Retrotec USACE - Manual (Page 403)

Appendix L L3
1.7 Moisture Penetration
1.7.1 Reduce air leakage.
1.7.2 Install vapor barriers in walls.
1.7.3 Install vapor barriers in ceilings and roofs.
1.7.4 Install inoperable windows.
2 HVAC Systems
2.1 Ventilation
2.1.1 Convert a constant air volume system (CAV) into a variable air volume system (VAV)
with variable speed drives on fan motors. A VAV system is designed to deliver only the
volume of air needed for conditioning the actual load.
2.1.2 Reduce air fl ow rates in HVAC ducts when possible
2.1.3 Install an economizer cycle. Instead of operating on a fi xed minimum airfl ow supply, an
economizer allows the HVAC system to utilize outdoor air by varying the supply airfl ow
according to outdoor air-conditions, usually using an outdoor dry bulb temperature sen-
sor or return air enthalpy (enthalpy switchover). Enthalpy switchover is more effi cient,
because it is based on the true heat content of the air.
2.1.4 Close outdoor air dampers when outdoor air is not needed.
2.1.5 Minimize exhaust and makeup (ventilation) rates when possible. Makeup air rate de-
pends on the needs of ventilation for personnel, exhaust air from workspaces, overcom-
ing infi ltration, machine air needs, and federal, state, and local requirements.
2.1.6 Use operable windows for ventilation during mild weather, when available.
2.1.7 Shut off unneeded exhaust fans and reduce use where possible.
2.1.8 Convert mixing air supply system into displacement ventilation system to create a
temperature stratifi cation in spaces with predominant cooling needs and contaminant
stratifi cation in spaces with combined contaminant and heat sources. Displacement
ventilation increases ventilation and heat removal effi ciency in such spaces.
2.1.9 Consider replacement of all-air HVAC system with a combination of a dedicated out-
door air system complemented by a hydronic low-temperature difference radiant panel
heating and cooling system.
2.1.10 Review current industrial facility conditions and install new local ventilation, cooling,
and heating systems and controls, as well as general HVAC systems to match new pro-
cesses and loads.
2.1.11 Convert constant volume central exhaust system into a demand-based controlled cen-
tral exhaust system when possible.
2.1.12 Reduce dilution ventilation airfl ow rate by encapsulating processes or using local ex-
hausts.
2.1.13 Avoid supply air short-circuiting by proper selection of supply outlets and exhausts lo-
cations.
2.1.14 Use dedicated outside air systems (DOAS) for ventilation and humidity control with a
complementary heating and cooling system to reduce energy consumption and reduce
the risk of mold and mildew growth.