heat pumps anyone ?

The house temperature is fairly responsive if you change the thermostat, so it can move it if you want it to. (often in nighttime the outdoor temps are falling which corresponds with a bedtime setback)

But it's more efficient to have a heatpump keep a constant temperature through small temperature corrections (low flow temps) than it is to turn everything off when you go out and then have it work hard (high flow temps) when you get back - that efficiency improvement trumps thermal losses.

So I don't bother changing anything when going out for the day - I'd drop the thermostat to a lower level (say 13C or something) if going away for a week, and then boost it when coming back.

Theo

No concrete? Against building regs.

There is still plenty of gas, Governments stop us from drilling for it. Gas prices are not unreasonable but electr8icity prices are.

Do you actually know the difference between the construction slab (over the DPC) and the screed layer on top ?

Have got a 1904 terrace house well end terrace did the down walls with 2 inch polystyrene with wood cladding on that and upstairs used 1 inch or as near as dammit foam backed plasterboard that made quite a bit of difference no mound etc behind such as wardrobes and the like..

Suppose thats thermal inertia by another name this place takes quite some time to warm up if heating left off for a few days in the winter months..

That's part of it. The main thing is that it's better to cruise along at a steady speed just adding enough petrol to compensate for air resistance and friction, than it is to turn off the engine and then redline the engine when you need get back up to speed again. Even if you theoretically save petrol when the engine is off, redlining it back up is inefficient..

(Not saying this is unique to heatpumps, a well designed modern condensing boiler system will do that too. But many boiler systems aren't well designed.)

Theo

In the case of CH systems that is not necessarily true.

My entire ground floor - even the party wall - has foam (about 2cm) backed PB. I think it helps a bit, but whoever installed it stopped at the floor and ceiling - it's supposed to go below/above about 15cm. So heat loss and potential cold bridging there. It's also coming away from the wall in a couple of places - the dot/dab has failed. Dunno why just yet.

The thing with internal wall insulation to watch in older homes is getting rid of moisture generated in the home. It was 'designed' (more by accident) to breath through draughts, and movement through the masonry. IWI creates a vapour barrier, and stopping up sources of draughts creates a potential perfect storm.

Design out as far as possible, ventilate if possible (not easy at the moment), and keep an eye on moisture levels. I just scatter a few of those bluetooth temperature/humidity things at suspect places. ThermoPro TP357 aren't bad - they log data on-device for a year, so I don't have to go near them. Just check what's happening on my phone.

It's not necessarily true of car engines either is it? If the car engine is more efficient working at full power than at (say) 20% of full power then stopping and starting the engine should be more efficient.

I seem to remember that BMW said it was more efficient to accelerate hard to cruising speed rather than accelerate gently (many moons ago though).

The same was stated by one of my university lecturers, who had researched it during the 1970's oil crisis.

I recall a magazine article on the subject, a while ago now, which found the optimum was 'brisk' but not 'hard' acceleration. I believe on the attempts at record low fuel consumption (e.g. with a model aircraft engine on a bicycle) the strategy was to accelerate to a reasonable maximum speed and then coast.

Which is one of the ways some hybrids are supposed to improve efficiency!

nib

There is an excellent you tube video made by a driving instructor in his 'learner car' on exactly this topic.

The answer is not to use high RPM. Short shift and accelerate gently And lift and coast up to corners if no other traffic will get annoyed.

That's what I do, What kills it for me is heavy traffic stop start motoring.

Hybrids do wonders in stop start traffic. On a long trip at speed they are just extra weight .

That is very true, and little incentive to do anything about it...

That was maybe true about gas heating and controls, a few years ago, but modern boilers and controls are much more sophisticated. My boiler and controls, decide exactly how much heat it needs to output, to get the room temperature to the demanded temperature. It does this by modulating, the amount of heat it creates, to precisely match the demand. It only gets to scalding, if there is a sudden increase set, for the room temperatures. After meeting the demand, my radiators will remain barely warm.

Rather than simple on off, it makes full use of modulation of heat output, to precisely match the demand.

I agree, with a modern gas boiler and something better than a on/off type control its possible to get the CH to act the same way as a ASHP which has a more sophisticated control than fitted to most (older) gas systems.

A modern controller plus weather compensation sensors connected to a modern gas boiler could also automatically adjust the flow temperature when full heating is not required. Many of the recent third party smart thermostat/controllers may not take full advantage of the inbuilt features of the boiler.

With regards cooling, the £7500 grant is only available for heat only heat pumps.