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Have you insulated the ductwork supplying air to the rooms? Do you understand the difference between air con and cooling too? Just before we get 'into it'

When we purchased our plot in early 2020, I decided to do the conveyancing myself (as I'm basically a tight-arse). I didn't want to pay a solicitor to take months to do something I could easily do myself. Having completed that successfully, the purchase was finalised, and I then filled in the SDLT form and sent off a cheque for the tax that I believed was due. At that point, being aware that this was a second property, I calculated that we owed SDLT at the higher rate, so £5,000 on a plot purchased for £150,000. Skip forward to September 2022, perusing on Buildhub I discover that a building plot is not necessarily a residential property for the purposes of tax. News to me! I went back to HMRC's website, and learned that if the plot was non-residential, then the tax I owed would have been £0 (as the threshold starts at £150,001). As the plot we bought had previously been an agricultural field, prior to the vendor having obtained planning consent, then it was indeed non-residential for tax purposes. I contacted HMRC's helpline to discuss, and the chap I spoke to kindly explained that I could write in and ask them to repay me. I'm not sure whether he was aware or not, but at that point there was actually 0% chance of HMRC repaying us. The rules said that I had only 12 months from the date of completion (June 2020) to revise my SLDT submission. After that, tough luck. Any incorrectly paid tax would not be repaid. HMRC replied to my first letter, rejecting my request on the grounds that I had not quoted the piece of law I was relying on to ask for it. I then spent an entire weekend researching caselaw on situations such as mine. What an exercise in disappointment that was, to put it mildly. I read every single published judgement on SDLT cases for the previous 5 years, as well as the relevant regulations themselves, and concluded that there was simply no basis for me to persuade HMRC to repay us. I was crestfallen, and had to admit to HWMBO that I had gifted £5k to the Treasury out of my own ignorance, and my unwillingness to pay legal fees. Still, I decided that it was worth one final try, and I sat down in January to write the mother of all letters to try to persuade HMRC to repay us. I explained my mistake, cited the regulations, and asked if they could exercise discretion to allow a late amendment to the SDLT1 form on the grounds that they had themselves checked the form at the time and had not identified my error, despite there having been enough information on the form for them to have reasonably suspected that the property was not residential. I said that if they would not do that, would they please consider opening an enforcement case against us so that they could review whether we had paid the right amount of tax, and calculate for themselves what we owed (which was the only legal route that would allow them to revise the SLDT1 form beyond the time limit). Then I went for the heartstrings, saying that we really couldn't afford to gift this money to the Treasury, and if they could please see their way to reimburse us, we would be eternally grateful. A couple of weeks ago HWMBO found a credit in his bank account of £5089.00 with a reference of 'HMRC SDLT'. They had not only repaid us, but added interest for the time they had had the money. They haven't written to us to say why they decided to do this, so I've no idea which part of the letter was effective, but it feels churlish to question it. A very salutary lesson in there for me. And perhaps for some of you too.

He’s one of the most helpful and knowledgeable people on here. I suggest you spend more time reading the forum to get a feel for the members and how and what they post.

To read the above replies, lol. You won’t get answers that carry any weight on any forum, and if someone does answer you then you can’t use what they say anyways, so you’re just wasting your time, sorry. Go ask your BCO or employ a drainage engineer. Simples. You will need to part with some money to get what you need, that’s not going to change.

As long as it's not organic material it's fine to bury under the slab. It's ventilated anyway so will be fine. Use it where ever you can, put some on the road in as a base or under the slab it's all saving you buying materials in to replace it.

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Consider how best to jamb the PIR upstands in place. You can put them in place first and then wedge them with the floor boards or stick them later with some expanding foam . I think I prefer the former. I would go for more than 25mm if I could. It's just a bit fragile at that depth. Wouldn't bother with the blue foam TBH. Just more PIR.

Hi. No the pipe is 50mm in the slab all the sanitary wastes are 110 out of the slab.

@NickfromwalesBrilliant, thank you for all your time and help

Maybe there's a good reason you cannot find anything, as they are two different independent systems. MVHR does around 0.5 ACH, so cannot carry enough flow to effectively cool the house, in heating mode, a passivhaus is designed around the max achievable heat flow through the ventilation system that being 10W/m2. The flow figures for Aircon are something like 47.0 - 60.5 L/S per kW of cooling capacity. That's about the same flow rate for our MVHR for near 200m2 house. So MVHR would be able to carry about 1kWh for our house, which would be rubbish and not worth the effort. If you want Aircon, get an Aircon unit or consider floor cooling etc.

Yes it suited us perfectly but everyone is different and when you throw kids into the equation it muddies the waters no end. We wanted a straightforward simple and economical to run house, which is what we built. No complex controls. When we put it on the market the people who bought it wanted the same as us and were willing to pay the extra to have it. PH wouldn't suit everyone, especially those who want windows open all year round and a WBS roaring away. When we built our PH we were members of the AECB and had a lot of contact with architects and PH designers. I was very surprised at some of the basic mistakes they made and yet they were supposedly experts.

I agree about the batteries stealing the PV which was previously available for water heating, and having to increase the amount of PV as a result, because I went through exactly that last year. But IMO it makes absolutely no sense to use the immersion at a time when no PV is available when you could heat the water using the HP for 1/3 the price. I can't believe the cost of the marginal wear on the HP is anything like the difference. I like the worked examples btw @markocosic and agree totally with yr conclusions. I think my Victron system could be programmed using the Node Red option to use the batteries for smoothing out the clouds/kettles etc. but it will have to wait till my HP is installed.

no they aren’t - warranty claims are down and NHBC aren’t paying out for a lot of issues that they used to. It’s an insurance policy and they will find every way not to pay. There is nothing in BS 13598 that states you cannot use the pipes above ground if adequately protected, nor in BS-EN 1329 or any of the others listed in Part H of the Building regulations as long as the pipe is manufactured within the standards.

Was my first thought. My car has both. One involves opening the window.

Thickness depends on size, intended traffic load and sub base prep. domestic decorative pavers are often 25mm thick while paving slabs are 40-60mm due to the increased area and therefore bending loads

Nobody can answer this other than the local water authority, and your intended building control person(s). I know they'll say 160mm, but I can't tell you that, as what anyone says here is an educated opinion, but just that, an opinion. Go ask the relevant bodies whom will reside over the correct / final specification of this project, as the installed systems will need to meet or exceed their standard to be signed off for your completion certificate.

Have you investigated the water table? Dig some holes in the ground in the area of the garden room and see after a period of heavy rain what depth the water settles to. This will inform a sensible level to put your floor at. If it low enough, a good french drain and well detailed DPM should allow you to drop the floor as low as you like assuming water cannot flow in the door of the room. Maybe incorporate a small sump and space for a plug in pump if you go down this route.

You could design your own. Use a 3D Printer service to make them and cast your own. However small block pavers are normally thick for a reason. It helps keep them flat, so I'd be nervous about the long term stability of this particular design..

She'll have to wait a few years, I see her regularly crossing off the days mind you. ..... Yes and No. YES: I'm completely on board with the airtightness, 3g, MVHR, attention to thermal bridging. The house "coasts" so well through outside temperature variations. The bitter and extra windy weather last night was imperceptible inside. We are living more comfortably than any other house I've lived in and despite being direct electric is still much cheaper than most ASHP new builds I know to heat. In terms of KISS our CH works and a plug in rad or two doesn't get much simpler. NO: The 10w/m² peak heating load target is based on space heating of the house with supply air from the MVHR and hence is a bit arbitrary. Similarly the 15kWh/m²/annum heating demand. Doing PH can be quite an evangelical process as you have to do so much conversion of the doubters. In so it's easy to become swallowed by the doctrine. In reality 16kWh/m2/annum or 14kWh is neither here nor there and probably far outweighed by how much your kids let the door open. I would have gone for 300mm EPS floor insulation rather than 200mm and 300mm rather than 250mm EPS beads in the walls if I was to go again. The cost is marginal and would have taken us to about 8w/m² and 12kWh/m². No reason to stop at PH targets either. PH assumes 20⁰ is fine for every room. It is, but really 18/19⁰ in the bedrooms and 24/25⁰ in the bathrooms would be better. PH can put the kibosh many lovely design elements like roof lights at the cost of some minimal active heating/cooling. When we were building however almost everyone who didn't sing from the PH hymnsheet with regard to targets, airtight, heating load/demand etc was a bluffer and would have I'm sure landed us with a house that fell far short of design levels. TLDR. PH and PHPP absolutely work, use them but don't treat them as targets/limits and don't let the methodology limit you from making an excellent house an exceptional house.

Yeah they won't until you hire them. If the planning condition doesn't specify what type of survey then I would get these 4 companies to quote for an "Preliminary desktop study" as that's the cheapest. Pick one of the quotes to accept and hire them to do the desktop study. Ask them to send you the report. If the report doesn't find anything submit it to the planners with the application and fee to discharge the condition. If the desktop study does find something or makes recommendations for more work come back here for suggestions. If they recommended massive amounts of work it might even be worth getting another co to do a second desktop study in the hope they will recommend less expensive work. Otherwise send the study report back to all 4 companies to quote for that next stage. Take it one step at a time. No need (yet) to spend a fortune digging on site.

Sorry I meant I put DPC band on top of the brick course then the timber wall plate. Its hard to drill 12mm holes in exactly the right place in the wall plate to suit the 12mm bolts cast into the slab as they may not be perfectly vertical. So I drilled oversize/clearance holes around 18-20mm in diameter and used large 40mm square washers under the nuts to bolt the wall plate down.

Assuming that the survey says "nothing to be expected here". Not copied by them to the planners but to you. Otherwise don't submit it and try again. I still think that the planners must have reasonable grounds to request the survey. In so doing they should explain why.

Yet to see it. Commercial projects that don't use cast ductile often use the terracotta stuff in basements and risers.

yep 4x3" although many of the legoland estates are using 4x2... Dont forget tie down straps every 1.8m and half lap any joins.

In terms of exporting pv excess it is indeed that simple, unless you are in Australia with a neighborhood/substation transformer, where there is so much pv excess with all the people at work not using the energy. If you are in UK, your next door neighbour will be the one using that export.

Erm, no I haven't used any paving, only ever built sheds on slabs. I just sketched it as you said that's the way you want to go. 3 2" council slabs would raise you 6" if you could get them for nothing/cheap. Or 140mm 7N dense concrete blocks. Cast your own plinths from knocked up timber boxes. Loads of options.

Done it plenty of times, just needs to be spotlessly clean and I rough it up with Emery cloth too. You don’t use glue for this, but instead use the proper ‘gap-filling cement’. Totally different beast.

When I designed my house back in 2009 I was using the 2007 version of PHPP which IIRC, (subject to my squishy brain), didn't have the room by room analysis option. I can see that there could be advantages in carrying out a room by room analysis in a very large, poorly designed house, but it wouldn't have been an advantage to me. It's really best to follow the PH design principles as closely as possible.

A different route would work here.... deduct the cost of the electricity from the final bill. I'm sure that @SteamyTea, @Omnibuswoman and other regulars know that, in the round, and if the circumstances are appropriate, reclaiming unjustifiably incurred expenses from a builder is a reasonable thing to do. I write this post principally for those who lurk here on BH, but then - too late - tell us a tale of woe which ends by telling us they paid their bill in full. If builders make unreasonable charges, pay part of the bill and then agree a final settlement later.

The numbers are easier after a jar or two. Want to save polar bears / eastern europeans? Create something (electricity) then use it to replace the most gas-intensive thing currently out there. At the moment this is electricity. Don't displace gas boiler use in your own home (80% efficient) by chucking it in a tank. Displace power station gas use in somebody else's home (40% efficient) by chucking it in the grid. It's a bigger win. Simple as that. Create something (heat) more efficiently than you could before. Don't burn gas at 80% to make heat. Burn gas at 40% then use the electricity to create heat at 300% for a relative efficiency of 120%. Ideally both.

E.g. long radius / rest bends. And if you have leftovers you can use them underground, but not the other way round if you use black/grey stuff.

Looking at it this may be the case, although for some reason Zehender's sales guy showed us this system when we visited (we live fairly close) It's an interesting approach to heating/cooling though. I always wonder if there is anything in the 40% saving claim they make and if these same savings apply to infra-red based radiant heating.

Look at the big picture instead of looking within your own four walls. Mr & Mrs Loadsamoney have a gas boiler and PV Mr & Mrs Conscientious have a heat pump and PV Miss Miggins needs electricity to something non-discretionary (e.g. the fridge) Mr Sun sells sunshine to PV generators for £0.0/kWh Mr Putin sells gas for £0.10/kWh; so it's £0.125/kWh for heat from a boiler or £0.25/kWh for electricity (boiler 80% efficient; power generation and distribution 40% efficient) Option 1: Mr & Mrs Loadsamoney send 1 kWh of PV into their hot water tank Miss Miggins buys 1 kWh of electricity from the grid which gives £0.25 to Mr Putin for gas Option 2: Mr & Mrs Loadsamoney buy 1 kWh of hot water by giving £0.125 to Mr Putin for gas and sending 1 kWh of electricity out to the grid Miss Miggins buys 1 kWh of electricity from the grid. Mr Putin gets nothing. Option 2 halves overall gas use and payment of tribute to Putin vs Option 1. This is why many folks would consider you to be a selfish penny pinching piece of work if you're diverting PV to generate hot water. Option 3: Mr & Mrs Conscientious buy 1 kWh of hot water using 0.5 kWh of PV in the heat pump and send 0.5 kWh to the grid Miss Miggins buys 1 kWh of electricity from the grid which gives £0.125 to Mr Putin for gas Option 3 also halves overall gas use vs Option 1. The COP of a heat pump in summer is over 3 though. So Option 4: Mr & Mrs Conscientious buy 1 kWh of hot water using 0.3 kWh of PV and send 0.7 kWh to the grid Miss Miggins buys 1 kWh of electricity from the grid which gives £0.075 to Mr Putin This is why you should be using PV in heat pumps. There is a separate debate to be had about how broken our electricity markets are. The suppliers should not be charging you for electricity imported (with a half hour period) that you subsequently export (within that same half hour period). It really doesn't matter if a little electricity shuffles back and fort in the wires as the clouds pass or kettles boil. We should have what they call "net half hourly" metering such that you only pay for what you have, net, used at the end of each half hour. But that debate on the commercial terms is different to the debate about what the morally responsible thing to be doing is. The morally responsible thing to be doing is minimising overall fossil gas consumption. Reduce fossil gas consumption for electricity by generating PV. Then reduce fossil gas consumption for heating y using electricity to move heat more efficiently than you can burn gas to generate heat. Does this make the absurdity of PV diversion clearer? It absolutely categorically does not achieve the reduction in fossil consumption that you thought it did. It's for selfish people who miserably count every last penny. It's not for people who care about resource efficiency. But you'd be forgiven for thinking that it is "eco" given how it is greenwashed. BTW the reason that its useful to run for longer at a lower power level is clouds etc. Look at the actual data from PV installations. It's much easier to meet 100% of a 1.5 kW load for 6 hours than 100% of a 3 kW load for 3 hours. (clouds rarely cover 100% of the sky) You CAN actually steer heat pump power use with the appropriate controls; but only between ~50% and 100%; so in time there will be devices to offer this type of service; but in the meantime what you should if you really care is buy a 1-2 kWh battery; which charges in the morning before the heat pump hot water; infills the heat pump hot water when clouds pass; then charges again after it's finished ready for the evening. Alternatively buy an imperial duck tonne of PV; such that you're invariably generating over the required amount; and spill / curtail the rest as appropriate. It lasts much longer than house batteries; is less inclined to catch fire or get nicked etc; and like insulation is one of things that you really can't have too much of. (Generation is an investment that you buy to create. Batteries are just paying to trade.)

Yes, as long as not exposed to sunlight.

It's great have other cooling means, for the summer but there will times when you need to cool house as well as heat the house during the same 24 hour period, so cooling the slab is not appropriate. Real example the other day, we had a low of -5 and high of +1, but the sun was out all day. So by 3pm the house was starting to get hot, so I opened the windows for an hour or so. If you need to cool a house naturally you do it by cross ventilation i.e you open windows and front of the property to wash air through the building. MVHR does little or no cooling due to flow rates being low.

People have been saying that for a decade now, does not seem to be happening in the UK. Here is a bit about lithium batteries. https://ourworldindata.org/battery-price-decline Here is a bit about PV https://ourworldindata.org/cheap-renewables-growth I can't find any data on heat pumps at the moment, but shall keep looking when I remember. I think one of the problems is that because we like high price houses, heating systems are considered a high mark up add on. There was a small estate of new houses built in St, Agnes about 12 years ago, nearly all of them had ASHPs fitted. Those houses were no more expensive than similar 'gas powered' ones built in Newquay, or Redruth, once the St. Agnes premium had been paid (the snob premium). Much of the high prices we pay are because of incentive schemes to implement domestic renewables, a recent report highlighted the low take up of the BUS scheme. The only scheme that was successful was the original FiTs on PV, but in reality, very few people could afford to spend between £8000 and £12000 on a PV system to get the 41p/kWh and the deemed 5.6p export. Realistically, I doubt that domestic generation is every going to compete with grid power and I say that as someone that would love to live off grid for the technical challenge. To get close to being self sufficient in electricity, I would have to halve my winter usage to around 600 MWh for December, January and February, which may be possible, and cover my house in PV, and my 5 neighbours houses. Or just buy in 90% of my power at 15p/kWh, which I currently do, and wince when I see the 10% at nearly 60p/kWh.

You will need 75 x 100 They don’t need to be treated Most merchants will stock these in 4.8 lengths Its worth going in the BMs and selecting your own As more often than not the Timbers can be badly bent if selected by the years staff

Yes, I’ll contact them and ask if their response to my letter has been lost in the post. And if it hasn’t, will ask if their decision maker would kindly like to set out their reasons for accepting our request. When I get a reply, I will share it here.

Quick, fag packet thoughts: Thinking leave the void but use a strip of rodent mesh around the perimeter. You could over clad with say uPVC or asbestolux type cement board...paint it black...

Welcome to forum, the form shows "and" and you wrote "or".

Just my take, without understanding how it looks from the outside, but I would centre all three on the same line - front door, French doors and glazed doors? Centre on the dining room/table so you can see through the side windows front to back.

Plus one

Is this just for aesthetics? It may be too late but I'd have had the blocks flush-pointed and simply painted. It is, after all, a garage... Also not sure you'd want a gritty top-coat inside, unless you don't like skin on your knuckles! @ProDave: Snap!

If it really is a garage, nicely pointed blockwork and a coat of masonry paint will be cheap, clean and hard wearing. Only if it needs to be something other than a garage would I waste time boarding it with anything.

There are lots of good people out there. Also plenty who aren't so good and don't give the best service because of a skill shortage. It must be very diificult to judge as a first yimer, when not from the so called industry. Our family team were quite shocked when I said we must confront the SE to save £20k, and sack the groundworkers. The former had a perfectly reasonable principal who accepted my alternative, but our assigned guy was not happy to be questioned. The groundworker, whose main skill was charm, turned nasty, but went eventually, and the family carried on and finished it. Slab &drainage. But neither of these were possible to first timers, and I can see how problems and costs mount. Thats prob why most of us on here want to help. A few words can save a lot of money and pressure.

I would get them to define what they mean by passivhaus ethos? Architects often specialise in asthetics, functionality, planning approval and the useability of a building. Not so much in the fabric quite often. If you are not too concerned with altering the house layout I would get a passivhaus consultant to do a PHPP of the building as is and also a suggested upgrade plan. Like Dave says enerphit is the natural target.

NOPE! Off the 'net; The new Thermino range contains a new and improved Plentigrade P58 phase change material (PCM) They did a PCM34 and then a PCM43 ( I was part of an 11 strong group to spearhead the design and implementation of this unit ) but they must not have pursued this as above. The lower temp units would have been way more reliable tbh, as the failure of the rest of these ( 58's ) has all been attributed to the immersion overheating ( and destroying ) the PCM. To 'melt' the PCM58 you actually need to heat the SA with much hotter water or it takes an inordinately long time to phase-change. I routinely set wet heat to go into these at 65oC which seemed to work quite well. The units with immersions were ( are? ) still prone to issues with spewing the overheated PCM out through the PRV. I've got a dedicated photo album of these gone 'pop', some where it was so violent that the nuts sheared off the lids as they bent upwards. By comparison, I have been to 2 failed UVC's in my 30 years on the tools, and both were either installer error or where the client had neglected to service / maintain the installation, so basically a near zero fail-rate for UVC's. I'm not a fan of the Mixergy tanks, sorry, just way too much faff / external components / flow switches / pumps and the associated heat losses from all the stuff mounted externally. A simple UVC wins the day, just get a low-slung secondary immersion installed and then you can use 100% of the low / sporadic / proportional energy from PV diversion control.

Basics are, there seems to be no real target values. Improve airtightness to what? Just a bit better or 1m3 per m2 at 50 Pa or better? Target U values, better than you find it is too vague. You need a clear statement of what you want to achieve, otherwise it's rubbish in rubbish out. As I mentioned in another thread linking an ASHP to PV and battery is daft. Let the PV and battery feed the house, if power is available the heat pump will use it.

Think you are trying too hard. Break it down into bite size chunks. Do you have G99 approval for 6+kW of PV? Any electrical driven equipment will take up excess PV electric, so you don't need anything fancy or complicated. Basically during the heating season PV generates next to nothing. A DHW cylinder with a 3m coil is all you need, half the cost or less than heat a bank, simple control, simple PV diverter. Concentrate your efforts getting the heating system to run as low a temperature you can, that way you get best CoP.

give the guys at Cool Energy a shout and see if any of their installers can assist.