Iceverge

Ok. Install 1 X A2A unit in a central area. We bought the Daikin FTXM25R. About £900 plus install. It should have good cold weather performance, cooling heating and WiFi out of the box. (Allow ducts + power supplies for other units if you think you'll need them, you probably won't, PHPP will guide you) Install a stand alone Heat pump for the DHW. Joule do some. @Thedreamer has one. Or my preference would be a stand alone one like I posted above. Say another £900 plus "as large as you can fit" SS cylinder. Then put some towel rads in the bathrooms. <£3k spent. COP of 4-5 on heating. COP of 2.5-3 on DHW. Zero chance of leaks associated with space heating. Surely the point of a passive house is you can do away with all the complex heating systems. Keep it simple and don't combine space heating and DHW unless there an obvious benefit to doing so.

Me too but the house I lived in had gas CH + UFH and minimal insulation. Sounds like a complex setup? What was the need for all 3? It sounds like a simple monoblock ASHP and UVC and UFH would be the most satisfactory setup in that case. The requirement for an F-Gas installer for any split unit is a disadvantage, perhaps outweighing the efficiency gains. Also the greater potential for a refrigerant leak could well undo any CO2 savings. I think you are over estimating the potential for a water leak from the UFH Vs DHW. One point to consider with a specific split unit system and various fan coils is that you may run into difficulty replacing one element if it fails in years to come. Better to have a separated system tied to no particular manufacturer in my opinion.

Ditto. Nothing really matches not needing the energy initially. Although I'm not sure a properly tuned UFH ASHP setup really feels warm to the touch. Maybe some others could comment? @ProDave @TerryE

Nilan do the Compact P. Lovely unit. €9k plus the Vat plus install in Ireland when I looked 5 years ago. 😬

Are you sure it's from UFH and not leaking DHW? In any case, time over again I would only have pipe joints and cylinders in a room with a floor level drain to allow any leaks to drain away safely. I'm surprised that insurance companies don't insist on it for new builds. Deciding on how to heat a passive house is a real pain in the ass. The heat demand is so low that any cash you spend on the capital install makes a massive chunk of the lifetime running costs, so any expensive system is almost impossible to justify over simple restive heating. We have a passive house in Ireland. Currently heating it with a single 900w plug in electric radiator in the living room. (It needs another rad added when the weather gets frosty) It doesn't really matter where you put it so long as it's downstairs, the heat tends to even out. I've bought a split A2A unit from Daikin, yet to be installed. It should reduce our spend on electricity from €900 to €200 so there's about a 2-3 year payback for a semi DIY install. I've also recently put some patio style heaters in the bathrooms for a bit of extra comfort when emerging from the shower. For DHW we just use an immersion. As this can run solely on cheap night rate time of use (TOU) electricity it costs €600/year for a family of 5. I'm hoping some PV install will reduce this to less than €200. Alternatively one of these might be a solution for a similar saving. If I was to do it all again I think I'd go one of two routes. 1. Install UFH pipes in a concrete slab and an UVC with a large coil. Run it all a cheap TOU electricity and pick up a cheap monoblock ASHP when the opportunity arose if the house performance justified it. 2. Install a single A2A unit in a central area of the house downstairs for heating. Install under tile electric UFH in the bathrooms for comfort or patio/IR heaters. Use PV with divert or a dedicated heat pump as shown above for DHW.

Are you sure it's closed cell? It's much more expensive than open cell so would be used sparingly. Any pics? For your own satisfaction you could just shove a screwdriver through the foam into the rafter and see if it's rotten.

@Clark Kent Sorry for the delay. Assuming you will suck out the mineral wool in the cavity and replace with foam or GPS beads. I've drawn some of the lightly escape routes for heat. The house will most lightly have brick closed cavities at the window jambs. When adding a cavity wall extension it's difficult to deal with joining to the existing building and you'll have a heat leak here too. That's why in an ideal world a complete wrap around blanket of insulation would be nice. You could deal with most of these by adding an internal insulation layer too but it'll rob a lot of space from the house.

That design looks fine, without accurate dimensions its a tad hard to judge but it's good really. However, (stroking my passive house chin) there's thermal bridges galore. I would love to suggest wrapping the whole house, including the new bit in 200mm Rockwool EWI but I have a feeling some Draconian conservation law will prevent that. I also think living there whilst building is ongoing will be impossible.

Add up the cost maybe. It might be cheaper just to add another panel.

What spec are the glass you've recieving? Centre pane U-Value and G-Value and edge spacer design? Windows are by far and a way the worst performing elements of our passive house, and of them, the window frames are the worst part. And they are passivhaus certified. You won't be within an asses roar of a good performing window unless you're prepared to become a complete expert, fastidious with details and spend days making each window. Then you'll be hoping that you've got it right in terms of stability and durability long term. Glass units are generally cheap to buy so I don't think your neighbour has done you any great favours. Flog them on eBay. They'll only make pounds each and like @nod says buy they best performing uPVC windows you can.

If you're willing to loose more space you could use 44*47mm battens @400cc for a service cavity and then infill with mineral wool. The 22*70mm is to create an uninsulated service cavity. (The stationary air will help insulation almost as much as insulation at narrow depths anyway) the reason for not using 22*44mm battens is they'll split from the plasterboard screws.

Agreed, think I wrote something very similar last week somewhere on here. Once you get to a COP of about 3-4 the maths really start to taper off. If your house is continuously heated I suppose you could get away with smaller radiators than an intermittently heated one. Perhaps making ASHP's more suitable for retired people and work from home occupiers. My parent's rads often run at very low temperature dumping heat from the solid fuel cooker. It's made a big difference to the comfort of the house, even though they'll be cool to the touch. I think ASHPs, like almost every other appliance, baring the kettle and toaster, are too complex to ensure efficient operation by uninterested users.

It's best method of getting a good COP from an ASHP for sure. It will deliver each kWh of heat to your house at the lowest price. However as a method of least overall cost use I don't think it applies to a house that has high losses and is intermittently occupied. It'll need to run far too long when nobody's in to get to a comfortable temperature when everyone's home from work. Much of this heat will be lost to outside with no benefit. Unless you can convince your electricity supplier to drag a cable to your house that can power a 40kW heat pump I can't see ASHP's being a solution for most working people without tacking the house fabric first.

A nice video that. Quite accessible. Did you consider oversizing even further and lowering the flow temp to benefit from a better COP?

Interesting. How did you size your radiators and what flow temp do you use?

I must look closer. A big business park near me was all insulated PIR panels surprising tidy construction but maybe that's the exception. A line of FM330 between every panel would be simple to do and make a good job of airtighess. Labour is becoming a real issue in Ireland. Too many old builders have retired and young people are not interested in the low wages and poor working conditions. Before you write off the quote for your roof make sure you are comparing like for like including labour costs. How much are you valuing your time at?

Ah you'll need some insulation then. 3 options. 1. Knock the wall and build the whole thing from scratch with a timber frame. 2. Use bricks to build the wall higher a d forget the timber frame. 3 Use your hybrid approach. For 2 and 3 I would put 50mm PIR internally, foamed and taped at the joints.Then a 22*70mm battened service cavity and plasterboard. Joining the wall PIR to 50mm (or more)PIR on the floor. Overlay with 2*11mm layers of floating OSB, joints staggered, glued and screwed.

I'm sure your builder is a good sort but they're very cautious by nature and will be slow to change from a method they understand. Put in the biggest radiators you can fit and forget UFH is my advice unless you're prepared to dig out the floor and put in 300mm EPS. A correctly sized ASHP work best with as low a flow temp as possible. To be able to extract the heat most efficiently from that flow you need the most emitter power. This means a shallow screed with closely spaced pipes or big radiators. Do you have any sketches of the extension (unidentified for a public forum of course) ?

Or they are prohibited from replacing them with something better because of conservative planning restrictions. Yes, some dreadful buildings were constructed, often with dystopian social engineering at their essence. The resulting social problems were influential in their demise,as well as the delusion of a consequence free fossil fuel powered future. My point is that continuous gradual improvement isn't needed, it's just a waste of energy, we know the finish line already. Passive houses, made from stuff that used to be plants and with lots of renewables is the end point. There's nowhere else to go after that. Going half way there and spending a huge chunk of money doing so is a waste of resources. Say we have £300k to spend on 5 houses. We're better off to spend £30k doing simple attic insulation, airtightness and an A2A HP on 4 houses and £270k on replacing one house with a perfect one that'll last 500 years. Then doing the rest when the cash comes. Spending £60k on each house to be half way there is a waste as it's just postponing the problem. Ultimately they'll need to be knocked and rebuilt anyway and the entire £300k will be wasted. Looking at modern warehouses and industrial buildings I would have to disagree with you. They're largely steel portal frames, clad in insulted steel panels. Extremely fast to erect with great efficiency of labour. The materials may be dearer than concrete blocks and mineral wool batts but the man hours are so well spent that there's no economic case for old fashioned build methods. Given a system free from restrictive planning regulations and a mandate to build as much top notch accomodation as possible we'd be doing something similar for houses. Labour is an increasing problem as we shift further towards thinking jobs and not doing jobs and we collectively become older. With less "doers" we need them to be driving a crane installing a wall at a time rather than handballing a single brick into place at a time.

Where are we with high temperature heat pumps as a direct replacement for fossil fuel boilers? Ideally in a big insulated box with an inbuilt DHW cylinder that could be mounted externally to the house. Core a 100mm hole in the wall, 4 pipes. DHW in and out. Heating flow and return. Power in and a lead for a controller. No G3 or F-Gas requirements then and a direct replacement for your old boiler that a monkey could install.

Gottya. Rest assured. The beatings will continue regardless.

Assuming you can get people to do the work and pay them then it's fine. However it's still a bespoke building. Every part of the TF cut to length on site, bricks laid one by one. Craftsman galore. Here's how we built factories in 1900. Here's how we do it today Here's houses in 1900 Here houses today. See my issue?

Sweeping generalisations are what I'm all about 😁. Had to Google "qv"..... And survivorship bias. So what you're saying is that all the crap Victorian houses have been pulled down?

What's this building going to be used for?

The Victorians built the best houses they could at the time with the given technology. Pity we can't collectively seem to learn from them.