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I believe this is correct but ONLY if it is invoiced as part of the total package and not separately. We had a staircase designed, manufactured and delivered. It was expensive, with a long design/manufacture schedule to suit our build and we reasonably agreed to stage payments. Unfortunately, Stage 2 Payment was invoiced as Design Service. it was only 10% of the total cost but HMRC rejected the invoice from our claim, because of the Invoice description. So, include the design services within the total package cost and if you are agreeing Stage Payments, make them Stage 1, Stage 2 etc and do not be specific on the Invoices,that is Stage 2 ( or whatever)for Design Services. The Stage Payment milestone achievement criteria can be described in a a separate document ( for, example the contract...)

It depends what the invoice says.. Safest way is just to ask them for the invoice to say "Supply of windows" "or perhaps "Supply of windows to customer drawing" or something like that. Then they would count as "materials" and their invoice should include VAT which you reclaim like any other materials. It gets complicated if they itemise everything and what the breakdown says.. If its got a "service" element such as "Design windows" I believe that can be argued either way because VAT 708 says in 3.4.1.. EDIT: Sorry one missing / and the formatting goes to pot and cannot be fixed. At least I cant figure out how to repair it.

Nope I don’t think so, I have just had a big steel beam welded off site and then supply only, vat was included and I will need to claim it back at the end.

It might just be the underfloor heating that's my waste of money. The mvhr is proving so efficient I never get to turn it on.

...and I think that is good way of looking at it. Like a good mattress I am happy to pay for it for the non-financial benefits it provides. All too often it seems that, like the original poster if I may be so bold, the chosen unit of measurement for assessing the value/benefit of MVHR is '£'. In my view this is wrong, and I can understand the potential for disappointment where it has been done. Sure, it might be the easiest to quantify but that doesn't make it right.

We have 48 spotlights in our ceilings. Not one of them has been sealed as there's no need to. If you have air leakage from outside to your ceiling voids then you're already fighting a losing battle, surely?

The invasion of privacy comes from audio data being constantly sent back to the servers of the companies selling these units, for almost all the processing of it into meaningful instructions. Some believe that the cheap box they have is actually doing all the voice recognition, when the reality is that all that cheap box can do is recognise a single key word, and then transmit all the audio from just before that keyword to some time after it, back to servers that are outside of your house, probably on a different continent, with different privacy laws, in order to be analysed. The same transmitted audio data is also recorded by those same servers, and may be listened to by people for any reason that the companies providing these services wish, as has recently been made public. Having one of these things in your home is exactly like having an open microphone connected directly to systems that maybe anywhere in the world. 24/7. If people trust that these units will only send audio data when they correctly interpret their keyword, then they need their bumps felt, as there is plenty of evidence that they can and do get key word recognition wrong. There's a good reason that, for example, the voice recognition capabilities of dirt cheap units like Alexa, etc, are so much better than the voice recognition system in my bit of fairly expensive tech on four wheels, and that's because, despite a fair bit of powerful processing power (enough to run some pretty capable AI), the systems in my car are nowhere near as powerful as the big servers operated by Amazon, et al, and the car has to rely on on-board processing for voice recognition. Because of this, its voice recognition is pretty primitive. It's a bit better than it was in my old Prius, but orders of magnitude less capable than the cheap boxes sold by Google, Amazon etc.

I spent a lot of time modelling the design of our house, and then measuring its performance, both when setting systems up, and through life with embedded sensors that are logged every 6 minutes and the data stored for later analysis. In terms of energy saving alone, our MVHR reduces our heating requirement by a significant amount, enough on its own to justify the expenditure. First, a look at the house heat loss, versus the difference between the inside and outside temperature, when not fitted with MVHR, but with the level of trickle ventilation/extraction required by building regulations: Note the blue line, which is the proportion of total heat loss attributable to the required level of ventilation to ensure that the house remains comfortable and damp free. Next, plotted to the same scale, the house as built with the MVHR system we installed. All other parameters are exactly as in the plot above, the only difference is the use of MVHR, rather than trickle vents, extraction fans, etc: Note that the ventilation heat loss is very significantly reduced, as is the total heat loss. In simple terms, at a differential temperature of 15 deg C between indoors and outdoors, the house needs about 45% less heating than if it did not have MVHR. That is, in my view, a massively significant benefit, nearly halving the heating requirement, just from fitting MVHR, and is, alone, enough to justify fitting it. Perhaps the most important benefit, though, is the one that everyone who visits our house notices almost immediately they walk in the door, and one that @NSS has made a very powerful argument for, the improvement in air quality. Having a house that is always fresh, has no residual odours from cooking etc, is free from pollen (that alone is a godsend for anyone who suffers from hay fever) and which results in bathrooms staying condensation free, with damp towels etc drying very quickly is probably as great a benefit as the saving in heating cost, and in my view probably worth fitting MVHR for on its own. However, there are many, many, examples of poor MVHR systems, either by poor design, poor installation, or a combination of both. There's also the fact that some people are persuaded to fit MVHR to houses that simply will not benefit from it, because they have an inadequate level of airtightness to allow MVHR to work effectively. Very few houses in the UK are built to an airtightness standard that will allow MVHR to work well, as even the current building regulations level of airtightness is inadequate for MVHR, and mass housebuilders struggle to even get houses to meet that requirement. There's little hope that a house built ten or twenty years ago could be made adequately airtight to allow MVHR to work efficiently, without a great deal of major improvement work to the core fabric of the house. I tried to improve the airtightness of our old 1980's built bungalow, and spent weeks air testing and going around sealing up every gap I found. Despite my best endeavours it still ended up at least 20 times more leaky than our current house. The main problem was that houses need to be designed to be airtight, it is pretty damned hard to try and bodge them to some level of airtightness when their basic structure was never intended to be free from many thousands of small air leaks.

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We had similar issues with our survey when we bought. After working through it with both our own solicitor and the firm appointed by our home insurance legal cover it turns out to be very difficult indeed to pursue any recourse for this. As well as the caveats others have mentioned, even if it is something they should have spotted you will not get anything if it's just a mistake. You would have to prove it was negligent - a mistake no reasonable person could have made if they were taking reasonable care. To do this you'd have to pay another surveyor for expert evidence that it was a negligent mistake. There's a fairly high bar for this - surveyors have a vested interest in making sure most mistakes are not negligent, in case any of their own come back to bite them. And of course if the defending surveyor can find an independent expert of their own willing to say "yeah, I can totally see how they missed that in the circumstances, I'm sure I've made similar mistakes" you will be bogged down in court trying to prove your expert is more believable than theirs. The cost of the case will therefore often far outweigh the potential damages, which makes it unlikely an insurer will cover it. More importantly, you have to pay your expert upfront to get their opinion on whether you can win. And an insurer won't pay for advice until they know the case is winnable. My legal insurer's solicitor told me that chicken-and-egg problem meant that although on paper the policy covers negligence claims, in practice they hardly ever take them. They're only interested if the mistake is jaw-droppingly-obviously-negligent (the house doesn't actually exist, or more usually the surgeon left the scissors inside the patient). If you have legal cover it's worth an ask, and if you have a tame solicitor of your own you could always try writing a letter to the surveyor demanding some compensation. Apparently below a certain level the surveyor's insurer will often take over the case and just settle straight away to avoid the cost of looking into it at their end. But if they refuse (as ours did) you don't have a lot of options. I'd be careful here. My understanding is the legal responsibility is with the person who commissioned/did the work. They have to make a declaration at the end that it's all compliant. Building Control may do some inspections to check that, and may refuse to accept the declaration if they find anything problematic. But I don't think that shifts the responsibility to them if they don't find anything. You could try and go after them if their mistake was negligent - but I suspect building control would argue a) they didn't owe you a duty of care, as you had no interest in the property at the time and b) your loss really stemmed from the fact somebody did non-compliant work rather than from Building Control not spotting it. Either of those arguments, if successful, would win them the case. Unfortunately they don't even have to prove the person that did the work was wholly responsible for your loss, they just have to prove they contributed. Liability for negligence can't be apportioned between people, so if there are two parties involved each of them only has to prove the other was partly responsible and that gets them both off the hook. However, building control do have the power to force you - as current owner of the property - to put right recent work that they discover is not compliant. I guess they probably wouldn't if it was minor (and/or not a safety thing), and they would potentially be a bit flexible if they knew you were trying to address a situation you inherited. But there is probably a risk that if you highlight that your house doesn't comply with regulations, and has an invalid completion certificate, you may open a can of worms that you'd prefer to leave closed. Again this might be an area where it's worth taking specialist advice if the mistakes are severe, but I'd definitely keep that conversation well away from the council till you know where you stand. You might possibly be able to go after the person that submitted the completion declaration if that was outright fraudulent, but again there might be issues in proving that you suffered a loss as a direct result of that. If I'd known when we bought our place what I've learned since, I'd have ignored the survey completely and spent a day here with my tools before we concluded contracts... For all the reassurance things like surveys and building control are meant to provide, it seems it's really still very much a case of caveat emptor if things go wrong.

Welcome, as we say to all newcomers, there is no such thing as a stupid question, stupid is not asking so ask away.

I’m totally with Temp here Splitting invoices can muddy the waters Safest is to get an invoice and claim it at the end

There's a lot more to the perceived temperature than just the actual temperature of the air. Drafts and humidity make a difference as does the radiant temperature of the walls, ceiling, furniture, windows, etc. The radiant temperature is about equally as important as the air temperature so if say, at work you have a large window which is a couple of degrees cooler that'll make quite a difference to how warm it feels whereas at home in the evening you'll likely have the curtains closed at this time of year and feel the effect of the windows a lot less. What confuses me is that they say that higher humidity makes you feel cooler but I'd think the increased evaporation from your skin in drier air would make it feel cooler. Odd.

Some units (especially of the flat-pack variety) depend upon the wall they are screwed to for their structural stability. If you use these sorts of units away from a wall, you often find you have to rigidly fix a back panel to them. If the back is to be removable, make sure the unit is rigid enough without it.

We have a passive-class house with MVHR which ensures that we have an airy damp-free environment. The HR element roughly halves the overall heat losses for the house. We only have ground floor UFH in the slab and this heats our entire 3 storey house effectively. Without the HR we would have had to design and install some form of secondary CH for the upper two floors. As it we don't so no rads, no boiler, no wet CH piping, and unencumbered walls. So for us, MVHR was a cost-effective self-install and far cheaper / simpler than the alternatives. And I strongly suggest MVHR is a no-brainer for anyone wanting a passive-class home.

@DamonHD (used to be on here for a time, but haven't seen him for ages) looked into this in depth some years ago, in the context of the school environment and the impact of CO2 concentration on the learning performance of children. IIRC, his findings (supported by some reasonably good science) were that learning performance started to fall off at concentrations above about 800ppm. That's not surprising, as we evolved to live in an environment with a CO2 concentration of less than 300ppm. From what I can recall of the aeromedicine stuff that was drummed into me at regular aeromedical and safety training school refreshers, the lower the partial pressure of CO2 in the air we breathe, the better our lungs are at expelling the stuff as a waste product. The rate at which CO2 diffuses from our blood stream to the air in our lungs is pretty much wholly dependent on the partial pressure of CO2 in the air, and that partial pressure is in turn proportional to the CO2 concentration. Arguably there is no optimum level of CO2 as far as our bodies are concerned, it needs to be as low as possible, and the closer we can get the internal CO2 level to that outside the better, as that global CO2 concentration is already a lot higher than it was just 50 or 60 years ago (in 1960 it was less than 320ppm, now it's around 420ppm).

That last bit should read.. But also.. My reading of this is that a design service that is primarily used by the window maker (eg to help them make the windows) it should be zero rated,. However if the design service was primarily provided to you (eg to get the shape and styling to suit your house) then it should be standard rated.

May be worth paying for an airtightness test before committing to the MVHR investment. Remember that your external doors need to be airtight, as do windows - no letterboxes or cat flaps, bathroom / kitchen extractors etc. I think there is general agreement here that there is air quality improvement with MVHR but the degree of that is somewhat subjective, as is whether it is a worthwhile investment. The heat recovery is more empirical but is highly reliant on very good airtightness (<2ACH). The title of this thread is a bit misleading - would be better phrased as a question or a 'In my renovation experience...'

I suppose it's a circular argument House is airtight to minimise ventilation heat losses therefore needs a ventilation system that minimises heat losses, or vice versa.

It's a nasty, wet, day here, and we've been shut indoors all day, not even gone outside once, so all doors and windows have been shut tight since yesterday. Just taken this 'photo of the hall display from the house monitoring/data logging system: That CO2 level is around 100ppm higher than we normally see, most probably because the MVHR hasn't been on boost since around 08:00 this morning, and because neither of us has been out of the house. If I started seeing levels as high as 900ppm then I'd be looking to find out why they had risen so high. We find that the CO2 level tends to fluctuate between about 450ppm up to about 800ppm, but never much higher than that. The outside CO2 level here seems to be about the global normal concentration ~420ppm. By way of contrast, this plot was from a logger placed in the bedroom of our old house, with a small window left permanently open for ventilation:

Pity it is a German kitchen, not a car. Then you would have a choice of 3 sorts of black, 3 sorts of dark blue, 3 sorts of grey, silver, white, and a red that really would prefer to be a further shade of grey :-0 . (ie the range of colours IBM Sales Executives used to wear for their suits) Mine is dark blue. And the kitchen is off white semi-gloss slab doors. I think I would take the cue from how much light it will get, and only go dark if it is a very bright room, but not go white either. Colours and textures which show prominently rather than "washed out" on Instagram are on trend. One interpretation of the look is called "One True Hipster" (says my interior designer). Ferdinand

We have done a mix of contractor and DIY second fix. Here's the breakdown. Stud walls - extra ones needed additional to those supplied by timber frame company: DIY Sound insulation in stud walls / ceilings: DIY Plasterboarding: Sub contractor Plastering: Sub contractor MVHR fit: DIY Internal doors / door frames: DIY Window boards: DIY Stairs: DIY (got a chippie friend in for some initial advice, thereafter doing it ourselves, including fitting landing glass and finishes - still to do) Second fix plumbing: Sub contractor Second fix electrics: sub contractor Kitchen fit: sub contractor Tiling: sub contractor (glad we did this particularly as a much better job over a huge floor area) Painting: DIY Skirting: DIY Wood flooring / carpet fitting: sub contractor Wallpapering: DIY And its not over yet.......(started in Jan, still not finished inside or out) So a real mix. Saved a lot of money. Worth noting that this has cost us a lot in time but has actually been fun. Learned a lot along the way too. And our finishes in some places would not be good enough for some people probably......

Thanks Joe and Peter. I’ve conveyed the points to our builder.

Remove existing chimney structure to roofline and retain bricks where possible. Install DPC tray and weep vents and rebuild stack to minimum 400mm above ridge. Install Code 4 step side lead flashing and soakers, front flash apron, back flash gutter, finishing the lead with a patination oil. Complete stack with 2.No courses Class 2 engineering brick, re-use existing pots and flaunch. All mortar joints full filled and flush pointed with 3:1 mix with suitable frost additives.

Same as the house, ordinary house bricks, Northumberland red (tumbled), from the way our west elevation soaks up the atlantic rain (bricks are not water proof) I am glad they were frost proof and I am going to seal them when we get a period of dry weather. I would be tempted to use engineering bricks and perhaps waterproofer in the mortar , see below. Engineering bricks have high compressive strength and low water absorption. They are used for their physical characteristics and not their appearance. They were traditionally used in civil engineering and are most suitable for applications where strength and resistance to frost attack and water are important.

No problem for me either. With the VAT reclaim I submitted a list of addresses used for deliveries or invoicing during the build and an explanation of what they were, and nothing was queried (eg, original home address, rented address, work address, plot/planning address, official postal address).

I'll dig out the trench and see what the earth is like before I decide which way to go. Thanks.

I agree with your definition, it makes far more sense, however it seems that the abbreviation that has been almost universally chosen is MVHR. May be we should start a thread to try and stem the use of MVHR, and get it changed to MHRV, a bit like my attempt to try and stop the use of "thermal mass" (although in that case it's because thermal mass appears to not have any defined units, so can't be measured). Much the same here. The UFH seems to only come on infrequently in the relatively mild weather we've been having over the past few days. I have tweaked things a bit to allow the MVHR post-heating (from the integral air-to-air heat pump) to operate over a narrow temperature range now, as a way to improve temperature control if we get a sudden drop in temperature. The UFH takes a fair time to warm up, and although we find the post-heated air from the MVHR a bit too dry, it does have the advantage of being able to respond relatively quickly, so seems to work well to just keep the temperature up by maybe half a degree or so until the UFH has had time to take over. TBH, it's really minor, though, as the house is massively more stable in temperature than any house we've ever lived in. It's just that, having got use to the temperature being pretty constant, we now tend to notice a half a degree variation. In our old house it wasn't uncommon to get 3 or 4 degree variation throughout the day in winter, sometimes more than this, so perhaps we're just being too fussy.

That's why I write MHRV, not MVHR which sounds awkward to me. It's heat-recovery ventilation which happens to be mechanical. You can also have passive (non-mechanical) heat-recovery ventilation. A minor advantage of a mechanical system (as opposed to most forms of passive ventilation which tend to be distributed around the house (in windows, etc)) is it's just one switch to turn it off until the neighbour's bonfire has gone out.

Will update on air score in a few months. Building regs measurement different to the ach as used by better houses. I think I read score has to be below 3 on building regs scale for mvhr to stack up? Less than 3 should be comfortably achievable on self builds where more attention to detail is the norm. Less so on developer houses

I sent an email to dwi-defra a very nice woman came back to me and we discussed things If stored water volume is only a 1-2 supply in the break tank then --she sees no problem as the rate of the chorine etc coming out of the water will be much slower than the usage ,so no need for UV In fact as the water is coming from a reservoir --eg surface collected water,then adding UV could in extreme cases cause conversion of dissolved organics into nasties not normal ,but possible --so her advice was --no UV drain down chalets at end of each season and just flush plenty of clean water through at beginning of next one along with careful cleaing of all spouts and taps and shower heads --normal good practice basically

Interesting topic, and if you look at the finances they probably don't add up. There doesn't appear to be many parallel comparisons either as most people fit it to new build houses or as part of a major refurb where lots of other work to improve the building fabric is being carried out. I'll be honest I've not done any work on the financial benefit in terms of reduced heating bills, this is my experience. We have a converted barn, about 50-55m², two adults and one child, converted 10 years ago, built to building regs from around 2000 (when work started), so by no means air tight. Double glazed, UFH etc. We've always suffered with condensation on windows, every morning I'd get up and wipe the bottom 3" of water from the windows and frames, the external door handles would be dripping wet with condensation. To try and combat this we'd keep several windows on vent and the bedroom skylight vent open all year round and even in the winter often have the skylight open several inches to help and reduce the stuffiness my wife complained of, and a chilly drafty bedroom on my side.... We never dried clothes in the house, have a tumble dryer in an outside shed. Were building a large extension (125m²) and I've looked into mvhr in the past before the extension was a reality and shy'd away from the cost. However I decided fitted mvhr to do two things, get rid of the need for a downdraft extractor over the island hob and also try help with the above in our existing part of the build. Over the summer I've fitted the unit and ducting and turned it in in October, set it up by feel for now in just the original barn as we've not properly broken through to the extension yet. Cost was higher than many on here, but I bought new everything and DIY'd the install for about £3K, I think to get the quality of what I've done off trades people it would have been closer to £6K. Since switching it on, doing a rough set up, I can honestly say the difference is night and day, the house is no longer damp, air in all rooms is fresh, as mentioned by @Jeremy Harris bathroom towels are always dry and we no longer need any window vents open, even dry a few clothes so reducing the tumble drier usage. If it cost me £250 a year to run then I'd still be happy, in reality it won't - I bet we were using close to that having a skylight open all the time. Like I said; same house, nothing else has changed, but the difference in feel is remarkable.

Whilst I am not in a position to dispute the theory I would from personal experience dispute the conclusion. I retrofitted MVHR to our 12yr old house (a Persimmon estate new build so whilst it wasn't 'drafty' I would not expect it to deserve any sort of air tightness label) and the results have been superb. All trickle vents have now been closed and extractors sealed up, and we now enjoy a noticeably fresher and more stable environment, no concerns about drying washing indoors, no cold drafts through the window vents, no noisy extractors etc. Heating costs are hard to compare year on year given the significant variation in winter climate however our annual gas costs look to remain at <£300 (for heating, hot water and hob) and this is a figure that I do not feel compelled to reduce or be concerned about. The only arguable negative has been the cost and effort to install it but, given I don't have concerns about heating costs, it wasn't done for financial reasons (and it was <£1000 given I picked up some bargains along the way) and the effort has been (mostly!) enjoyable and rewarding in my view. Believe me I wouldn't hesitate to label it not worthwhile if I had any doubts as I believe there's no shame in learning through first-hand experience and admitting if/when things haven't turned out quite as expected.

I always look at the delivery time, a good indication of which side of the planet they come from!

I had some light fitting delivered to my address which at the time was in Belgium ?.

@joe90 I think your site is an exception as it is so very flat. Not sure how this affects the flow, but I suspect that most of the rain that falls on your place stays put initially. Unlike the A30 earlier which has a new brown river flowing across it

You've basically got no come back against building control as far as I can see. We bought a house with a large single storey extension. When purchasing it our solicitor made sure there was a building control completion certificate. When we moved in and found no cavity wall insulation nor roof insulation we were told that the council were not liable for failing to ensure it met building regulations, it was the builder who was liable, but as there was no contract between us and the builder there was nothing we could do about it!

I was tempted to put a smart speaker in my bedroom. Then realised that nothing happens there. Could make up stories to tell it, then see what they try to sell me.

Bought one of these "fakitas", having seen this review (caution, AvE's language is definitely NSFW...):