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Fixed Set Points Are Impacting Your Operational Costs
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Indoor swimming pools are among the most thermodynamically demanding environments in any building. Temperature and humidity constantly shift, driven by bather load, water temperature, the time of year and external weather conditions. Yet many pool HVAC systems are still designed around fixed set points: one temperature target, one humidity target, running the same way in January as in July.
The result is a system that works harder than it needs to, consuming energy and increasing operational costs to chase targets that don’t reflect what the space actually requires at any given moment. Recotherm’s VTVH (Variable Temperature Variable Humidity) strategy is designed to change that.
The Problem with Fixed Set Points
A conventional pool ventilation system is set to maintain specific conditions, say, 30°C air temperature and 60% relative humidity. When conditions deviate from those targets, the system responds by ramping up heating, dehumidification or ventilation to bring things back into line.
For example, in a busy evening session with 80 bathers in the water, evaporation is high and latent heat loads are substantial. At 6am with two lane swimmers and the pool covered overnight, the demands are entirely different. A fixed set point system treats both situations the same way.
The consequence is energy waste and often discomfort too. Systems frequently over or undershoot or simply run at higher output than conditions require because they’re reacting to fixed targets rather than actual need. Operators who notice the mismatch often compensate by manually adjusting settings between summer and winter, adding management overhead without ever fully solving the problem.
Why Indoor Pools are Inherently Variable Environments
The variability in a pool hall is structural and several factors drive it simultaneously:
Bather load
More people in the water means more evaporation, more latent heat and rising humidity. A capacity session on a Saturday afternoon creates fundamentally different conditions than a quiet Tuesday morning.
Water temperature
Warmer pools such as leisure, hydrotherapy and spa pools, evaporate more than cooler competition pools. Water temperature also fluctuates slightly through the day as heat is extracted by swimmers and topped up by the heating system.
Pool cover usage
A covered pool has dramatically lower evaporation rates. During closed hours, the thermal and humidity load on the ventilation system is a fraction of what it is during operation.
Fresh air conditions
The humidity and temperature of outside air varies significantly across the year and even across the day. In summer, warm humid fresh air contributes to the latent load. In winter, cold dry fresh air changes the energy balance entirely. A system that doesn’t account for this is always working from incomplete information.
Taken together, these factors mean that the optimal operating point for a pool ventilation system is a moving target. The question is whether your system is designed to track it.
The Foundation: Fully Variable Speed Systems
Responding intelligently to variable conditions requires a system that is itself variable. Many pool ventilation units operate at fixed speeds or with limited two-step switching, high or low, with nothing in between. These systems can’t modulate their output to match real conditions; they can only switch between predetermined settings.
Recotherm systems use fully variable speed fans across all operating modes. Rather than switching between settings, the system can continuously adjust to precisely the output required, which is the mechanical prerequisite for everything that VTVH adds on top.
What VTVH Does Differently
VTVH replaces fixed set points with agreed comfort ranges. Instead of instructing the system to maintain exactly 30°C and 60% RH, operators define acceptable operating windows: temperature might be comfortable anywhere between 28°C and 32°C, humidity between 50% and 65% RH.
Within those ranges, the system uses real-time sensor data, including fresh air humidity and temperature, to continuously select the most efficient operating point. Temperature and humidity are optimised together rather than independently, which matters because the two are thermodynamically linked: changes in one affect the energy cost of controlling the other.
The practical effect is a system that works with conditions rather than against them. Ambient humidity, cold dry outside air and bather load variations are tracked and responded to in real time, not averaged out into a fixed target that’s only accurate some of the time.
The Benefits in Practice
For operators, the most immediate impact is energy reduction. A system that tracks real conditions and adjusts continuously uses significantly less energy than one sized for peak load and running at constant output. The operational cost savings are particularly visible across seasonal transitions, where fixed set point systems are most likely to be poorly matched to actual conditions.
Beyond energy, VTVH reduces the need for manual intervention. Operators who currently make seasonal adjustments to their controls or who routinely chase comfort complaints by tweaking settings can hand that responsibility to the system. VTVH operates automatically within the agreed comfort ranges, requiring no day-to-day input.
There are building protection benefits too. Condensation on windows and structure and corrosion in pool hall environments are often symptoms of humidity control that isn’t keeping pace with changing conditions.
A system that responds dynamically to real-time humidity, including the contribution of fresh air, is better placed to maintain conditions that protect the fabric of the building.
Is VTVH Right for Your Pool?
VTVH is suitable for leisure centres, hotels and spas, schools and commercial pools, anywhere that comfort, energy efficiency, operational costs and building protection matter.
It is built into Recotherm control strategies and many existing units can be enabled for VTVH with the addition of appropriate sensors and, in some cases, a controls expansion module.
If you currently run your pool hall to fixed set points year-round, make seasonal adjustments manually or find that comfort varies significantly through the year despite your system running correctly, VTVH is worth exploring. A review of your current system can confirm whether it’s suitable and what, if anything, would be needed to activate it.
The fundamentals of pool hall ventilation haven’t changed: you need to control temperature and humidity, recover heat efficiently and protect the building. What VTVH changes is how intelligently the system does all of that and how much energy it uses in the process.
Find out if your plans or system could benefit from VTVH, contact the Recotherm team for a review.