Water in the Air of a building

water vapour molecule
H2o

Controlling the excess water in the air of a buildings can be a major problem, especially in ground floor flats. The high proportion of severe condensation and mould growth problems occur in ground floor flats, bungalows, and basements.  The surrounding landscape and weather will affect the internal environment.

The potential for air buffering in a single-storey property is much lower and therefore it is more sensitive to excess moisture generation within the building.  In a two-storey building, the amount of air available to dilute water vapour is significantly larger.

Using wall and floor surfaces to buffer water vapour may be problematic as the occupier will want to cover the surface with decorative coverings.  Therefore, avoid sealed or laminated flooring etc., Carpeting and curtains etc will absorb and release moisture by heating and ventilation to dilute trapped water.

condensation is caused by excess water in the air of a building
condensation

To give the building air a chance of buffering the excess water vapour you must heat the property for a reasonable time to an ambient 12-15oC. This will extend the time before any excess moisture will condense (Dew point) on walls and allow low-level ventilation to reduce moisture in the atmosphere.

The Relative Humidity in the building is the sum of the external RH and the moisture generated in the building.  The external environment is controlled by the tilt of the earth.

affect of seasons on water in buildings
The seasons

For 8 months of the year the average extern RH is 83% for the other months the average is 78%.  Internally we are looking for an average of 60% RH.  To achieve this, we need to heat the air brought in and ventilate the building in a balanced manner.

To have a healthy environment in your home you must

  • Control water vapour at the point of production
  • Heat the building in a balanced manner to allow dilution of the damp atmosphere especially during Sept to March.
  • Insulate to move the dew point which gives the building a long time to balance itself and reduce your energy costs.
  • Maintain the building in good condition to prevent water ingress externally and any internally escapes of water.

Some reading on condensation https://en.wikipedia.org/wiki/Condensation

Nigel Foster