TerryE

In terms of the total specific heat of the internal environment, the slab is the biggest element, but don't discount the SH of the plasterboard and effectively ½ of the cellulosic filler. The other big element in our case is the ringbeam and two transverse structural beams at 300×300mm cross-section adds another big chunk. I haven't even got around to buying my ASHP yet and we survived happily last winter on my 3kW Willis heater heating the slab overnight on E7 low tariff. Our daily top is pretty much a simple calc based on average outside temp, and we can stay within the cheap rate 21kWh overnight down to about +3°C below that and we need a daytime boost. (Of the top of my head, our internal slab area is 70m² and we have 3 floors so the total floor space is around 200m²). The slab responds almost exactly as my simple 3D heatflow model predicted. Our DHW is Sunamp again heated overnight by E7. My house performs within 10% of my initial JSH-style spreadsheet that I did in the early planning stages. But as Jeremy has said, the MBC warm slab and cellulosic filled Larson strut construction pretty much eliminates all thermal bridging. Our one design cockup was that our slab has an outer ringbeam bearing our Cotswold-type stone outer skin that is mechanically coupled to the main slab with 200 odd 20mm rebar sections which is a fine mechanical solution but one hell of a thermal bridge. Luckily I picked this up during the slab construction and was able to mitigate perhaps 80-90% of this flaw (see my blog post on this for more details); I suspect that the unmitigated residue is why our actuals are maybe 5-10% worse than our initial estimates. I've never bothered working it out in terms of annualised kWh/m²/yr, but based on our actuals over last winter through spring and summer (which was a cold one) our total annual heating requirement is around 4,500 kWh/m²/yr . We were required to conform to a traditional cottage style (= small windows) on an SW principle access so we have little solar gain and weren't allowed PV. But this is around 3W/m² averaged over the year so I am not sure where the discrepancy is with your 10-20 figure. DHW is on top of course as is normal energy use for electrics, lighting, cooking, but these combined less than double this, so our total energy use is well under 6W/m² averaged year-round. As well as the overall heat balance, you also have to consider internal heat flows and heat gradients. At our design point we only have the groundfloor UFH. We have a slate floor throughout and usually bare footed indoors -- cheap and low maintenance; the floor also feels nice and cool underfoot in the summer and warm in the winter. We don't have any upper floor heating, so no radiators or the like and associated pipework. Tell a lie: we do have an oil-filled electric towel rail in our master bedroom ensuite, but the only time that we have turned it on so far was during commissioning tests. Even so our upper floors are maybe 1½°C cooler than the ground floor in winter. This suits us for the bedrooms, but I do find that my office is a little too cool for my liking, so I have a small Dyson fan that I use as an occasional top-up when I am working in the office and it is very cold outside. I think if you were to double or quadruple the overall systematic losses, then the main design consequence would be that you'd need some form of upstairs central heating with all of the complexities that that brings. Stick to 400mm cellulosic filler or better, IMO.

I've got mine to the right of the front door in plane sight, but also in clear shot of a security camera; one of these: https://keysafe.co.uk/products/key-safes/c500-keysafe.html Yes, someone could take a sledge hammer and angle grinder to it to open the safe, but they could also do the same to one of your doors or windows. A sufficiently determined thief can always gain entry. They question is how long are they going to take and how much damage are they going to do in the process. IMO, in general thieves act rationally: if the effort needed and possibility of detection are sufficiently high, then it is a lot easier to try elsewhere. https://www.googleadservices.com/pagead/aclk?sa=L&ai=DChcSEwj8_O7OnIvdAhXtve0KHXkwCzoYABAHGgJkZw&ohost=www.google.com&cid=CAESEeD2Z8RXsozFnRcRcv15K5ET&sig=AOD64_3ix_HWSWaiKje9LV-F_V2jtJa0LA&ctype=5&q=&ved=0ahUKEwiCuufOnIvdAhUiM8AKHR7dBxAQ9aACCDQ&a

I do, but only after you've had that sysAdmin chat with me ?

Most LPAs are now under severe financial restraints and the need for cost recovery. So in our LPA we are at the other extreme and there is zero chance of walking into the planning office and expecting 5 mins of advice. So we went the PPA route, and to be honest we found it very good value. Our LPA had a fixed schedule of charges; the fees are for new builds 1-9 houses are: £160 + VAT for Meeting + written advice + site visit £80 + VAT for Follow up requests for further meeting + written advice (+ site visit if needed) But look online: your LPA will publish guidelines and a schedule of charges. IMO, it is a good idea effectively to prepare a decent draft of the full application. What we got for our money was the PO read through our application in depth and he then came to the site and we had a sit down and detailed discussion where he told us what the LPA would like and also made some very useful suggestions. His write up was also very useful and I did regularly refer back to it. TBA, the £160 was very good VFM given his effort and input. He answered a couple of emails but also suggested a follow up which we didn't take up, because we didn't like the 6 week response cycle, but in retrospect we should have done so. Three points: Your case officer assessing your application will also read the PPA. If you follow the PPA then the assessment will say this, and this will greatly help in getting you application approved. However, it isn't a guarantee as I have heard of cases where the subsequent application follows PPA and is still turned down, but much of this is street tales from by builder, I don't know. If you have PPA and go against it in your application, then this is a definite black mark; better to prepare the evidence and to try to get the POs support in a follow up. IMO, the whole planning cycle is a potential nightmare. PPA is the one time that you are paying for LPA services and they are committing to a face-to-face engagement; the fees are reasonable and I think that this is money well spent. I personally disagree about using the planning application cycle as a way of getting free advice. The only time that we tried this was when our LP enforcement officer told use that we had to put in a NMA because our front door was not consistent with our application. "You can discuss the application with the allocated officer". The only problem was that our LPA leaves allocation to the last minute, so there wasn't anyone allocated a few days before the SLA deadline. We then got a rejection without him even contacting us: submit a MMA. I don't think that he even bothered to read the submission properly. Unfortunately NMA vs MMA is entirely at the discretion of LPA, and there was no way that the planner was going to change his mind, once the paperwork had been posted.

@Lizzie, we used MBC like you for both the slab and the frame. It sounds like you had your unfair share of problems arising from quality issues during the laying of the slab. In our case, I didn't have a PM, but my wife Jan and I did this all ourselves, and we monitored the progress on a daily basis during both the slab work and the frame erection. In both phases (as we have previously discussed on the forum), we found a major thermal design flaw in the slab and another issue with the frame. If either had been left undetected then like you we might have had similarly serious defects to air, but in both cases I picked the issue and discussed it with the TF company's PM and agreed remediation; doing this immediately involved minor rework. Also after the slab was finished I double-checked all of the linear and diagonal measurements, and used my Dumpy to check levels. The maximum error on the line measurements was about 5mm; the maximum off-level was a 3-4mm slump along the centre of one of the gable walls, and the placement of one of the foul water risers was about 2cm out. However this was all within acceptable tolerances so we knew that the TF erection could proceed. I feel that the root of this issue is the culture of poor on-site quality assurance in the (domestic) building industry. IMO, this is true across all construction methods. Things can and do go wrong, but the impacts will be small if such errors are picked up immediately and rectified there and then. IMO, your PM should have also done this sort of check on the slab before TF erection and identified the defect at this stage. It would have been fairly straightforward to remedy this at this stage with maybe a 1-2 week delay on the TF erection and you wouldn't have had all of the consequential issues with trying to erect a TF on an untrue slab. Jan and I have a TF house; we are absolutely delighted with it, and have no regrets about this choice. Since we did all of the interior work less the boarding out and electrics, one thing that we found amazing was that we went from a bare slab to weather-tight house that you could lock up in 8 working days. Also as the interior had over 18 months to dry out before we moved in we've had absolutely no issues with movement and cracking in the plasterwork. Reading this thread top-to-bottom, there has been a lot of negative comment on this thread from proponents of method A pointing out a lot of issues with method B, all based on street tales rather than evidence. (This clearly doesn't apply in your case, Lizzie.) IMO, this is about as relevant as me spouting off about the "problems" of being a woman -- how on earth am I qualified to do this?

You need to look at the pressure drop curves for your pump at your flow rates and have a sensible margin. Too low and the pump starts to sound noisy. I might have had a memory mindfart: ours might be at 1½ bar, I will have look the next time I am sitting on the can in the downstairs loo.

Mike, we didn't even bother pressure testing ours until we commissioned the system , but that's because we used an MBC in-slab UFH so the slab team laid the UFH pipework straight from the drum and the concrete went down a day later. I filled the system and left it for a day to get into thermal equilibrium and cranked it up to 6 bar for a couple of hours, with just the manifolds and no expansion, just to double check for leaks, so even a few cm³ of loss would have collapsed the pressure. We have manual top-up from the rising main after the DCV through a double valve system to the expansion vessel if and when needed, and set it up to run at 1 bar. 9 months later and it's still at 1 bar. Though as Peter says some +/- around this because of the varying expansion of water in the system as the temperature varies. IMO, you only need to run the UFH at whatever pressure needed to prevent cavitation for your flow rates. I can't see any advantage in running at a high pressure than needed.

@Nickfromwales, I considered a geothermal loop in the early days, but the simple issue is that we didn't have a big enough plot to fit one in. An ASHP in ground floor UFH chill mode would help, but the main issue is my son's room in the loft. The bugger has to many electronics chuffing out maybe 300-400 W, and with him, the thermal gradient and the high insulation, his room gets too hot in this weather.

@Triassic, not sure why I missed your post. Sorry. 8 months into occupation and the SunAmps work fantastically. OK, they are Gen 1 product and the Gen 2 kit is more cost-effective, but that's the price of being an early adopter. I need to do another post on our space conditioning. Heating hasn't proved to be very much of an issue. The 3 kW Wills is easily man-enough to handle sub-zero winter demands; the 1st and 2nd floors are 1-2°C colder than the target GFL temp (21.5°C), but that isn't an issue. Our house has no S facing windows and the roughly E/W aspect works well in the summer. (At least until this week.) We just leave windows open on the shaded side (yes with the MVHR running) and a roof light in the apex, and this gives us enough heat dump to keep the house cool and airy. This current hot spell has been breaking this operating model. The GFL is now climbing to ~24-25°C and we have a strong thermal gradient up the house with the 1st floor maybe 2°C warmer and the 2nd another 1-2°C again. This seems to be bearing out my hypothesis that an ASHP might have a marginal payback for savings in heating costs, but might prove essential for height of summer cooling. Though I need to think more about the heat gradient issue.

We managed this -- by the skin of our teeth. We built our new house at the bottom of the garden. We started our build using our savings. This got us through all the costs of design, planning and works up to warm slab. We borrowed from the kids to make the first stage payment on the frame. As with the others we took out a mortgage on our old house (which was otherwise unencumbered) up to the limit of the value that I could get on my company pension. We were quite open that we were using this in effect as a bridging loan and in fact the Monmouth BS allowed us to have an interest only mortgage at ~1¼% for the first 2 years. Once the boundary fence was up and the outside skin was complete (so the house looked like it was complete from the old house) we put the old one on the market. BTW, prospective buyers look on a building site next door as a risk and a hassle, so this is going to impact on the price and ease of sale. It is far better to do as we did. Even so, it took about a year to find the right buyer and in the end we completed the month that the MonBS mortgage went from ~1¼% to 4%. Even so the mortgage lump sum wasn't enough, once we paid back the kids so we ended up borrowing from them towards the end again to get to the point where we could at least move in. But one the sale on the old house completed, we could clear off the mortgage and do all of the finishing off. If you are looking for cash to bridge the build period, that your lender needs to be able to view it as a low risk hassle-free loan to get a decent rate. In our case the money was about a third of the value of our farmhouse and I passed the affordability assessment based on my pension income. A loan for 80% of the value, with a new development on an adjacent plot is not low risk. We also had our new build planning approvals and the plans available, so even though the new build was outside the scope of our mortgage we had a clear exit strategy. Getting to this point can take 1-2 years or more, so it make no sense to be paying interest payments during this period if you have enough liquid savings to cover this phase. £500K seems very expensive for a build without the price of the plot. You can build a nice 4-bed detached house for under £300K so long as you resist the temptation to create a grand design. Also a surprising amount of the bill is after 2nd fit, so another option is to look at the minimum requirements for "lawful development" , which IIRC are basically that you have a weather-proof living space, running water and waste, toilet, shower and some form of cooking arrangement. Once you are weather-proof, you could arrange to temporarily fit out 1-2 rooms to qualify and once you've got the certificate there is nothing to stop you completing on the old house sale and legally moving in to the new house. So if you are looking at the type of build that I suggested then you might be able to get your loan requirement down to ~200-250K which means that you need ~50K income with minimum commitments to get this sort of loan, as well as being healthy, etc.

Q: "Who should do the wet room tanking?" A in my case: SWMBO. Or in our case Wetroom × 3 ? I am quite a good carpenter (by hobby and anal attention) so I fitted all our formers. And did the plumbing. Our tiler was excellent, but he only did the tiling. So I offer an alternative opinion to Ferdinand, but the main thing is that whoever you get to do it doesn't cut any corners and gets all of the details right. I personally trusted Jan to do a pukka job here more than an unknown tradesman. This isn't something that you can fix up or correct later: if the tanking is compromised then you are in real trouble and are in for major rework.

Ni.....sssshhhhhTeamyT, if you are fluent in Python then stick with it. ?

And a lot more in Lua if you want to go that route ? You can bread board everything up, but as you have seen from earlier posts, I just use perfboard for my project boards, and a couple of headers to take my Wemos Module.

Our TF was sarked with 22mm OSB which was also a structural stiffness component (we have a warm loft as part of our living space). Our supplier gave a similar comment about our BM, but in Nov - early Feb (the gap between the TF going up and the roof being slated) this was less of an issue. What more of an issue was the risk from high winds getting under BM overlaps and damaging the fabric which we addressed by adding extra temporary battening on the gables etc., and also going over all overlaps with a tacker where needed. It worked well in the end, with no problems despite some gale force winds, and dusting of snow, and the internals were dry and were a far better working environment than if the build were still open to the elements.

We could lock our front door and secure our house on day 9 of the frame erection. The interior was 100% weather tight, so as J says TF can have huge advantages if you get the supply chain aligned.

In my, Jack's and Jeremy's slabs we have 100mm of concrete directly poured in a single pour slab with no covering screed (as the pour itself is power floated flat). The UFH piping is embedded in it. The slab also has 200 mm box cross-bracing ribs and 300ml (in my case) ring beams and centre beams. The concrete itself acts as a thermal store and is a key part of ensuring the thermal stability of the house. My peak input into 70m² of slab is 3kW, and I rely on the mass of the slab to smooth the transfer into the environment. I discuss this in more detail in my blog.

To be honest, it depends very much on the usage patterns and house design, and it also varies tremendously by season. We have a 3 person household, 2 retired and one live-in adult son effectively in his own flatlet in our loft. Ours is a passive-class new build electric only, and no PV because of planning restrictions. Our current daily energy bill is around £2.10 but a reasonable chunk of this is my son's 2×PC + 2×TVs. In the depths of winter it might get up to £6.50 if it is freezing outside, but we have no maintenance costs as we have no equipment like gas boilers or ASHPs that need annual service contracts.

@joe90, my main point is that if you do want to maintain a comfortable environment then it is a good idea to design in your cooling temperature control as part of the build, as this will be cheaper than doing a retrofit. In the case of what looks like a near south facing conservatory, then your should consider opening lights in the roof, preferably servo controlled, and internal shading. Internal shading will work fine so long as you have opening lights to let out the baking air. If you want to keep plants in the conservatory you should think of temperature controlled windows and blinds.

I have very mixed views about CL. To much of his series just seems to be product placement. He got his window placement wrong for his skin construction. I added a polite constructive comment, pointing out the issue that he missed and suggesting an alternative placement and asked his views. I went back to the page a couple of weeks later to see his answer and the post had been removed. And as to his tongue design, yes this is a good solution, but IMO a simple reinforced concrete tongue is just a lot simpler; you just need to surround it on the external cill side with something like foam glass to create the thermal break. This is what we did and it definitely works fine. PS. He hid the post, and checking his latest video on stonework, he has reposition his windows as I suggested that he would have to do. ?

Cat 5E will happily drive 1Gb at house scales. That's what I used, and that's what I get when the device NICs support it. Maybe I will be kicking myself in 10 years time, but it works fine for me.

This is probably the wrong Q anyway, but in our case we use cellulosic filler rather than PUR etc. OK, this requires a deeper profile to get a decent U value, but it is also a lot denser so has a better decrement delay, we also have 15 tonne of slab and ring beams inside the thermal envelope. The thing that so many self builders miss is the DD of acres of glass is zero, and this can play havoc with temperature stability for 9 months a year whenever you have a clear sunny day. Architects seem to love designing in large areas of glass even where there is no real added value for the occupants. This isn't to say that you shouldn't do this, if there it's genuine value to you as occupant, but don't kid yourself: your major thermal design challenge isn't going to be how to warm your house; it will be how to prevent it becoming a tropical hot house on a sunny day.

That set only has 3 reviews, one bad and one doesn't count so I'd give them a miss. I would go for a more expensive set such as the 450mm Draper ones. There are just some jobs where having decent cutters is just so useful. Also there is a knack to using them, such as taking two bites. Push the wire or rebar as far as possible into the jaws for the maximum leverage and squeeze in the handles. If this doesn't cut first time then it will cut into the sides and squeeze the cross-section more oval. Now open the jaws again and you can push the rebar further into the jaws for a second cut with more leverage. If you are cutting bolts or screws (useful if your screws are just too long and the points are braking through and you don't have a suitable smaller screw size), then the trick is to do a 2-cut but turn the bold / screw through 90° for the second cut so you end up with a more squared break. PS. If you are worried about strength then you might need to go for 600mm cutters, but they are also a but more heavy to manipulate.

Either pre-drill the hole with a drill that is 2mm smaller than the outer screw thread, or make sure that you use a fast start screw (those are the ones that have a longish point and a quarter segment ground out) and use a Glasgow screwdriver to get you started (position the screw and give it a couple of taps with a hammer, because it will just bend if you try to get it too deep; the idea is just to get the tip of that first 5+ mm, so that the screw isn't wobbling and the self cutter is biting when you do use the powered driver). Another trick is that it is easier to hold the shank of the screw in a pair of piers with one hand and the drill with the other. Don't try to hold the shank of the screw directly with your hand, especially if you are using thinnish work gloves -- as the screw will end up eating your glove fingers, and (if you aren't quick enough letting go of the drill trigger) your fleshy ones as well. ?

The wonder of Spax hex heads. They might be more expensive, but they are far more tolerant to the drill shank being off-coaxial to the screw.

bolt cutters and yourself. Jan uses ours.