jack

Most likely they're proposing this because that's how it's generally been done. Stuctural slab (no insulation underneath), insulation (and historically not much of it), then a screed on top. This works well in a poorly insulated house, because you probably can't afford to run the heating all the time given the energy losses. You therefore want to be able to heat the top surface of the floor quickly when the heating is on. This is the same paradigm as using radiators in poorly insulated houses - blast with heat for a couple of hours in the morning and the evening. You get fast heat-up of rooms, followed by fast cool-down as the heat escapes and is absorbed into the walls etc. With decent underslab insulation, the slab surface stays at similar temperature throughout the day, irrespective of whether the heating is on or off. In winter, our slab temp varies by a fraction of a degree over any 24 hour period. If I turned all the heating off in the middle of winter, we'd probably lose a degree a day. In short, with good insulation levels, using the structural slab as a heat buffer makes a lot of sense. I have polished concrete floors with this exact arrangement - UFH pipes in structural raft slab, and a ~65 mm screed over the original slab, with just a slip membrane (basically thick plastic sheet) between them. No issues at all. The extra concrete might even help with buffering.

This won't work in a set-up that has separate terminals for cool and heat demand (which is how mine works). You could temporarily rewire the thermostat across the cool demand terminals summer and do what you say. I don't know that I'd risk having the thermostat wired across both demand terminals. While I'm sure there's probably some sort of priority involved, simultaneously calling for heat and cooling feels like a bad idea!

Yes, this. In addition to what @JohnMo says, I imagine your radiators won't do much for cooling, so should probably be turned off during summer (remember to turn them back on before the heating season!) You'll probably need a thermstat for cooling. Most thermostats for heating applications are configured to close (i.e., switch on) when the sensed temperature is below the set point. For cooling you'll want the opposite. I think (but am not 100% sure) that some thermostats can do both. If so, there'll be three electrical terminals: common, NO (normally open) and NC (normally closed). It's possible you can do something manual - i.e., no thermostatic control - by wiring a switch, or better yet a timer, across the cooling demand terminals. Either way, hopefully whatever wiring was used for your current thermostat has at least one spare core so you can use that rather than running another wire. I suggest you post answers to JohnMo's questions and go from there.

Engineering and service manuals are available here. See this page for setting cooling mode. Midea is correct that you want to be sure that your system is correctly set up for cooling.

That's probably it. I think a lot of wild flowers very much dislike clay.

Hi Nick, just bumping this one now I have some time coming up where I might be able to take a look at this. Thanks!

We actually have a reasonable fall on the side of the roof where we had the problems: But yes, better falls to and through the scuppers would certainly help. One thing that would still concern me is the amount of crap that would end up going down the downpipes and into the soakaway. I have some screens on the outlets to catch bigger stuff to reduce this, but over the years a lot of stuff still gets through. To an extent this is an issue for all roof types, but it feels like at least some of the leaves that fall onto a pitched roof get blown off eventually, or get shot over any anti-leaf measures in the gutters.

I've told the story before, but within weeks of moving in, we woke one morning to water coming through the ceiling in our bedroom. We found found another leak in the bathroom 6-8 metres away. The weld of the membrane on two of the scuppers through a parapet wall had failed (including the one on the left in the drawing above). We'd had words with the roofing contractor over the welds when they were originally done. I thought they looked terrible but he assured us they were fine. He ended up getting out the Resitrix rep to assure us that all was good. The rep wrote a "everything done to the contractor's usual high standard" email, despite a lot of the rest of it looking like a dog's breakfast. When they came back to fix the scuppers, we made them check and replace all the others. The welds on two of those had failed too, so 4 out of 7. He assured us (and I believe him) that they'd never had this issue before. I personally think they didn't clean the scuppers properly before installing them, and there was a film of dust or whatever from storage preventing decent adhesion. Touch wood the repairs have stood up for over 9 years so far. I'd never have a flat roof again, although the real weakness is the parapet wall. Keeping the outflows clear is a massive annoyance given how many big trees we have nearby, and the difficulty of getting onto the roof.

We had a lot of room to play with, and ours dealt with it like this: As built, we ended up with a parallel-sided channel rather than the complex things the architect drew. It's important to make sure that there are decent falls all the way to the exit of the outlet into the downpipe. In our case, some of the falls were a little marginal. As the underlying USB has sagged a little over time, there are now places in the gutters where water pools.

I'm not sure whether they cover NI, but try Frontier Insurance.

Looks like it changed in 2023: I think this must have been when the changes I mentioned above went through. I assume that's also when they moved to electronic submissions.

No guarantees, but I had 3 or 4 (out of a couple of hundred) receipts that were in a tradesperson's name. I just made a note in the covering letter when submitting the VAT reclaim and they paid out. One was for exactly your scenario. In our case, our tiler could get insane discounts on certain stuff - way better prices than I could source the same things anywhere else, even after VAT reclaim. My thinking was that we'd either get the refund even though the invoice was in the wrong name (which is what happened), or the refund would be refused for that invoice, in which case we'd still be ahead compared to having paid for it ourselves at the higher rate. One other thing: a reason that some companies will refuse to give you the same discount as a business (such as a tradesperson) is that you are a consumer. A consumer sale comes with far more protections for the user (and hence potential hassle/risk/cost for the seller) than a B2B sale.

This has all changed over the last 2-3 years. Before that, there were a few years where HMRC regularly rejected VAT reclaim applications based on all sorts of odd definitions of "completion" (including some definitions that went against their own written instructions to applicants and internal employee guidance documents). Eventually, a few appeals went against them, and thankfully they appear to have become a lot more reasonable.

Welcome. Is it his customers who have complained about noise and performance, or is he repeating the Daily Mail's opinion? Agreed GSHP is a lot more expensive. Even assuming you have the space for a GSHP, chances are it'll cost at least £10k more than an equivalent ASHP. They're also rarely specced in the UK so there isn't much knowledge about them in the industry. For that reason, from a performance perspective, I think installing a GSHP is as big a risk as installing an ASHP. Having too small a field (or bore), or burying loops at the wrong depth, or if you have ground that is sandy and often dry - any of these factors can lead to poor performance. We've had a 5 kW ASHP on our new build for nearly 10 years. It hardly makes any noise and has had no problem at all handling heating and hot water for our ~290 m2 house (admittedly PassivHaus-class insulation and airtightness, and we're in the South East, so not much energy required, but still). Until last winter, I'd been running ours with a base flow temp of 25°C, with a bit of weather compensation up to the high 20s in very cold weather. I now run the base temp a few degrees higher, and keep the heating period concentrated around the cheap period, so I use less energy in the expensive period.

You'll almost certainly get better and quicker answers if you start a new thread. A lot of people will see "VAT reclaim" in the title of this thread and not read any further.

Worse, after weeks of blue skies, it turned cloudy and rained for several days as soon as I switched the immersion back on.

Thanks for that, very interesting. It was a while ago, but i thought I read that once you gave up the deemed element from the government there was no going back. That's partly what's put me off finding the time to dig into this in more detail. I'll take another look! We're on a 2015 tariff too. From memory, it was from right before the rates dropped significantly. I'd have to look it up, but I think the rate was something like £0.15/kWh generated, and £0.07/kWh for export (deemed 50%).

Ah, I knew one of the components wasn't affected but I've never got around to looking it up. Good to hear it's the lower value component, thanks.

Is your electrical connection 3-phase or single-phase? There's no point getting a 3-phase inverter if you aren't on 3-phase power. Sure, although there are some good online PV generation estimation tools available. What might be harder to predict is your usage. Worse, even if you can estimate your usage patterns now, that will change signficantly if you get a battery. Assuming you don't expect to add more PV in the future, an inverter that can handle the peak power output is fine. Some people slightly under-rate the inverter, because in the UK, it's unlikely your panels will ever deliver their rated power output. A 5 kW (or more) inverter would be fine for this installation, but even a 4 kW inverter would rarely top out. You might also need an inverter with an output limit if you don't get approval to install more than the standard ~4 kWp in solar panels. If you've considering adding batteries in the future, you should consider getting an inverter (e.g., a hybrid inverter) that will work with a battery system.

If the groundworker measures out the trenches and also digs them, then the cost of both should be zero-rated (if on the same invoice), because digging a trench is in the course of construction. Just to be clear, the VAT isn't recovered - it's never charged in the first place. If the groundworker pays a contractor (or whoever) to do it for them, and then the groundworker digs the trenches, then again, the groundworker's invoice should be zero-rated. I believe that's the case irrespective of whether the contractor charges are listed on the invoice as a disbursement, or just borne by the groundworker and not separately billed on. There are probably some limited situations where careful planning can allow zero-rating of services that would otherwise incur VAT. For example, if you can get design charges for your UFH onto the same invoice as installation charges, then the design is also zero-rated. Or maybe your window installer can hire the telehandler you need for installation (zero-rated to you on the same invoice as the installation charges) rather than you having to hire it yourself and pay the VAT. Or your builder could hire a portable toilet and pass the costs on to you without VAT. I'm sure there are better examples, plus all of this assumes that the providers you're engaging are willing to play ball.

I'm thinking vaguely in that direction (except for 3 - I have no more space for additional PV!) There are a few ways to skin this cat. All of this paragraph is from memory, so I need to confirm that my recollection is correct, but some people have done the maths and concluded that it's best to fill up batteries at the cheap rate overnight. This is slightly at odds with intuition, which is that it's better to leave the batteries in a depleted state when a sunny day is expected, and allow the (free) PV to fill them rather than pay even a cheap overnight rate. Turns out it's often better to pay the cheap rate to charge the batteries and to sell the PV as you generate it. This is the sort of stuff I want to have a think about before taking action. No individual component is difficult to understand by itself, but the complexity grows exponentially when you start trying to optimise so many variables. I also need to be sure that, however I set things up, there's enough flexibility to implement a reasonable variety of approaches. And that's before you start trying to predict how things like TOU plans might change over time.

Half your luck. I discovered on the weekend that the switch for the immersion element that should have been driven by our immersion diverter was switched off at some point, possibly by the handle of a vacuum cleaner leaning on it. Based on the diverter logs, it happened... sometime last year, since we've had zero diversion this calendar year! *sigh*

When we had our PV installed in 2015, we just caught the last of the decent FITs payments. I think we get around £1100-1200 a year at the moment. Before the Ukraine situation kicked off and prices jumped, the payments easily covered our entire electricity bill. No chance of that now, especially with an EV in the mix. I've been watching battery prices fall over the last few years, and I think they've reached the point where they make financial sense for my circumstances. For example, Fogstar is selling a 16.1 kWh battery and BMS for only £1750. Add an inverter for £1k or so and you have something that would have cost many multiples of that only a few years ago. The only thing putting me off buying now is finding the time to research, design, and vaguely model how batteries would work with our current setup (8.5 kWp PV, Zappi EV charger, Eddi immersion diverter, ASHP). There's also the issue of potentially giving up the balance of our FITs in order to access smart tariffs. TBF, it still might work just using the Intelligent Octopus Go tariff, but again, lots of research and thought is required, using bandwidth I just don't have at the moment!

It makes sense within the logic of the system, but the system is the problem. Excluding things like professional services when they're provided alone but allowing them when they're on an invoice that has a zero-rated component leads to all sorts of weird outcomes. To extend your example, if the builder had hired the same surveyer for the same price to do the same work, he'd have reclaimed the VAT charged by the surveyer, then zero-rated it on his invoice to you. However, that assumes that the invoice includes a zero-rated component in addition to the surveyer's charges. If he invoiced the surveyer's charges on to you on an invoice that doesn't include a zero-rated component, then he'd have to charge VAT.

Crikey, even for rip-off Britain that's taking the piss! We had an entire large scots pine taken down for much less than that a few years ago.