From Victorian Eco - Just installing ASHP and rads in the property.

Best practice suggests flow into rads should be top and return should be at bottom. (Opposite ends if length more than 4x height)

So that means TRV's on top and standard lockshield on bottom. Would you even use TRV's on rads or only in bedrooms?

Secondly to avoid surface mounted pipes, I intended chasing all 'tails' and using transition pipes to come out of the walls. Is there an easier way to do this minimising joints or any tips? We intend to use 25 and 16mm PEX pipe as suggested by ASHP company

Ceilings currently down

Thinking of:
1. Chase downstairs rads fed form above
2. Updatoirs rads perhaps going UK conventional and just have tails straight up from floor?

Thoughts?"

I don't think it matters where TRVs are mounted so either flow or return so long as flow direction follows the valves requirement, if any.....there's no directional flow arrows on our TRVs.

As I understand things if you're running weather compensation then room temps are set/adjusted by balancing the flow rate through the rad to give the design temperature drop. TRVs wouldn't be needed but if they are already fitted I wouldn't remove them but just open them wide....that's our plan.

That's silly though as with ASHP the whole house heating method is better from my understanding to run lower temps. overall to increase efficiency.

I still wonder how they reach that conclusion particularly when houses can be empty (going to work in day etc). It surely would make better sense to heat when needed within reason

I think for all the upstairs rads for convenience I'll go for bottom entry both sides, but downstairs I think I'll do Top entry, bottom exit. Same side for ease of chases in walls

That France 2027 idea seems to be the 1980s-era ideal.

Posted By: PeterStarckin France it will be mandatory* by 2027 to be able to separately control the temperature of every room in every house by at least time and temperature."

How does that work with a Passivhaus that doesn't have a conventional central heating system?

Under the exception: *Unless proof is provided that the return on investment is >10 years.

I hope to be entering an exception myself for as my current apartment renovation - pretty well insulated (though not close to Passivhaus) + MVHR + advanced UFCH controls. I doubt that adding separate actuators for each room would achieve the ROI, but I've not attempted to calculate that yet.

Posted By: fostertomThat France 2027 idea seems to be the 1980s-era ideal.

And most of the French housing stock pre-dates 1980, so for most of that it's not unreasonable. I'd guess it's not unreasonable for most of the more recent stock either.

Posted By: djhBut it does mean that simple heaters and suchlike now have complicated 'Lot20' control systems and wi-fi interfaces and suchlike and cost a fortune

For everyone with non-collective heating, there are grants available to subsidise the cost of conventional programmable controls (€260 for a 35m² apartment or smaller, for example).

For those with electric radiators there are also a couple of companies offering free controls as part of a distributed load shedding scheme; that is, the companies get paid by the grid for slightly turning down the heating during peaks - by up to 1°C (but often much less) and, from memory, for no more than 15 minutes, though that could happen several times a day.

I think I may go for a manifold system for the rads and use 16mm pipe as opposed to a trunk and branch system.

Seems a bit difficult retrofitting with newer technology but now is the time while it's in renovation stage.

What annoys me is the piecemeal, disjointed nature of it all. Heaters with complicated controls that only talk to a proprietary controller, and which can't live with their mains power being interrupted, for example.

Were I in France with a heat pump & actuators on every rad, I guess I’d just take all the actuators off & leave them hanging & let the pump sort out the temp & flow for the radiator system; all the installers here (Sweden) say it’s better for the heat pump to not have trv or other “brakes” on the system. We have all ours fully open, apart from the odd person who closes their trv a little at night; we have 21 everywhere.