NailBiter

Wholeheartedly agree. By credentials I don't necessarily mean qualifications I mean has this person worked with this stuff before. Are they speaking from a position of knowledge or are they guessing? It is hard to tell sometimes. It becomes clear the more you read from a certain user who is knowledgeable about each field but I don't think it is unreasonable to ask someone to clarify not just what they were saying but what makes them say that. I don't know you guys that well yet but in time I'll need to do that less as we get to know each other. Admittedly my comments fell a little on the "appeal to authority" side of things but that isn't my general position. I was being somewhat reactive to abrupt claims of things not working or being impossible despite prior art. This is very impressive and was likely the result of a ruthless focus on the data in front of you, great work. I'm very much at the top of the funnel trying to work out what works and what doesn't. As I get further down the funnel I will rule more and more things out until the solution comes into view. This will involve challenging assumptions, both my own, those of our team and the assumptions here. I've probably misrepresented my position here as I know painfully from first hand experience how true this is. Above I accidentally thanked another user for referring us to the timber framing supplier when I meant to thank you, apologies for getting the two of you mixed up. We will have a quote from them on Friday (incredible turnaround). I'll try to anonymise and publicly post what I can so others can make a direct comparison between Nudura and the timber frame.

It isn't so much a case of dreaming on as much of a case of trying to get the maximum efficiency from installed systems. As has repeatedly been pointed out this house is large but that means even small efficiency savings can have a large impact. I'm slowly discovering how much conflicting information is out there and it is hard to know what to do. I really appreciate you citing your data source, I don't mistrust anyone in particular but data wins arguments.

Ok that's interesting to know thanks, if I remember correctly your build is Durisol? It must still take a significant time to heat and cool that mass though?

The plans and the information I've given already would identify me and our address. I've sent a few renders privately to a few people that responded here. I will do the same with the plans once the latest changes are incorporated. I'd love to just stick them up here but I really don't want it indexed on Google / Wayback and here forever. If I could just share them with the people replying (or set a minimum level to see them e.g. full member) I would.

We are building with passivhaus principles in mind, it would be rather foolish of us to have paid extra for a passivhaus trained architect and not to do so. The above was in reply to someone who suggested we could get all the heating demand from an hour of sunshine in winter. I wish that were the case but it simply isn't unfortunately. Apologies if I came off a little blunt with them but how does someone with little to no knowledge of our build guess the time of day our thermostat clicks off? It simply isn't possible to even have an educated guess at that. Very good tips about fabric first, we are definitely taking that approach. Thanks so much for the recommendation of the timber framing company. We have spoken with them and they are doing a quick turnaround quote for us which we will have on Friday (very impressive!). I really do appreciate you taking time out your day to share that with us.

Sure and if we were talking about a Passivhaus that would be a fair enough point but we aren't. It came down to wanting more glazing than the passivhaus standard would allow.

I don't know how to share this with you but I'm lucky enough to get journal access as part of my job. Your local library / university / pirate paper repository will have access to a copy https://www.tandfonline.com/doi/full/10.1080/1023697X.2017.1313134

The issue is a lack of power in December and January due to a lack of sunshine. I am totally unconcerned about power demand during sunny months when we need cooling. We only have a 6kw system in our current house and it provides for most of our needs 8 months of the year. Yes true but it isn't just sunny / warm for 1 hour a day. The goal would be to move both our heating demand and our DHW demand to the period when there is minimal difference between the temperature of the inside and outside unit. With DHW this is easy as you can just store hot water. We can also explore oversizing the ASHP slightly. The heating is a little harder however. My understanding is we can bank heat from about September / October onwards in the thermal mass of the building. On cloudy / very cold days we may be able to avoid running the system entirely. The goal is to put as few units of energy in during winter whilst preserving stable internal temperatures. If the council decide to let me have a wind turbine (tall order but you never know) then I will have all the power I need all year round as December / January is typically plenty windy round by me. I asked the architect about this and he didn't seem hopeful however. This is in response to a comment other than mine, personally I wouldn't install high thermal mass I'd just put it in the sun. If I were to surround it with materials I would be looking for low thermal inertia materials that heat easily in the sun (ever trodden barefoot on lead flashing on a roof in full sunshine?). The ASHP for the UFH does not just use a single internal thermostat. We will be measuring both the air temperature and the floor temperature in each zone and can adjust the heating in each zone accordingly. This will be integrated with our Home Assistant instance and will have knowledge of past conditions, current conditions and future predicted conditions (extrapolated from the past combined with weather). The ASHP does not run at night, we have plenty of heat in the building fabric and we will have several hundred litres of hot water at this point. Plenty for the night and the morning. This is the point the differential between inside and outside temperatures is at its highest and therefore efficiency is at its lowest for running the ASHP. Again I personally wouldn't surround the outdoor unit with high thermal mass / thermal inertia materials, I'd also put it somewhere where it was insolated first thing in the morning (very easy for us on our plot). Can I get a source on these numbers please? They feel like they might be bum plucked. If I could get my entire heating demand via solar gain then I wouldn't have any issue with needing to make sure I am efficiently making use of an ASHP in the first place. This is exactly the point I would be putting a good couple hours heat into the building. In a house the size of ours 0.3. CoP benefit is not to be sniffed at. That is nearly a 10% uplift on standard performance. Almost nil != nil so it would depend on the cost to site it in a insolated location vs in the shade as to cost / benefit. Besides by this time the heat pump is off again because the internal / external temperature differential is high again. Cooling is not a concern for multiple reasons. Mostly the heat capacity of the building but also the fact it is mostly solar powered. When there is cooling demand there is available power. I know there is no such thing as a free lunch which is why I'm trying to shift demand from when I don't have spare power (winter) to when I do (9 months of the year). This is a solved problem, the manufacturers worked out you can place the sensor in a sensible location and run the fan at full quickly before taking a reading. It is all detailed in one of the links above.

We put in the access route this week! We are now awaiting a second report from the ground investigation team as unfortunately we found some soft deposits but fortunately I'm told the news from the second drilling is positive. The drillers left site on Friday so hopefully only a few weeks till we get the report. Hoping to avoid a piles or at least to avoid percussive piles, not a great way to introduce yourself to the neighbourhood. I believe our planning permission is now extant due to the access route and we would be looking to do the reduce level dig once the weather improves somewhat.

I look forward to it.

That's fair enough, I don't mean to be dismissive of advice provided just trying to sort through what to take account of. There is some more info here: https://sustainability.stackexchange.com/questions/9621/air-source-heat-pumps-does-prevailing-wind-matter It seems that it is complicated but broadly: Definitely need: Airflow, don't create a cool micro climate near ASHP (but consider creating warm one) Definitely helps: Run ASHP during hot part of day when heat differential between inside and outside low. Might help: Sunlight (for defrosting the coil if run in low temperatures) Definitely avoid: High winds (causes frosting of the coil), Placement where servicing is hard. Restricted Airflow Don't forget: Noise and pipework likely more important than most of the above.

I certainly welcome all opinions but hopefully those opinions welcome being challenged. It's my job to work out which opinions seem reasonable (in my opinion and with expert help) to implement this build accordingly. Hopefully leaving a paper trail behind for the next person that finds themselves in my position. There seems to - hopefully the above wasn't an instance of it - be a real habit among humans (particularly as they age) to claim things aren't possible or don't work without taking the the time to properly look at and consider new ideas. "When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong." I wholeheartedly agree there is almost always more than one way to skin the cat however.

Would the air not be heated up as it passed through the casing to get to the heat exchanger (or if the heat exchanger itself is directly insolated perhaps even via that). I'll do some more digging to get to the bottom of it but any increase in CoP (particularly by something as simple as where you site the system) is a good thing.

Your solar system is very impressive particularly how you mounted those vertical panels. There was some recently published researched suggesting vertical panels are more efficient than first realised. https://www.pv-magazine.com/2023/11/10/researchers-shed-light-on-mysterious-higher-energy-yields-in-vertical-pv-systems/

I was really tempted by Durisol (although their administration issues are obviously nerve-racking) or even Isotex but enough people said enough bad things about them that it would have been foolhardy to continue. I don't really have much frame of reference for how true everything said about them is. Apologies but with it being so important to get right I will have to listen to the accredited professionals. I really don't have the knowledge to say if any of this is correct but I'd imagine the case surrounding the heat pump could be heated up by the sun hitting it. It is also likely that on the roof insolated it will be significantly warmer than if it were sat on a North wall for example.

Apologies to be forward. I know the credentials of the person making the claim (that it works) but I don't know the credentials of you making the counter-claim (that it does not). Would you mind me asking you what credentials you posses to back your counter-claim?

Perhaps I moved the decimal point in my head, I'll email the architect so I can't transpose it.

National Grid can't confirm anything until the G98/G99 certificate is in but they said this: There was also some discussion of some weird named network they had which could increase this significantly but I can't currently find the correct email. It will take a long time to get setup but I've also been speaking with a nearby https://energylocal.org.uk club to try and understand what it would take to sell this power directly to neighbours. It is highly likely we will never fit a system with 114 panels, I was more interested in the cost to do so and whether it would fit to see if it were notionally possible. Whilst brackets to get the panels on the roof or a frame to fit ground mount panels would add expense I was surprised at how cheap it could be. I set a fictional power budget of 50kwh a day which is approximately what our combined houses use right now. Obviously this is likely high for a build like ours if we do it correctly. Export can be limited, solar systems can be DC oversized by up to 200% and with the east-west orientation of the array there is only a very short period of total generation but a much wider time period of generation. I am a little stuck on working out how this compares to a south facing system in the winter. It may be a different way of doing things but it isn't necessarily wrong (although if you know any specific areas I've messed up or made poor assumptions please let me know, it is super useful).

Noted, although it is likely the mistake is my end, our architect is a Certified Passive House designer so is unlikely to have made such a mistake. I'll double check though thanks for flagging it.

The idea came from this house: https://architecturetoday.co.uk/introducing-the-uks-first-net-zero-carbon-home/ My understanding is a heat pump steals heat from the environment. This is the opposite effect of a fridge that behaves poorly when it has no ventilation to its coils. I'm no expert though.

Thermal mass, thermal mass, thermal mass! This is very much the goal, trying to avoid chemical batteries for now as the price of lithium batteries is set to continue falling. https://rmi.org/the-rise-of-batteries-in-six-charts-and-not-too-many-numbers/ A 114x 600watt panel solar array (not including fixings but including cable, optimisers and inverters) is only around £12,000 which would be paid for within 2 or 3 years by the bills we don't have to pay let alone anything we can export in summer. The issue with solar is not installing it has an opportunity cost. That said the cost of solar has decreased a lot lately which offsets it. Without a battery and with usage roughly estimated it would look something like this: With deferrable loads it should be possible to use a lot of the power as we generate it and worry less about storing it in electricity form. I intend to use a tool called EMHASS to manage these loads (https://github.com/davidusb-geek/emhass) There are also some interesting tricks others have used such as putting an ASHP outside unit in the sunshine and using it during the sunny parts of the day. I grew up on a building site (family ran a small building company) so I don't even really see unfinished rooms when I'm walking through them. Floor coverings are easy as it will be some kind of floated monolithic floor covering throughout the whole house. No fancy tiles here. Agreed, our guys are currently targeting 5 ACH, do you feel that is reasonable? I had a long call with the architect yesterday and they seem to be suitably concerned about the MVHR and how the ventilation will work. We do need a really good engineer though, can you recommend one? Definitely looking to bank cheap energy inside the thermal mass of the building. Insulated concrete raft would be great but we may have issues with heave on the site due to the mature trees and brackish clay. Will know more when we get the full report back. Good tip on avoiding skinny screeds cheers. He really is! I'll pass along your compliments. Agreed re: getting cold and getting hot. There are also rooms we want cold (e.g. gym, larder). We have extensive glazing so a design goal from the beginning has been insulated thermal shutters on the outside of every single window. That way we can have our cake and eat it, in the winter we get solar gain all day and trap the heat in at night, conversely in summer we can do the opposite. We spent far too long looking at various ICF systems over a period of years. Firstly fell for the Durasol / Mineralised block marketing and then came to understand more about cold bridging and the other issues they have. We looked at sheet based systems like Polar Wall. In the end it came down to Nudura having a good product, good support and the Fell Partnership being just up the road for us. They have trained most of the teams in the area, they started as fitters themselves and are now suppliers and they keep a lot in stock. As soon as we met our build team that work with Nudura it was love at first conversation. They are ground workers originally but now have 4 concrete trucks and a number of site running. We knew instantly these were the guys to get it done. I'm sure as your clients would have had a similar realisation as you seem incredibly capable. Thanks, lots of the credit to our architect though but I did push for some of it. You have raised a really interesting point regarding MBC twin wall which I raised with our architect. He has a meeting arranged with them tomorrow to go through our plans. I really really appreciate you taking the time to post. You may have saved two stories at 42m x 10m from being built out of ICF and all the embedded carbon that entails. Obviously it will come down to cost, time and other factors but if we can do right by the planet and right by ourselves we will definitely do it. I'll keep you updated and I'll get some floor plans posted (we are making some tweaks for now so no point posting yet). Good luck with the rest of the week! Cheers

See my comment above about the larger homes scheme, it is another option open to you and is distinct from full planning permission. Theoretically the planning process is supposed to be collaborative, that means they are supposed to work with you to pass something if possible. That doesn't always happen in practice with planning officers being so busy. You will get a "free go" if they refuse the permission and you reapply with a similar planning permission. It is not really in their interests to do more work for free. If you engage with the planning officer nicely you may find them helpful or they might just not call you back. We had a weird one on a previous build we did where the planning officer actually insisted we made the extension bigger and put a dormer in!

It won't get you the full 10m but it might be worth looking at the Larger Home Extension scheme. https://www.planninggeek.co.uk/gpdo/house/extensions/larger-home-extension/ As your neighbours are in agreement and you are in a detached house you maybe be able to get up to 8m without full planning permission. I'm no expert though so you would need to check this very carefully.

Thanks Glad you are all moved in and happy even if your step count has increased somewhat. The nature of my job means I am quite sedentary so I'm looking forward to the workout. None of us are getting any younger so we could all do with a good bit of exercise! Now where did I leave my phone again .... All joking aside you raise a very valid point, don't forget we are effectively 3 separate families living under 1 roof and we all want garage parking. Divide our square meterage by 3 and you still get a big number (400m2) but not an aggressively big number. In truth I've always been envious of the way our American cousins live particularly their homesteads. That was very much the space goal for us. I know that makes us different to many on here but that's part of the fun of self building right?

Probably best I subtly steer the thread away from what sounds like an old debate. In any case as with any primarily solar powered house the issue is you can only generate when the sun is out and December / January is hard to get through without slurping on the grid (which I'd rather avoid if possible). My goal is to be able to store as much energy as possible. Chemical batteries will only get me so far, storing heat is significantly more efficient. In an ideal world I'd have some sort of inter-seasonal heat storage but the house can perform that role to an extent. Our architect seems significantly more worried about overheating, I'm personally not because if it is sunny enough to overheat it is sunny enough to generate plenty of power for cooling. I'm told no chance of a wind turbine due to nature of the plot but I think attitudes to this will change, particularly with horizontal ridge mount turbines.