Pool HVAC
Indoor Pool Heat Recovery Ventilator (HRV)
A standard 16” x 32” uncovered pool at 84°F will lose 75 gallons of water through surface evaporation every day.
Both the thermal integrity of the pool enclosure and the design/installation of the HVAC System are critical to maintaining comfort levels, controlling operating costs, and avoiding problems due to excess humidity.
Ventilation can not stop evaporation. However with adequate heat and a well distributed air delivery system, ventilation has long been proven to control relative humidity to safe levels.
An ENEREADY™ indoor pool HRV, together with both proper pool room and HVAC design, construction and operation can together help protect the health of the enclosure and that of its occupants.
Indoor Swimming Pools
During winter, an indoor pool will stress its enclosure. Pool surface evaporation (typically 2 to 4 gallons/hour) will create a warm moist environment. This may cause condensation to occur on interior surfaces if the building is not designed, built or operated correctly. Done properly and when it is fitted with a suitable HVAC system, one can expect a long service life and the lowest operating costs possible.
Unfortunately if problems do arise they can be serious and expensive to repair. Fault can be caused by an inadequate HVAC system, but may just as likely happen due to an oversight of any of the 3 building deficiencies listed above. For these reasons, expertise in indoor pool enclosure design and construction, including the proper selection of the HVAC systems should be sought. It should be noted that some cities and municipalities now require that letters of assurance for the HVAC system be submitted for permit.
Enclosure, Design & Construction Firstly, the designer must clearly establish a ‘line’ to separate the pool room, including its associated bath/change rooms, from the rest of the building. Air must not be permitted to move between that pool room and any adjoining rooms. The separation wall may have windows (single glazing is adequate) and doors as long as both are air sealed into place and the latter are weather stripped with thresholds. There must be no breaches of this separation by any standard electrical boxes, pot lights or duct system, etc.
The most critical part of the enclosure is the detailing of exterior walls and ceiling. All of these surfaces must be carefully insulated and completely devoid of thermal bridges. The latter will cause localized interior surface sweating. The enclosure must be air sealed to reduce exfiltration of pool room air and, just as importantly, effective air sealing will enable the HVAC system to maintain a continuous and necessary depressurization of the enclosure. Pool room surfaces exposed to the exterior must have a low perm vapour control layer (poly) or, alternatively, foam insulation. Detailed execution of these 3 critical features will help confine the pool room’s warmth and moisture to where it belongs, i.e. the pool room built to withstand it.
While the pool tank walls are typically insulated, repositioning this same insulation to the enclosure’s foundation walls, both above and below grade, will reduce losses from the pool system overall; the pool deck will indirectly become radiant heated while retaining pool water temperature as originally intended. This will help keep the lower edge of the room’s wall and perimeter edge of the deck warm, dry and comfortable to walk on.
Exterior glazing must be low ‘e’ or ideally low ‘e’ with argon gas fill. Insect screens or shutters, if used, must be placed external to the movable glass or, if internal as is standard with casement windows, must be removed in winter. The interior lower 5′ of the wall must be finished to withstand direct water splash.
HVAC System: The HVAC system must serve 3 main functions; control the interior RH by ventilation or dehumidification, heat the room during winter and ‘air-blanket’ the interior of all exterior facing windows, skylights and doors. This system must maintain 80°F minimum air temperature when the main pool is 85°F and the hot tube is 105°F. If warmer main pool water is required, as with therapy use, the HVAC designer must know in advance.
Ventilation/dehumidification capacity is primarily determined by water temperature, pool surface area and swimmer activity . If the water temperature must be raised, moisture control capacity must be increased. The system’s heating capacity is dictated by the enclosure heating requirements; its air circulation capacity is determined by that and the area and insulation value (interior surface temperature) of the windows. Note that the air quantities required for ventilation and air circulation rates are seldom equal.
Maintenance: A maintenance manual for both the pool HVAC and pool water systems should be provided and the owner must be cautioned that correct operation is important. In extreme cases, misuse may actually jeopardize longevity of the enclosure itself. Note to owner: “Do not store pool chemicals in any mechanical room”.