ProDave

Nope. A near neighbour had started installing basic whole house mechanical ventilation, had his air test done, better than 3, Building control told him he had to have full mvhr.

I did on my sun room.

A lot on here (including me) have gone with an architectural technician. For what most self builders need, they seem to offer a better service. In my case I had a plot with OPP and a pretty good idea of what I wanted. The AT took that design to something actually buildable that would pass building regs, produced all the drawings and in conjunction with a structural engineer all the details and calculations required for building control. That gave me a building warrant and a COMPLETE set of drawings to build the house all for a reasonable fee that seemed to be based on the amount of actual work done not some notional value of what the house was worth. That set of drawings was given to the builder to build it. As I said in my first reply, it was the simple inability to get that package of work at a sensible cost from an architect that put me right off them. Perhaps they don't want "simple" tasks like that? Perhaps all they are interested in is managing a complete project, putting the build out to tender and delivering a turn key solution to the client. But I suspect that is not what a lot of self builders want?

Our brickie charged by the block laid, so I could not give two hoots how long he took.

Yes ours is silent at normal speed. It can be a little noisy on full boost. Just don't let anyone take a shower in the middle of the night.

Some of us have low opinions of Architects. Nothing personal but here is my reason. When stating on our first self build I had a pretty good idea of what we wanted sketched out so I approached some architects. What I got back was quotes based on astromomical figures. they both wanted to charge a fixed percentage of the estimated build costs and both managed to estimate the build cost at roughly double what it actually turned out to be and neither would negotiate. All I wanted was someone to do some design work and produce drawings and I was looking for a fair fee based on an acceptable hourly rate and hours actually worked. That sorry experience means I have never spoken to an architect since. It would be good to hear that things have moved on since then (nearly 20 years ago)

In terms of living with it. Almost nothing to do. Just enjoy the fresh air and lack of condensation. Ours has a manual boost to speed it up for showering or cooking so we just press a button. Some systems boost automatically based on humidity. Routine servicing is simply inspect the filters and clean or replace as necessary.

That's why we painted ours. Ask me in 5 years how it is doing.....

Ignore panel efficiency. Nobody has yet invented a PV panel much above 20% efficient. It only affects the space they take up. Concentrate on minimum price per kW of panel unless you are really restricted for space.

My panels came from Bimble Solar. Some they had on offer at the time, a pallet load split with another forum member. Inverter and other bits like isolators and generation meter from ebay. Mounting frame made of Unistrut. Cheaper than aluminium rail.

Stick with 4kWp and a 3.68kW inverter grid tied so no DNO problems and self use as much as you can. anything else gets expensive with obstacles in your way. You can buy all the parts and DIY install that pretty cheap or pay an electrician. To claim the insulting 5p export payment requires an MCS install which we all know adds ££££ to the bill and you will never reclaim the MCS surcharge with the export payments. I export about 100kWh per year that I am unable to self use for which I would get paid about £5 were I able to claim the payment. Simply NOT worth paying the extra than an MCS contractor would charge. If you want even more than 4kWp them make that off grid for battery charging to be used in the evenings for example?

Since the thread has woken up again, my finished sun room

If your wife will tolerate putting the washing in the machine and then waiting some unknown time before the electricity is cheap enough to process it, she is more tolerant than mine.

I don't agree. The alternative is no ventilation and trust to natural leaks in the building which is usually poor and unreliable. Or mechanical extraction that draws COLD air in to replace the heat you are expelling from the building and in 99% of cases allows cold air to blow IN when the fan is not on. Of course mvhr works better in an air tight building but I bet it would still be of benefit in a less than perfect building.

I can see some merit in smart light control, self closing curtains etc. BUT I can see no merit whatsoever in a smart dishwasher or fridge etc. That is a "solution looking for a problem"

The doors don't look good. Bifolds have a reputation for being leaky and hard to make reliably air tight. But the whole frame looks cold. What make are they?

Just to add to this debate, we have an enthalpy mvhr unit. It was not deliberately chosen, but like a few other bits in this house one came up cheap on ebay. Kingspan had been re badging mitsubishi units and I believe Kingspan abandoned that enterprise and several ended up cheap on ebay. I did not know until we had it that it was indeed an enthalpy unit. I have had no problems with it, and the only window that gets any condensation is the 2G velux window in the en-suite. At the time of buying that window I debated 2g or 3g and as it was a small window I concluded the heat loss of a 2g window was low enough not to worry about. I do wish now I had paid a bit more for the 3g version to reduce or eliminate the small amount of condensation we get around the edges of the window.

Can we see thermal image pictures of the flow and return pipes into the ASHP. Assuming they are covered in pipe insulation, remove a section of that for the photos so we can see the actual pipe temperatures.

It seems common that mass market house builders have a reputation for poor service. Get a bucket stood up in the loft to catch the drips for now to save the water soaking into the insulation and wetting the ceiling, you might need a board or a plank to stand the bucket on.

That picture looks to be rotated, i.e. south up, unless you are in the southern hemisphere. How about a ground mounted PV system at the southern end of your garden? Then make it into a shed:

When measuring a building, e.g. a shed, they count the eaves height as the height at the lowest point. Personally I would just do it, you don't want to have to put a step to keep it under 300mm do you?

That looks like it was concrete, and the passing travellers put a very thin coat of tar on with no preparation and it has predictable failed. As above get it done properly next time.

Get the installer back and pose this question to them. Or check with for example an IR thermometer what the actual flow and return pipe temperatures are at the heat pump. Is there a buffer tank in this system?

So it's a 10kW heat pump then. Probably half the power of the previous oil boiler (that struggled to heat the original house) so lets hope the now enlarged house really has some better insulation. you NEED to pester the builder to find what calculations they did about the expected heat loss of the enlarged and hopefully improved house now, AND find out exactly what insulation has been placed under the UFH pipes. Assuming the enlarged, but better insulated house still needs the same amount of heat, then 14890kWh of heat delivered by a heat pump at a COP of 3 and a present electricity price of 20p per kWh will cost £992 pa

So you had an oil boiler that struggled to keep the house warm. You have replaced it with a heat pump that is probably lower power than the previous boiler (I have failed to find what output power this heat pump is, Daikin don't make it easy to find out) and still have the problem that downstairs does not heat up enough. You are relying on the improvements to insulation to even make the new lower powered heat source work for your house, but don't seem to know much about the insulation fitted. You talk of 40mm floor insulation, if that is all you have it is WAY too little for under floor heating. Did you pay for all the upgrades to insulation and the heat pump install as a package to one company? If so I would be getting them back to sort it out. If you are struggling with an outside temperature of 8 degrees, you are really going to struggle when it gets properly cold. To give us some idea of expectations, how much oil did you burn in a year with the previous boiler? That will give an idea of the heat losses of the house prior to any improvements. Unless they fitted a dedicated electricity meter for the heat pump, or your has it's own metering built in, it is hard to actually measure how much it is using. In our house the heating is only about a quarter of all electricity usage.