CEMP-E
TI 810-10
1 February 1999
3-5. EVAPORATIVE COOLING. Use evaporative cooling where the facility in question is
eligible for air conditioning, and evaporative cooling can provide the required indoor design
conditions based on the appropriate outdoor design conditions. In many locations where
evaporative cooling cannot provide the required indoor conditions year-round, give further
consideration to its use as a supplement to the primary cooling system when preliminary life
cycle calculations show the supplementary system to be cost effective. For special applications
where close temperature or humidity control is required, consider two-stage evaporative cooling
or indirect evaporative cooling in the life cycle cost analysis as a supplement to, not in lieu of,
the primary cooling system.
3-6. COMBINATION HEATING-COOLING SYSTEMS. Combine heating-cooling systems to
avoid duplication of system elements and to reduce costs.
a. All-Air Systems. Where outdoor design temperatures are -6 degrees C (20 degrees F)
or below, consider all air systems only in conjunction with double glazing, where sedentary
activities are a minimum of 1 meter (3 feet) from the glass, and where proper peripheral air
distribution is provided. Use preheat coils whenever the mixture of return air and ventilation air
at outside design temperature is below 2 degrees C (35 degrees F).
b. All-Water Systems. Use two-pipe dual-temperature systems for comfort applications
where feasible. Four-pipe systems may be used where two-pipe systems are not capable of
providing the specified indoor design conditions. Generally, three-pipe systems cannot be
justified for comfort applications and will not be used.
c. Air-Water Systems. Consider combinations of air and water systems such as radiant
heating supplemented with single-zone interior air supply for ventilation; hydronic systems at the
periphery of a building to offset skin transmission losses only, combined with the use of an air
system for space cooling and ventilation loads.
d. Heat Pumps.
(1) When considering the use of heat pumps, a thorough engineering analysis is
required. The requirement for possible additional power transmission and substation capacity,
the added impact of demand charge power consumption, and peak demands must all be
evaluated.
(2) Select heat pumps on the basis of life cycle cost effectiveness and include the
following types, including combinations, where advantageous:
(a) ground source heat pumps, using wells or ponds as a heat source
(b) where the perimeter spaces of a building must be heated and the interior cooled
concurrently, water-to-air heat pumps utilizing a closed-water loop system air source heat
pumps
e. Radiant Heating and cooling. Radiant heating and cooling systems are gaining wider
acceptance among HVAC designers. The designer should carefully review the most current
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