I bought a Heat Pump

QrizB

Martyn1981 said:

Here's a fun question that someone with a better mind than mine, may be able to advise on.

Thinking back to many of Zeupater's comments about the benefits of a thermal store, and also thermal mass, to help stabilise temperatures, I started to do some maths, and based on an 18 inch wall, that's 20ft across, roughly 20ft tall, and 30ft to the side, I came up with 1,500ft3, and for calculation purposes, a 15kg concrete block being 0.375ft3, so a total of roughly 60tonnes.
I'm guessing that the stone is denser, so perhaps closer to 100tonnes of thermal mass inside the house, which will help to stabilise temps?

50 linear feet of wall, 20 feet high and 1.5 feet thick? Yes, I make that 1500 cubic feet too (42 cubic metres). Rock used for house building is around 2-3 tonnes per cubic metre, so yes your estimate of 100 tonnes is pretty much on the money.

Compare that to a typical storage heater; this one weighs 109kg:

https://www.tlc-direct.co.uk/Products/DXXLS18N.html

One caveat is that a lot of older stone biuldings, at least in my part of the world, might have stone facings but the fill inbetween (where the cavity would be in a modern wall) is ballast, a mixture of small rocks, fravel and sand. What did your sister's installers find when they drilled their cores?

It's too late now (by around 140 years) but it would have been an interesting experiment to install heating elements in those walls and use them as storage heaters

Coastalwatch

Martyn1981 said:

1st rule - Insulate, insulate, insulate!

Great musing Mart which I'll happily go along with. I'm sure it's reasonable thinking and would work brilliantly if there was a thermal break between the inner thermal walls and the two outers. But accept it's being rather picky.

I guess if there are doorways between inners and outers to reduce the heat sink effect then it may not matter much at all!

Martyn1981

Coastalwatch said:

Martyn1981 said:

1st rule - Insulate, insulate, insulate!

Great musing Mart which I'll happily go along with. I'm sure it's reasonable thinking and would work brilliantly if there was a thermal break between the inner thermal walls and the two outers. But accept it's being rather picky.

I guess if there are doorways between inners and outers to reduce the heat sink effect then it may not matter much at all!

Hi CW, hopefully there is a thermal break, that's why they had to install the IWI on those original solid walls (the ones that are still external). But it wasn't a problem for them as it was part of a major renovation, so insulation panels with plasterboard already attached, were used and the rooms look normal, though a few inches smaller. (I used similar in our smallest bedroom bay that had a single skin wall around/under the large window).
Certainly a lot of work needed to best size the ASHP and meet efficiency standards, but of course all of that makes sense whatever the heating method.

My sister still finds it funny that when I arrived the very first time to see the house, and she was desperate to show it off to me, I was still stood outside and trying to explain to her that I was 90% certain that the pole across the street from her had 3phase going to it. And then when we got inside, I was more interested in pointing out the huge size of the radiators (all double panel and double fin), and that the pipes were all 15mm.

S'funny what excites me these days!

Coastalwatch

Aaah! If IWI stands for internal wall insulation I certainly appreciate the need for this, but it doesn't actually form a thermal break.

I did say I was being picky after all!

In the two opposing corners where the inner and outer walls are joined there will be a direct path to the outside world for the heat to escape through the masonary. Admittedly only a percentage of heat would escape this way as presumably the masonary does have some insulating effect if only of a minor nature!

Other than for heat loss I know it wouldn't make sense to insert a thermal break, either from a cost of structural point of view, just couldn't let you be the only one who finds odd things intiguing.

Martyn1981

Coastalwatch said:

Aaah! If IWI stands for internal wall insulation I certainly appreciate the need for this, but it doesn't actually form a thermal break.

I did say I was being picky after all!

In the two opposing corners where the inner and outer walls are joined there will be a direct path to the outside world for the heat to escape through the masonary. Admittedly only a percentage of heat would escape this way as presumably the masonary does have some insulating effect if only of a minor nature!

Other than for heat loss I know it wouldn't make sense to insert a thermal break, either from a cost of structural point of view, just couldn't let you be the only one who finds odd things intiguing.

Of course, you are absolutely correct, and I missed that completely. I do love all the little details, always great to learn, many thanks.

michaels

Coastalwatch said:

Aaah! If IWI stands for internal wall insulation I certainly appreciate the need for this, but it doesn't actually form a thermal break.

I did say I was being picky after all!

In the two opposing corners where the inner and outer walls are joined there will be a direct path to the outside world for the heat to escape through the masonary. Admittedly only a percentage of heat would escape this way as presumably the masonary does have some insulating effect if only of a minor nature!

Other than for heat loss I know it wouldn't make sense to insert a thermal break, either from a cost of structural point of view, just couldn't let you be the only one who finds odd things intiguing.

there is also potential heat loss downwards into the ground and upwards depending what happens at the top of the walls - perhaps IWI on the internal sections of these walls might also make sense?

Martyn1981

QrizB said:

One caveat is that a lot of older stone biuldings, at least in my part of the world, might have stone facings but the fill inbetween (where the cavity would be in a modern wall) is ballast, a mixture of small rocks, fravel and sand. What did your sister's installers find when they drilled their cores?

Hiya. Quick update. I popped down today, nice to see the shiny new 3phase input and 3 100A fuses, plus the consumer unit with 24 'options'. I'm very jealous, especially as my house fuse was upgraded for the car charger, and though they installed a 100A fitting, I only got upgraded to an 80A fuse.
I had a look at one (now) internal wall, which has been cleaned up, and repointed, and looks gorgeous, and I was able to match stone slabs from one side to the other (office to kitchen). They are, for want of a better description, roughly the size of a concrete block, but laid so that you see the ends, one on one side/room, and the other on the other side/room.

shinytop

@Reed_Richards

I thought I'd bump this thread to ask how things are going now electricity has gone up so much and temperatures are going down.  I'm just settling into my first ASHP winter and trying to find the best way to run things.  

matelodave

I guess @Reed_Richards is the best bloke to give us an evaluation as he's got a modern system and data from his previous oil system.

Mine is now eleven years old and was completely new installation when we moved in a refurbed our bungalow to replace manky storage heaters.  We never had any reference  data except that the previous owners had taken to using LPG cabinet heaters becaue of the cost of leccy.

We also had an overlay wet underfloor system installed so it's not really representative of what most people are installing. Although that said, my leccy bill has just gone up by around 70% because SYMBIO went bust so I'm sure that cost wise his bill has now become significantly higher all of a sudden.

Reed_Richards

I will have had the heat pump in place for exactly a year on 12th December.  My plan is to give a detailed update then when I have a full year's worth of data.