JohnMo

Posi rafter has basically the same thermal losses as the same size wooden beam. The metal webs are about 1mm think, so the cross section is pretty small. I used them in my roof, but then underneath counter battened 100mm and full filled with insulation. To limit any thermal bridges further. Then a vapour barrier and a further 50mm service void. Your first floor, floor build inside the thermal envelope, makes zero difference to heat loss, could be all metal if you wanted.

All really depends on the house and the insulation levels and heating system. If it's very well insulated a thick screed or concrete may be best, a big chunk of concrete to slowly release heat, either drip fed in to floor or added in chunks on cheap rate. No need for zones or complex control, super simple. Retrofit a different story, UFH to free up wall space, not the best insulation, mixed in with a few radiators you may be better with system that takes heat and releases quickly. Horses for courses. No one solution fits all homes.

Things you need from your door. Draft proof, consider a full door set, so frame and door, with double seals. Get a mail box not a letter box. Get as good a u value as you can. But most of all make sure it's draft free. Our door was made a local company , they also made the windows; it's basically looks like a modern door, made with a wooden frame, infilled with insulation and a wooden skin either side - U value is 1.0. Nothing is scratch resistant - if they say it is, they are telling porkies. Treat it well and don't abuse it, it's going to cost you and your wife a fair bit.

Now I am on the computer I can see where you are. Yes we have a strange orb in the sky

That's what I also thought, living between Aberdeen and Inverness, but had under floor cooling on most days when the sun came out, from May to September.

Give you one of the factors that affects flow rate. The other as you mentioned is So you choose the higher of the two flow rates, to set the min flow rate. So you just need to increase extract to match supply and you have your target flow rates set.

You need your volume of the house in m3 divide that by 2 to 3 to get your overall flow rate in m3/hr. Just increase the extract rates to match the supply rates if required. But living room flow look too low, it will end up a stuffy room, it should at least be the same or more as a double bedroom.

A few on here read the rules and can quote most of them because they read and reread them, we are the exception, the normal population don't read them nor care to read them. So many things get done, which really should not. But that's life.

No, the one on the manifold will move the fluid around the loop I wouldn't, not really suitable for 13A for a long period.

So your pressure drop is well within the limits of the MVHR, so all fine there. Your furthest away grille will be as far open as it goes, you then tune the output of the MVHR to get the flow rate you want. Then close in the other rooms outlets to get them where you need, then repeat a few times until all are ok. Goes into a duct, I used a Testo 425 (it will read in flow rate also), used a 150 to 125 adapter and some 125mm duct and secured the probe in the center of the duct with a cable gland.

The rules don't care if it's an A2A or A2W, so either if used on cooling duty its not permitted development. Not sure many would take much notice. Might be a noise thing?

So you could play statically and say beer and wine at outside temperature is ideal. Or you could say they are (or want to be) drunk and just don't care.

Some MVHR control schemes will give out as set flow rate, once commissioned and automatically adjust fan speed to compensate for blocked filters etc. I would just disengage the 2 systems - KISS is always best

You basically use the most onerous run length. Not all of them, as they are parallel.

Solar powered? options are available fully packaged, battery and solar panels.

https://www.nationalheatershops.co.uk/p/powrmatic-airco290-packaged-heat-pump-air-conditioner/?utm_source=google&utm_medium=cpc&adpos=&scid=scplp&sc_intid=&gad_source=1&gclid=CjwKCAjwvfmoBhAwEiwAG2tqzOigC0BdWiKss7-4CEd4t84cnJhyveYsY0mp-DBeeY0WRn6ibre-vxoCZzIQAvD_BwE No outdoor unit, so not a planning concern.

You strictly need planning permission for any product that can do cooling (the house not a fridge). As it's excluded from permitted development rights, irrespective of MCS or otherwise.

glad its all sorted now

You don't need to be that exact, measure your house internal footprint multiple by height will be a near enough ballpark. Didn't mention your extract and supply rates should match each other.

You need to calculate pressure drop - use duct suppliers table for your duct and bends to calculate the max pressure drop and ensure that is ok for the fans, the bigger the pressure drop the harder the fans have to work and that means more noise. Are you going through a manifold section? If not you may need attenuators between rooms to stop cross talk.

The easy stuff 1. Work out house volume in m3 2. Divide to 3, that will give you a min flow rate in m3/HR. 3. Work out the flow rates to each area. Use attached as guidance.

You would really need do some calculations, but I have the following comments Flow from AC will exceed that of the MVHR by a considerable margin. Could the flow from the MVHR actually break in to the flow of the AC? To understand this you need to understand the pressure drop over the AC system and where on the curve your MVHR fans are when AC is running and when it's off. Once set up to work with AC your MVHR would most likely be completely out of calibration if the AC fan wasn't running or any speed changes occur. Nice idea, but think it would be difficult (impossible) to set up to run correctly all the time. Run them as separate systems.

If you back to basics, you need to get the circulation pump duty point, and know what the acceptable pressure drop is. You work back from that, so you need to know distances and what bends you will have and the pressure drop per metre and per bend and also any pressure drops through valves.

If you haven't specified anything, you get what you get.

Not too bad price wise, the kit is pretty much complete with everything you need, except pipe and cables. They offer a good range of sizes of cylinder and ASHP.