Desiccant vs Refrigerant (Mechanical) Dehumidification

When we talk about large-scale drying out, we mean removing moisture from the air to lower the relative humidity of a space.

We often think about open-air construction projects that have been subject to unpredictable weather conditions, flooding or leaks that then need to be dried out. However, regardless of the time of year and moisture exposure, effective drying out can be vital to the integrity of work completed.

As technology develops, new and innovative solutions mean dehumidification can be achieved, without needing to employ the traditional methods associated. Whilst the methods change, the one thing that remains the same is that drying out and moisture management is a year-round requirement.

When you need drying out on a project, it is important to understand that the best dehumidifier for the job will depend on the work being carried out. This article will help identify common uses for temporary drying out solutions and which dehumidifier is best for your industrial drying out project.

How does a dehumidifier work?

Desiccant and refrigerant dehumidifiers work in different ways, which is why the best solution for your current project may not necessarily be the best solution for your next project.

Desiccant dehumidifiers

Humid air is drawn into the dehumidifier using a fan and passes through a rotating wheel with a drying agent, also known as a desiccant. As air passes through the rotor, water molecules stick to the desiccant in a process known as adsorption. This dries the air without the need for additional heat.

Refrigerant dehumidifiers

Similar to a desiccant dehumidifier, humid air is drawn into the unit via a fan. It then passes over evaporator coils filled with cold refrigerant. As the air cools, the moisture condenses into droplets and fall into a collection tank or are drained away via hose. This process is why heating the air makes for more effective dehumidification when using a refrigerant unit.

Once the moisture has been removed, the dry air passes back over condenser coils to warm it back up before entering the room.

RVT Group’s effective drying triangle was created to maximise moisture absorption for commercial drying-out projects when using refrigerant dehumidifiers and follows three simple principles:

• Air movement across a substrate draws the water to the surface, where it evaporates.
• Dehumidification extracts water from the air, to be transferred from the work area.
• Heat raises the room temperature and so lowers the relative humidity of the air. This allows the air to absorb more water from surrounding surfaces.

You can read more information on the effective heating triangle and refrigerant dehumidifiers by downloading our whitepaper.

External factors like the weather also influences humidity levels to begin with, so what is recommended for an open-air project may differ from an internal project where moisture levels and temperatures are unlikely to change as dramatically. Ensure you speak with a consultant about which solution would work best for you.

What are the key differences between the dehumidifiers?

The way that each dehumidifier works means each unit thrives in different environments. Some key features to remember are outlined below.

Desiccant dehumidifiers

• Works as effectively in cooler conditions as it does in warm ones, does not necessarily need a space to be heated for optimal moisture removal

• Tends to be more energy efficient in cooler environments, making it suitable for applications where low humidity is required such as industrial environments

• Typically require less maintenance, especially when hired from a specialist hazard control company where dehumidifiers are tested before being deployed to a project

TOP TIP: Each desiccant dehumidifier will operate best in certain temperatures – check the temperature range for the unit you’re hiring to ensure you’re getting the best possible results for your environment.

Refrigerant dehumidifiers

• Works better in warm environments so is often paired with heating equipment to maximise results making them well-suited for environments with higher humidity such as residential new builds

• As well as effectiveness, refrigerant dehumidifiers tend to be more energy efficient in warmer conditions

• The more intricate design may require more frequent maintenance if used for long-term hire or purchased

What type of projects are they best suited to

Below are some examples of how each dehumidifier can help supported with commercial drying out:

Desiccant Dehumidifiers

• Controlling moisture during fit‑out and finishing, speeding up drying of concrete, plaster and paint so trades can work continuously and projects stay on schedule even in cold or damp conditions.
• Inside enclosed assets such as water tanks or tunnels, desiccant units provide low‑humidity air to enable safe inspections, surface preparation and coatings, preventing flash rusting and ensuring linings cure correctly.
• Maintaining stable humidity levels in manufacturing plants, warehouses or process areas to protect sensitive equipment and materials, reduce corrosion, and support processes like drying, packaging or product storage.
• Preventing corrosion and condensation in confined spaces like ships, submarines or in naval dockyards, protecting weapons systems, electronics and hull structures during maintenance or lay‑up.

Refrigerant Dehumidifiers

• Commonly used during later construction stages to manage general dampness in warmer conditions, helping prevent condensation, mould growth and damage to finishes once buildings are enclosed.
• Used during construction or maintenance of assets such as pumping stations, bridges, or service buildings to manage general humidity and reduce condensation on structural elements to improve conditions for operatives and installed equipment.
• Provide an energy‑efficient way to control excess moisture in factories and storage areas with moderate temperatures, supporting workforce comfort and reducing the risk of corrosion, spoilage or moisture‑related defects.
• In dockside facilities, workshops or shore‑based naval buildings, refrigerant dehumidifiers are used to manage humidity in occupied spaces, limiting condensation on equipment and improving environmental conditions for personnel.

How can RVT Group help with drying out?

At RVT Group, we offer a range of dehumidifiers and relative humidity monitors including the following:

CLIMEX^® Desiccant Dehumidifier DD20

• Removes moisture from the air in temperatures down to -10˚C
• Weighs 12kg and features a carry handle for convenience and ease of movement
• Compact size for dehumidification close to the damp area, minimising ducting requirements and disruption
• If your project has access to power, simply plug-and-play for airflows of up to 250m³ per hour

CLIMEX^® Desiccant Dehumidifier DD130

• Achieves a very low % relative humidity levels, perfect for precise humidity control
• Removes moisture without the need to heat the space, saving energy and reducing operational costs for the project
• Can also be used for ventilation, providing fresh, low-humidity air and improving air quality whilst controlling moisture levels
• Can be installed either inside the project or outside with ducting and the in-built airflow

CLIMEX^® DD450 Desiccant Dehumidifier

• Suitable for cold environments
• Powerful Airflow of up to 2500m³/hr for consistent performance based both inside or outside of the project
• Uses specialist technology to monitor inputs, triggering precise and specific outputs to your environment
• Includes a pre-filter to remove large and bulky dust from the air during the dehumidification process

CLIMEX^® Dehumidifier 96 Litre (refrigerant)

• A humidistat starts the machine when the humidity surpasses your chosen, pre-set level
• Has two large wheels for transportation around your projects and for drying different areas effectively
• Ideal for large-scale drying on a wide variety of projects and suitable for drying even highly saturated materials
• Fits through a standard doorway and features a drain pump for convenience

MONITEX^® Temperature and Humidity Monitor

• Access data remotely from any PC, tablet or smart phone. This means your project’s data is available 24 hours a day, 7 days a week
• Measures a temperature range between -25°C to 65°C and a relative humidity between 0 to 100% meaning you can react or adjust controls in place to achieve project success
• The monitor affixes to an upright stand or can be mounted to a wall, railing or other structure to continuously measure the temperature and humidity of the environment
• You will receive an alert if the temperature and humidity deviate outside your pre-defined parameters so you can react accordingly

The best solution for you will depend on the environment and end goal. RVT Group offer free site assessments to understand the full scope of a project and recommend the most appropriate drying-out solution for you.

Weather conditions, leaks and water ingress is unpredictable, especially on a busy project with lots of moving parts. Should you find yourself in need of a drying-out solution at short notice, speak with a consultant who can help you overcome your challenge quickly and efficiently, allowing your team to focus on the job at hand.