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Thermal accumulation in a passive house

Thermal accumulation in a passive house

Thermal accumulation is, in short, the ability to store heat by the interior of the house.

Different materials have different accumulative properties and hence we can have, for example:

    • chalet house (wood), in which the lack of heavy construction materials results in low heat storage capacity. The house heats up so quickly, but also cools down quickly.
    • a brick house with a large number of concrete structural elements will have a high thermal accumulation, i.e. it will heat up longer and cool down slower.

To put it figuratively - if we move into a house in the middle of winter and we need to warm it up – in heavy, a brick house takes more time to reach the desired temperature than in a wooden house, because we need to warm up not only the air, but also walls, which become a kind of "store" of heat, useful during e.g.. power failure and lack of heating (then they release the accumulated heat). We will feel the lack of heating much faster in a light wooden house, in which this "warehouse" is capacitively small.
The accumulation is mainly determined by the materials used to build walls / ceilings and the interior of the house. Wooden walls will have the lowest accumulation, the greatest – made of concrete, silki etc.. Additionally, the same material may have different thermal accumulation depending on the type (e.g.. cellular concrete)

In a passive house, this is the standard pursuit, that the house has a high thermal accumulation. This helps to stabilize the internal temperature and make better use of periodic excesses (e.g.. solar energy) and lack of thermal energy supplied to the home.
In an almost passive house, low-energy and energy-saving, also high thermal accumulation is considered an advantage. But there is no rose without thorns.

From my personal experience: living in a house with a high thermal accumulation, I wanted to save a little on heating expenses by lowering the temperature in unused rooms (attic - during the day, ground floor - at night). Lowering the temperature by a few degrees (more does not make sense) has a real impact on lower heating costs. Unfortunately, achieving this goal turned out to be very difficult because of… high thermal accumulation. Despite the heating of the radiators, the temperature dropped all night in unused rooms by a maximum of 1 degree - the walls gave off heat, which later, of course, had to be delivered to them all over again. I will add, that the heating system had low thermal inertia, thus, there was no slow temperature drop factor in the heating medium (like for example. in underfloor heating), which would also make it difficult to quickly lower / increase the temperature.
Also note, that in the countries of the cold north, a lot of houses are built of wood (probably due to the availability of raw material) and they do great with heating there.

In homes, in which we stay periodically (e.g.. holiday homes) Also, low accumulation will be an advantage rather than a disadvantage - such a house can be quickly warmed up in a colder one, autumn weekend.

I would personally summarize the topic, that thermal accumulation improves the comfort of living (stabilizes temperature fluctuations), but it makes it difficult to precisely control the temperature in the rooms (e.g.. periodic temperature reduction). Certainly, high accumulation is needed, if we are focused on gaining large profits from solar energy, but this is not the case in every home.

The matter is complicated by the fact, that in many cases low-accumulative materials (e.g.. wood) they are also better insulators. We need to insulate more highly accumulative materials, so spend more money on warming. The choice is yours, as usual, to the investor.