The effects of moisture inside a building under construction can become a serious problem for contractors as well as a danger to future occupants. Unless this moisture is reduced to acceptable tolerances, a contractor may be confronted with a variety of problems. They may be as small as construction schedule delays or as large as flooring failures resulting from elevated moisture content in a concrete slab.
In an attempt to manage moisture, contractors typically use one of two methods to dry building materials during the construction process: desiccant dehumidifiers or heat. While there has been much debate as to the most effective technology for construction dying, scientific fact cannot be argued.
If one were to evaluate a desiccant dehumidifier and heater with respect to their moisture removal capabilities, a heater does not compare. To simply introduce heat into a building space will not remove the actual moisture that is present in the air.
Heat-Only Systems can temporarily reduce relative humidity but it does not remove moisture from the air and, most importantly, it does not reduce vapor pressure. In fact, heating the space with particular types of heat-only systems, such as direct-fired heaters powered by combustibles such as propane or natural gas, will actually add moisture to a space. Heaters are also very ineffective at maintaining conditions and eliminating mold growth.
Desiccant Dehumidifiers used for construction drying are different from those used in permanent installations for commercial buildings, they are designed to withstand the construction environment and provide the drying capacity required to establish and maintain proper environmental conditions. In direct comparison to a heating system, as air passes through the desiccant material inside of a dehumidifier, the moisture is literally assumed by the desiccant material and consequently removed from the airstream. Because there is a direct correlation between moisture content and vapor pressure, by removing moisture from the airstream, one simultaneously lowers the vapor pressure of that airstream. For this reason, desiccant dehumidifiers are very effective at reducing relative humidity and maintaining conditions and eliminating mold growth.
For most professional trade organizations there is no longer debate as to which technology is most effective for drying building materials. For example, the Northwest Wall and Ceiling Bureau, which serves general contractors, material manufacturers, dealers as well as labor groups, in a statement about wallboard in weighed in technical bulletin #303, said “Cold damp weather contributes to joint bond failure, delayed shrinkage, ridging, nail pops, joint flashing and board sagging. Proper temperature and humidity levels (environmental conditions) are important factors in achieving satisfactory results. Some sources of temporary heat will cause high humidity. The NWCB recommends a desiccant dehumidification system for best results in joint finishing and final decoration of gypsum wallboard.”
A common misconception is that the building’s permanent HVAC system can address moisture problems during the construction process. The building’s permanent HVAC system is engineered for temperature control with much less attention paid to moisture removal. This system does not have the capacity to remove elevated ambient moisture. Operating the building’s HVAC system too early can also spread mold spores.
In summary: moisture control = mold control
Moisture can wreak havoc on a construction site affecting all types of building materials. By factually comparing the two most common technologies used for construction drying applications, it is evident that heat alone cannot reduct the moisture content or vapor pressure that is present in a construction space.
As the construction industry has evolved, and through practical application as well as scientific fact, it is evident that a desiccant dehumidifier is much more effective at drying construction materials than a heater. Because a desiccant dehumidifier reduces both humidity and vapor pressure, it is the most effective method for providing a construction environment where materials dry at an accelerated pace and the potential for mold growth is considerably decreased.