Conor

Sounds like a commercial use, so if in a residential area, planning will be required no matter the size (even if an existing structure, as would be a change of use.) Might be better off leasing an industrial unit where you won't have so many hurdles?

Remove everything and brick up the hole, with bricks.

I've said this on many threads before, we bought five of the basic dehumidifiers from Screwfix. Found them far more effective than the large industrial type units. And at 300w each, the five were able to keep the house warm when we moved in Feb 2022, with no other heating.

Do you have an air release valve on the system? If there was air in that loop, has to go somewhere. Re flow rate, 5lps is huge. Refer back to the design sheets and take it from there

Flying ends are standard here anyway. Overlap and tie.

Hmmm... Have a look around and there might be existing connections at the front oft he site. If 1980s then they'll be small metal boxes, sometimes with Water written on the lids. Your plumber or builder will know what to look for. Likely they'll need to be dug up and replaced with modern meter boxes, but that will be much cheaper than a new pipe across the road.

I'd be wanting a few more pipe clips up there. If it's a hot water recirculation system you absolutely would want to insulate. And insulate well. They are wasteful enough systems to start off with.

TM is traffic management. It's a full road crossing on a made road. Presumably open cut? Presume this is a new site and not a replacement dwelling with an existing connection?

Storage radiator? At least it's direct electric heat during the day but charged up on cheap rate.

Can't remember how our architect modelled our basement but the heatlosses are far less than predicted. I think good drainage around and under plays a big part I'll dig out the report so you know how not to do it.

I've mine to start right at the low rate... On basis that unit will be working at full rate getting the flow temp up to target and dealing with a temp delta of 10c. As things heatup, the return flow rate will be higher and unit modulating down and using less power. The long it's on, the lower the flow temp delta, the better the COP. Also... With the clear skies the temp at nigh here is below zero but 5-7c during the day, so that helps a bit.

Why not try increasing the flow temp by 5c, reduce the flow rate to the main house and increasing it (if possible) to the summer house?

Salda smarty. Do not reccomend.

Hotter. And also cooler... I use mine as a slow cooker. The controllability and efficiency are unrivaled. Only downside is I've yet to try a wok that comes close to a traditional thin carbon steel wok on a big gas burner. With induction you can only really heat the base of a pan

We've oversized units, has four fan speed modes. Runs on the second step most of the time, occasionally drops down to the lowest mode temp / humidity dictate. Never known it to jump up a step to deal with excess humidity. Make sure the unit can be set at a lower speed... Ours is about half of the "requirement".

Anybody that prefers gas to induction is, objectively, wrong.

When steel beams are in play, window companies need to allow for deflection. So your usual 25mm can be 35mm. Was the finished floor level clearly marked and agreed on site? The trickle cent unit looks cumbersome. Did you know what was how it was going to be?

Is be sticking to rads in the existing part, tbh. You'll not get enough insualtion in.

Who measured up, and what drawings / sheets did you sign off before manufacture?

Another point. Last December's cold snap was damp and dull and lasted two weeks. That was a particularly bad combo as we lost a lot of solar gain during the day and the high humidity meant even more defrost cycles for the heatpump. All in all, I estimate that 2 weeks of struggling cost us an additional £150 in electric. At no point were we cold, tho. This spell is forecast to be a bit less cold, bit more importantly sunny during the day with temps initially 5-7c. So much less of a challenge . And yes I know a lot of people here know their heatpumps better than their partners, but some of us just plugged the things on and got on with life 🤣

Last year was our first winter in the new house and I was getting used to the heatpump. Ahead of last December's cold snap, I was running the heatpump as I am now- ~34c flow temp, economy 7 hours of 1am to 8am. That was perfect , until it got cold! It was a day or two before I really noticed that house was losing a fair bit more heat over 24hrs than the heatpump was providing in its 7 hours. So, turned it on to an 18hour programme. All good? Nope, because the house had lost enough heat energy, and it was cold and damp outside, so that the heatpump really struggled to bring the temp back up to our desired comfort level. Lots of defrost cycles etc. So this time, I've had the thermostats set 1c higher than we did last year and yesterday I had it running during the day, and will do again today. Basically, I'm pre-charging the house with a little bit more heat energy, and preempting the additional demand buy changing the programme to 18hours before the cold snap bites. Might be of some use to use to anybody else who tries to get by with their heatpump on off-peak hours only. Of course, running 24x7 on weather comp would mitigate all this....

You want about 150mm insualtion for UFH to be effective and economical. How much and what type went in to the extension? For the block and beam, you can get EPS blocks in place of the concrete blocks, but may not fit your existing beams. And you'd still want more PIR above this anyway. I'm not sure on the option of completely removing the beam floor and replacing with a solid slab, a structural engineer would be needed.

The system you are describing sounds like EPS, reinforcing mesh with base coat, and silicon / acrylic render skim on top. These are somewhat breathable (EPS is like a sponge and is vapour permeable) and moisture will make its way out eventually. I'm sure our in-house render expert will be along soon. In the mean time, ignore the rest of us.

Need to see a drawing, floor area, required flow rates etc. In the meantime, I've a hybrid system. MVHR, 125mm ducts to each floor (three floors in total), then a 6 port manifold serving each floor. Keeps almost all of the 80mm runs to the valves under 10m, and meant only two cuts through the slabs at 125mm each.

I found the roof lights upstairs had to be open a good couple of inches, or else the reveals would be soaking the next morning. Rest of mine are tilt and turn so just left them tilted in, so about a 80mm gap. Experiment and see, but I'd leave the top floor windows / roof lights on more than just the trickle latch. Also, don't raise the temp of the house too quickly. Start at 12c and bring it up a degree or less per day. Two weeks to get to 20c. We soon sealed up and used dehumidifiers tho, more efficient and effective. Bought five £120 ones from Screwfix and sold them all on a year later for £80- £100 each.