Wood is a living material - air moisture vs. wood.
Its moisture compensation wood floor products adapts to the air humidity of its environment.
This means that the wood humidity continuously adapts to its surrounding climatic conditions (relative room temperature and especially the room humidity).
As Example an inhabited space normally has a room temperature between 15 °C and 30 °C and relative humidity between 30% and 70%.
Translated into practical terms, this means that at a relative air humidity of 30% the self-regulated moisture of wood will set it self to approximately 5–6%, where as a humidity level of 70% corresponds to a compensation humidity of 12–13%.
In the various seasons, the moisture of the wood may vary from 5–6% to approximately 12–13%. The parquet may be subject to warping, as with every other product made from wood.
When ventilating the room in winter, cold and usually very dry air will enter the room from the out doors that, by warming up to the room temperature, will diminish the humidity level.
The wood adapts to the lower air humidity and dries out.
Parquet deformation in the form of gaps or joints may occur between the floor boards when humidity is low or high.
Since wood is a natural product, it swells in summer when the relative humidity rises. Most gaps will close and some parquet elements may even show bevels.
To avoid all this you need to keep all time air humidity 45-60%, and ventilated rooms .