SimonD

We are 4 plus dog in a volume of above 900m3. But as I mentioned above, ventilation requirements change dramatically once a hydrophilic fabric is introduced into the equation. So, to quote from an earlier study I read when deciding on my design: https://web.ornl.gov/sci/buildings/conf-archive/2004 B9 papers/002_Simonson.pdf Now, it does acknowledge that consideration regarding air polutants is probably separate, but other studies using MVHR show similar reductions on ventilation requirements simply because moisture drive such a significant proportion of those ventilation requirements. Yes, indeed. At some point when I actually find some spare time, I might draw together my collection of research into this and building physics just so there more readily available reference.

SS is used for traditional metal standing seam roof clips and screws.

There are some articles out there that talk about this. If using over-lay, then it must be one that uses an insulated backing such as pir. In effect, this creates a decoupling with the slab and as it increases thermal resistance to the slab, it pushes it upwards instead. However, you need this to be properly calculated by someone who knows what they're doing because floor down losses also depend on the shape of the floor and external sides.. It's probably going to be better than over-lay on a suspended floor, but neither are that ideal into uninsulated floor. The other thing you need to consider is that you'll be raising the finished floor height and this will have an impact across your entire house and will also impact your stairs, which may need modification to still comply with building regs.

Not necessarily, it depends on the ventilation strategy or mixture of strategy, of which buoyancy, is just one aspect. Mine mainly utilises pressure which is either vapour pressure difference or wind pressure. I do have a stack effect used for when it gets warm, and a limited stack from ground floor to first floor. But one of the things often overlooked is how building a house which uses materials that buffer moisture significantly reduces the ventilation requirements of the space which in turn reduces the energy requirements, whether through heating incoming air, or running mechanical ventilation. The calculated ventilation rate we have is about 0.38ACH and complies with building regulations minimum vent rates. Thermally, we now know that the building outperforms the calculated heat losses too. IAQ is fine. We've on a few occasions had raised CO2 but nothing to worry about at all. All the other measures like particulates etc. are always good, other than immediately after doing a load of dust inducing building work, but that clears pretty quickly.

This whole thing is a bugbear of mine ever since I did the detail design of my house, which is so fundamentally different to most building methods that I've even had extensively long debates with the powers at be on the green building forum and the understanding here on BH is also narrow when it comes to the full understanding of ventilation in relation to moisture management and building physics, and particularly the differences and relationships between vapour permeability and hygroscopicity in the building fabric. This is why people still think I'm mad for designing my house to be low energy while also naturally ventilated. But suffice it to say that when I not long ago had some people planning a self-build round to look at my house, they asked why would I seal the whole building up and then introduce air supply - the simple answer is of course so it's then properly controlled while also adequate for good indoor air quality. When explained it was good that they accepted this having seen it in practise. Well, that is the million dollar question when people try to calculate the roi of upgrades that will provide them with a lifetime of better comfort in their home (even if it costs a few quid, versus spunking goodness know how much on crap quality tack on extensions, kitchens and bathrooms every 10 or 15 years and trying to mask the problems with dehumidifiers, over-sized boilers and radiators etc.

Thank you, you're on my tester list ☺️

Just to be aware. SAP calculates heat loss slightly differently to the industry heat load calculations as defined by BS EN 1283-1:2017 and CIBSE Domestic Heating Design Guide. SAP is interested more in energy consumption and energy efficiency whereas CIBSE is about sizing the heat source and system appropriately for peak loads. SAP is absolutely fine to use to gain an understanding of the thermal performance of the building, but just be aware of the differences and you might need an alternative calculation for final system sizing and design. For BH, please keep and eye on a free design tool coming soon that can do both, which is something I've been working on since the latest implemented changes to heat load calculations last summer, but I need to test it on a couple of real world projects first 😉 I might be able to make it available sooner if I can receive bug feedback as a beta test kind of thing.....?

I completely agree. Investigate first. For example - when we bought our shell for development, the bungalow built in the 1920s, which we had to live in for a few years was extremely damp - I installed a pretty heavy duty extractor in the bathroom as a first step because there wasn't one in there. We found problems in a few of the rooms that had to be addressed and when we stripped out the old kitchen, we found black mould completely covering the wall behind the cupboards.

Sorry if my post wasn't clear enough. There's the unfortunate tendency in construction of using terms interchangeably in unhelpful ways. By sarking boards I do indeed refer to the 100 or generally 150 x 22mm boards and not the woodfibre sarking boards. If you were to use woodfibre sarking boards your roof buildup would change dramatically and you would dump the pir and instead use woodfibre bats between rafter with woodfibre sarking boards on top, then battens running inline with the rafter fixed through the sarking to the rafters then 150mm sarking boards/plywood, membrane, standing seam. This gives you a cold roof, which is still preferred in traditional standing seam roofing design due to the requirements of very careful detailing if doing a warm roof. If you wanted to go down the warm roof, then have a look at the buildup provided by pro clima, but which uses woodfibre batts between rafters, 150mm sarking, pro-clima metal roof underlay, metal roof. https://proclima.com/products/external-sealing My view is that if you're going down the route of natural materials such as woodfibre or celulose, or even sheepswool, you stick to a buildup with all those materials as a homogeneous system. Likewise, if you want to go down the route of kooltherm/pir, then use a system buildup as specified by the manufacturers. This reduces your risks of cockups, misunderstandings and mistakes during the build, especially when you might have trades that don't know the system. JMHO.

Good point. Given his background, experience and attention to detail, I just assumed @saveasteading would have it all covered off.

The Panasonic M series Aquarea is available in a 9kW 3ph unit. It is very nice indeed and super quite, even if it is physically quite large.

Stop fiddling!!!!! Be PATIENT 😉😊 You are barely into this by a week. This is not enough time for the system to balance itself out. Get the information from the manufacturer technical support you need to input a baseline WC curve correctly. Calculate your heat co-efficient for your house in W/K and use those to calculate your flow temps at the controller inputs. Then leave the system alone. And if you're tempted for reach out and make adjustments, slap yourself on the wrist and go do something else. Yes, of course look at the data to make sure it's running OKish, but let it do it's thing over at least 24 hours or preferably a week - as long as the WC curve is nice and low. Use this period not as a fiddling period, but one of research - gather data to understand how the heat pump is working in context - then you'll understand when it starts to cycle (if at all), what it really modulates down to etc. etc. I know you want to play, but heat pumps, big specific heat capacities, new building and all that do not like this. They want to chill out and relax, take it easy and watch the world go by 😉

Let the battles of SCOP begin, eah. And it's not even pure open loop, but actually has some room influence in the way of TRVs due to large solar gains! Shock horror 😁

At what temperature? These figures are often quoted at 10C so below that may be a lot less. My own heat pump is a 6.5kW unit (at -5) and has a quoted minimum output of 2.4ish. I regularly see a very comfortable 1.2kW output. So best to test it out to see what it can do. You still need to give your unit and house more time.

The electric power only goes to 1 decimal place and is rounded up, for whatever reason, so at 6.8 actual electricity input is 0.276kW. Likewise in this screen grab showing cop of 7.2, actual input is 0.28kW, so the display is a little annoying. I'm wondering whether to get the open energy monitor kit installed before next winter.

Dont't want to blow my own trumpet, but I was a bit dissappointed when mine dropped from SCOP of 6.2 to 6.1. This is for the whole winter so far since October and it's a system on radiators 😉:

It's more of a reminder to myself of how I was once in a self-builder mentality doing the begrudging! Experience is a wonderful teacher! 😁

Yes, indeed, it's not uncommon for markups to be in the order of 20-40% sometimes, but as I've learned now being in the business, the whole transaction costs as a trade sourcing and buying in materials is significant - there's a lot of time involved. As a self-builder, I'd take my time doing materials lists to the nth degree, time I wouldn't have if I'm trying to earn money at the same time. I think the reason for me asking is to primarily to keep control of costs and moreover to not be overcharged. It's all swings and roundabouts, but having a comprehensive materials list to start is essential and a very important part of bargaining down prices. With my build I sent my spreadsheet to the various merchants and the one I chose, put the list on the account for the agreed discounts and each time I needed more materials, we just drew down on that list at the agreed prices as the project progressed. With places like Midsummer, there are always the alternatives like Renewables Centre, City Plumbing etc. or even the other online suppliers - plenty of choice really.

It's ironic isn't it? They ask for reference to the standards, but don't seem to know them. But the big warning bell that's ringing for me is that they're using an umbrella company. I assume you have a separate contract directly with the umbrella company too? So the actual MCS Design Standard (both current and redeveloped schemes) say this: As you can see, this does not stipulate that you have to have an emitter in each room. It is just assumed by the designer and installer, probably because they have no experience dealing with low or ultra-low energy buildings and therefore don't understand how a passivhaus would perform thermally. I'd recommend you have a good think about using these people as this is not a good start. But also, have a think about your design - at some point you may want additional heat and be able to have cooling, in which case you can use fan coils or UFH to provide this. I saw some very neat fan coils by Panasonic today. Very unobtrusive. I think definitely try to find a good designer and installer who can discuss the options with you. Plenty of help on here should you want help to diy instead.

This could just be the shift settings need adjusting but at the moment, if you've got min set to 28 and max at 32, your curve is definitely too flat. What's the calculated flow temp and min outdoor air temp? And what is your calculated heat loss at this temp? You can simply calculate your heat co-efficient W/K to establish a baseline curve at all relevant temps.

Well, this is just plainly naive, isn't it? What about all the infrastructure and energy required to run all the cloud functionality? I've worked in the tech. sector since the 1990s, mainly on the business side and I have specifically designed my house to not have any smart technology baked in whatsoever - you just can't trust them in any way whatsoever.

No reason as far as I'm aware. I'm fully Nibe trained for both ASHP and GSHP and will soon have completed the NIBE Pro accreditation, so I could be considered slightly biased.

If you do osb sheathing @ 11mm you can use this as your VCL, just tape and seal all the joints. With respect to your buildup sub the metal roof, you need to be a little careful. There are only a small number of standing seam metal roofing manufacturers that explicitly have a buildup that doesn't require a ventilation gap so double check with them that the Tyvek metal underlay system on warm roof is accepted by them (I know it's been designed to allow condensation to drain from below the metal roof and there are approved systems) - and double check with building control. You are also much better of using sarking boards, which are the preferred substrate, second is plywood and 3rd is osb. Pull out resistance of your standing seam clips is greatly reduced in osb where you really need to use screws not nails, which most contractors will use because they won't want to spend the time screwing the clips into the board. So you have to look at this in the round and how the metal roofing contractor designs the clipping for the wind exposure of your house.

What are the property heat losses this scheme has been designed for? What are the proposed outputs of the ufh and what flow temp? What is the zoning plan the designers have suggested (red flag already). What is the plan for 1st floor heating? Are they proposing a circ pump & mixer on manifold or more sensibly electronic mixer if going with other emitters on ff? Lots missing in this design to give a full picture of the system first.

Thanks Gus, I get you now. My reading of this is about taking a wider view of heating design beyond cost cutting via material, initial design input, and doing it in the quickest most convenient way. Instead invest for the long term rather than just look at the engineering redundancy. Yes, whole life cycle makes perfect sense and is ultimately a more sensible approach. And from a design perspective I'd suggest it's more about the principle of understanding the space as a whole rather than what the plans indicate. In this sense it's still important, if not absolutely necessary to vary the design for different areas of the building - e.g. a large living space with acres of glass compared to enclosed individual rooms with small glazing factors, but at the same time look to provide reliable heat distribution throughout the building. Although temperatures will tend to equalise across a well insulated building, there is still very real possibility of localised over-heating if not considered carefully, and therefore the system has to be designed with balance in mind, but not to get distracted by variables occupants can easily change over time. If my understanding is correct, I think we're pretty much on the same page.