TerryE

I would say one benefit. I think that the other major plus is that the plumbing is 1-1 point-to-point, so no hidden joins or branches. The "Clapham Junction" of runs in the ceiling running into manifolds is also worth planning out and routing properly to avoid getting into a rats' nest of pipework. Certainly in a new build pulling the Hep20 was a doddle: you just had to be careful to keep the pipe clear of any sharp edges such as EcoJoist webs. We used 15mm throughout for simplicity, but in retrospect we should done what Nick suggests and that is to plum the hot runs in 10mm. Oh dear, we loose an extra ½l of water and wait an extra 5-10 sec for the hot to run hot. 🤣 Picking up @Russdl's point, I went round carefully trimming all the flow rates before the final inspection, but our inspector never even bothered checking. However the only two that we changed back were kitchen and utility sink mixers. TBH, we doc't find the low flow rates on the ensuite basins an issue. If anything it's an advantage: before I fitted the regulators, if you turns the tap on full, then the flow was so strong, that it would shoot out of the sink and soak evertything.

Broadly the situation on non-heating days is that the indirect heat sources (solar gain, warm bodies, waste heat from misc electricals) generally exceeds the fabric heat losses, so the house will steadily heat above your desired setpoint. Having your MVHR bypass its heat exchanger so the outgoing house air is swapped for unheated external air is one mechanism for dumping excess heat. However, you don't want to do this if the external air is warmer than the internal setpoint as you would want the heat exchanger running to keep heat out -- hence the min / max setpoints on the MVHR. You can do the sums on flow volumes + temp delta for your system to work out the kWh equivalent effects. Or you can set them by experimentation, but there is no standard "right" values -- these will depend on the characteristics of your house. My Ventaxia has a set of zero-volt contacts which can be used by a home automation system to fine tune all of this strategy, and I did initially plan to do this, but in the end we adopted my wife's strategy: we just open the odd window when needed. (We live in the country so the air quality is good, so long as the farmers aren't muck spreading. 🤣) However, we do exploit the fact that our 3 storey house is a sun trap on the principle SE aspect and the rear NW stays cool until mid-afternoon, so we crack a rear window in the morning and (if needed) a front one in late afternoon; this plus the roof light at the top of the hallway gives a very effective heat pipe to dump excess heat. I know that some members would regard opening windows in a house with MVHR as heresy, but as we don't have special needs (e.g. asthma suffers), we don't see why not when we want to dump heat.

According to regs, compression joints in slab have to be accessible. No need for soldered joints once tested to be accessible. They fail because of cold spots / contamination preventing solder wetting / flow and so (typically) the flux residue is acting as a temporary seal that will ultimately fail. Ring fill have already got a 360° wet on the joint. So long as the pipe is clean and fluxed, then this will also wet forming a permanent seal. Same applies for elbows bringing pipe up from slab level. As Nick says, you can always pressure test before you pour concrete.

I know the professionals like Nick make it look easy, but just about anyone who is modestly handy can do this So if you aren't familiar with soldering, then just buy 28mm ring-fills. You can dry fit and cut the pipe to length, then joint the pieces conveniently positioned out-of-place. Look at some YouTube demos of soldering ring fill joints. So long as everything has been cleaned to virgin bright copper and fluxed, and the area is clear of contacts / cold spots then you can heat the pipe uniformly and let the heat flow into the joint. Once the ring of solder wicks out under heat completely around the ring, then you know that the joint is sound. Clean. Ditto any end 90 elbows that are in-slab And remember that any piping in-slab must be decently lagged both for thermal reasons and to ensure that the concrete does not come into contact with the copper.

I use a Sonoff Power-usage plug that I can control with my Home Automation system, but you can also get Android timer apps and they are also programmable with Google Home if you are happy letting Uncle Google control your devices.

You can take smooth changes to the going (we have them on our staircases which have smooth 90° turns), but even the smallest variation in rise is a real trip hazard:

Mortar has almost zero tensile strength. For more precise removal, use the SDS to drill a couple of holes side-by-side in the mortar course you want to yield, and bang a 25mm chisel in; a few sideways taps will loosen the brick. For rough removal a sharp bang with 3 kg sledge hammer works wonders though you will lose some bricks, so if you want to reuse them just work steadily breaking the mortar courses. What size digger needs to go through; just once or daily? I'd leave the brickwork to the RH side of the window alone if possible and remove the house side. If you do go the right try to keep 2-3 bricks intact on the turn, otherwise you could loose the end wall.

This was my original intention. However as the convective radiator has to heat the air first of all, and then the air heats the structure to buffer the energy for later. It doesn't seem to work as well as directly heating an insulated slab. If we pumped in more heat the air temp would get too high and there'd be complaints! As it is we run the rad slightly colder during the night and turn it on again at about 6pm on a low setting to keep everything toasty. I agree that heating a lump of concrete in the 10s of tonnes does act as a good smoothing buffer, but I did play around with a simple thermal model to investigate the characteristics of the house dynamic. Do you have a digital spot thermometer? You can get them for under £20 now; borrowing one is even cheaper. Probably not wonderful in terms of absolute accuracy but good within ½°C or so relative. What is your total daily electricity use in winter? Let's just use 35 kWh as a strawman. You can really just about ignore the split between DHW, rad, other use because thanks to entropy every kWh you use (excepting perhaps HW that goes down the plughole) ends up as heat in the environment. And that heat is slowly lost externally through MVHR losses, radiation through fenestration, and radiation through other external facing surfaces. Let plug in some rough numbers, but you can do the exact ones. If 50% of the heat is lost through surfaces and you've say 400 m2 external surface, that's about 3½W per m2, so your external walls will be roughly ½°C cooler than the average air temperature. In other words 2 shades of bugger all. Try checking external and internal surfaces with a spot thermometer. I did. The worst I found in our house was along the edge of the reveals where the plasterwork meets the window frames which was maybe 3°C colder than room temp. Basically everything else was within a degree or so of the same temp. The lag transferring heat from airspace to surfaces isn't that great. Though local overheating can arise if you put the rad in a room and shut the door. That is why I suggest that you invest in a second rad, and as Nick suggests more child-safe digital timers. (Masking tape over controls to denote "do not touch" and whatever your favourite admonishment techniques should be effective with tinies.) A good location for the rad is a hallway, and leave some adjacent doors open. The MVHR can help circulate the heat throughout the house as well.

@Iceverge, I would get too upset about the delta. As you say, there are a lot of reasons for the variation as we've also found, e.g. you find that you prefer a warmer environment than your PHPP set points; laxness about sealing the house on ingress/exit, ... Like us, you now have a baseline, and you really need to base any potential changes in terms of RoI and any assessment of increased benefit vs hassle and stress of change, and we've found that this sets a high barrier to change. However, a couple of thoughts: What sort of time constant does your house have? E.g. ours loses about 1°C per day in deep winter if unheated. With this sort of house response you can shift heating times without noticeable effect: you need to put X kHr into the house per day, and it really doesn't matter when and where you do it. I don't know if you use a dual tariff, but when we did the calcs this saved use about 40% on our cost of electricity: heating, DHW heating, dishwasher and washing machine are all on cheap rate. We have a larger (~260m2 IIRC) house, and use a 3kW Willis + UFH for our primary heating, but I also have a 2kW oil-filled rad on our 1st floor landing in the winter that I run for a few hours overnight to top up the heat in the upper floors. You could just run your heater overnight (or add another if necessary). To keep your house near setpoint, you just need to top up the heat daily. It does really matter where or when. You could consider adding a split aircon unit in a hallway or living room (something like this sort of unit). There are lots of choices at around 12K BTU / 3kW for around 600€. This can easily dump a few kW into the house at a CoP of around 4. Don't put in a bedroom, because they still generate around 30 dbA at a medium setting which is audible and you will probably want to run it at night for cheap rate pricing. Jeremy Harris fitted one and did a topic on doing this (here). He used a pre-charged one that can be fitted without any specialist certifications. So long as you do and seal the through-wall duct and run the external SWG feed (the internal unit is powered from the external), and mount the units physically, then paying someone to wire it in should only be in the 100€s. If you are looking at Home Automation, then HomeAssistant can be used to schedule your rad timing and control most WiFi enabled aircon units.

My wife and I are both retired. We like wandering around in comfort and in bare feet etc. When we visit our kids' homes, we really notice how cold it can get when you wander from room to room, and the heating is on say during a daytime window, but the temperature drops rapidly when the heating goes off. Slippers and thick jumpers are pretty much mandatory in the winter. In our house, the temperature drops by about 1° C per day if the heating is off in the winter.

Sounds like a load of marketing bollocks to me. Overall any house acts as a system that can be characterised and controlled given enough measurement points and data. However, I doubt that any acts as a linear system, and do it is still extremely difficult to realise as characterised control system. Some example: Most houses leak like sieves, to prevailing wind speed and temperature has a tremendous impact on air-exchange related losses Solar gain and direct radiant losses are critically dependent on the area and orientation of fenestration. We've got a top grade passive-class house and our heating system uses two main inputs: (i) the forecast daily average temperature, and (ii) how much the average house (actually central hall) temperature has deviated from the target set point. This give us a pretty stable 24×7 house-wide temperature with a ~1 °C ripple (all of our heating is done overnight). IMO, anything like this would be impossible to achieve with a minimum BReg compliant house.

@7dayworker, If you do have an decent energy efficient design then one thing that you can consider is using room-style bi-block ASHPs. @Jeremy Harris did a blog entry on his fitting one on his upper floor -- not in his bedroom but in a landing area. The 9,000 BTU / 3 kW units are pretty cheap and will pump / dump enough heat to equalise inter-floor heat layering. As to lantern lights, the LED versions are typically under 10W.

I agree. None of the Govt subsidy schemes work for me. We would only need about 1-2 kW direct into the slab, and we can't take more than about 5 kW peak, so using the sort of standard template install just isn't a fit for us and we don't have any room in out services cupboard for buffer tanks, etc. (that we don't need anyway). Another big problem is that Samsung et al ASHP will not supply direct but only through a registered MCS installer. I have been looking at getting one of these cheaper ASHPs that are really for heating a Jacuzzi / swimming pool as these are optimised for an temp of ~40°C and the right power range. The tend to be a bit noisier than a decent unit such as an Ecodan, though.

When Jan and I redid the fire surround in our first house I found some newspaper packing around it, dated Sept 1916 and it included part of a column listing war dead probably from the Battle of the Somme.

No excuse. You can get a replacement in 24hrs from Amazon, Scewfix, etc. 🤣 Doing this would have probably saved you effort in the long run. I don't have one now so I can't personally recommend one, but a friend used to swear by them. There are various profiles; using t handle screwdriver as the search on Amazon gives a good selection of the alternatives. I suspect some would be worse for someone with Dupuytren's and some better. I think that this is a case for using your own knowledge and try it to see. The 300mm extension piece can also be really useful as this can allow a 2-handed grip in most situations

I did all the plumbing in my old farmhouse 35 years ago. I still remember the then rule "all buried pipework should be sleeved to prevent mechanical or chemical degradation of the pipework". So it was a botched job waiting to fail. ☹️

Humm. This sounds like a thread to bookmark 👍

Ian, leaving aside the sloppy tradesman issue which would have truly pissed off even the most saintly of us 😤 There is a separate point about how you could mitigate finding yourself in this situation – that is you have difficulty in using conventional drivers + PZ type screws which require a coordinate down pressure and anticlockwise torque to remove the screw. A couple of suggestions: Have you tried using a decent cordless impact screwdriver? There is a decent selection on Amazon, Screwfix, etc. from ~£70 up. These can shift most screws and can be used twohanded, and a 150mm or 300mm extension bit can help you position it. Are the T bar style manual drivers easier for you? Lastly have you got a screw extractor set? Using them is a bit of a knack, but at worse they enable you remove the head so you can remove the clamped (wood) piece without outward damage. The remaining stub can often be unscrewed with decent locking grip pliers. I realise that you may have already tried some of these, but they might just help mitigate your disability.

We have UFH in the slab and slate tiling throughout the ground floor. We just walk around in bare feet; never had any problems with feet feeling cold.

Have a look at any of the MBC warmslab videos and you will see that they use a similar technique. It is extremely effective at stopping any material bridge at the floor TF junction. Typically EPS 300 is used for the last 60cm of the base and upstand. If you look you will see that the inner leaf of the Larson strut cassettes is the load bearing one and it is standing directly on the sole plate and warm slab, so isn't going anywhere soon.

@Rubecula, we have a passive-class house, but TBH reducing annual energy use wasn't our primary goal. We made quite a few trade-offs between build costs, run-rates life style etc.. For example: A low energy house allowed to remove a lot of things that we would have needed in a classic build: we only have underfloor heating that was laid before the slab was poured and this is heated by a 3kW immersion heater. No complex central heating, no wall mounted radiators, no cold rooms, no cold ToD: everything in the house is the same temperature 24×7. The house has forced air circulation using MVHR so the air inside is always fresh. We could add ASHP since the UFH system was designed to allow adding ASHP, but to be honest we wouldn't get a net payback in maybe 7 years and especially given that ASHPs have a typical working life of 10 years. We also took the opportunity to make sure the outside was as near zero maintenance as possible, so we won't need to redecorate or do maintenance replacement in our remaining lifetime (we are 140 between us🤣).

It's OK; Sadly Jeremy isn't around to tell me off for this sloppy terminology. 🤣

@7dayworker, you miss an important benefit of living in a passive-class house: all of the insulation is on the outer barrier, and the thermal mass on the inside. So there is minimal room-to-room or time of day variation: essentially everything is always at the same temperature within a degree or so. This allow you to remove entirely a lot of CH subsystems and control complexity. As Nick says UFH on upper floors isn't needed, and adding it adds a lot of cost and complexity for no benefit. No wall rads, though I do use a free standing (<£100) oil-filled rad which I control with a Zigbee plug for maybe the 3 coldest months each year. (It's back in the storeroom now.) In the winter months it puts maybe 6 kWh into the 1st floor hall, and this is enough to keep the 1st floor bedrooms toasty. DHW is by electrically heated SunAmps (search the forum for more info). They are super insulated so you really only put E7 kWh into these to heat the water you actually use. Surprising cheap to run.

To quote Elon Musk: the best part is no part. You only need 1 air barrier. You need to seal this by construction design. Eg. Sika tape the OSB joints and then top with the service cavity battens. The filler needs to breath outwards from the barrier through the Panelvet and outer breather membrane. As others have said extra cost and work for negative benefit. Lastly having added quite a few service through pipes on my twinwall after the cellulose had been blown / filled, it is amazingly dense so with the inner OSB is pretty airtight. I used a 60cm 15mm bit to pilot inside to out; then a 25 / 40mm / whatever hole cutter on the inside and out; then notched the end of the ABS 25mm / whatever with a sawtooth so I could twist / cut its way through to maybe 5mm excess on one side and multitool off excess on other. Silicon and Sik tape to finish.

@AccidentalSkydiver out of interest if you google youtube MBC timber, then you'll get lots of examples. Here is one example which shows their warmslab and Larson struct cassette builds. In terms of your profile a few thoughts: You only need one racking layer and also a vapour barrier on the inner surface of the TF. You can use something like 12 mm OSB3 for this. If your verticals are at 40mm centres then you can join the OBS on every 3rd upright (or 2nd if you use 60mm centres). (These would need tweaked so save a lot of OSB ripping, if you are buying in 1220 OSB rather than 1200s.) We then had 44×25 battens oner-pinned on the vertical upright lines after taping up the OSB butt joints, to create a service cavity. This made first-fit a doddle. (Your SE would need to sign-off on 40 vs 60, racking, etc.) I can't see any advantage in having an outer OSB layer between the main TF verticals and the standoff fill section. In terms of the stand-off, remember that you need to tie this structurally to the outer blockwork leaf. The ties need to anchor to something in the TF. This will require some decent uprights that are tied to the main TF uprights, say 38 x 63 CLS minimum and made up a frame to mirror the main TF. You would need some structural spacer noggins to stand the outer TF from the inner say 60 × 89 × 38 if you want a 300mm fill void, but you could easily up the 60 to fit whatever you paln as the profile. You'd want some form of through anchor to fix the two frame; probably the simplest method would be to use 200mm timber fixing to drive through the out CLS, the standoff and into the inner TF. The vapour breather (panelvent + membrane) layer goes on the outside of the outer TF. Mark the upright lines so you know where to fix the ties. Remember that you want the frame to breath outwards, not inwards. Put in through-pipes for any services that you need to take through the frame. These pipe exteriors can be sealed to the frame for air tightness and the the pipes themselves foamed and sealed once the services has been pulled. You can leave the cellulose blowing until before 1st fit. (Our guys just cut a 100mm hole at the top of each panel section and pumped the stuff in section by section, then taped up the hole.)