Top Tips for Energy Efficient Dehumidification

With ongoing tensions in the Middle East and Russia’s conflict in Ukraine, the cost of energy will remain uncertain for all of us. We’re already seeing this unpredictability push facilities managers into a state of survival, and while prices may dip in the short-term, a long-term approach is needed for UK businesses reliant on dehumidifiers.

At National Heater Shops, we’ve spent years advising the industry on balancing equipment with operational overheads and can tell you that the significance of a strategy is just as important as choosing the correct unit itself. With dry air being easier to heat than damp air, maintaining an optimal level of relative humidity (RH) will reduce the strain on your HVAC system and lower your total kilowatt-hour (kWh) consumption.

Energy efficient dehumidification comes from understanding the science between extraction capacity and airflow dynamics. Miscalculating your required “litres per day” extraction can lead to units running continuously which will inflate energy bills and possibly leave the problem unsolved. In this guide I will be telling you how to precisely size a unit, the strategy behind where equipment should be placed, and general maintenance tips that will not only help to reduce running costs but contribute to extending the lifespan of your equipment.

Key Takeaways: Your Strategy for Energy-Optimized Dehumidification

I would recommend you prioritise these core principles to maintain an economical approach to dehumidification in today's unstable energy markets:

• For performance and efficiency, maintain humidity between 40%–55% RH
• Avoid continuous operation where possible and use humidistats to reduce runtime instead
• Stop units from running constantly by matching extraction rates to moisture loads
• Keep airflow constant and move dehumidifiers close to sources of moisture
• Stop moisture ingress and control drafts
• Support efficiency by keeping filters clean and cleaning units regularly
• For warmer environments choose refrigerants, desiccants for cooler conditions
• Apply extra focus to a long-term energy strategy

Why Energy Efficient Dehumidification Matters

We scratched the surface of this earlier and the fact is that damp air has a higher heat capacity than dry air. We use dehumidifiers to lower moisture levels to reduce the strain on your heating system which not only impacts your energy bills, but will affect the overall performance of your boiler too. In my experience, I have noticed this the most in larger commercial environments where even the smallest of changes in humidity levels has a noticeable impact on running costs overall.

Impact on Operational Timelines

When using flood dehumidifiers and water damage dehumidifiers, humidity stalls the evaporation process from deep beneath porous material such as timber and concrete floors. As air already saturated now refuses to accept anymore moisture, dehumidifiers have to work harder for longer. This now means more time has to be spent on site which leads to increased labour and equipment costs.

This actually reminds me of something we refer to in the industry as the infinite loop dehumidification. This is the constant reintroduction of moisture through open doors or the lack of plastic sheeting partitions which often leads to high-performance units being left running as the environment has not been properly managed.

Usage Patterns & Humidity Control

The best way to improve energy efficiency is to control how the dehumidifier is used and for how long it operates. My aim here is to explain to you the relationship between relative humidity (RH) and power draw and dispel the myth that all you need to do is to switch on a dehumidifier and let it get on with things. While many modern units feature integrated humidistats (hygrostats) that are great tools for success, they’re only as effective as the parameters you set.

The 40%–55% RH Industrial Benchmark

This is what us industry boffins would refer to as the “Goldilocks Zone” of 40–55% relative humidity that is applicable for the vast majority of commercial and industrial applications.

• The CIBSE Standard: As noted by our friends at the Chartered Institution of Building Services Engineers (CIBSE) that maintaining an RH within this range is optimal for looking after the the buildings fabric and indoor air quality (IAQ) while at the same time minimizing the carbon footprint of HVAC systems.
• The Law of Diminishing Returns: An attempt at pushing RH below 40% in an industrial setting such as a warehouse will require a huge amount of energy for only minor improvements. You would need to run a dehumidifier indefinitely and that wouldn’t really provide any additional benefits but would lead to a large spike in your kWh costs.

Continuous Running of Units

One of the biggest pitfalls I have experienced first hand is workers leaving industrial and commercial dehumidifiers running continuously without monitoring RH levels. Without monitoring levels and leaving a dehumidifier running 24/7, you run the risk of not only increased energy bills but this misuse also contributes to unnecessary mechanical wear.

This is not to say that there will be times when dehumidifiers will absolutely be required for continuous use. It’s not uncommon for wet trades or flood restoration projects that the first 48–72 hours require a continuous run. However, once the surface moisture has been removed, using the humidistat to control the humidity can often reduce energy costs by up to 30–50%.

Correct Sizing, Placement & Airflow

The efficiency of a dehumidifier is unfortunately not based solely on specification but will be driven by the environment in which it lives in. I recommend to everybody I speak to, to look past the square footage and focus on factors such as the total volume of air and moisture ingress to bring about a setup that has been optimised for energy efficiency.

Precision Sizing

Choosing a dehumidifier should be based on a calculation of its extraction capacity against the latent load of the space. If a unit is too small it will run constantly without ever reaching its setpoint while oversizing will lead to it short cycling. I have seen this before in warehouses I have worked at, the dehumidifier is working but humidity levels are still high. This is because the extraction capacity has not been matched to the moisture load.

For those working in wet trades or flood restoration environments, I would typically recommend choosing a unit based on Air Changes Per Hour (ACH), where you often require a higher ACH to prevent moisture accumulating in areas that slow down the drying process.

Airflow Dynamics and the Micro-Climate Trap

Time and time again I see this common error where placing a dehumidifier tucked away in a corner or behind pallets creates a micro climate, the air here becomes dry but the rest of the warehouse remains at 80% humidity.

• Clearance Standards: Do not choke the dehumidifier by placing it directly in front of objects, by allowing 50cm to 100cm of breathing space around all inlets and outlets this will enable the unit to operate at full capacity.
• The Source-First Rule: If you are using the dehumidifier for construction or restoration projects, directly positioning it close to the source of moisture like floor screed will help to speed up drying times while also reducing costs and time spent on the job.

My last piece of advice here is that if the environment you are trying to dehumidify has poor air circulation, don’t be fooled into buying a bigger dehumidifier – buy a smaller one and use it with an industrial fan or air mover. This may sound confusing at first but moving air evaporates quicker and it will also help the dehumidifier to remove more moisture.

Environmental Factors That Affect Efficiency

I often tell people that the correctly sizing and positioning of your dehumidifier is only half of the battle. A building's boundary, or the space between the controllable inside and the uncontrollable is the other half. If this boundary, be it through open windows or doors, can’t be controlled then regardless of how advanced your equipment is, your energy efficiency sadly cannot be controlled either.

We’ll all be familiar with drafts either at home or at work, and we'll all be familiar with the excess moisture that they unfortunately bring with them.

Managing Infiltration

Uncontrolled moisture ingress is the main drain on efficiency that I can think of and in busy warehouse environments where loading bays are left open for convenience, it can feel like a losing battle. The best solution here, and the one I always advise, is to use PVC strip curtains in these areas. I’ve used them in practice and while they contribute to keeping the boundary secure, they can often reduce unit runtime by over 25%.

Maintenance & Long-Term Efficiency

With the focus being on our energy bills now more than ever, maintenance can often be overlooked. However, it is when maintenance is neglected and the unit’s Coefficient of Performance (COP) drops that equipment starts to fail.

In my experience, restricted airflow is when units begin to lose their efficiency. You would be surprised at how quickly filters clog up with dust and other airborne particles, this causes the fan to work harder as the static pressure increases. I recommend inspecting filters weekly as reducing resistance can lower the load on the motor and decrease energy consumption by up to 15%.

Total Cost of Ownership (TCO)

The feedback from the technical team is that 70% of performance failures are actually related to poorly maintained filters. The advice often provided from them to customers is to keep a maintenance log of when filters and parts need to be cleaned and when they are advised to be replaced.

Remember, a well maintained dehumidifier will easily out perform a brand new unit with a clogged filter.

Choosing the Most Energy Efficient Dehumidifier Type

Selecting between a Refrigerant (Compressor) and a Desiccant unit will definitely have an impact on running costs and both offer advantages depending on the conditions they are used in. Conversely, choosing the wrong technology will almost certainly lead to increased running costs and even unit failure.

Refrigerant Dehumidification

Although their efficiency lies solely in the hands of the dew point, I would refer to refrigerant units as the workhorses of the industry. They work by drawing moist air through a cooling coil to condense the air into a liquid and are most effective in environments above 15°C.

It is important to remember when selecting a refrigerant unit that as the temperature drops towards 5°C, they will spend a significant amount of energy on "Defrost Cycles." The compressor will completely shut off during these cycles and the fan will run simply to melt ice that has collected on the coil. It will not remove a single drop of water while it does this, but it will cost you electricity, so definitely one to remember.

Desiccant Dehumidification

Desiccants work by using a rotating silica gel wheel to pull water molecules from the air, and because they do not rely on condensation, they maintain a consistent rate of extraction all the way down to 1°C. If your dehumidifier is destined for these kinds of conditions then you should know that a desiccant will outperform a refrigerant 3-to-1 in terms of drying speed per kWh.

It is also worth noting that they can drive humidity levels down to as low as 1% RH, so if you’re trying to dry out a floor following a flood, a desiccant unit will extract moisture much faster and more economically than a refrigerant model ever would.

FAQs on Energy Efficient Dehumidification

What is the most energy-efficient humidity setpoint?

40%–55% Relative Humidity (RH) is what I would recommend for most commercial and industrial settings. Targeting below 40% RH will require dehumidifiers to work longer, increasing kWh consumption for not much reward.

Should I leave my dehumidifier running 24/7?

If you are using a dehumidifier directly after a flood, then you will want to leave it running for the first 24–72 hours to extract the bulk of the moisture. After that, running 24/7 is a waste of energy and the unit should be switched to be controlled via its humidistat.

Can a dehumidifier actually lower my heating bills?

Yes, significantly. As damp air has a higher capacity for heat than dry air, your heaters essentially have to work harder to heat the water suspended in the air before actually heating the air itself.

Does the temperature of the room affect my choice of machine?

It does, and if you’re running a business this is where you risk losing money by choosing the wrong technology. For example, if you know the area intended for use will be below 15°C, selecting a refrigerant (compressor) model will consume a lot of power in a defrost mode while extracting very little water. Whereas a desiccant dehumidifier process of moisture extraction is unaffected by low temperatures and spends every penny of electricity on removing water from the air.

Conclusion: Long-Term Stability in a Shifting Economy

I predict that the businesses that will survive in the long-term will be those that can adapt and change how they work facing the unpredictable energy markets. Long gone are the days when we didn’t have to pay so much attention to the energy we consume, true energy efficiency is now the result of a climate strategy that combines the hardware with a strong understanding of the science behind the drying process.

Similarly at National Heater Shops, our expertise no longer solely lies in the equipment we provide, but in the success of the clients we support.