open and so need a quick heat boost. jsharris, 17 Dec 2014 09:12 AM My position has gradually shifted in the light of experience, which has revealed subtle differences between theory and reality! The biggest difference is that I didn't bother to model either time constant of the house or the full impact of solar gain initially. This was an error, because if I'd done this then I would have been better able to understand the way the house can heat up quickly with even a modest amount of solar gain and that it takes a relatively long time to cool down. The slab can heat up pretty quickly if fed with water at around 25 to 28 deg C, but takes a long time to cool down, plus the slab sensor takes an hour or two before it sees the true slab temperature, as it's deliberately placed around 150mm to 200mm away from the nearest UFH pipe on the "cold" side of the house (the bit that never sees solar gain). If I get the slab to a temperature just a bit below that needed to heat the house to the target temperature, I can hold it to within about +/- 0.2 deg C, but if I want to increase the slab temperature it does overshoot by up to half a degree or more initially, and can get the house a bit too warm, especially if there's a bit of solar gain that comes along unexpectedly. The defining characteristic of the UFH in the slab is that it responds fairly quickly (half an hour or so) to increased input and heats the house quickly, but responds very much more slowly when the house is warm enough and doesn't need any more heat. This is what I expected, as there is a high delta T between the flow water and the slab, so the heat transfer rate in is pretty rapid, but there is a very small delta T between the room temperature and the slab (often less than 1 deg C) so the heat transfer rate out is pretty slow. I hadn't anticipated the impact of solar gain on this though, which can make the slab temperature overshoot before the heat has soaked through to the sensor and got the heating system to shut down. Running the slab a little cooler (20.6 deg C seems to be about the sweet spot for outside temperatures between +8 deg C and down to just below freezing) seems to work well. There is a small heat input from the slab, enough to keep the house between around 19 and 20 deg C with no other heating and the Genvex can quickly trim the temperature by one or two degrees up or down as needed. A fan heater, or better still a thermostaically controlled duct heater, would do much the same job, at little or no overall additional cost. as the capital cost difference would pay for many years worth of additional energy use I think. I'll admit to being surprised at how effective the Genvex is at doing this, until I worked out that it was only being asked to deliver very small amounts of heat in reality, just a few hundred watts throughout the whole house at the most. I am pretty sure that the Genvex would not be up to the job of heating the whole house efficiently if it wasn't for the background heating from the slab, so I've sort of accidentally evolved our heating into a two stage system that can both heat and cool the house to within pretty close limits, yet without making either system work particularly hard. TerryE, 17 Dec 2014 11:48 AM Probably the topic for another blog post, but we've had an enforced delay in our plans. That delay plus your input and the experiences of the other forum members have given me the time and data to do theoretically what you have been discovering by a mix of theory and practice. I had a look at how you could use the slab to track / mitigate these short term largely solar-driven variations, and I discovered that you can't: the time constant means that I get horrendous overruns. The only thing that works is to have the set-point for the slab pretty much fixed on a seasonal basis, and if I do that all I am left with is a trim control issue. So my modelling and your evolution have converged to similar conclusions. Your suggestion about a thermostatically controlled duct heater is a good option to consider. I am still mulling over the pros and cons of this external earth loop, but that's another topic. Thanks for your support. stones, 18 Dec 2014 12:10 PM In my own house, we have a mix of low temp radiators providing most of the background heating, and a wet duct heater in the ventilation system which warms the supply air. The combination of these two things gives us a comfortable and very responsive system. Whilst we can deliver the actual radiator system flow temp to the wet duct heater, we have throttled this back to a maximum of 26C, as we have found this the optimum level for our house. In effect therefore we have two variable heating delivery methods (albeit the supply air temp only really operates in a 5 or 6 C band). If we so wished we could deliver less through the radiator system and increase the supply air temp or vice versa. The point, as Jeremy has found, is that the combination of heat delivery methods gives you options and a high degree of control over your internal environment. Wet duct heaters are not especially expensive and can be sized according to your heating requirements. They also have the advantage (over direct electric duct heaters) that they can use the low temp water as provided by an ASHP as part of a low temp UFH slab or low temp radiator system. bitpipe, 18 Dec 2014 12:41 PM > I assume that you aren't going to lag the ground floor (bad idea in this case) so you are going to see that 7-10 W/m²K transfer between floors which is enough to couple the basement to the rest of the house. This is the dilemma - we want to minimise sound transference between the basement and ground floor as the former will be used for teenager space, music etc.. however doing so reduces the ability to transfer heat/cooth upwards. We are considering have a UFH loop on the ground floor also. We're trying to avoid a concrete lid on the basement as it's more expensive than timber and complicates services. > Whether a straight MVHR bypass will work you need or more active solution like Jeremy's Genvex approach really depends on your window configurations and whether you have alternative active shading on the S facing larger windows. Doing the trick with PVGIS will give you a good handle on the order of magnitude on this issue. Luckily we have very little south facing glazing as our house has an W/E aspect. Most of the glazing is on the west side which is slightly north facing. TerryE, on 16 December 2014 - 12:18 AM, said: If you are using Gas for your active slab heating then you'll probably need a buffer tank, because you'll want to have decent burn runs on the boiler. You also need to thin about how you chill the slab down in the summer. A heat / cool ASHP is excellent for both heat input and dumping, but you will still need a dump approach with gas heating. I am trying to get to grips with how well Seamus' idea of a ground loop will work. In your case if you haven't built the basement one possibility might be to run a loop around the outside of the basement wall EPS before you back fill. Opening this zone would effectively allow you to bypass the basement wall insulation and dump heat that way. I am doing a bit more research and modelling on this ground loop approach (I'll post a new topic on this in a week or so). I'd be a lot happier if Seamus had some reference examples of it working in practice. This is exactly what we are thinking of - running a loop of UFH external to the EPS - should be easy to do and I hope the pipes would be sufficiently robust? Given we're on mains gas (even though I've just paid nat grid £1500 for a service disconnection to facilitate demolition, reconnection is subsidised) we've never given consideration to ASHP - still debating on how much solar PV we can afford on our W facing roof. TerryE, 18 Dec 2014 03:49 PM You want to talk to Seamus about the dump loop placement. You've also got a long back garden so another option would be to add it there. You can compare my floor plans and elevations that I gave on an earlier blog post with yours. You need to do the internal heat balance calcs, but with a house split over four floors you might need active heating. bitpipe, 18 Dec 2014 05:41 PM Seamus recommended a capillary mat product which, to quote: "buried 2m deep will be in close proximity to 27m3 of soil and can avail of its coolth. 1 degree x 27m3 = 27kWh cooling sufficient cooling for 5 days.' If taking this approach, I'd likely place it against the north basement wall no point digging up more of the garden when we have such a large hole already We've also done PHPP which showed a total annual heating requirement of 13kWh(m2a), but not figured any internal heat balancing. What so you mean by active heating? wmacleod, 18 Dec 2014 10:21 PM Nothing here about how big this mat is or how he is working out the 27m3 soil contact, I would be very careful to double check exactly what is being calculated. You are talking about installing into a backfilled area, it isn't likely to be soil going in, it will most likely be stone which will have very different conductivity than damp soil. Also you may see heat from the basement walls. This is likely to give very different results than just burying it deep in the garden. Also remember that backfill should be compacted against the basement walls in layers, this may cause grief if you puncture the mat. TerryE, 19 Dec 2014 12:18 AM If Seamus had some hard examples installed, working and with performance data, then I would be a lot happier. For me, I see that going this route is going to be at my own risk, so I want to do some modelling / simulations to get a better understanding of how these loops work in practice, much as I did in the earlier blog post, Modelling Thermal Lag. The difference is that I need to use the heat equation in 2D, rather than in 1D. (2D will be good enough). I don't want to go into more details here. Let me do the maths and run the simulations and post separately. By active heating, I meant a space heating fall-back given that your house is on 4 flours, especially if you have sound proofed floors between your top-up heat source in the basement and your upper stories. This might simply be a inline air heating in your MVHR as Jeremy suggested. You need to do the heat calcs per floor just to make sure that the kids don't start turning the heating right down because they find the basement too hot and the first floor is a tad too cold. This shouldn't be a problem but if it is then remedying post completion might be a pain. jsharris, 20 Dec 2014 02:56 PM I've done a few quick and dirty calculations on using the MVHR with duct heating as a "trim heating" system, and it looks very promising. As a base assumption I've assumed that the UFH puts a constant 400 W into the house whenever it's on. At the moment this is for 13 hours per day and that seems to be enough to keep the house at around 19 deg C at the lowest, and over 20 deg C at the warmest, over the current range of weather (which has varied from a few days at zero overnight rising to maybe 6 deg C during the day, to the last couple of days where it's been around 5 deg C overnight rising to maybe 11 deg C during the day). Without the MVHR duct heating the house temperature has dipped to just over 19 deg C first thing in the morning. Using the MVHR duct heating it is back up to 20 deg C within around half an hour. So it looks as if the MVHR duct heating (which is about 1.5 kW maximum) can increase the house temperature by 1 deg C in half an hour. It's doing this with the MVHR fan speed still at the minimum setting though, so clearly isn't delivering full power (the MVHR adjusts the fan speed up if it needs to deliver a lot of heat). The total flow rate through the MVHR in trickle mode is about 46 l/S, so at a typical heat capacity of around 1.21 J.lt.K and a heated air temperature of 40 deg C (typically the MVHR heats the air to between 40 and 45 deg C) then the MVHR duct heater can deliver nearly 1200 watts to the whole house at around 19 deg C. Given that this is nearly three times the output of the UFH it's no wonder it's so effective as a very powerful trim heating source. It's also very efficient, as the exhaust air heat pump is running with an inflow air temperature that is around 3 deg C warmer than the outside air temperature, keeping the COP of the heat pump up at well over 3. In practice, the MVHR only goes into heating mode for a very short time on the very coldest mornings, and is set to get the house to 20 deg C. The MVHR does have the advantage of being as programmable as a full, zoned, central heating system, too. The controller has the normal timer settings with a weekly calendar, plus has the option of controlling air valves to turn some parts of the air feed system on and off for zone control. For example, I could fit zone valves in the ducts feeding the bedrooms to cut the heating to them, allowing them to be a little cooler, and the controller would allow those valves to open and close at preset times and days, As it stands, with the UFH only on the ground floor and the warm air from the MVHR being distributed fairly evenly between the ground floor and the first floor, the first floor tends to be a little bit cooler (maybe half to one degree) than the ground floor. I think that this is about right for us, as we prefer the bedrooms to be a bit cooler, but if others wanted the upstairs to be warmer than fitting duct heaters selectively to the upper floors would allow that (assuming they only need the same sort of modest heating that we do). TerryE, 20 Dec 2014 04:06 PM Thanks Jeremy for documenting the conclusion that I'd also come to. For almost the whole year the MVHR ,when in bypass mode, acts as an equally effective trim down because the same flow rate is dumping hot air and the heat it carries with it. This won't be the case in the height of summer daytimes and possibly early evenings but here we can just accept some slight internal heating, because the house will still be a lot cooler than outside especially is we are running the slab in cooldown mode. The one area where we may need to consider a separate zone is my son's bedsit room -- mainly because his computer equipment and something 2-3 extra warm bodies etc. will result in it being a local hotspot. jsharris, 20 Dec 2014 05:15 PM You could look at fitting wet duct heaters/coolers and driving them from the heat source. If this is a reversible ASHP then you'd have the option to selectively cool the air to particular rooms, with just the penalty of some additional pipe work and control valves. If you opt for a radial duct system then all the duct heaters/coolers with their associated flow, return and condensate drains could be in the same location. A wet duct heater is a pretty simple device and fairly compact. TerryE, 20 Dec 2014 08:02 PM Hummmnnn. More research is needed Thanks

Here are the key elements in the discussions following this post: jsharris Posted 26 October 2014 - 09:28 AM This tallies well with my direct experience. Our internal wall temperatures don't show any diurnal variation that I can detect by ad hoc testing with an IR thermometer. There is very little difference in wall temperature between the North and South internal walls, for example, The house seems to be exceptionally temperature stable as long as the external doors and windows are kept closed, with the exception that solar gain does have a significant impact in heating the house through the windows at times. I'm coming around to the view that floor temperature control may not need to be very sophisticated, and almost certainly doesn't need weather compensation. I suspect that just manually setting the floor to close to the desired room temperature (maybe a fraction of a degree warmer in winter) and then letting the active bit of the MVHR do the fine control will be the best strategy. The active MVHR can warm the house by half a degree pretty quickly when needed, I've found, even though the air flow rates are modest. I tested this last week, after I'd left the front door open for 20 minutes or so whilst cutting some skirting out in the garage and found that the house had dropped to around 19 deg C. The floor was at around 19.5 deg C and when I would the MVHR thermostat up to 20.5 deg and turned the fans to speed 3 the house gained half a degree in around 20 minutes or so, such that I turned the MVHR back down to passive mode, trickle ventilation and the house then sat at its usual 20 deg C or so. This shouldn't be surprising, as the effect of the additional heat from visitors is easily detectable (as anyone who'd visited may have spotted). An extra person or two in the house tends to increase the temperature slightly after half an hour or so, just from their body heat. TerryE Posted 26 October 2014 - 11:03 AM One of the things that isn't covered in the discussion of wall specs is this thermal lag effect. Clearly we need to balance overall U value with the wall thickness (which in effect removes usable living space) and unit cost of the wall itself. But the thermal lag is largely dictated by the ratio of the specific heat to thermal conductivity. Cellulose filler is a very good material in that it has a very high specific heat for its conductivity (compared to PIR say). This gives it excellent lag properties. Once the lag through the wall is over a day or two, as you observe there is almost no observable diurnal variation observed on the inner wall. Another thing which isn't immediately obvious is that whilst clear cavity gaps have almost no effect in U value calculations, they are important in acting as a rate limiting barrier for heat flow. You can see this in my Std Dev of thermal flow where my airgap is at 30-35cm between the stone outer and the frame inner. In the case of your wall profile, Jeremy, the stand-off between the wood cladding and the frame helps limit excess solar gain through the wall fabric itself. My views re windows echoes yours: windows are necessary if you need the light or if you want to see a "to die for" view, but don't put them in just to have a view of the neighbours gardens or houses. Thermal gain though windows is totally uncontrollable as are the thermal losses. TerryE Posted 26 October 2014 - 06:10 PM I just looked at the impact of sunshine on the surface of my wall. Roughly 99% of the energy gets re-radiated or convected back off the wall surface, and again roughly 1% ultimately makes its way through the insulation to the inside and warming the house, or more strictly the extra heating reduces the otherwise heat loss, but the mode delay is 6 days!! jsharrisPosted 26 October 2014 - 06:15 PM Compare that to a really good window.................... TerryE Posted 28 October 2014 - 09:27 PM Jeremy, I think that I might be getting too anal here, but I've think got a pretty good handle on the whole thermal lag issue now: it's just so large that you can almost just ignore any daily temperature variation and you really need a material step change in temperature of days for it to start to make any difference. As we've just said, the main control challenge in terms on unpredictable variations in heat loss are the solar gains from an windows -- and black-body radiation out of them at night. What I have been trying to get a better handle on are the feedback mechanisms relating to unpredictable variations in internal heat sources -- your vacuum cleaner challenge. It seems that we have two overall feedback mechanisms: surface coupling and air control. In terms of surface losses, I will typically have ~1 W/m² heat loss though my walls (including sloping roofs) in the milder winter months, and maybe 10x this through my windows (albeit with less than 10x the total area). This surface transfer is a mix of radiative and convective heat losses. The radiative loss is essentially driven by the Stefan–Boltzmann equation. The T^4 delta is practically linear for small ΔT around 20°C (293K), and cranking the numbers for black body radiation gives 5.72 ΔT W/m²K. OK, wall plasterwork isn't black body, but for most matt surfaces it will be 60-80% of this. The convection element seems to be another "proportional" to ΔT rule of thumb, except that the "constant" is itself a function of ³√ΔT for a still air assumption. Even so, the linear term dominates for small ΔT around the ~1 W/m² heat loss centre point, and typically maybe 40-60% of the radiative amount, giving an overall ballpark of 8 ΔT W/m²K, or roughly an eighth of a degree delta between the wall and air temperature at steady state. The actual value (8 quoted here) is pretty much secondary as if this was only 4, say, then the wall surface temperature drop would be a whole 2x greater at ¼°C! The main point is the the linear term dominates in this feedback, and that the rough scale is as I've discussed. Our living room has roughly 50m² of wall and ceiling and another 20m² slab under foot, so an extra couple of warm bodies would raise the temperature maybe ½°C before reaching dynamic equilibrium again. My answer to the hoover effect is that we're getting a couple of Dyson battery cleaners -- less power and less time before the battery runs out However the time constants are sufficiently separated from those of an active MVHR (even with 0.5 ACH, say) that as you say, setting the slab setpoint weekly, say, depending on overall weather trends and using active heating/cooling of the MVHR input -- or even just controlling the bypass mix should give an adequate level of control. SteamyTea Posted 28 October 2014 - 10:48 PM I have been looking at this very issue for years. I soon seem to go around in circles. Some analysis of temperatures, solar radiation and windspeeds I did over on the 'other place' seemed to show a better fit between windspeed and temperature loss that anything else. Trouble was I bored people with it and was not getting feedback. I am willing to see how long it takes to raise the temperature by running my vacuum cleaner tomorrow. I need to tidy up as I have been fitting multiple temp and RH sensors around the place, along with a weather station and a more accurate energy monitor. So should be able to get the data. I do seem to remember that the equation for thermal inertia is very sensitive to 'shape'. Physicists will make any shape a sphere to make life easy. I do have my 5 sided box made, the 6th side is for testing materials and their properties. Just been sidetracked for the last few weeks with other things. But willing to share data and experiment design if it helps. TerryE Posted 28 October 2014 - 11:58 PM I am fairly comfortable with the cp, ρ and K coefficients and the 1-D finite element approximation. It's getting a handle on the surface transfer modelling and how that's going to interact with the variability of heat inputs and the consequential air temperature. In one aspect I differ in my personal tastes / tolerances from Jeremy: I have a place on a Greek Island where I spend 3 or so months a year: I am used to living temperatures in high 20s and low 30s indoor. I don't really see a 2-3 variation in room temperature as a big issue -- but as Jeremy will no doubt point out: anticipation isn't the same thing actual experience. I'll still be interested in your vacuum tests. You could even stick your wall profiles into my little C program to see if its response curves are similar to what you find with your house SteamyTea Posted 29 October 2014 - 07:20 AM When you put the wall surface in, do you take into account the texture. This could easily add an extra 30% to the area of an external wall. TerryE Posted 29 October 2014 - 11:03 AM Nope, but it's a good point and could largely balance out the non black-body effects. The main point here is that the heat loss is predominantly of the form h.ΔT. I've played around picking h values between 4 and 12; it doesn't make a material difference to the macro response of the system, just the that the wall is at 19.6 °C rather than 19.8 °C, say, for an internal room temperature of 20 °C. SteamyTeaPosted 29 October 2014 - 11:23 PM Have you read this: http://lup.lub.lu.se...fileOId=2518433 About 100 pages. TerryE Posted 30 October 2014 - 10:18 AM For the benefit for others, this is a detailed academic analysis of the "Possibilities of using thermal mass in buildings to save energy, cut power consumption peaks and increase the thermal comfort" by a researcher from Lund University. The main paper is 50 pages long and it includes as an appendix other paper of a similar size. Thanks, it's an interesting read. I've just had a quick scan because I am visiting friends at the moment. I'll have to go through it in detail. But it largely echoes what I have discussing here, in various other posts and in my blog entries. I'll have a proper read over the net few days and either post back here or reflect it in my blog. Going for a decent walk with friends now. SteamyTea Posted 17 November 2014 - 09:02 PM Been playing over at the other place and as usual the topic came to inter seasonal storage and how the ground under the house can be helpful. As I know it can't, and felt I had to show this yet again, I quickly knocked up a little model in LISA, then made a video of it. Here it is, it shows that there is hardly any thermal penetration: Youtube - Thermal Inertia TerryE Posted 18 November 2014 - 01:46 AM Unfortunately LISA is closed source and windows only. I am wary of the former and don't have any machines running the latter so I can't play with this myself. However, I agree with your conclusions. IMO the one thing that the ground is good for is as a semi-infinite (at a domestic house scale) heat source / sink that could easily be used as a heat sink for those using a gas heated low-temperature UFH slab to allow summer cool down within the house. SteamyTea Posted 18 November 2014 - 07:02 AM Yes, a large mass is good for keeping a place cool. jsharris Posted 18 November 2014 - 07:40 AM There are some very stubborn folk, who should know better, that have persistently argued elsewhere that the ground doesn't act as a semi-infinite heat source/sink, though. Some insist that the ground under a house can be used as a seasonal thermal store, even. I stopped trying to make the point that the thermal conductivity of soil was such that it simply wouldn't stay warm for long if heated up above the temperature of the surrounding ground, as even an architect was arguing that I was wrong. SteamyTea Posted 18 November 2014 - 07:53 AM I am still arguing with that architect, its fun when there is nothing else to do. DavidFrancis Posted 01 February 2015 - 05:01 PM Terry - I couldn't follow the detail of everything you said above. Would it be much work to produce a small table showing your expected heat losses in your new house assuming an internal temp of, say, 20C and an external temp of zero? The table would show the losses from radiation, conduction and convection for windows on the one hand and roof/ceilings, walls and floor on the other (assuming there's not much difference in any of these three last mentioned elements). And would there be any difference between daylight and nighttime losses if there were no blinds/curtains/shutters? Many thanks if it is possible. TerryE Posted 01 February 2015 - 11:17 PM David, have a read through my blog posts on my thermal design where I have already given this sort of detail. Ditto Jeremy's. Amongst these and the various discussions in the threads, you'll find days of provoking reading Do you see how my two graphs in my first post work? What I've done here is to solve the 1-D heat flow equation for my wall profile in the somewhat artificial case where the air temperature is a sine wave from 0-20°C over the day. The result is just the output profile that the model chuffs out. I've got a lot more different analyses, but no one seemed interested in that level of detail. Putting it descriptively the diurnal variation does cause a damping wave of heat flow through the wall profile, but because of its thermal capacity vs conductivity this cyclic flow is almost totally attenuated by the internal layers. The 1 std dev of the heat flow at the outside (as a response of the cyclic air temperature) is 30 W/m² but by the internal plaster layer it is down to 0.0003 W/m² -- that's 5 orders of magnitude less. I also tried looking at the effect of a 3 day cold snap, and it took days before there was a slight response showing itself on the inside. (You can see this delay effect in outer stone skin in the corkscrewing of the heat curves.) This is why I said that you can pretty much use per month average external temperature data for doing your heat calcs. Yes, of course you are correct in pointing out that the external temperature pretty much directly impacts on the MVHR recovery and the Window losses, but these are roughly a third of my winter losses. We only get solar gain during the day of course, so there is some residual ripple but the thermal capacity of the slab and internal fabric, (plus the slab's active control in Jeremy's and my case) keeps this under 1°C, and most people don't mind their bedrooms cooling slightly overnight. Yes, having drawn curtains might drop the heat losses, but to be honest IMO the main benefit is a subjective one of not seeing black windows.

Original comments from eBuild: stones 19 Jun 2015 10:27 AM Terry, just plugging in the numbers to try and establish solar gain for my own house - to clarify, once you have obtained Hd figure from the PVGIS website, you multiply that figure by the m2 of glazing you have on each orientation to obtain your average daily solar gain in kWh? TerryE 19 Jun 2015 12:07 PM Broadly yes. I calculated the area of glass rather than windows. In practice I did this for each face of the house (well front and back, since the gables don't have windows) and added the result. I also use a transmission factor (off the top of my head something around 50%). I remember Jeremy, Damon and I talking about this on a post. The point here is that some of the radiant energy gets reflected before entering the house itself, or is absorbed by the window layers and re-emitted outwards. The actual factor depends on your window technology. The whole thing is just a rough estimator of average solar gain. If you have a clear autumn or spring day, then the actuals can easily be double this. In some respects there are two separate issues here: one is the average expected solar gain which feeds into your likely heating / cooling costs; the second is the likely maximum daily gain which is going to inform your design of how you keep your house within comfortable living temperatures. I know that Jeremy has problems with overheating due to solar gain, and I keep coming across people who are designing passive houses with huge S facing windows. IMO, unless they design in adequate cooling, they are going to be living in a hothouse.

The original eBuild comments: warby 21 Sep 2014 109:17 PM Excellent Blog. Have you considered using an inexpensive cooling/refrigeration unit, instead of using the ASHP in cooling mode, to cool the slab. The ASHP would be cheaper and could be replaced directly by a gas boiler if required in the future. The ASHP would only operate in heating mode and I would have thought made the overall heating and DHW design easier. Looking forward to your next instalment. Martin TerryE 21 Sep 2014 11:24 PM I am sufficiently confident in the figures that the only scenario where a gas boiler would come into pay is if we ever decide to sell the property and the potential new owners don't believe the data. They will have the option of fitting a gas boiler. In fact one of the decisions that we have taken is to dispense with gas altogether. Jan prefers an electric oven and modern induction hobs are as good as gas. We want a monoblock inverter ASHP to avoid the need for an expensive certified installer and for acoustic reasons. Prices start at around £2K and most include cooling modes anyway. As we have seen in Jeremy's discussion, the main issue is the control system and getting one off-the-shelf is problematic, so I am currently planning to implement this myself, but that's for a later post. TerryE 21 Sep 2014 11:28 PM One other thing. I mentioned mining various topics in the site for background info. Here is a list of some of the ones that I found useful. I've added the originating poster, post date with the number of replies and views in parenthesis. UFH For A Low Temperature Slab. jsharris, 2 Jul 2013 (143/4135) Heating And Hot Water Options.....please help!. Ness, 20 Oct 2013 (63/1580) MVHR System Design. Alphonsox, 8 Dec 2013 (36/1741) Solar PV, A Little Clarity Please. Nickfromwales, 28 Jan 2014 (42/1023) UFH - ASHP Or Gas Boiler..?. couplands, 23 Feb 2014 (15/357) Negative Feed-In-Tariffs & Batteries. greenshell, 6 Jun 2014 (30/480) MVHR - Location Within The House, inlet and outlet positioning. Rooskey, 6 Aug 2014 (24/558) Heating Headache - Please Help.. bubbs, 12 Aug 2014 (56/842) Solar PV Recommendation vs G/ASHP. Nickfromwales, 25 Aug 2014 (13/162) Chinese Heat Pumps. slidersx200, 26 Aug 2014 (26/379) Heating And DHW Using An ASHP Or Immersion Based System. stones, 30 Aug 2014 (43/592) Solar PV For Dummies. lolliedog, 31 Aug 2014 (42/381) Solar PV Viability. Alphonsox, 2 Sep 2014 (23/175) Good Suppliers Of MVHR Kit. dellboy13, 2 Sep 2014 (30/287) Hope this is useful. joiner 22 Sep 2014 05:17 PM I bet you have a hell of a job getting to sleep, and wake up at some ungodly hour to go looking for pen, paper and a calculator! jsharris 22 Sep 2014 06:39 PM I wish I'd been in your position when I was trying to get to grips with this! Just like you, I found getting good information very difficult, and, as you know, I seriously under-estimated the solar gain and my pessimistic view that the house would need a fair bit of heat was just wrong (although the numbers were telling me this, I frankly didn't wholly believe them!). Today was a good example for our house. I'm currently laying bonded bamboo flooring to the first floor bedrooms and landing. Today wasn't that warm (around 19 deg C max) but around 14:00 the Genvex went into active cooling mode, as the ground floor air temperature went up to 21.7 deg C. The slab temperature was around 19.1 - 19.2 deg C, and within a couple of hours the temperature was back down below 21.5 deg C, and then the Genvex switched back to normal ventilation. I think that a cheaper air-to-air heat pump (such as the ~£500 split units that are readily available) would meet the quick air cooling requirement more effectively than the Genvex, and would also provide a quick air heating system if needed, but this does depend on the house layout (we have the advantage of a tall, central, hall). If doing things again I'd probably fit a standard MVHR, keep the current ASHP and UFH heating/cooling system but fit a reversible air-to-air unit high in the hall space. TerryE 22 Sep 2014 11:17 PM Thanks. Just standing on the shoulders of giants. Need to think about this quick response issue though. PS edit. Jeremy, Jan say this comment reads a little unctuously, but the fact is that the only reason that my and your starting positions are different is because your learning curve has been pretty well documented on this site and the GBF, as well as thought provoking input from Nick, David, Neil and so many others, so one of my main reasons for writing this up is to help others going down the same design path. And not all of us have been on TV (it's amazing what Google can throw up): Jeremy Harris and the Beach Bums! joiner 25 Sep 2014 03:25 PM LOL. Tried to find that clip ages ago. "Come on, Jezza!" jsharris 26 Sep 2014 07:26 AM I'm just grateful that there are only a few, relatively recent, clips of bits of TV with me in that are online, really just some BBC stuff and some of the Scrapheap stuff. I know someone with a boxed set of the Onedin Line, who delights in telling me that I appear in every episode. I was a deckhand helping to sail the Charlotte Rose, the pretend square rigger used in the series, that was really a converted Baltic Trader (and which sailed like a pig with the square rig). Thankfully I was out of shot on pretty much all of the Poldark filming, as I was just bent down keeping horses still for any shots where Robin Ellis and Angharad Rees were chatting together on horseback, and the pilot science programme I did for a TV production company (for Channel four, I think) never made it to the screen. TerryE 28 Sep 2014 07:57 PM A footnote to this post: I've just tweaked the power figures after cross checking with Jeremy Harris's figures -- though it's not enough to change any of the other content. Out of interest the figures for Slab, Walls, Roof, Windows and Air change are: My house: 9%, 32%, 15%, 28%, 16% Jeremy's 13%, 26%, 18%, 31%, 12% In otherwords, they are broadly similar because we are both using similar insulation technologies. The main reason for these slight shifhts is that Jeremy's house is 1½ stories and mine is 2½, so the ratios of roof:walls:volume are different since my house is more cube-like and I have a smaller percentage of window space. NSS 05 Oct 2014 04:45 PM Just made some swift calculations based upon our own design (for a 160m² 1.5-storey chalet) using a combination of known values for walls/roof/windows, a guestimate for the slab (of 0.2) and an assumed similar value to your own calculation for the air change figure, and it gives me the following... The internal footprint of the slab (117m²) The internal surface area of the external walls, less windows (155m²) The internal surface area of the roof, less roof windows (164m²) The area of windows (33m²) The total volume of the internal living spaces (355 m³). Slab: 304 W (21%) – 117 m² x 0.200 W/m²/K x 13° Walls: 290 W (20%) – 155 m² x 0.110 W/m²/K x 17° Roof: 306 W (21%) – 164 m² x 0.110 W/m²/K x 17° Windows: 387 W (27%) – 33 m² x 0.690 W/m²/K x 17° Air change: 151 W (11%) – 355 m³ x 0.025 W/m³/K x 17° Total = 1.44 kW Appreciate it is only part of the calculations needed, but does that seem a reasonable starting point? TerryE 05 Oct 2014 05:10 PM You can also download Jeremy's spreadsheet (you need to do a SaveAs and explicitly use an xls extension), but this sounds the correct ballpark for a near Passive design. The one important caveat is this issue of detailing and (i) linear heat-losses around windows, meets of panels, slabs, etc., and (ii) air losses at the same if the frame designer or constructor doesn't know their stuff, which is why supplier selection is important. Jeremy's spreadsheet also shows how to factor in seasonal average temperatures to get overall per month figures. Have a look through the topics that I linked to. One of these is probably a better place for discussion. NSS 06 Oct 2014 09:52 AM Have now downloaded Jeremy's spreadsheet. Suspect it will take me a while to get my head around it! recoveringacademic 17 Oct 2014 06:26 AM Thanks folks for a really interesting exchange of ideas. Remind me to get some sleep sometime soon.....

Yup let's avoid the pithole. I deliberately bought all of our bathroom and shower room fittings from Megabad before the 23 June at 1.31 € / £, IIRC (even though I wasn't anticipating installing them for another 6 months) for my own reasons. Since then for whatever reason the rate has bounced around between 1.10 - 1.18 €. None of the credit forecasts anticipate the £ strengthening in the foreseeable future. @jack, I agree that the reasons for this drop in the £ might be controversial amongst some of our members, but the fact remains that importing goods from abroad it now a lot more expensive, and this fact is relevant to this thread.

Original Comments coopers 25 May 2014 06:46 PM How fabulous. Hopefully you will be able to get exactly what you want. Have you approached planners yet? You could build something very similar in size to Jeremy's, and you'd be very comfortable. Then maybe a detached garage with studio over for your son? You will get all the info you need from this forum. Some fantastic contributors here. TerryE 25 May 2014 07:36 PM I am sort of in catch-up mode. We've been through pre-planning and now submitted our planning application, so we're "in the process" now. It's going to be a few months before we have the "go" or not, and have any details to report. declan52 26 May 2014 05:40 PM That's not to to far away from how i got started. I wanted an extension built onto my present house but got turned down so some how got talked into building in my parents front garden. Loads of builders had offered money for the site but always said no thanks so i thought i would have a go and so far i am loving it. You will get all the help you need here as i have found out any time a question has been asked.

Original comments: ProDave 07 Sep 2014 12:29 PM That looks a nice efficient layout. About the only thing I would change, is try and get a window in the rear gable end of bedroom 4 in the loft. TerryE 07 Sep 2014 04:22 PM I know; we liked like this idea as well, but our TA strongly recommended against because of possible overlooking objections. As it then turned out, the two material objections from neighbours were two that will be able to see the upper storey of the new house at the bottom of their gardens. Both objected to the roof lights, but these don't count as overlooking. A gable end window would have been another situation entirely. declan52 07 Sep 2014 06:36 PM The window in bedroom 1 can you move it over slightly or increase its size to let more light into the room. Every other room has a lot of light getting in except it. The staircase will look really nice. TerryE 07 Sep 2014 07:26 PM Declan, it's funny you should mention that, but Jan and I were sitting outside with a glass of wine early discussing Dave's comment and she said exactly the same declan52 07 Sep 2014 07:39 PM Great minds!! If it was slightly wider it would look better on your elevation in that it will be a closer match to the doors below. I increased both of my gable windows by 200mm but maybe the lpa won't allow you to increase their size.

I went through the technical pack that the SE supplied and which I passed onto my BInsp. It was quite an eye opener for me. There was were as many calcs to do with stiffness / racking strength as there were to do with load. Or in my summary they were as much concerned about the stiffness of frame and its ability to take hurricane force winds without folding like a deck of cards as the loading to carry its own weight and the contents.

I've already added it some time ago. First button in the second group from right when using the large edit window (PCs, Laptops, and most tablets) Duhhh!

Nick, thanks for the reminder to other readers that my whole discussion is only applicable to passive-class houses. I should have emphasised this earlier. I hadn't forgotten that, which is why I added my predicate. I've discussed this use before: my concern is that for ~8 months a year if I used a buffer tank then I would only be cycling the ASHP to keep it at 35°C say (with the associated heat losses) to save some E7 units. Averaged over the last 4 years, we use ~240 ltr /person / per day and maybe (on average) 30-40% of that is DHW, say 240 ltr raised from 10°C to 40°C or 7.2 MJ or 2 kWh at E7 rate = ~13p/day. (We run our dishwasher and waching machine coldfill overnight to use E7 units). Using a buffer tank would save maybe half of this, but the electricity would be mostly at peak rate, so when you factor COPs vs E7:Peak and heat loss from the buffer tank, then I might be looking at a saving of £10 p.a. I accept that the other major advantage is that doing this effectively doubles his SunAmp capacity. But I've also been thinking of taking this "use the slab as a buffer tank" paradigm one step further and adding a PHE into the UFH circuit. This way we could use the slab to preheat the main CW feed going into our SunAmp to ~20°C year-round, which will increase its effective capacity in winter by roughly a half -- for the cost of a PHE. So yes, having a bath in winter will suck a bit of heat out of the slab. Big deal. I plan to do the major top up using E7 electricity anyway. The rest of the year, taking a little bit of heat from the slab is no bad thing as we are in heat excess. @ProDave, we have an MBC frame and the thermal capacity of the cellulosic filler is pretty high -- roughly half of that of the slab. But yes, there is no point in circulating water when you don't need to. What I am planning to do is to monitor the out and returns sides of each UFH circuit with a DS18B20 digital thermometer. This have an absolute accuracy of ~½°C but an an adjusted relative accuracy of far better than 0.1°C. I am monitoring all loops to help me balance my loop flows. But yes once the slab is in steady state (and the temperature monitoring will tell my system this, then there is little point in having the circulating pump on.

Note to self: need to add a Strikeout icon to the editor bar!

@ProDave Dave, this is the point that would like to challenge: the need for a regulating manifold (and therefore a buffer tank to prime it). Let's just say that you want to circulate maintain a steady state by circulating water at 22°C which results in a heat transfer rate of ½kW into the slab. One method of doing this is to your ASHP continuously at an O/P of 22°C, say; another is use to buffer tank and pump 3kW into it at 35°C for 30mins or whatever your hysteresis on your buffer controls dictate, and then have a "space" of 3 hrs or so whilst this is slowly bled into the slab at this constant 22°C. A third strategy could be to take your ASHP down to whatever is can run at at its lowest output temperature and run it for 30mins say heating up the slab then turn it off, but leave the recirculation going. You don't need any temperature sensors in the slab, just a temperature sensor on the return flow from the slab. Circulate the water and wait whilst the slab (return flow) temperature falls. When it reaches 22°C, give it another 30 mins of ASHP top up and repeat as necessary. You don't need any fancy control of the ASHP, just a simple on off demand, as all you are controlling is the mark-space ratio. The numbers might need tweaked (and trimmed down to average out the sawtooth effect) and you might need a compensating adjustment for typical ambient/trended air temperature which modifies the turn on temperature, but in principle this could all be done with a few sensors and some control logic. No buffer tanks, no precision manifolds. OK I am a little different from most of you guys in that I am comfortable with this sort of instrumentation and IoT devices, and I've done quite a bit of embedded development over the years, so I am a lot more comfortable in doing this in S/W than COTS control H/W, but once I've gone around the buoy a few times and (if I've) got a workable system, then the approach once documented should be transferable for others to an off-the-shelf implementation.

I've been thinking about this issue of the buffer tank. Jeremy uses one with a precision mix-down as Nick and Neil have described above. Jason and Dave don't; Jack has one but doesn't use it at the moment. OK, Jeremy's approach clearly works, but I've really got to ask myself: If you are using the buffer tank for heating only, then why run one at 35°C, say, when you have a humongous concrete buffer at 20°C ? OK, the buffer tank approach is essential if you are using a Gas boiler or equivalent with can't modulate below 10kW, say, but if your heat source is an ASHP which can modulate down to ~ 1kW, then what does it does this complexity really add apart from another tank in your equipment room and a source of heat loss into a small room? The discussion might get a bit nerdy so maybe this is better addressed as a Boffin's corner topic. Give me a few days and I'll put together a decent strawman to explain my thinking.

I never had a problem with the plans provided by the TA, MBC and my staircase company all came out in the right metric units. So I don't know what the issue is. Sorry. When I have this problem I just set up a simple 2 column scaling spreadsheet to enter the data values and get the conversion automatically.