Controlling Humidity in Natatoriums/Indoor Pools
How to get the PERFECT BALANCE of Water and Air from Building to Dehumidification
Much information has been distributed over the years regarding indoor pools, for "how" and "why" to properly control the humidity in an indoor pool. Questions arise as to what works and at what cost - from exhaust fans, exchanging outside air for indoor air (waste ventilation), opening windows, plug in basement style dehumidifiers, 100% Outside Air systems, to mechanical refrigeration based dehumidification systems. A pool room is like a pot of boiling water on a stove... the moist warm air coming off the pool in the form of evaporation rises and stratifies in the ceiling areas and walls of the pool room. Left uncontrolled, this 100% humidity eventually destroys all building materials and equipment, ceilings cave in, mold, rot, mildew occur.
Today's heat recovery refrigeration based dehumidification systems reduce this humidity to the recommended ASHRAE Guidelines of 50-60%, maintains temperatures, provides heating and cooling, and adds resource of free "reheat" to room and pool while in operation. In many cases, dehumidification is an afterthought or after moisture problems become apparent. In some cases equipment not appropriate to these types of structures is installed and in ashort time becomes apparent that it does not work to control the environment. Costs of preventing deterioration problems with pool rooms can be prevented in the design stage and are much less than the costs of repairs down the road. What we see today is a lack of knowledge in building envelopes, engineering, installation of dehumidification systems and the properly sized air delivery system installed to reduce humidity, and control the pool room environment 365 days/year.
Many companies have written articles that recommend utilizing expensive and unnecessary building materials, which in reality-- are neither "bullet proof" nor water proof against "mother nature's heat pump". An engineer who specialized in indoor pools and dehumidification once said "if it is a battle with water... water always wins".
In the past 30 years we've experienced indoor pools/natatoriums, manufactured enclosures that self destruct in less than 5 years- due first - to not taking the proper preventive measures in the design and building stages, and secondly, not installing the proper dehumidification environmental control system. There are several areas to cover as you are introduced to understanding the requirements of your indoor pool, the building and the dehumidification system required. Do not leave all of the research to architects/engineers, builders and HVAC firms to provide... most are not trained or schooled in either indoor pool buildings or dehumidification systems. They do the same research you must do. We often hear.... "We were never told about a vapor barrier"... "We were never told we needed a system"... "We were told we did not need a dehumidification system that we could use exhaust fans", "We thought we could use a plug in dehumidifier like the one in our basement".... all of these myths can easily be dispelled by little bit of research. Budget for dehumidification: Do it now at a lesser cost, or budget higher costs for tearing down, replacing drywall, windows and structural materials in less than 5 years. Often times the cost of a properly designed dehumidification system is less expensive than renovating the structure.
Sizing of a system is based on specific guidelines provided by ASHRAE (American Society of Heating & Refrigeration Engineers), ACCA, SMACNA and other consortiums in our industry. Under sizing and over sizing is common in this industry. This also may cause increased costs in operation. Along with your design requirements, all aspects are taken into consideration to design the properly sized system. Building requirements - Standard building materials can be used (vapor barriers, negative pressure, lighting, windows, mechanical space should be discussed with your consultant for your application). Certain products will hold up better than others in a high humidity envelope. Most companies do not have the knowledge to consult with you on the building side of the equation. You'll want to look for companies that provide consulting along with their design and dehumidification system. HVAC - the dehumidification system.
Many companies will tell you to buy a commercial grade dehumidifier, the lowest cost unit, with the lowest installation cost, buy a smaller unit that uses less electrical voltage than the standard, the lowest operating cost and to stay away from complex options. This is a bit misleading for several reasons: Dehumidification systems are sized today to accommodate all types of applications; there are residential projects with 5-50 Tons, and commercial projects with small 3 tons. Whether residential or commercial application, you want a dehumidifier that is built for your application, your evaporation rate, your air flow and your design requirements. When companies want you to install a "smaller" unit because it is less expensive, or it is a plug in style unit, your question should be to any manufacturer "does your system meet or exceed all ASHRAE Guidelines for Indoor Pools"?
Air Delivery (duct work). This is the most critical aspect of any installation. Great heart-bad arteries. Without ductwork, the heart (dehumidification) cannot work. Think of building a new home. As an owner, you would not install a furnace and an outdoor air conditioning system and then not attach it to the duct work system to move air flow at certain air turnover rates throughout the home. You would also not just run ductwork to your family room and skip the rest of the house if you want the entire home to be comfortable. Energy efficiency, least cost of operation, least cost of equipment, are based on numerous factors such as the size of your natatorium, your utility rates, using a pool cover, not over sizing or buying a smaller dehumidification system than your project requires, the refrigerant charge, the equipment design, your building, heat loss/heat gain, etc.
These are a few of the variables that must be taken into consideration. It is difficult for any manufacturer to guaranty the lowest operating cost of any system when "how you build" also affects the operating costs. The most effective way to reduce operating costs is to utilize a pool cover when the pool is not in use and maintain temperatures at the recommended levels. Secondly, look at your design; is it standard construction with insulated walls and ceilings, or is at all glass? Building design also leads to a reduction or increase in utility costs.
Environmental Pool Systems, Inc. is an expert in indoor pool humidity control. Our company provides consulting to the natatorium industry and has been building dehumidification systems since 1985. Feel free to browse http://www.dry-air.com, for additional building information, call Chris Leonetti at 800-514-7051 or email chris@dry-air.com for specific questions! We're here to ensure you will have a pool room that provides a healthy, stable, warm and dry environment for years to come!
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