Using a wall as a thermal store

[Annpan]

The rear of our house faces south but basically we have a crappy extention including a corridor the full length of the house, which makes it cold all the time, however the sun does stream in the (small)windows for about 5 hours a day (currently).

I have done a wee bit of research into solar heated thermal stores (basically something dark which absorbs and retains the heat from the sun and releases it later)

Does anyone know if it is worthwhile stripping the plasterboard off of the rear internal 2' thick (originally external) wall to catch the suns heat???

The wall is rendered with pebble dash but we were going to paint over it in a dark colour.

Any suggestions most welcome

[Muddypause]

A little while ago I read a statistic which suggested that for an average house in the UK, the windows would provide for no more that 7% (IIRC) of the thermal capacity of the walls inside the house. There were no references to that figure, so I don't know how accurate it was, or what research it was based upon - it may even have been just a guess on the part of the writer. But the implication was that you would need far more window area to make effective use of the walls as a thermal store in a typical British house.

I also had a recent conversation with an 'alternative' builder who reckoned that only the first 2 inches of the wall thickness had any bearing upon how much heat energy can be stored in it. My feeling is that must be wrong, although it will depend upon the nature of the wall in question, and how much solar radiation it is subject to. That theory may also have been an interpretation of the first theory. Either way, the builder in question was intransigent about her facts, and wouldn't explore the idea further, so I didn't get a very full understanding of her notion.

However, what is pretty certain is that small windows won't act in your favour. I would also guess that the plasterboard on the wall is only going to be detrimental to it's ability to absorb any solar radiation that falls on it.

But being south facing is good, and I don't see why it couldn't be used to some advantage if the plasterboard was removed - though it may not be a terrifically big advantage. Also, being so thick, and with limited radiation for it to absorb, you may find that most of the heat is only radiated back out of the side it is absorbed from.

[mybarnconversion]

I also had a recent conversation with an 'alternative' builder who reckoned that only the first 2 inches of the wall thickness had any bearing upon how much heat energy can be stored in it. My feeling is that must be wrong...

Yes, depends on the thermal properties of the material that the wall is made from.

The pebble dash would concern me as I'm not sure that the heat energy will transfer efficiently to the masonry behind which you'll need for an effective store. As a rule of thumb for masonry you want a minimum of 5cm to 10cm, below 5cm storage will be compromised, above 10cm you'll get marginal improvement.

As hacking off the pebble dash will be a big job give it a go in place, but be prepared to remove the dash if you're not getting results.

As you suggest a dark colour is best.

Let us know how it goes....I love to know how well the pebble dash performs (or not).

[Wombat]

I have heard of tubes of calcium chloride solution used to act as thermal storage........

Nev

[mrsflibble]

be warned that pebbledashing can hide a multitude of building sins, so only remove it if you are certain your walls are ok underneath.