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That's really interesting @Bonner - we had UFH set at 21 and in those times it wasn't running (ie anytime it was 21 degrees plus in the room) we didn't have that sucking heat from our feet feeling - which is basically what I'm frightened of. I always put it down to the insulation and overall thermal mass stopping it ever getting colder than room temp. Low flow temps meant it was never noticeably warm to the touch either. But maybe that was just a feature of the flamed basalt we had on the floor, smooth stone/tiles might feel different. Indeed thinking back, I did feel it sometimes on smooth tiles in the bathroom at night. More food for thought.

https://www.totalhome.co.uk/ventilation/?pid=615 https://www.totalhome.co.uk/ventilation/?pid=595 Yes it will have an insulated concrete slab (down stairs). I'm considering a lewis deck and screed upstairs too (where we'll actually live) but more to support the weight of the flooring than to house UFH. I dont want to put in stuff I dont need. Any experience of how it might actually feel - not what you'd do in my place? Its real life experience I want...so thank you.

Thanks, I asked about future maint if they went bust...and was told it was a largely a badge engineered Genvex system with nothing exceptionally complex in it - so its good to hear that you've been happy with yours.

Many thanks for the responses @ProDave , @JohnMo, @Russdl, @Russell griffiths, @Redbeard @Gone West, @saveasteading And yeah...our prejudices are exactly the same hence my asking the question about feel. The numbers are fine. Requirement under 6kW - 10 available and more if we need a short burst. The THE system uses a micro HP within the MVHR unit to generate the heat so its not an element - and will be (within margins) a similar cop to any other HP. I want the house to be relatively "efficient", but I'm not overly concerned with running costs - it will be a fraction of our last house whatever we do. I guess we will therefore be able to market that we have "heating" - although we're not planning to sell (accepting that you never know) but the design is for an old couple and takes into account likely eventual outcomes on health etc - so its intended to see us out and changing circs not force us to move ever again. Also we will effectively have a "flat" on the 1st floor - where we would expect to spend 99% of the time. The ground floor is services/utilty/gym/garage/and guest suit (which could eventually become accommodation for a live in carer if required). So I don't really want to concentrate any effort on heating downstairs - its all about maintaining a comfortable feel on the first floor. But as we're likely to have stone/tile floors on the 1st floor, rather than carpet (because that's what we like), I can see that we may achieve the numbers but still not "feel" cosy. We had an ideal set up before with wet UFH so its would be easy to replicate that....but we didn't have a passivehaus spec, we didn't have MVHR, and we did spend a fortune on both installation and running. I'm trying to embrace something new rather than falling back on what I already know. Hence I'm really asking for what others with a similar set up have found in practice rather than what each of our attitdues to risk is.

We've got a tricky decision coming up. We're planning a Passivehaus standard timber frame build. We've engaged with Total Home Environment for their MVHR +Heat systems. I understand the calculations and can see a decent headroom for the minimal heat needed to overcome losses, etc. So the numbers work...but I'm interested in how that might "feel" in practice. I've seen a few threads discussing feel on here - some preferring what I'd call cool, other relatively hot so obviously interpretation is going to be tricky. Our past experience is with a GSHP feeding wet underfloor heating which was nominally "on" 24/7/365 at low flow temp and kept the house at 21 degrees which we found our ideal. What we are being offered I can see will be able to keep the house at a measured 21 degrees. But there is no thermal mass of the type we were used to. If we again opt for stone/tile floors but without UFH will that then "feel" cold despite the room being the same temp that we're used to? Important because we have the option now to have underfloor heating pipes built into the floor "just in case" we later want to add another heat source (eg ASHP). But I hate waste. If I wont need it I dont want to build it in, even as just an insurance premium. So just asking if there is any real world experience of this type of MVHR +heat set up out there and how it "feels". Thanks

I've just ordered mine and asked for 25kVA. Spoke to the National Grid surveyor about the load - in our case 2x car chargers, lift motor, induction hob, heat pump, and all of the other normal applicances. His recommendation was that they supply something that he initially called 2 phase - but with both phases matched ... so its really 2x 80a connections ... and to split the load across them, particarly 1 car charger on each. Cost had to include a new pole and new overhead cables (as I need insulated to build within the 3m exclusion for uninsulated), so not cheap, but at under £6k way cheaper than when I asked about 3 phase - and if its needed....the DNO pay for a new transformer - whereas I'd have to pay for a 3ph transformer.

What fall are you targetting? I understand just 25mm would be enough over the 2m that it will be in the En-Suite (or 60mm total from the stack - 4.8m away) - have you not got a 190 void? I think if you break out the soil pipe into the above floor en-suite, you're going to have to be very imaginative with how you box in and disguise it - but I guess it could be done.

Not necessarily - horses for courses. The 110 more often than not will be rubber seals push fit. Adaptors are often solvent welds. Traps most often compression fittings. The rest can be any of the above. Think in terms of future maintenance and any potential long term changes. No change hard to get at places - solvent weld for permanent trouble free fixing. Everywhere else consider the other options - especially if you might need to move something to get at something else (eg to replace a tap).

No not separate runs, just one pipe right across the back wall into the stack. Each toilet will need its own local branch. The other wastes can all individually go into the nearest point on the main 110 pipe using adaptors. Don't really like the sound of a dogleg on the stack - didn't realise that was the implication of moving it into the bathroom. I'd probably leave it straight ... but its no different really to your 110 pipe feeding across from the en-suite so would work.

It may be worth considering the longer game. I went with Roger's plan bought Kubota KX36 2A in 2009 for £6k and sold it on with my last property this year for about £5k. In the meantime its had had a couple of £k worth of fixes incl new tracks about 4 years ago - but was a fantastic workhorse despite living outside. My prejudice would say your new Chinese digger will work well and look the part...but come time to sell it on and the value will have plummeted (you'd need to research that...I haven't!). But probably less risk of it needing work in the first 2 or 3 years.

On the surface water management...you're likely to get a condition in your planning saying that its got to be dealt with within the plot. Soakaways are the answer but sizing them is a bit of an art form these days with the changing weather patterns (ie deluges giving several weeks worth of average rain in an afternoon.)

Will be interested to see the "right" answers to this, but my layman take is: Have the soil stack in the bathroom rather than bedroom if poss - it will make a noise but can be lessened with boxing in and sound deadening insulation. You only need one 110 pipe with a suitable fall running from the top right corner of the En-suite to the stack in the corner of the Bathroom. The toilets will need their own branch in at 110, but all of the other elements can be run in their individual 40mm/32mm pipe to the nearest point on the 110 and connect in there with an adaptor Of course they all will need their own individual trap near their outlets. The stack needs to run up and out above roof level for venting - and if it was me I'd put an air admittance valve above the outlet of the basin in the en-suite (the furthest element from the stack) and that will stop any gurgling - but many don't seem to bother with AAVs and accept gurgling.

All good points above. We had our last set of soakaways sized "for the 100 year storm". Which happened at least 5 or 6 times over the next decade. In fact I did put in (more than) enough capacity - but still got caught out by the failures. I had 8 downpipes on the house, 2 on the barn and 5 Acos across the drive. My early warning was the one on the front of the barn which would always block first (leaves, helicopter seeds, muck). That was the signal to check the Acos - cos if they blocked, a flash flood was a serious possibillity. Clearing the downpipe head baskets was on my monthly jobs list - and in max drop season could be needed weekly.

Thanks for the welcome Susie. I'll always help if I can....but much more likely to be asking Qs than answering. So much has moved on in the last decade ... and not just the pricing!

Just joined - have already found lots to interest me. We are about to start building our final home to see us out. If you don't want a flat or small house with tiny rooms when you get old, the UK housing market has nothing for you so clearly self build is the (only) way. It will be our first as well as last, but we're not entirely new to the game. I've done major refurbs of houses in my spare time for all of my adult life. The last one had a false start in 2012 when we found more issues than we'd planned for and were in a caravan on site from Feb 2013 to May 2014. The unexpected issues story repeated throughout the refurb and we realised too late we would have been significantly better off bulldozing the original and starting again. We even had to dig up and replace the slab when otherwise half way through! Anyway, although others did "the build" to a water tight shell, and others did the plastering, laid the slabs and installed the GSHP... I did the rest. Heating, plumbing, electrics, tiling, bathrooms, kitchen, hung the doors, etc etc. When we moved back in in 2014 we had 4 rooms and I didn't finish the rest until 2016. Worked on the landscaping thereafter and still had little projects I wanted to do right up until we left a month ago. So I'm incredibly slow....but I do it how I like it. Hoping to follow a similar plan this time with others doing a timber frame Passivehaus for us and then to clad it, etc. before I can take over for fit out and services. We'll see. Not expecting it to be even remotely as easy as that sounds - energy levels approaching 70 are nowhere near the as good as they were in my 50s. We've already been on it for over 2 years just getting through the planning stages - how hopelessly depressing that process is! Anyway, hoping to learn much from the experience and expertise here...