In Mediterranean countries thermal mass has been and continues to be used to stock wines at stable temperatures, not too hot and not too cold. These are buildings that are built outside of the ground and have gravel floors.

I've worked on the design of these types of buildings using modern building materials, usually thermal panels with a great big air conditioning unit. This approach is now used due to the cost of construction. Otherwise the older buildings are still used to great effect without any air conditioning system.

The notion that thermal mass, in temperate climates doesn't aid in maintaining an even temperature both during summer and winter months is just not born out in reality.

Posted By: bot de pailleIn Mediterranean countries thermal mass has been and continues to be used to stock wines at stable temperatures, not too hot and not too cold. These are buildings that are built outside of the ground and have gravel floors.

I've worked on the design of these types of buildings using modern building materials, usually thermal panels with a great big air conditioning unit. This approach is now used due to the cost of construction. Otherwise the older buildings are still used to great effect without any air conditioning system.

The notion that thermal mass, in temperate climates doesn't aid in maintaining an even temperature both during summer and winter months is just not born out in reality.

I'd love to know more about these structures and how the gravel floor fits in to the scheme.

This chais de barrique (wine cave) was built in 2001 and used 35 thick stone walls and natural ventilation system to keep internal temp and humidity levels stable. It is located in the south of France near the Spanish border where seasonal temperatures range between extremes of hot and cold.

http://blog.midi-vin.com/rencontre-avec/domaine-des-aurelles-coup-de-coeur-midi-vin-002830
"La cave construite en 2001 par deux architectes, est d’une prestance rare. Assemblée de blocs de pierre du pont du Gard dont chacun pèse 3 tonnes, le tout s’imbrique en harmonie avec le paysage. D’une épaisseur de plus de 35 centimètres, ces blocs assurent des écarts de températures minimums, gardiens de l’élevage des vins. Le tout est ventilé par un puits provençal dont le principe repose sur un système simpliste et économiseur d’énergie. L’air est pris à l’extérieur du bâtiment, descend à moins 4 mètres sous le sol où les températures sont plus fraîches. Un échange thermique se produit et est redistribué dans la cave. Le tout est suffisant pour rafraîchir et ventiler les lieux. C’est en quelque sorte le principe de la géothermie mais sans circulation de fluide."

and a photo of the gravel under the wine barrels:

Here is a very interesting project by the French Architect Gilles Perraudin. He built a 900m2 wine store for himself and by him self out of large blocks of stone using a crane!

http://www.perraudinarchitectes.com/projets/chai_vauvert/chai_vauvert.htm

google translated from French:
"Situated in a Mediterranean climate, cellar requires a high thermal mass to avoid large thermal variations detrimental to the preservation of wine.
The building was an opportunity to experience the economic viability of reusing the massive stone as a building material of a contemporary architecture.
The stone used is the "stone of the Pont du Gard", which was used to build the famous aqueduct, wonderfully preserved after 2000 years old! The construction follows a simple pattern. A series of spans of 5.20 m. wide are covered by a network of wooden beams laid on walls or Moisees primary beams, and carrying a wooden decking continued support of the seal and the earth.

"Située dans un climat méditerranéen, la cave exige une grande inertie pour éviter les variations thermiques importantes dommageables pour la conservation du vin.
La construction fut l’occasion d’expérimenter la validité économique de la réutilisation de la pierre massive comme matériau de construction d’une architecture contemporaine.
La pierre utilisée est la " pierre du Pont du Gard ", celle qui fut utilisée pour construire le célèbre aqueduc, merveilleusement conservé après 2000 ans d’âge ! La construction suit un schéma simple. Une série de travées de 5,20 m. de large sont couvertes par un réseau de poutres en bois posées sur les murs ou des poutres primaires moisées, et porteur d’un platelage bois continu support de l’étanchéité et de la terre."

Fascinating, thanks for posting.

Going back to the original question:

Posted By: SteamyTea: “Does thermal mass in a building really help stabilise and raise the overall internal temperature or is it just an illusion?�

I think Bot's example clearly shows that thermal mass can stabilize the temperature in a building. Can it raise it?

I don't think it'll raise the average temperature¹ but what it will do is fill in the holes in the temperature swings allowing less or no heating to keep the house comfortable. To play with this I wrote a quick-and-dirty simulation script:

https://gist.github.com/ed-davies/8498229#file-thermal-mass-py

Output as shown there is:

https://gist.github.com/ed-davies/8498229#file-tm-txt

That tries with the given conditions with thermal mass roughly equivalent to 50, 100, 200 and 400 mm of concrete on the floor. Even 400 mm is not that much when you consider that includes the mass available in the walls (including internal walls), ceiling and furniture, etc.

The results were surprisingly (to me) sensitive to the conditions set up but still it confirms my assumption that the amount of heat required to keep a place comfortable (15 °C overnight, 19 °C during the day as set in this program) reduces with increased thermal mass.

I'd recommend having a fiddle with the program if you're interested.

¹ Assuming heat loss follows Newton's law: loss is proportional to temperature difference. With convection it's easy to see that heat loss can increase more than proportionally to Tdiff as convection effects kick in in various voids and due to stack effect (heat loss per kg of air exchanged is proportional to Tdiff but you'd also expect the exchange rate to increase with Tdiff as well). I think with these effects the more moderate swings of a thermally massive house will result in less heat loss and therefore a higher average temperature even without explicit heating.

Thanks Steamy. I should tweak the code to produce a graph automatically.

On reflection, I think 50 mm is unrealistically small. It corresponds to having not much more than just plasterboard as thermal mass, really.

More relevant than the temperatures, though, are the heating requirements.

Mass thickness   Heating
 50 mm           1.91 kWh
100 mm           0.90 kWh
200 mm           0.23 kWh
400 mm           0.00 kWh

No account is made of ground temp - losses are assumed the same in walls, roof and floor. E.g., could be a ventilated floor under the insulation. Actually, there's just one heat-loss coefficient calculated from the areas and the given U-values without really caring if it's the same in the different surfaces or not. It's essentially a very simple one-dimensional model but people are not so familiar with the overall coefficient so it's expressed initially as areas and U-values.

Assumption is that all the thermal mass is inside the insulated envelope. Any outside is not of interest and the thermal mass of the actual insulation is neglected.

The big assumption you'll probably hate is that the heat can flow in and out of the mass as quickly as needed (it's a thermal superconductor). Still, even at 400 mm equivalent thickness it's only like, say, 100 mm on the floor and walls which will heat and cool pretty quickly.

Nice to see a minister saying something sensible and detailed. However, am I right in thinking that SAP only deals with a fairly small amount of thermal mass - didn't somebody say 100 mm on the other thread?

Exactly. Hands up anybody who thinks tony would have been comfortable enough not heating his house for a few years and now only heating it a bit for a short season if it had otherwise had the same geometry and insulation but much less thermal mass?

(PS, how's it going so far this winter?)

What's the basic config of your place tony? You've peeked my interest.

Right, been looking at the temperatures for Jan this year and my house is pretty stable, the temperature difference is the same between night and day. Daytime temperatures are flat, night time ones rise. This may be because I have storage heating or not (needs more investigation).
One thing that we all think happens is that windspeed can make a difference. In the past I have just treated this as a linear relationship, but I am starting to think that it is logarithmic because as windspeed increases an even lager amount of air passes the building (thoughts on that please).
Anyway here are the charts.

Had a look at my weather data and plotted the relationship between windspeed and temperature.
Apart from March, June and July, there is a pretty strong correlation (on a log scale) between windspeed and air temperature. As windspeed goes up, so does temperature. No surprise there then (even the months it does not is probably down to sea surface temperature to the West of me).
There are 3 parts to each chart, Mean Temperature (columns), Percentage of time at given Windspeed (dashed line) and the Logarithmic Trendline (solid line). Grey is all the years data (last 4 years) and red is the month data.
It should help discount windspeed on house temperatures. If anyone wants to try it with there local data I can pass on the spreadsheet so you can drop your own data in.
Made a very short video of it as it shows it better than 12 charts.
http://youtu.be/IrXFYLHfvtk

Now to do the same for solar.

No, I stopped collecting it a few years back, but may see if I can incorporate it.

Right, have had a chance to look at what is happening around my area weather wise. As I am surrounded by the sea (2 miles to the North, 8 miles to the South) I thought I would look at the effect of sea surface temperature (with some prompting from MikeL). Eventually found a website that has historic data so picked my two nearest buoys and started plotting.
To save some processing power I had to average over a 6 hour period, but do have 4 years worth to look at. Also the Atlantic Ocean is a huge 'thermal store', so should dominate over the air temperature. This it seems to do. 65% of the time the air temperature is colder than the sea surface temperature by a mean of 2.9°C colder. When the air is hotter it has a mean of 1.7° hotter. The sea temp mean is 12.35°C. So the sea (or the dominant thermal mass) is keeping the area cooler.
Easier seen on charts.
The first chart is the temperature anomalies, these are just the differences in temperatures over the time period.
The second chart is the general weather, the solar power is the mean power, this is why it does not show a 'night time' as such.