Systemair - Swimming Pool Ventilation Guidelines - Menerga
Pool Hall Humidity - Energy Consumption - Heat Recovery - Air Distribution - CIBSE Guidance
While the water temperature in most public 25m pools is maintained between 27°C and 30°C, the air temperature should be 1-2°C above the water temperature for bather comfort (which helps reduce the evaporation rate). Pool hall humidity should be in the range of 50-60% to reduce the risk of condensation and help maintain the structure.
Pool halls require more energy than any other public building (by an order of magnitude) with virtually year round heating (in the UK). Fan motor power consumption is high because the ventilation system runs continuously. Ensuring minimum energy for the air supply has a much bigger impact than focusing on the water (which can only be heated at a rate of 0.5°C per day and once at temperature requires minimal input).
When calculating air volumes you need to consider:
- Transmission losses, infiltration losses & the heat loss to evaporation
- Dehumidification requirement
- Air changes per hour (looking for 4-6 but depends on air distribution & pool usage)
- CIBSE guidance, currently states 10l/s per m² floor area (based on public 25 x 13m pool)
Temperature & Humidity Control & Energy Consumption
Most pool units are designed to ventilate, heat and dehumidify a space.
To ensure the best performance at the lowest lifecycle cost, several key factors should be noted:
- Fully controllable eC direct drive fans – no one should be using belts in this day & age
- The ability to maintain a small negative pressure at all times – through varying usage & volume requirement, with as close to balanced air flows to maximise heat recovery
- High passive heat recovery efficiency – so there is no penalty for introducing outside air <95%
- Minimal (ideally no) metallic parts in the air paths to avoid corrosion or acid attack
- Polymer based recuperators, ABS grade fixtures & fittings, flexible duct connections, plastic damper cogs
- Accurate, self-contained, real time control systems – the unit must be able to calculate the most efficient mode of operation from real time measurements of outside & return air conditions at all times
Pool Hall Air Distribution
The best unit in the world cannot compensate for poor air distribution. It is critical the supply air mixes as efficiently and effectively as possible with the pool hall air. The best method for this is a floor level induction diffuser.
No stagnant spaces should occur and supply and extract should never form a short circuit. This can help to minimise required air flow, eliminate condensation and result in a good atmosphere for those in the pool and those sitting at the side.
Outside Air Requirement
Under UK CIBSE guidance, a minimum of 30% outside air is required at all occupied times to supply a public swimming pool. In reality, for much of the year, this proportion of outside air is sufficient to dehumidify the pool hall.
By maximising heat recovery efficiency there is no penalty to introducing more outside air when required, ensuring running costs are simply for top up heating to overcome fabric transmission losses within the space, and power for the constantly running fans. The ability to have full outside air bypass is critical to ensuring good conditions year round in the UK.
By eliminating the need for a heat pump you can reduce electricity costs, maintenance costs and minimise the number of components that can fail.
Why pay for a heat pump and additional circulation electricity when the outside air required by law can dehumidify for you for the cost of running the fans?
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