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What's the issue making you retain the Gas Boiler? What SCOP do you have estimated for the ASHP, that gives rise to issues with the anticipated electricity costs? 6m³ hot water tank, 6000l, really? Is this just for a domestic property or is there more to this install? Loose the Gas Boiler?

With 16kW, you'll have no issue with heat-up time on the cylinder, so go larger if you can fit it in. The larger it is the lower you can drop the temperature and the more efficient the ASHP will run. You can work out your own RHI payments: https://renewable-heat-calculator.service.gov.uk/StartCalculation.aspx I've plugged your figures in below and have guessed the improvement expected from loft and wall insulation. When you do it, remember to change the SCOP from the default 2.6. It makes a big difference. I think the F2040-16 has a SCOP of 4.48 Edited to add: 4.4 SCOP relies on an emitter size that allows a 35°C Flow temp.

Nibe are a very good heat pump manufacturer, and their prices tend to be a little higher than the direct competition. I have the 12kW F2040, so not sure how much more the 16kW is. (I remember it was an extra £400 ish from the 8kW -> 12kW). To my 2017 pricing (which shouldn't have gone up much for ASHPs) I'd say you're quote is around £2K - £2.5K more than I was charged. Edited to add: That's a small UVC for ASHP size. Is your space heating requirement driving the size rather than DHW requirement?

You seem to have posted this question twice. I answered over here:

You could get the MVHR system designed and supplied, and install yourself or by your builder, or Project Manager. They're not difficult to install if they've been designed along with your house. Airflow will do your design free of charge and give you the bill of materials to then take to all their distributors to achieve the best price. There are single units that will easily deal with your size of property, although volume is more important that floor area. I have an Airflow DV1100 for my 421m², 1650m³ property and it's oversized by quite a factor. Airflow class it as a small commercial unit, but it's made to the same standards as their domestic units, is PH Certified with pollen filters etc. I remember Paul also do MVHRs that were more than large enough for my place and I'm sure there are others. If you do want to hand it over to someone else to design and install, then I'd try Mango Projects Ltd. https://mango-projects.co.uk/ I haven't used this company (it's a recent venture), but the people involved were all involved with my build. I see little point in MVHR unless you are targeting better than 3m³/m².h @50Pa air tightness. But if you are, then for building regs you have to have a centralised mechanical ventilation, so it might as well be heat recovering.

I used Dr. Rod Williams at Williams Energy Design https://passivehouse-international.org/memberSearchDetails.php?member_id=2349 It was a great experience for me and helped make a number of design decisions. Really highlights where the money is best spent for maximum effect.

As it is very Important to you don't leave it to guesswork, get your house design thermally modelled. PHPP would really help with this aspect, even if not considering achieving PassivHaus levels of energy loss. External venetians and roller blinds have large head boxes. They are best "designed in" to the building fabric, they're not such a good look as a retrofit.

By full Change of Use Planning Application.

It's unlikely the LPA would allow PP for something larger than what is already there. Most Barns are within countryside, so LPA's have to follow the NPPF to not allow development in the countryside unless it improves the openness of the countryside. The Class Q permits the Change of Use, so it's then down to convincing the LPA that a knock-down and rebuild would lead to a better house (performance, layout, sustainability) and an improved setting (higher quality materials, less visually intrusive). I can't see a larger volume, or one that is not in keeping (non-agricultural in form and materials) improving the setting, so I'd think they are not options.

I would expect the two to be able to run in parallel, and can be on the same application, but I wouldn't count on being able to achieve it. My experience is that you need a very strong argument to redirect a PRoW. ie. examples of theft or arson and no alternative means of securing the buildings that are exposed to the PRoW. To be successful you'd also need to own the land that would contain the diverted route for the PRoW.

No that's unfortunately not true. An Agricultural Unit gets one allowance to convert, with no renewal. They can now convert up to 5 properties, although not more than three large (greater than 100m² floor area) and the max cumulative area converted to large properties allowable is 465m². Small properties are those with less than 100m² floor area. But, the Agricultural Unit can not benefit from Class Q PD if it has used Agricultural PD (Class A(a) or Class B(a)) since 20.03.2013, until 10 years after that PD was used.

Yes, Full PP is the only option. Here's an example of a successful Change of Use Application at Maldon. A bit of trading off was done, removing a couple of structures to allow another to be converted. https://cdp.maldon.gov.uk/planning/planning-documents?SDescription=20/00994/FUL Maldon do seem to make you work for an Approval. I have a feeling they'll want Stage I surveys for most things as part of the Application. Your Planning consultant needs to try and push them to pre-commencement conditions, but might not get away with it. For the Application linked to, the surveys required were: Bat and Owl (Protected species), Preliminary Ecological Appraisal and Heritage, but no contamination The recommendation was to Refuse, but it appears to have been pulled in to committee and been Approved against recommendation. I'm locallish to Maldon, and I hear they are a little difficult...

The first one was refused because... Q.1 Development is not permitted by Class Q if— (f)development under Class A(a) or Class B(a) of Part 6 of this Schedule (agricultural buildings and operations) has been carried out on the established agricultural unit— (i)since 20th March 2013; or (ii)where development under Class Q begins after 20th March 2023, during the period which is 10 years before the date development under Class Q begins; The second one was refused because the Council were not convinced that the subsequent splitting off of the Barn from the original Agricultural Unit that had done the Class A(a) or Class B(a) development after 20.03.2013, into a separate Agricultural Unit, had actually happened. So, in short, no barns/sheds that are part of Lower Barn Farm Agricultural unit will qualify for Change of Use to Resi, under Class Q PD, until 10 years after the date that Class A(a) or Class B(a) development was completed. Doh! Your Consultant was correct. Class Q is off the table. Edited to add: Lower Barn Farm appear to have built a Hay and Straw barn and an Implement shed, untillising Class A(a) or Class B(a) Agricultural PD between 2014 and 2016. Since this is after 20.03.2013, it starts the 10 year clock running before Class Q can be used on the Agricultural Unit.

I'm not sure I've understood, wouldn't you need a handy hot spring in the garden to heat a pool with a COP of 6 using a water source heat pump. Where are you moving energy from and to with this WSHP?

This is the only one that relates to a Class Q. Have you got the full Officer's Report to see the reasons for Refusal?

Have you had an outdoor pool before? Never, ever again for me. Although, mine was a '90's built Penguin pool, with an uninsulated concrete tub. So, on top of the time it took keeping it looking OK, the cost to heat was ridiculous.

Yes...but... I have low heat loss/gain, so for heating only require a low flow temp. For a 21°C target temp, I have around a 31°C flow temp and keep the slab at around 21.5°C. ie. the slab temp only needs to be slightly above the desired room temp. For cooling, similar offsets are required. ie. I take the slab down to around 19°C with a flow temp of around 14°C (avoiding dropping below the dew point and causing condensation problems) and it keeps the indoor temp stable. The caveat is, that with a low flow temp heating system it is slow to react, so you can't wait until it is 27°C degrees in side before taking action on cooling. And for me, because I chose to have a fair amount of glazing on south-east and south-west aspects, I need to mitigate the solar gain risk, which I've done with external shading. AC does have a quicker effect on cooling, as it works directly on the air temp, but as soon as you switch it off the temps will rise again as you are unlikely to have significantly lowered the temp of the building fabric. If I was doing mine now, with the knowledge gained from this forum, I'd be considering adding some fan chillers cooled by the ASHP to get the same quick benefit as AC, while still getting the stabilising effect of the UFH cooling. When I was asking timber frame specs, it was in relation to being an "eco build". ie. what level and type of insulation and what air tightness target. I have an I-Joist structure with 300mm walls and 350mm roof, filled with cellulose fibre insulation and sitting on an insulated raft foundation with no cold bridging, and a sub 0.1 ACH air tightness. Nothing high tech at all, nor particularly expensive, but good value for the energy losses it delivers. If you drop below 3m³/m²h @50Pa buiding regs will require you to have mechanical ventilation.

There's lots of knowledge on the forum regarding ASHP cooling via the UFH, and there's a few that additionally use fan chillers, cooled by the ASHP, for additional cooling in specific rooms. I have ASHP cooling via UFH and it is effective. GSHP can be more efficient than ASHP with cooling since their medium is already at a lower temperature (8°C - 10°C), so can offer cooling without the compressor running. Finding installers confident with ASHP/GSHP Cooling can be difficult. What's the spec of your timber frame? Are you going with traditional founds? have you taken any steps to mitigate cold bridging, beyond standard building regs?

There's more energy to be saved with the spec of the timber-frame (and foundation) than with the renewables you choose to heat it. What stage are you at? is the detail design done? Have you a view on an energy loss target for the building fabric? What spec of frame and foundation are you considering. +1 for cooling via ASHP (or GSHP if your loads justify it). AC can be avoided.

Hello @ukjamie and welcome "Eco" build" conjures up all sorts of options. Are you sticking with the practical "low energy" options, or venturing towards earth homes or straw bale walls and composting toilets.

Location 2 sounds the better location for the installation, but there are risks. Would there be insulated stud work between the back of the built-in and the MVHR? My DV1100 is within a storage area in the loft. There's 100mm of Rockwool above the ceilings and the unit is barely audible when running at a boost of 75% and you are right below it. My unit is a little over-sized so in general it doesn't boost above 65% Any ideas what sort of boost speed you will need to run at? Will you have any automation that would allow the boost to be turned down over night, just in case. I've used some flexi-ducts on the inlet and exhaust, and to the plenums. Most of the air noise comes from these. I'd stick to rigid and semi-rigid on your location 2 scenario. I'd also have a back up plan to isolate the mountings for the floor (or wall) it's mounted to if it turns out there is a resonance issue.. Bolting through some rubber blocks should be enough.

The devil's in the detail with Class Q. From what you've put above the rejection of "other barns" is a little vague. Have you looked on the Planning Portal yourself and read the reasons for Rejection, and would that also apply to these barns? Or, has the Planning consultant given you a full explanation of why it would not work for these barns. Just make sure you are satisfied that that option is really off the table. Feel free to upload the (anonymised) Officer Report for the previous Class Q applications, to get comment on them. There has been no easing of the Class Q rules, since they were first introduced as Class MB, however it is now possible to convert a greater area of barn(s) to residential if you juggle your large (over 100m²) and small (under 100m²) houses effectively. Guidance has been added though to help LPAs be more consistent with their decisions. The alternate route your planning consultant is suggesting is certainly an option. National Planning Policy Framework rules are strongly against development in the open countryside, but there are caveats, such as "unless the development enhances the openness". Trading off existing structures in order to convert another is one of the arguments that LPAs will accept. It's quite possible that as well as the archaeological survey, the LPA will also want a contamination survey and a protected species survey. Better though that these are pre-commencement conditions rather than all having to be done up front with the application, to avoid your costs spiralling.

I have the same unit, although with the SMO40. I have cooling enabled on mine and when I purchased in 2017 it required an additional cooling module to be able to cool. I was also told I needed the SMO40 controller.

I'm guessing its space for the Sunamp/HWC and buffer that you are short of. How about the loft? Can you make space up there, even if you have to cut a larger hole to get what you need into the area. There are hot water cylinders that can be mounted horizontally.

It's got to be more subtle than just that you're using electricity for space heating. On my EPC it lists the same ASHP and UFH (above insulation), but gives 5 stars. On the as built SAP it records the "boiler" efficiency (SEDBUK), it's got mine as 384%. I thought it might be Design Flow Temp, but on my SAP that's recorded as "unknown", so that can't be effecting it.