Solid walls

[Equus]

kambites said:

Equus said:

The energy stored in thermal mass wouldn't be released back into the building unless the internal temperature dropped below the average temperature of the wall.

This is true, but the walls do provide a "damping" effect on the internal temperatures, both in terms of the night/day heat cycle and to a lesser extent over longer periods.

Absolutely; but that works both ways: they will keep down the internal temperature in the daytime (or when you're trying to increase it by means of heating), as well as bolstering it during the night-time (or when the heating is switched off).

If you think of the heat cycle as a sine wave, with the mean temperature being the X-axis of the graph, all thermal mass does is reduce the amplitude. The sum of the +/- areas under the graph, either side of the X-axis, does not change significantly.

In plain English, the peaks and troughs cancel each other out to an equal degree whether you have high thermal mass or low thermal mass, and the mean heating demand remains the same.

It's a bit more complicated than that, admittedly, but when Yellowtang is suggesting that thermal mass keeps a building warm, it's equally accurate (or inaccurate!) to say that it keeps it cool. It just depends on what part of the heating cycle you're looking at,

Look at the full cycle over a period of time and it has no net effect.

[EireEng]

Equus said:

Absolutely; but that works both ways: they will keep down the internal temperature in the daytime (or when you're trying to increase it by means of heating), as well as bolstering it during the night-time (or when the heating is switched off).

If you think of the heat cycle as a sine wave, with the mean temperature being the X-axis of the graph, all thermal mass does is reduce the amplitude. The sum of the +/- areas under the graph, either side of the X-axis, does not change significantly.

In plain English, the peaks and troughs cancel each other out to an equal degree whether you have high thermal mass or low thermal mass, and the mean heating demand remains the same.

It's a bit more complicated than that, admittedly, but when Yellowtang is suggesting that thermal mass keeps a building warm, it's equally accurate (or inaccurate!) to say that it keeps it cool. It just depends on what part of the heating cycle you're looking at,

Look at the full cycle over a period of time and it has no net effect.

If you overlay the square wave of the central heating coming on/off the thermal mass will also offset the phases by more, correct?

[Equus]

Correct.

There are a myriad 'ifs' and 'buts', of course, around things like occupancy patterns and changes in the weather, but it doesn't change the fundamental truth: that Yellowtang is talking bks.