Structural Drying

We offer a comprehensive range of structural drying services.

What is Structural Drying

What are the benefits of Structural Drying?

3 Phases of Drying

Phase 1 – Removal of Liquid Water – Extraction

Effective removal of standing water will significantly affect the amount of drying equipment and the time required to return the building and contents to equilibrium moisture content. Effective extraction will also ensure less destructive methods of restoration are required.

Phase 2 – Surface Drying

Surface drying of carpet underlay and surface water from building materials such as timber and concrete.

Phase 3 – Drying of Structural Materials

Drying of water already bound in materials. To assist in the third phase of drying of water damage property, knowledge of how materials dry is of great importance and how drying actually takes place within a building. Different methods, knowledge and tools are required to get the energy required to the bound water to ensure phase change.

Airflow

Air movers are used to facilitate evaporation by removing the boundary layer of humid air from around the wet surface. Air movers rapidly supply dryer air directly to the wet surface and thereby lower the vapour pressure at the surface which facilitates faster evaporation. The more moisture a material contains the faster the water will evaporate. When using air movers alone, greater evaporation rates require more airflow to maintain the lower vapour pressure across the surface.

Air movement creates thermal loss (cools down). Cooler air and cooler surface materials means that less energy is transferred to the moisture molecules which does not give them sufficient energy to make the phase change required to escape the material.

Large quantities of air movers create a lot of heat energy (BTUs). In theory the heat created by the air movers aids in the drying process as the heat energy is transferred to the water molecules and surfaces thereby giving the energy required to make the phase change. The problem with excess heat is that often the BTUs created by the air movers can generate temperatures that are outside of the efficient operating ranges of refrigerant dehumidifiers.

Humidity

Air movement is used to create evaporation. Air will hold a limited amount of moisture before the air becomes saturated and cannot hold any more moisture (referred to as “dew point”). Dehumidification is used to remove moisture from the air lowering the vapour pressure, so that the equipment used to create air movement, can continue to facilitate moisture evaporating from the wet structure or contents.

Extraction

Effective removal of standing water will significantly affect the amount of drying equipment and the time required to return the building and contents to equilibrium moisture content. Effective extraction will also ensure less destructive methods of restoration are required.

Vacuum equipment is recommended for standing water extraction. The greater the air flow and vacuum pressure, the more effective that equipment will be. Truck mounted equipment have significantly higher airflow and vacuum pressure than portable extraction equipment and generally are more effective in removal of standing water. Specialised portable flood extraction equipment that uses shorter hose lengths and larger diameter hoses (2 inch) can be effective. Portable equipment exhaust air should be vented outside of the building. Portable equipment exhausts air from the vacuum blowers into the surrounding environment.

This not a job for an amateur. When extracting contaminated water in category three drying situations, consideration needs to be taken as to the position of the machine to prevent spread of contaminants. Small vacuums such as shop vacs or wet vacs and domestic vacuums do not provide adequate power for effective extraction.

There are various extraction tools that can be used in conjunction with vacuum equipment that will improve the effectiveness of water extraction.

A weighted compression can use heavy weights or as a stand on machine and works on the principle of extracting/pushing the water out of the underlay through the carpet and into the extraction machine. This tool allows greater water removal with the same vacuum equipment than many other extraction tools.

A vacuum sealed (water claw or equivalent) can be used with truckmount and portable extraction equipment. As the vacuum sealed tool requires water to create the vacuum seal, it is recommended to first extract with the tool to remove as much water as possible from the underlay prior to completing extraction with a conventional carpet cleaning wand. Note that a conventional carpet cleaning wand is not efficient at removal of water from carpet underlay. Where specialised extraction tools such as weighted compression or vacuum sealed tools are not utilised, it is recommended the carpet underlay is removed. A conventional carpet cleaning wand is nevertheless effective for extraction of standing water from direct stick commercial carpets.

An extraction test to gauge the effectiveness of extraction on carpet is recommended. After extraction, lift a small section of carpet and ‘wring’ the underlay to see if there is any dripping water. If so, a further extraction will be required.

Air movement

Air movers are used to facilitate evaporation by removing the boundary layer of humid air from around the wet surface. Air movers rapidly supply dryer air directly to the wet surface, thereby lowering the vapour pressure at the surface which facilitates faster evaporation. Secondly air movers are used to manage air movement around the structure. Air management eliminates the need to use dehumidifiers, heat drying equipment and air filtration devices in all affected areas and can be used to manage air pressure, humidity, and temperature or air quality.

Different types of air movers

Traditional carpet dryer air movers are commonly referred to as air movers or blowers. A traditional carpet dryer is a snail shell type centrifugal blower with a minimum of a 3/4 hp motor. Air movers have the most static pressure. Static pressure is used by air movers to lift carpet, to place an air mover under carpet and push the carpet up to generate air flow under the carpet or with the use of accessories can be used to duct air into small spaces such as wall cavities and under cabinets and under hardwood flooring.

Low amp air movers are a snail shell type centrifugal blower that uses motors smaller than 3⁄4 hp. Low amp air movers generate lower air movement and lower static pressure. The advantage of using low amp air movers is that more air movers can be used on one circuit whilst generating large volumes of CFM and generating less heat than traditional carpet dryer air movers. Low amp air movers are typically used with less destructive restoration processes, where excess heat generation will affect the performance of dehumidifiers and where power supplies are limited.

Low pressure axial fans are specialised air movers used to move large volumes of air with lower amp draw. Low pressure axial fans are efficient for drying long surfaces open areas and carpets. Because of their low pressure they are not useful for pushing air into cavities and through duct work. The advantage of using axial fans is they can deliver large volumes of laminar airflow whilst using much less power and generating much less heat. Low amp air mover are typically used with less destructive restoration processes, where excess heat generation will affect the performance of dehumidifiers and where power supplies are limited.

Dehumidification

Air movement and heat is used to create evaporation. Air will hold a limited amount of moisture before the air becomes saturated and cannot hold any more moisture (referred to as dew point). Dehumidification is used to remove moisture from the air so that the equipment, used to create air movement, can continue to facilitate moisture evaporating from the wet structure or contents. Dehumidifiers are used to remove moisture from the air to create a balanced drying system. A balanced drying system is achieved when the rate of dehumidification exceeds the rate of evaporation. Where the rate of evaporation exceeds the rate of dehumidification, excess moisture can cause secondary damage such as mould.

Desiccant Dehumidifiers

Desiccant dehumidifiers use a special humidity absorbing material called a desiccant. Intake air (referred to as process air) is passed over the desiccant material which absorbs the moisture. Usually 75% of the process air exits the dehumidifier as warm dry air (process air). The remaining 25% is heated and passed across the wet desiccant material to dry the material (reactivation air). The reactivation air takes on the moisture and is exhausted as warm wet air. The warm water is either vented from the structure or cooled and condensed and purged as water. Desiccant dehumidifiers work more efficiently when the process air is cool and dry.

As usually only 75% of the process air is returned to the structure negative air pressure is usually created in the structure. Care must be taken to ensure the quality of the makeup air (25%) entering the structure. Desiccant dehumidifiers can achieve a very low specific humidity of 10 grains per pound and are particularly efficient at drying structural components such as hardwood floors and wall cavities.

Desiccant dehumidifiers can be smaller portable electric units or larger more powerful trailer mounted units that have onboard generators and use either LPG or diesel to generate the heat source for reactivation. Larger trailer mounted units are often used for drying of larger commercial buildings. Capacity of desiccant dehumidifiers is expressed in the volume of air that can be processed per hour either, cubic feet per minute (CFM) or, cubic metres per hour (CMH) of the process air exiting the dehumidifier.

High volume desiccant dehumidifiers are very good at structural drying as generally they produce large volumes of warm dry air.

Data Collection

The most advanced meters offer data collection capabilities that include job grouping. Job grouping can be helpful if you are checking multiple rooms at a site, or multiple jobs throughout the course of a work day. The user can set the temperature and wood species for each individual job, and set the meter to read on a particular material. Individual readings then may be stored for on screen recall or can be downloaded to a PC.
Once the readings are downloaded, the user can save them in a spreadsheet, assign name and address, and add notes to each job. This enables the user to provide written documentation and proof of the readings for each job. This way, the customer or insurance company can easily track the contractor’s work to ensure proper drying took place.

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