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If the furthest internal point of the house is more than 45m from the road you need to provide access for a 12t pumping appliance, and if they have to come on to the property by more than 20m, you have to provide a turning space. You don't need to provide space for a pull off at the entrance, the fire tenders will just block the road when they are needed. I don't think it's actually stated in Part B, but building control wanted to see 3.7m kerb-to-kerb for the access at mine. This is needed at something like a hammer-head turning point, but not really needed along a straight length of drive.

I keep the Nibe controller in Manual mode and use the MODBUS add-on to allow Loxone to send an "allow cooling" and "allow heating" instruction. It could be done directly on the Nibe SMO 40 controller in Auto mode and setting a "Cool/Heat set point" to change the mode and a "Cool at room over" temp for when to start cooling.

The MVHR can not move a sufficient volume of air to cool the house, but it can assist the UFH a small amount (~ 1kW) To avoid condensation on the floors, you can't chill them below the dew point. The due point varies with air temp and relative humidity. You could set an overriding minimum temp for the buffer, say 13 or 14 degrees C, if you wanted to just rely on the ASHP controls, or if you had some other automation that could put some logic into the temperature and an RH sensor as well as temperature, you could let it calculate how low you could take the floor temperature to improve on the 13 or 14 degrees. The downside of UFH cooling, compared to an AC unit, is the time it takes to react. You can't let the temperature rise by 5 - 10 degrees above target and expect the UFH to bring that down in an hour. The cooling needs to start it's job as soon as the temp moves above target. I've no experience of the chiller units, but I'd expect them to provide a much more noticeable temp reduction in the room they are situated, as they are working directly on the air in the room, and air holds a lot less energy than the concrete slab. You could potentially also run the chiller with cooler water as the condensation is more manageable. However when you switch the chiller off I'd expect the air will warm back up quite quickly as the fabric of the house won't have been cooled by much.

If I've understood the "wiring up" question, the Controller (SMO40) comes all set to run Heating, Cooling and Hot water, so its just a comms line from controller to HP. I run mine either heating or cooling the buffer. The buffer then feeds the UFH and a heat exchanger on the MVHR supply duct.

If you haven't purchased an ASHP yet, and you want cooling, just purchase one that offers cooling out of the box The requirement to "hack" existing ASHPs to gain the cooling function stems back to the RHI scheme not allowing HPs that could be used in a cooling mode. Manufactures then had to disable the function for the UK market that was available in other territories. RHI changed in 2017/8 to allow HPs with cooling so more ASHPs with cooling should be available in the UK market. The Nibe F2040 series is the one I have, but I'm sure there must be others.

Is it aluminium, of galvanised steel? You really need to replace the whole sheet, or how about the whole roof, or is it only a short-term fix. You'll struggle to find a profile to patch it, that matches exactly, unless someone is still making that sheet. and you'll have an edge along the top that the water will be trying hard to enter get in to.

As @newhome states. This is how mine worked. The only caveat is that you can only claim back correctly charged VAT. So if a company that is supply and install insists on charging you 20%, you can't claim that back. You have to work with some companies to help them understand the reduced rate (5%) charge. Be aware also that if you contract a trade directly, that is not VAT registered, you will not be able to claim back the VAT on the goods they supply. Better for you to buy the goods directly, and for them to install and only charge you the labour.

"Open" countryside, just refers to your site not being within a developed settlement (hamlet/village), where the rules are more relaxed. A lot is made of Greenbelt, but the development rules are pretty similar in open countryside as they are in Greenbelt. You are requesting a change of use, so you need their buy-in. While you may feel you have a logical reason for the choices you have made you need to calibrate your view to their priorities. Brick piers and solid gates are not typical for an agricultural access, they are being reasonable rejecting them (unless they have allowed similar in neighbouring properties on similar sites)

Sounds a fantastic location, welcome. It also sounds like you are very rural, and while there are other permissions granted around you they must be pretty spread out so you are not within a built area and are firmly in open countryside. If the post and rail is truly agricultural/equestrian type, then they can't really argue, if you weren't changing the use of the patch of land the access crosses from agricultural/equestrian to residential, they could do nothing about it, however they've included this as it adds to the picture they are painting of what they are calling a "grandiose" scheme. If you are in open countryside, then it is fair for them to be minimising the impact of your development, and if the most visible part of that development is the entrance (due to house being 200m away from the public road and mature hedge rows etc.) it is quite reasonable for them to want that to be "in keeping" with its surroundings. Our LPA would only allow a 5 bar gate. Nothing solid, nothing over 1.2m, no fancy gate posts. 12m inset in the field also seems a little excessive, yes you need provision for a car/van to pull off the road before they are stopped by your gate, but they may be happier with 6m. I can also see their issue with it being through the middle of the field, but maybe if you reduced the visual impact they'd compromise on this. Again, if it was a field entrance, on to an uncategorised road, you wouldn't need planning permission, so they couldn't actually stop a 5 bar gate being in the middle of the hedge row, however as you want it for residential use you need to reach a compromise with them.

But installing a GSHP and ground loops for unrequired cooling isn't Joking aside, I have a 12kW HP and my PHPP calcs estimated a worst case 6.4kW heat loss. My HP has an easy time, the house performs slightly better than PHPP calculated, although not PHPP's mistake, I make better use of solar gain than PHPP had allowed for. Even with an oversized HP, the house can still be slow to react. This is all my own fault, as I don't allow the HP to heat the house in the morning if the forecast is either sunny or only partially cloudy, knowing that by 11:00 an average house temp that was say 19.5 @ 07:00 will be sailing passed 21.5, without the heating on. On the days the forecast is wrong or mis-timed it has a bit of catch up to do, and when it does it takes a little while to do so. I should be clear, if I wasn't playing games trying to predict the solar gain, and allowed the heating system to maintain a constant temperature, this wouldn't typically be an issue. Similarly, cooling is effected in the same way, but more acutely. Solar gain is far more powerful that heat loss, so is able to rapidly change the internal temperature. If it is "allowed" to get to 30, it will take a long time for the ASHP to bring it back down, and will generally have to wait till the evening ambient temp drops to allow our stack ventilation to dump heat out the roof vents. This has taken quite a lot of tinkering with to get UFH circulation, external blinds, and roof vents working to minimise the solar gain so that the HP can do the rest, but it is not always successful.

Is that your calculated energy loss? So you need 2kW to maintain say 21 internal at -10 external? If so, I wasn't comfortable sizing my HP on this value, I felt a bit of head room was needed, so that in the same conditions the heating was sufficient to raise the internal temp from a lower value (in the case there'd been a heating failure), as well as heating a tank of water up in a reasonable amount of time. Or does the 2kW already factor that in, in which case it is a very low value, could you not just go with electric duct heater in your MVHR,

I also looked at both, the small additional efficiency of the GSHP didn't outweigh the extra capital cost and extra maintenance cost. Add into you comparison the maintenance cost (there's a lot of antifreeze in a GSHP that needs replacing). In the GSHP flavor is the option for "passive" cooling.

Take everything that is the same, out of the equation. ie. from the price of the ASHP & controls + the extra cost of a 25% larger HWC + say a 90l buffer (just in case you need it) + twin pipe insulated duct of required length, take away the price of the Gas boiler & controls. The install may be a small amount more due to the MCS requirement for RHI, and a bit more copper pipe and brass fittings for the buffer.

Yes, you have to fund the Install and you then get the money back over 7 years, index linked. So, you could add it on to your borrowing, if you're not already on the max the banks will lend. A correctly sized ASHP will not lead to any temperature issues with either the house or the water. The better the insulation and airtightness, the smaller HP you'd require. UFH is perfect for the lower temps of an ASHP, ideally under 35 degrees flow temperature for maximum efficiency of the HP. If you are using rads upstairs then they would need to be sized larger than they would for a fossil fuel heated house. You would also need to have a HW Cylinder, and it would need to be larger than fossil fuel heated one again as the temp will be around 50 degrees rather than 60 to 65. From 2022, building regs will require new builds to be designed for low temp (under 55 degrees) systems anyway, in order for them to be future proof and require no retro-fitting for when the 2025 Future Homes Standard comes in and heating systems in New Builds will have to be low-carbon. Even if you don't fit an ASHP now, it would be wise to ensure one could be fitted in the future without replacing all the heat emitters and trying to squeeze in a cylinder where one wasn't planned for. BTW, redo the RHI calc with a higher SCOP. It's really worth getting your flow temp down and having a higher COP ASHP, something over 4 if possible.

Advanced Foundation Technology have some innovative solutions for poor ground conditions. ie. a Suspended slab on piles. Luckily Olof is a better Structural Engineer than web designer, you may struggle to find the details on his website, but here it is: https://www.advancedfoundationtechnologylimited.co.uk/wp-content/uploads/2019/01/aft-groundshield-designs-2018.pdf While your timber frame company is supposed to be doing the raft getting AFT involved may be a lot better than a 1500mm excavation. I have a standard Insulated raft from AFT. They're happy to do design, supply and install or just design and install, or somewhere in between, and can include the UFH as well.

If you don't want to have a full sized tractor on there, find a landscaping company with a Stoneburier and a compact tractor. Blecavator make a range of sizes and are the well known brand. They create a fine tilth and push the stones down, and give a nice flat finish. It would only be a couple of hours work. Edited to add: Looks like they can be hired too https://www.fthhiregroup.co.uk/hire-products/landscaping-and-groundscare/groundcare-equipment/blecavator-stoneburier-attachment as an example.

Is that your interpretation of the new regs? The change is supposedly to lower CO² by 33% from current standards It's not going to work if you just have to design the system to be low temp, but can still run it as high temp.

Any low temp systems needs to run a "legionella" cycle every 14 days to lift the temp to 60°

I believe there will be an update to Part L building regs at the end of this year requiring a maximum flow temperature of 55 degrees, so that all new build hot water and heating systems are "designed" for renewables.

RHI would pay for the ASHP. It's worth considering, yours is an ideal build. If you are already going with UFH, then it's a decision you can make later in the build, although putting an insulated twin pipe duct in from where you would site the ASHP to the area of the Hot Water Cylinder would be beneficial, while your ground works are being done.

Takes a matter of seconds, yes, but it is very local, so as you move around the house, you need to take it with you and plug it in. That's not how I personally wish to live, and not suitable for a family. Even if I took the hot water requirement out of the equation I would want a heating system. I personally want the convenience, plus the house I built needs to be saleable, and I don't believe the general public are ready for a house without a heating system. You can't however take the hot water requirement out of the equation. So with a heat source needed, it's there for space heating too. A carbon neutral large property has no more impact on climate change than a carbon neutral small house. Any democratically elected government is going to find it very difficult to legislate on house size.

The MVHR has too low a flow rate to transmit 6.5kW to the house, and to provide the required heating via electric radiators would need them to be placed in more or less every room so the capital cost is not insignificant - probably similar to the cost of the UFH system (not the ASHP). In reality, I didn't consider electric radiators, or in fact radiators of any description, because I didn't want them on my walls.

My house was PHPP calculated to be at the 15 kWh/m2/year energy loss threshold. In reality it's slightly better than that due to making the most of solar gain. But I still need a 6.5kW heat source at times to maintain 21 degrees. ie. when it's been overcast for several days and the average temperature hasn't got above 0 degrees. I didn't at the design phase, nor do I now feel that the peak heating demand could realistically be provided by an electric heat exchanger in the MVHR and some electric radiators. And combine that with the need for Hot Water, an ASHP absolutely makes sense. That is based on a Big 6 Standard rate for electricity of 19.43p a unit and a 2011 "best" COP 2.7, and the result is 2.7 times more than gas. At an actual 11.725p per unit of electricity and an average COP of 4, the ASHP cost comes down to 2.93p per unit - slightly cheaper than gas.

I guess yours was a badly matched install then. Works fine for me with a family of 5 and 450m^2 house You've not considered how much hydrogen may cost, should they ever work out how to produce it in the volume that would be required to heat homes. The future will be better insulated and more airtight homes with a mix of hydrogen and heat pumps. Heat pump prices will come down, hydrogen will be more expensive than gas.

Paid for by RHI, so not the case Not a limitation I recognise - have you had an ASHP and experienced these issues? It's no "niche" now, and certainly won't be when Natural Gas is switched off.