Mold is a growing concern for commercial buildings
The issue of mold in buildings has entered into public consciousness as a result of some high-profile examples of its existence in commercial buildings, resulting in temporary relocation of staff and other expensive measures.
This particular problem can be rather pervasive in a climate like ours that for most of the year experiences hot humid conditions. Unfortunately, there is a tendency for designers and building owners alike to overreact when faced with the presence of mold in their structures. This often leads them to use high energy consuming solutions that may or may not be effective in resolving the issue once and for all.
Mold is a very broad term used to describe a wide range of fungi and it reproduces through spores that are spread by wind, rain or physical movement. It colonizes and thrives in indoor environments where the control of moisture is an issue and ineffective management of it can lead to many indoor air quality concerns. In fact, we breathe in these spores all the time in the indoor or outdoor environment. This is only a problem when the concentration levels become great and is especially difficult for persons with allergies or asthma to handle.
The role in the air-conditioning system, often the primary consumer of electricity, is partly to extract excess moisture from the building to create comfort conditions. Most of the time the air-conditioning system is blamed for the existence of the mold when in fact this is not the case. However it can usually be blamed for its spread, which can be just as bad.
Maintaining a mold free building is as much a function of design as it is of building operation. Every effort must be taken to keep excess warm moist air away from your building and the key arsenal is to build an air-tight structure. All wall penetrations for windows, doors and mechanical ventilation shall be properly sealed so as to prevent air from leaking into the building around these openings. No more air should enter the building than is designed to keep the humans occupying the space well ventilated.
There is also the matter of ensuring the building delivers a positive air pressure whether occupied or unoccupied and this is where we often fall down and go a little crazy with overuse of air conditioning.
Simply put, we just need to ensure that when exterior doors are opened, for example, this results in air slightly rushing out the building and not the other way around and this is why for most structures in our climate we will need to have the air-conditioning system pretty much always on. But to be clear, use of a programmable thermostat will mean you can set the temperature just that much higher for times when persons are not present in the building to reduce cycling of the air-conditioning system. To achieve the right pressure over the lifetime of the building, the design intent must be available and known by anyone operating the building.
Rightly so, visible mold growing on walls and other surfaces in a building is a cause for grave concern. It is not an excuse, however, to drive the thermostat down so low that the air-condition system never cycles off.
Indeed, this might end up keeping more moisture in the building. Your steps to guarding against the proliferation of mold are simple – seal the building envelope, maintain a positively pressurized building and control indoor devices that generate moisture. The double benefit you get is that these good practices will also reduce the energy consumed in keeping your building cool.
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•Sonia Brown is the principal of Graphite Engineering Ltd. and is a registered professional engineer.