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The major problems are obviously related to the substantial quantities of water which evaporate from the pool surface. This in turn leads to excessive air humidity, uncomfortable conditions, condensation and unsightly mould growth. Taken to it's extreme, structural failure and building collapse can result.

The climate in which we live also plays it's part. If the UK weather was similar to the tropics, with the ambient (outdoor) temperature remaining above 25 degrees C (78F), then there would be a greatly reduced need for humidity control. The majority of problems related to high humidity involve condensation. If the buildings were constantly warm, then cold surfaces would not exist and condensation would not occur. That's the ideal world. In the UK ambient can drop to minus 15 degrees C and are regular around freezing point. The UK's annual average for temperature is around 12 degrees C. In a typical UK pool environment, condensation will occur on anything colder than 22 degrees C (ie most of the year!!)


Given the above primary consideration, the following list highlights the major effects suffered when the designers have given insufficient consideration to the special needs of an indoor pool in the UK


  1. Regular condensation on external glass and glazing frames, which clears with difficulty.
  2. Surface condensation on masonry elements, in particular external walls and lintels which are thermally bridged.
  3. Internal condensation within masonry elements, known as "interstitial condensation".
  4. Roof space condensation, timber degradation, insulation saturation.
  5. Where fitted, roof light/velux window/cupola condensation.
  6. Adjacent area condensation and /or uncomfortable conditions. In a domestic private pool, this may be a link corridor to the house, or perhaps a living area. In a club or hotel this may be the changing areas or perhaps a gymnasium.
  7. Uncomfortably hot/humid/stuffy conditions with inadequate or non-existent fresh air provisions.
  8. High room noise levels exacerbated by the naturally reverberant environment produced by hard surfaces and expanses of water.
  9. Excessively high running costs, due to inadequate heat recovery, poor controls and unwise primary fuel choice.

A successful pool environmental control scheme will control the following elements

  1. Pool water temperature.
  2. Pool hall air temperature.
  3. Pool hall air humidity (or more correctly relative humidity).
  4. Pool hall fresh air introduction.
  5. Pool hall stale air extract.
  6. By a combination of items 4 and 5 above, pool hall air pressure.
  7. Temperature of any other water surfaces (such as a spa/Jacuzzi).
  8. Air distribution around the room
  9. Noise levels in the pool room, adjacent area and to atmosphere/neighbours

For more information on the above items, click this link

Further to the above basic pool parameters, a number of further aspects deserve consideration as follows

  1. Under floor heating to the pool surround
  2. Heating to adjacent rooms and changing areas. This is normally recommended as a separately controlled scheme, independent from the pool room heating.
  3. Dedicated ventilation to the changing areas, in conjunction with item 2, to provide a cooler environment than that in the pool room.
  4. Hot and cold water supplies to the changing facilities and showers.
  5. Air cooling to adjacent conservatories and/or exercise gymnasia.
  6. Boiler plant required, flue requirements, fuel to be used, fuel storage, fuel line sizing, fire protection requirements.
  7. Incoming electrical service, sizing, number of phases, co-ordination with general small power and lighting requirements and distribution boards.
  8. Control of equipment such as room and underwater lighting, perhaps using low voltage systems, infra-red or radio frequency signals.


What are the most popular forms of dehumidification systems?


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