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As others have said, multiple times it'd be an idea to do a test dig. Yes btw I've done similar in a single room. First clear the room! -Kango the floor: -Remove the floor to separate pile outside. Think I shifted about 70 or 80 rubble bags then the soil on top: -Dig down. The depth will vary according to your floor build up/design: -Distribute the soil where you can outside. It grows btw. -Grade the removed floor / break up to reuse as a sub base. I used max 40mm. -Level this off. The paint splodges are where I had stakes banged into the dirt to ensure a constant hardcore thickness: -Compact: -Blind with sharp sand: -Lay a layer of 25mm EPS: -Lay a DPM. Note there's a 2" thick upstand of EPS around the perimeter. This is to help take up the expansion of the slab when it heats up. (I did too add extra expansion strip). -Lay PIR min 150mm. Did mine in 2 layers, 50+100, staggered the joints and foil taped: -Lay UFH pipes, cheap even if you don't use them. I used Polypipe panels but you can staple to the PIR if you put another plastic membrane over the foil face: -Lay A142 mesh: -Lay concrete 100mm deep. I had various areas shuttered off for the part sunken bath and wet room corner. I used "wet" mixed concrete. I forgot to add strengthening fibres to the mix for this! The mesh should negate the need.....I hope. The concrete comes to the height of the expansion/perimeter strip. -Tile: Ask multiple stupid questions along the way and take years off forum member's lives in the process! 😂

Without looking it up, think it's a dual silicon diode. BAV99 That's how sad I am.

When I installed my heat pump two years ago I was buying electricity for less than 13p per kWh and the average price I had paid for heating oil over the previous two years had been 45.2 p per litre. With these numbers I expected the heat pump to be cost competitive with oil - and I think it was for the first year. Now electricity costs me 33.67 p per kWh whilst heating oil, currently is less than 90p per litre, I understand. So now my heat pump is probably cost competitive with mains gas but heating oil is the cheapest fuel you can get. Who knows what the situation will be like in another two years.

These phase change materials have been around for decades. They are usually a coated wax sphere embedded in a sheet material. If they were any good, we would all have them. None at all, thermal mass is a nonsense term. It assumes that the mass is the important part, not the heat capacity and the thermal conductivity. Paraffin Wax has a latent heat of fusion of 190 kJ/kg and a density of 900kg/m³. Plasterboard has a SHC of about 0.84 kJ/kg.K and a density of 1000kg/m³. So on the face of it, for the same mass, phase changing wax seems useful. But that is comparing phase change with non phase change. Paraffin wax usually has a SHC of around 2 kJ/kg.K. so a little over twice as 'good' as plasterboard. So adding thicker plasterboard would have, except in the small thermal window of phase change, the same effect. And that is if the whole area was covered in phase change material. If the miracle board had less than 45‰ wax in it, it would have very similar storage capacity and response times. So my verdict, not worth the bother. Thermal conductivity is of little relevance as any sheet material should be backed up with good insulation on the cold side.

Yes, but you have reduced the heat demand. If your reduced demand house had the same gas boiler as your flat, guess what, it would cost less. Drives me bonkers when you keep reading that the ASHP is more efficent, but you need to insulate properly first. Insulating is always a good idea. That how you reduce the heat load. It will be cheaper to heat than a poorly insulated house, regardless of the heat source.

I would think it is a bit hard, probably achievable with a, and we have to say it again, properly sized and operated air to air heat pump. Thing is, not worth basing the whole running the cost on a few very cold days. If we did that, we would never have a spare room (mine has been used twice in the last 9 years), or a large car.

Check the layout guy's work. Ours made two mistakes - each mistake was exactly one meter out. It took me ages to pluck up the courage to ask him back on site. I must have rechecked my measurements half a dozen times

When we first decided to self-build in 2014, Jan and I visited quite a few passive house builds and talked to various experts; we soon decided that a low energy approach was broadly the way to go for our build. One of these experts, a passive-house evangelist called Seamus O'Loughlin, emphasised that a conventional heating approach (where boiler demand is based on some central thermostat set point) doesn't work well in a passive house, because the time constants of a high-thermal capacity low energy house are a couple of orders of magnitude longer than those anticipated by conventional CH control systems. At the time this seemed a controversial assertion, but because I have done some mathematical modelling professionally, I was able to and decided to do some time-dependent heat-flow modelling and control strategy simulation of how our designed house would behave and this very much supported this assertion. I have already covered a lot of detail of my CH approach in previous posts and discussions, but it’s probably worth summarising some key headlines to set the context for my changes to our heating strategy: We were cash-flow limited during the build phase, so had to make various cost-benefit trade-offs on our build, like most members here. I based these on a general net 10-15 year payback, and it was clear that we wouldn’t be able to achieve a true zero-input passive house largely because of design compromises owing to planning restrictions and our plot size and orientation. However, we would be able to build a low-energy house that would need generally low levels of supplemental heating for maybe 6 months a year, with overall heat losses an order of magnitude less than a conventional build, and the thermal capacity of the heated fabric be many factors more. We decided to go all electric in the house with wet UFH embedded in the ground floor slab only. Cost benefit trade-offs didn’t even support installing an ASHP, though I did future proof the installation to simply the later addition of one if the cost numbers changed. I decided to adopt a simple but unconventional strategy for heating the house: calculate the total heating requirement for the coming day daily at midnight; this is based on actual averages for energy use, average house temperature and forecast average external temperature for the coming 24 hrs. This allows me to dump as much of this heat into the house fabric as practical at the cheapest electricity rate, and for us this is in the 7 hour overnight off-peak window on our E7 tariff. We used to get some spill-over into peak rate top-up in the coldest months, but a year ago I added an oil-filled electric radiator on my 1st floor landing, and one in my son’s 2nd floor bedsit controlled by my Home Automation System, with these scheduled to come on in the overnight E7 window to dump extra heat in the upper floors. This simple addition reduced the thermal layering from ground to second floor, and almost eliminated the need for daytime slab top-up. In practice we have roughly a 1°C daily ripple on overall winter house temperature. Because using a daily forecast computation does have some intrinsic prediction error, this can add typically less than 0.2°C day-to-day ripple on top, but any longer term drift can be corrected by the daily feedback. I have RPi3B running NodeRED attached to some digital thermometers and 4 GPIO controlled solid-state relays (SSRs) to control the time of the UFH pump and Willis heater, plus the 2 × SunAmps for DHW. This was very cheap to implement, and basically has no monthly or annual maintenance. With the current Electricity price hikes, we have decided: To trim our house temperature set-point back from 22.3°C down to 21°C To hard limit automatic heating of the slab to the cheaper 7-hour off-peak window. (We can still do peak by request in one hour chunks if we want to.) To use electric oil-filled radiators overnight to do any additional top-up. I can automate this through my Home Assistant (HA) that runs on a separate RPi4 and do this using MQTT via WiFi connected powered/metered sockets. This strategy currently limits heat into the house to: ~21 kWh through the slab and ~7 kWh through the two radiators. 28 kWh is enough to maintain overall house temperatures so long as the external temperature is at ~7 °C or higher, and it clearly isn’t the case at the time of posting. The house needs about 2½ kWh/K, so with the average daily external temperature at zero today this is 17½ kWh too little to maintain house temperatures. The long term Dec / Jan average where we live is about 4°C, so to maintain temperatures in this case we would need an extra 7½ kWh/day. (This last year, we had 26 days where the average external temperature was 4°C or below and only 2 where temperature was below zero or below.) So what happens when we underheat our house? Simple: it slowly cools down, and very slowly. For example, in the last 5 days of cold-spell, capping the heating has dropped the average house temperature from 22.3 down to 21.3°C, and given an average of -1°C for today, it will be down to our new target of 21°C by tomorrow . At this point I will need to add more heat or to accept that the house temperature will fall further. I will definitely need to add another 7kWh or so extra radiative capacity for overnight topup. We will play it by ear over the next week or so. I can either accept that I will be paying £0.38/kWh for extra peak period top-up during these really cold spells, or let the average temperature fall a little further if we find it comfortable enough (wear a thicker jumper, etc.) This approach works well for us because our house is so insulated and it has a huge amount of thermal capacity within the heated envelope. If we accept a small heating ripple then it really doesn’t matter that much when we heat within the day and so we can time-shift our demand to make use of the best tariff rates: currently over 85% of our electricity use is at the off-peak cheap-rate price. This latest exercise of clamping the heat output to 28 kWh when the maintain level is closer to 40 kWh underlines that the heat budget for and given day can be off by 30% or so and the net temperature drift is still on 0.1 °C or so; the time constants of the system are of the order of a week rather than days or hours. By way of a contrast my daughter lives in a pretty large but conventional 1990s house. When her heating goes off in the evening, the living room temperature drops maybe 4-5°C within an hour.

We put in a 3500l rainwater harvesting system when we did our house 12 years ago, for WC flushing, running the washing m/c and garden watering. I wouldn't do it again. Issues include: The water is of course unchlorinated, so you get brown toilet u-bends after a while (and the insides of the cisterns go black with mould, not that you see those of course). The washing never felt entirely 'clean'. We switched the toilets and washing m/c to mains after a few years for the above reasons. The tank ran out regularly each summer and the automatic top-up seemed to waste quite a bit of water down the tank overflow as it was delivered to the tank via the drainpipes and thus the leaf filter. The pump failed after 8 years and cost about £300 to repair (versus £700 to replace) The electric controller failed last year, so now we just switch the pump on manually when we want to water the garden. And it still runs out as soon as we have a dry period (ok we have a big garden and a lot of watering. So in short: nice idea but really not worth it. It's certainly never paid for itself. Sorry to be negative.

Worth a listen https://www.bbc.co.uk/sounds/play/w3ct3j7x

Dating probably just to maintain published hazard data: DUNLOP CF-03 FLEXIBLE FAST SET ADHESIVE GREY Hazard statements H315 Causes skin irritation. H317 May cause an allergic skin reaction. H318 Causes serious eye damage. H335 May cause respiratory irritation.

You can have a play with Fixit 222 on ubakus

So at least it's nothing fancy like an inverter power drive. Although you'd think it was something exotic from the exorbitant replacement cost. Can you identify what voltage rails are used? The 50V caps probably filter the 24VAC after rectification giving 33V. The inductors don't look like SMPS buck components. Possibly line filters for the AC in. Looks like there may be a solitary SM inductor hiding behind one though. I'd expect a SMPS regulator IC around there somehwere. You probably have as much chance as me in getting this going again but I think I'd try identifying the supply rails in use and do two things with that info: Cut the track for each voltage as close to it's origin as possible Use current limited bench psu's to provide those voltages to the rest of the PCB (and slowly bring up the current to see if sensible) If all seems OK, try and repair the on-board PSU To do the repair probably means identifying and replacing all the blown parts in that area - which would be aided by tracing out the schematic which will probably look similar to any app notes for the SMPS IC if you can identify it. Then just power it up with the rest of the PCB still disconnected - and use current limiting on the input. This could be from a DC bench supply as the 24VAC probably gets rectified almost immediately. Of course it might not be that simple if its a multilayer PCB with internal power planes. Still, it looks like a pretty basic 2-sided board to me.

I'd mix up a small test qty. Try it on some scraps.

Thanks. you can rely on buildhub to solve a problem.

It'll be an S. A7 = Type = BAV99 S= Manufacturer = Infineon 64 = Date Code (YM) = 2006 April Here's the datasheet.

I tried drilling a hole in the skirting board but couldn’t get to it. I probably should have another look. There is no obvious draught. The IR camera is very sensitive so that area is just 2-3C colder. There might be a gap in the foam around the edge of the slab creating a bridge. I did find a gap in one room which I was able to foam up. Thet room is the gym and has never had the heating on. It gets heat from the UFH manifold which is in the wardrobe and maybe the pool room next door, considering this I am amazed how warm it stays. 23C in there today and we just exercised which has pushed it up to almost 24C just from our body heat.

Tado published an article a couple of years ago showing that UK homes lose heat significantly faster than European neighbours, even when factoring in outside temperature: My thanks go out to all owners of Tado smart heating controls that made this embarrassing data available. Good on ya!

'Many' is not good enough. Really has to be all. I often think that technology is often self serving. Just because something can be done, it does not mean that it has to be done. Good engineering standards are all that is really needed, and those are based on basic physical properties. It is those basic properties that often get lost, and often misunderstood.

Im not sure this is helping the OP much though

The correct way to do it is to tape around the reveal between the frame and the wall to make it airtight. This might be on top of any foam to fill the gap around the frame. You would then probably use insulated plasterboard in the reveal on top of this. The issue is that depending on available space, width of the frames etc this is not possible, Within reason the small cold bridge is not the end of the world. The cold air getting in around the frames and behind the plasterboard is the bigger issue and if you can address anything this is what to look for.

Agreed...i looked at the picture again. When brand new, the building was available for industry visits, but I never managed to go. Since then, I think silence.

I agree with Iceverge. I have done many a roof in sensitive locations, using steel, either grey coated, or aluzinc, and the planners have been happy that it looked like traditional zinc. The magic words were 'wide pan, low profile'. I.e. Not crinkly. I never used standing seam either because of the cost, and being difficult at joints and junctions. The screws are visible but a minor thing. Also, if ever damaged, standing seam requires specialist repair, wich simply won't happen, and it gets patched up. Does your design brief cover economical design? That would concentrate your architect's mind on getting this changed. Beware of him being prescious of the zinc, and not being very convincing with the plannners....I have had that and taken the discussion on myself. Don't tell the planner it is about cost though. Sustainability....less material, easier maintenance and repair, longer life...whatever.

OMG I really hopes hope it's not a lot, but I know what you mean. One of the main learnings for me is just how much the defrost and ramping back up compromises the nominal power of the unit. Mine takes 20 minutes to get back up to the flow temperature at which it cut off for a defrost cycle. Nine defrosts so far today between 5am and 4pm. To a lesser extent, but same principle, the extent to which hot water breaks need to be taken into account when doing calcs purely for heating.

I used W profile foam strip. Just remember an air test will almost certainly be sucking air out the house, so depending on how the hatch is fitted, you may have to fit a different sort.

Worse still given we have some of the most expensive houses stock in Europe. We are also one of the worst European countries for supporting self-builds.

I never wanted to get mine certified as a passive house, I didn't see the point. I just wanted to do the best that I could and know it was using a lot less energy than most new builds. I was a little surprised when I gave the as built EPC to building control and they remarked it was the first A they had seen. And I do wonder if I had built the same house in a much less cold place, just how low the heating bills would be.

One thing that I have noticed is that we lose maybe 10-20% of our slab heat because of a partial thermal bridge that I discussed in an earlier post. Space heating using the rads doesn't have this loss, and so is slightly more efficient. @ProDave has done a fantastic job, hasn't he? @RandAbuild, about 80% of our electricity use is at the cheap which is currently 17.96p / kWh so our energy cost during this cold snap is around £12 / day. Do whatever you think works for you. @jack, I remember that episode, back from the days when Grand Designs was watchable. I always wonder what the actual as-built performance of these builds is.

That is the coldest area in all the walls in my house. Almost my definition it will be. The walls are insulated with a very low U-value and the triple glazing has a low U-value. The weak spot is the window frames, plus any bodges around them when the windows were installed. So I guess the question is are these areas colder than the should be. I would expect them to be a good few degrees cooler than the glass and walls especially when it is as cold as it has been. My windows have aluclad wooden frames, I think most uPVC frames would be worse. When you say they are "draughty" do you mean that you can actually feel a draught. This would suggest that the windows are not tight in their frames. Or is it just that the area feels colder than the surrounding area. I actually tried the experiment of injecting foam into the reveal on one side of a window to compare to the other side. I just took an IR picture of it and it has made no difference. Both sides are basically the same temperature. The RHS has foam, the LHS does not. The worst points seem to be the corners as you can see.

Too true Jack. It's looking bad but I guess we've got a selection effect going on here. I've only seen one member posting up about how well his ASHP is doing but that doesn't mean he's the only one with a correctly installed system.

Luckily wind has been notably absent coinciding with this cold snap.

The enerphit standard is 25kWh/m2/year so if you're doing that you have to achieve that, not some other number. You can aim for 35 if you prefer, but that's not an enerphit. (People discuss like they're going for a 1st class honours degree, by renegotiating what score is required to pass)

That's last weeks figures before it got colder. I worked it out as an average of about 0.9kW of heat into the building. I normally read my meters once a week on a Friday, but did a mid week reading yesterday and in this cold snap the ASHP is consuming 13kWh per day space heating so witht he same assumed COP of 3 (might be a bit less now it's colder) that would be about 39kWh of heat per day or an average input of 1.6kW House temperature is 20 degrees downstairs, unheated upstairs currently about 18 degrees. Night temperature has been down to -7 and day temperature not above 0 since the weekend. A few days like today has been good sunshine so probably some useful solar gain, and "as good as it gets" PV generation with the sun at almost it's lowest. Actual heat input per square metre as measured suggests it is just about reaching passive house levels, but it would fail passive house certification if we had tried as the air tightness was only 1.4

Pretty close at CoP 3. The difference is probably lost in statistical noise. I would not be basing a long term space heating decision on today's skewed prices. 18 months ago the market was totally different. What we do know is that in the medium term we are heading for electrification, no getting away from that.

You’ll want a site surveyor who will come and survey the site (usually using a GPS gizmo to be accurate to within few cm) and then they’ll set out using stakes for the corners for your groundworker. Our groundworker then sprayed his dig channels on the ground between setting out engineers posts to get the corners. Often with planning there will have been a site surveyor at the beginning who would have surveyed and generated a site layout plan for the planning application?

Completely agree. They also haven’t got a clue how much it costs to build so don’t ask them. They were nearly 100% off our actual build cost with their estimate.

My experience of a couple of architects: they won’t design something that is cost effective to build and there will often be points on the build where the contractor scratches their head because the drawings don’t make sense. Case in point: architect designed our open eaves and didn’t think about clearance for windows on top floor. They hit the eaves (timbers now being cut down). Structural engineers will design things that are hugely over engineered to cover themselves, and aren’t specialists in things like trussed roofs so will design things using traditional steels and loose rafters rather than an engineered product. Case in point: our SE designed loose lay rafters with a chamber floor and about 12 steels for our attic room. They said attic trusses wouldn’t work. Builder got a truss roof manufacturer to design attic trusses - it passed engineers calcs and saved 11 steels and £7k in our pockets. If I knew now what I know I would try and ensure the architect and SE were designing a house that was economical as possible to build. We were so excited to design the floor plan and we didn’t know to pause and make sure the thing was as economical to build as possible. My view would be try and minimise on site labour for things like roofs, minimise steels, and maybe liaise with your builder at the design stage to point out any complex or expensive bits in the build that could be designed out.

Very limited choice round here (north Dorset) but yes, I take your point. If anyone can recommend a good plumbing firm that knows something about underfloor heating and ASHPs near Shaftesbury, that would be great but it seems the vast majority of firms don't have experience of ASHPs and UFH.

If you are on a cheaper night time tariff, it will be most cost effective compared to gas, particularly if you can heat during the cheap time period

Yep. If I’ve learnt anything this last 8 months check absolutely everything that the professionals send to you or do on-site. I’ve spotted numerous errors and omissions. The architect has been the worst culprit for this.

At present gas in in the region of 11p per kWh and electricity abut 33p per kWh, so a heat pump achieving a COP of 3 will cost the same to run as a gas boiler. What are the present prices of oil per kWh? @SteamyTea ? (Boilerjuice suggests about 90p per litre so what's that per kWh?) I get the impression some people are "selling" an ASHP as a super cheap means of heating. They are not. Set up properly with a properly designed install they can offer heating to an all electric house at comparable costs to mains gas. They won't improve on the cost of mains gas in many situations. They also give environment benefits as the raw energy use and CO2 emissions are lower.

Can you replace with a PVC coated steel roof? https://www.gusclad.ie/products/standing-seam-profile/

yeah. groundworkers do the stuff in the ground like foundations, drainage, STP etc. maybe you could pick up a copy of Mark Brinkley's Housebuilders Bible (https://www.amazon.co.uk/Housebuilders-Bible-14-14th/dp/1916016812) . it's a very good book and has loads of great information for self-builders in there to help you not use the wrong terminology! 😉

Architects like spending other peoples money and often not practical to build

Our groundswork guy brings someone in to do the setting out.

Architects love zinc. They must be trading in it. I started with zinc but we are now fitting a Catnic Urban metal standing seam roof. I got a quote for Greencoat but it was much dearer than Catnic. Can you not getting a change of material? Most of our warrant says blah blah material or equivalent.

Stick a repair coupler in and be done....that's what I intend to do fir my damaged pipe🤷‍♂️

kWh I suspect. 50 kW would blow the main fuse on a single phase installation.