The Buildings Site

Condensation and Mold Prevention in Homes/buildings

When it comes to condensation -and therefore mold-prevention you will have to systematically undermine the main pillars these  supporting these  phenomena:

1st pillar: Quantity of produced water-vapor

Water vapor is produced mostly due to human activities. Heaviest loads are produced from:

- cooking

- showering

- high plant concentrations

- high people concentrations

- clothes drying

- uncontrollable moisture ingress from basements lacking a vapor barrier.

All these factors contribute to the raising of indoor relative humidity. Increased R.H. means that dew point becomes higher for the same air temperature. This fact multiplies the condensation probabilities.

Let's have a numerical example:

Internal air temperature: 22oC.

Internal relative humidity: 50%.

Dew point of internal air under these conditions is 11oC. This simply means that when the air temperature falls to 11oC, condensation will happen.

Now, if R.H. increases to 60%, dew point will raise to 14oC. It's by far easier to have condensation phenomena under the new conditions.

It's obvious that control of relative humidity - which actually is control of absolute humidity - is of prime importance to prevent condensation in buildings!

2rd pillar ' Ventilation

Ventilation should be ample but without long duration air currents. Remember that extreme ventilation would lower the room temperature and underheated rooms are more prone to condensation.

Ventilation for 2-3 times per day for 5' could be a good option. Fresh dry air can dilute big concentrations of water-vapor.

Ventilation should be controlled and not random through e.g. gaps and slots. Extreme random ventilation could cause underheating and additionally could downgrade indoor air quality.

Kitchens and bathrooms should be provided with mechanical ventilators. During vapor production activities, doors of these rooms should be losed. Don't let furniture come in touch with external, inadequately insulated walls. Let air pas through the gaps.

3rd pillar ' Thermal insulation

Thermal insulation should be sufficient and thermal insulation bridges should be avoided. Thus internal surfaces temperatures will be kept above dew point.

Additionally thermal insulation will help to keep higher indoor temperatures, a good thing against condensation.

4rth pillar: Heating

Underheating increases condensation probability. When air cools down it's energy reduces. If you consider that less energy means less tendency for liquid phase to turn into a gaseous state you can deduce that condensation is encouraged.

Seeking economy by underheating will increase condensation risk. So don't underheat and don't keep rooms closed and unheated. There should be a steady, decent temperature all around. Surface temperatures of external walls should be kept well above the dew point.

Chris Strogilis 

http://maconwaterproofing.blogspot.com

About the Author:

Civil engineer with postgraduate studies in MBA and Marketing