30 Sep 2020

What causes moisture in buildings?

Construction site humidity
  • Written By

    Ryan Stanley, Moisture Control Sales & Product Manager

  • Published in


For construction site and project managers, moisture can be less than ideal for a number of reasons. From persistent mould and damp issues to irreparable damage to materials and building structures, incorrect dehumidification can end in large repair costs and a besmirched reputation.

With so much on the line, it is important that those in charge of construction projects are aware of how to full deal with a humidity problem on their site. To be able to do this they must first understand where the moisture comes from. This blog outlines the sources of moisture on a construction site and what it takes to reverse the effects of them.

Where does moisture come from?

Whether its free moisture – the surface water or water that has been absorbed into a material – or the water that is chemically bound into the cells of materials in the room, there are several sources that are found on construction sites. The following are the most common:

  • Water vapour diffusion – Water vapour from outside a building can permeate into the space through cracks or by being absorbed into materials. The moisture coming from outside to within the room does so through this water vapour diffusion.
  • Water evaporation – Any water that is introduced into a space for cleaning or mixing with building materials can evaporate and contribute to moisture in the room.
  • Evaporation from materials – building materials that have been brought on site with hotter conditions can release water absorbed in their cells into the space.
  • Intended ventilation – Ventilation systems that have been installed may not be able to keep up with high moisture levels in a space, so humidity in the room remains high.
  • Unintended ventilation – leaving windows and doors open on a construction site can allow moisture-filled air from outside to permeate a room through unintended ventilation.
  • Human-derived emissions – those working on site may release moisture into the atmosphere by breathing and perspiring.
  • Plant and machinery emissions – any equipment used in a space onsite can produce moisture from its exhausts, particularly in enclosed, poorly-ventilated spaces. 

How to reverse the effects

Sometimes moisture on site is unavoidable, however, it is possible to remove the moisture before any of its harmful effects take hold on site.  At Aggreko, our global fleet of equipment can be implemented to carry out the three key steps of dehumidification.

Once a space is correctly sealed, we can heat the area, circulate the air with fans and removing the moisture from the space entirely using dehumidifiers. When controlled dehumidification is required, Environmental Conditions Monitoring ensure that the entire process is carefully carried out as comfortable relative humidity is reached without causing damage.

For more information about temperature and moisture control on your construction site, check out our guide the hidden cost of humidity on site.

Download humidity guide