SPS provides contractors with the information needed to confidently include indoor pools, spas and fountains in their design capabilities. Input from original equipment manufacturers (OEM), mechanical contractors, and consulting engineers have been incorporated into the HVAC industry's first ANSI-Recognized design manual for indoor pools and spas.
Manual SPS addresses the unique dynamics for pools and spas including:
- Controlling dew point temperatures of space air as well as space temperature.
- Compatibility with moist air and pool chemicals.
- Sealing and insulating duct work.
- Code requirements.
- Designing for higher operating and installation costs, higher efficiency systems and the expense of ongoing maintenance.
- Dehumidification systems and indoor air quality.
Manual SPS assumes the practitioner is very familiar with comfort conditioning systems, equipment and design procedures. The prerequisites for using Manual SPS procedures are summarized here:
Overview of the manual
- General understanding of the concepts, components, arrangements, procedures, requirements and terminology that pertain to commercial and residential building construction.
- Extensive experience with commercial load calculation methods and procedures.
- Mastery of psychometric principles and processes, and related altitude adjustments.
- Extensive experience with designing commercial heating and cooling systems for comfort applications.
- Extensive experience with using manufacturers performance data to select and size heating and cooling equipment.
- Mastery of air distribution principles, and experience with using manufacturers' performance data to select and size commercial supply air hardware and return air hardware, and associated devices.
- Mastery of duct design principles, and experience with designing low velocity duct systems.
- A general understanding of HVAC controls, control strategies and control cycles.
- Experience with designing HVAC systems that adjust performance to maintain space set points for temperature, humidity and engineered ventilation at full load conditions, and at all part load conditions (i.e., mastery of capacity control issues and strategies).
The First Edition of Manual SPS provides guidance for projects that range from a hot tub in a home to a large natatorium that has an Olympic-size pool with seating for hundreds of spectators. Even though these projects appear to be quite different, they are identical as far as construction requirements and mechanical system performance requirements are concerned. So for this manual, any enclosed space that has a spa, swimming pool, decorative pool or immersion tub is a natatorium.
This manual does not provide guidance for indoor water parks. The reason for this is that there is no standard method for evaluating the moisture loads for water rides and water toys. In this regard, a swimming pool has one or two water features (water slide or small water fall) is not a water park.
Finally, the mechanical system must be designed to continuously control the dew point temperature of space air then measures are taken to control space temperature. If this is not accomplished, moisture can cause visible and concealed condensation, wet sagging ceilings, wet framing, wet structural surfaces, wet insulation, visible or concealed mold and mildew, corroded or discolored fixtures and finishes, rust, or masonry that has been fractured by ice. In addition:
- Dehumidification system must provide indoor air quality and space air motion.
- System materials, components and devices must be compatible with moist, chemical laden air.
- Duct runs must have appropriate insulation and moisture membranes.
- Duct runs must be tightly sealed.
- Mechanical system cost and system operating costs are higher than for comfort applications due to the need to control the dew point temperature of space air and to provide indoor air quality.
- Energy use should be minimized to the extent possible. Higher efficiency will increase installed cost.
- Maintenance requirements and costs are generally higher than for comfort conditioning systems.
Section 1: Design Issues for Humid Spaces
The Mechanical system designer must consider moisture issues, condensation issues, chemical issues and zoning issues. The mechanical system designer is advised to verify that the construction details for an existing structure or a proposed structure are suitable for a natatorium enclosure.
Section 2: Contract Set Points and Outdoor Conditions
The design value for water temperature, and the related values for indoor humidity and indoor air temperature are contract set points. Outdoor and indoor design conditions for a natatorium are significantly different than the conditions that are used for comfort conditioning. There is a winter design condition for outdoor moisture and temperature (the 99.6% dry-bulb condition). There is a summer design condition for outdoor moisture (the 1% dew point condition), and a summer design condition for outdoor temperature (the 1% dry-bulb condition) Figure Al-1 shows that indoor air temperature is warm (78 F 86 F) and that it has a relatively high humidity ratio year-round.
Section 3: Space Humidity and Surface Condensation
The mechanical system designer is informed about R-value calculations, vapor retarding membranes, and condensation calculations. The mechanical system designer needs to verify that the architect and/or builder has performed appropriate condensation calculations.
Section 4: Water Treatment and Water Heating
The mechanical system is designed for appropriate and scheduled water treatment, adequate pool-spa maintenance and diligent water system maintenance. Odors and smells indicate inadequate or improper for maintenance practices. Water shocking affects the design of the mechanical system (the associated purge cycle requires a large amount of outdoor air for a limited time) Water systems for pools and spas are provided by companies and vendors that specialize in this work. These entities are responsible for water pumping, water circulation, water filtering, water heating and water treatment. They are also responsible for information or estimates pertaining to annual water use, annual sewer charges and annual water heating costs. There are procedures for calculating water heating loads.
Section 5: Indoor Air Quality and Ventilation
Natatorium air contains chemical compounds caused by water sanitation and safety treatments (or the lack of proper treatment). All efforts to control indoor air quality are based on the assumption of proper water treatment. Engineered ventilation (outdoor air) dilutes the concentration of offensive pollutants. Outdoor air is required for the actual water surface area and the wet deck area, and if there is spectator seating, outdoor air is required for spectators. The outdoor air damper can be closed when the space is not occupied (use low leakage dampers). If the spectator load is large and occasional, consider using a dedicated outdoor air system (DOAS) for spectator events. There may be a temporary ventilation Cfm requirement (purge cycle) for water shocking. Condensation or freezing condensation may occur when cold outdoor air is mixed with warm-humid return air, or air discharged from an evaporator coil. Condensation may occur when heat reclaim equipment processes exhaust air. Condensation droplets must not impinge on a heating coil or heating surface. Mixing boxes must be designed to capture condensation, contain condensation and dispose of condensation. Preheat may be required for cold outdoor air.
Section 6: Evaporation Load
There is a special procedure for calculating the latent load for the water evaporation at wet surfaces. This load depends on water temperature, space air temperature and humidity, water surface area, water activity and wet deck area. A change in the space temperature and/or humidity has a significant effect on the evaporation load.
Section 7: Heating and Cooling Loads
Mechanical system design shall be based on comprehensive load calculations that are as inclusive and accurate as possible. A twelve month, twenty-four hour procedure for comfort conditioning is used for everything other than the evaporation load. The latent load for water evaporation load varies with water activity. Latent and sensible load calculations are made for the winter design condition and both summer design conditions. The latent load from evaporation is added to the latent ventilation load, the latent load for spectators, and the latent infiltration load (which can be very small or negligible for a structure that has appropriate construction). Latent outdoor air loads can be large. They are negative during cold weather (moisture loss); may be negative during warm weather (dry climate), or positive during warm weather (climates that have a summer moisture load).
Section 8: Moisture Control Methods
Space humidity may be controlled by a refrigerant evaporating coil, with dry outdoor air, or by a desiccant wheel. These methods vary in concept, complexity, installed cost and operating cost. The primary concern is matching system capabilities with application needs. If two or more methods provide the required performance, installation cost and operating cost may determine the system of choice. Under certain conditions, it may be possible to assemble a dehumidification system from comfort conditioning components. A dedicated outdoor air system may supplement the space dehumidification system when a large spectator area is vacant most of the time.
Section 9: Heat Recovery
A significant or relatively large amount of outdoor air may be required for the humid space. The space must at negative pressure, so the exhaust air Cfm is somewhat larger than the outdoor air Cfm for r air quality. Exhaust air may provide a heat recovery opportunity. The latent heat of evaporation is a )us source of reclaimable heat. Heat recovered by the evaporator coil can be used to heat pool and/or supply air (priority may depend on the dehumidifier equipment manufacturer). A dehumidifier may have an air-side economizer. There is no industry standard for quantitative comparisons of energy use, operating cost and return on investment.
Section 10: Supply Air Cfm
The desired air turnover rate for the humid space ranges from 4 to 8 turns per hour. This amount of supply air Cfm may not equal the Cfm required for the space loads. This difference is reconciled by routing some air around the evaporator coil (through a bypass air damper). The final value for supply air Cfm is determined when the equipment is configured to satisfy both airflow requirements.
Section 11: Equipment Selection
Performance data for evaporator coil dehumidifiers and desiccant dehumidifiers emphasize moisture removal in pounds-of- water-per- hour units. Data for evaporator equipment also provides values for total capacity and sensible capacity in Btuh units, and values for supply air Cfm and maximum outdoor air Cfm. Data for desiccant equipment provides values for supply air Cfm, maximum outdoor air Cfm and exhaust Cfm. Air to air heat recovery equipment has a Cfm rating and an effectiveness rating. Control dampers have performance curves.
Section 12: Air Distribution and Space Pressure
Exposed glass (windows, glass doors and skylights) should be completely washed with dehumidified supply air (this may not be possible if the facility has a large amount of glass). Skylights are especially troublesome and should be avoided. Primary and secondary supply air must not blow directly on wet surfaces. The relative location of supply outlets and returns should, to the extent possible, induce low velocity air movement across the surface of the pool water. The humid space must be at negative pressure relative to the outdoors and relative to other spaces, except for the chemicals storage space. These pressure conditions must be in effect at all times.
Section 13: Duct Systems
Low pressure, low velocity duct systems are typical. Practitioners may use the equal friction method for air way sizing. Use efficient fittings and avoid duct entrance and exit conditions that cause a system effect.
Section 14: Design Example for a Spa and Pool in a Home
Load calculation for a Spa and small pool in a dedicated room in a Tucson, AZ home.
Section 15: Design Example for a Pool-Spa in a Motel-Hotel
Load calculation for a Spa and mid-size pool in a dedicated room in a Miami, FL motel or hotel.
Section 16: Design Example for a Competition Pool
Load calculation for an Olympic Pool with space for a large number of spectators Milwaukee, WI.
Appendix 1: Good Practice
Appendix 1 summarizes the requirements for the architectural project and the mechanical project. Check list items that pertain to preventing building condensation and controlling conditions in the humid space are fully explained in the body of the manual. Appendix 1 check lists may contain some items that are not discussed in the body of the manual, these typical relate to installation and maintenance.
Appendix 2: Equipment Capacity at Altitude
Appendix 2 explains how heating equipment, cooling equipment and air moving equipment is affected by altitude. The discussion focuses on comfort equipment, but it also applies to dehumidification equipment. For the locations above 2,500 feet, altitude adjustment guidance must be obtained from the equipment manufacturer.
Appendix 3: State Point Psychrometrics
Air state points depend on altitude. Appendix 3 provides formulas for altitude sensitive psychrometrics.
Appendix 4: Symbols and Terminology
Appendix 4 provides definitions for the symbols and terms used by this manual.
Appendix 5: Summary of Tables and Equations
Appendix 5 provides a summary of the tables and equations used by this manual.
Appendix 6: Summary of Dehumidification Methods
Summary of the attributes .and capabilities of the various types of moisture control systems.
Appendix 7: Codes, Standards and References
List of related codes and standards, and documents for additional study.
Appendix 8: Comfort Conditioning Equipment
Comfort heating-cooling equipment may be used for a pool-spa space if all performance issues can be satisfactorily resolved. These issues are discussed in general, but this is not sufficient for producing a design for a particular application in a particular climate.
Appendix 9: Equipment Performance Data
Exhibits and discussions of performance data supplement Appendix 6, and conditionally supplement comments made in the body of the manual.
Appendix 10: Forms and Worksheets
Blank copies of Form DH and Form DC.
Table of Contents
Copyright and disclaimer. Acknowledgements. Dedication. Overview. Prerequisite Knowledge and Experience. Introduction. Design Team. Part 1: Design Issues and Procedures.
Section 1: Design Issues for Humid Spaces. Section 2: Contract Set Points and Outdoor Conditions. Section 3: Space Humidity and Surface Condensation. Section 4: Water Treatment and Water Heating. Section 5: Indoor Air Quality and Ventilation. Section 6: Evaporation Load. Section 7: Heating and Cooling Loads. Section 8: Moisture Control Methods. Section 9: Heat Recovery. Section 10: Supply Air Cfm. Section 11: Equipment Selection. Section 12: Air Distribution and Space Pressure. Section 13: Duct Systems. Part 2: Example Problems
Section 14: Design Example for a Pool and Spa in a Home. Section 15: Design Example for a Pool and Spa in a Motel-Hotel. Section 16: Design Example for a Competition Pool. Part 3: Related Guidance and Procedures.
Appendix 1: Good Practice. Appendix 2: Equipment Capacity at Altitude. Appendix 3: State Point Psychrometrics. Appendix 4: Symbols and Terminology. Appendix 5: Summary of Tables and Equations. Part 4: Ancillary Guidance and Aids.
Appendix 6: Summary of Dehumidification Methods. Appendix 7: Codes, Standards, and References. Appendix 8: Comfort Conditioning Equipement. Appendix 9: Equipment Performance Data. Appendix 10: Forms and Worksheets. Index.