An all too common building problem involves the formation of condensation (water) on the interior surfaces of windows. This can be caused by a variety of factors including deficiencies with the windows, the use of heavy window treatments that prevent air circulation on window surfaces, and excess moisture in building interiors. Sometimes, when too much condensation is present, water may even drip down the wall into the wall cavity or onto the floor to cause water damage, growth of mold and mildew, staining, and other problems.
Normal human activities (such as respiration, bathing, laundering, cleaning, cooking, pets, houseplants, aquariums, etc.) produce water vapor that must be accounted for in the design of the mechanical (heating, ventilation, and air conditioning or HVAC) systems for the building. In today’s air-tight buildings, window condensation can result from insufficient fresh air. Unless fresh air is introduced into conditioned space, humidity can accumulate until, in cold weather, the temperature of the interior window surfaces becomes so low that the air at the surfaces become saturated, causing water, or even ice, to form.
Why does fresh air help to reduce humidity? In a cold weather scenario, the outside air is dry and by introducing sufficient fresh air (increased ventilation) into the building, the humidity is diluted and reduced. However, too much fresh air may not always be a good thing during the heating season. In addition to high energy cost, too much fresh air may also render the space too dry for a comfortable environment.
Sometimes the issue may not be as simple as it looks. Improperly designed or installed HVAC systems can fail to remove the moisture and cause elevated indoor humidity. Undersized systems could produce inadequate air movement to remove water vapor. Oversized systems could prematurely satisfy heating and cooling demands, resulting in short-cycling, and reduced air movement. It is important to conduct a thorough investigation to identify the real cause of condensation issues in order to develop a successful and cost-effective solution.
ETC has first-hand experience with these problems and the methods to successfully correct them. Our mechanical engineering staff has the ability to identify and correct ventilation issues involving condensation or other concerns