HVAC energy efficiency and noise

Heating energy

Water heating is more efficient for heating buildings and was the standard many years ago. Today forced air systems can double for air conditioning and are more popular. The most efficient central heating method is geothermal heating.

Energy efficiency can be improved even more in central heating systems by introducing zoned heating. This allows a more granular application of heat, similar to non-central heating systems. Zones are controlled by multiple thermostats. In water heating systems the thermostats control zone valves, and in forced air systems they control zone dampers inside the vents which selectively block the flow of air.

Air conditioning energy

The performance of vapor compression refrigeration cycles is limited by thermodynamics. These AC and heat pump devices move heat rather than convert it from one form to another, so thermal efficiencies do not appropriately describe the performance of these devices. The Coefficient-of-Performance (COP) measures performance, but this dimensionless measure has not been adopted, but rather the Energy Efficiency Ratio (EER). To more accurately describe the performance of air conditioning equipment over a typical cooling season a modified version of the EER is used, and is the Seasonal Energy Efficiency Ratio (SEER). The SEER article describes it further, and presents some economic comparisons using this useful performance measure.

Moisture and Humidity Control

Uncontrolled moisture indoors can cause major damage to the building structure, as well as to furnishings and to finish materials like floors, walls, and ceilings. Uncontrolled moisture can trigger mold growth which not only damages the school facility, but can lead to health and performance problems for students and staff.

Primary causes of indoor moisture problems in new schools include:

  • Use of building materials that were repeatedly or deeply wetted before the building was fully enclosed
  • Poor control of rain and snow, resulting in roof and flashing leaks
  • Wet or damp construction cavities
  • Moisture-laden outdoor air entering the building
  • Condensation on cool surfaces

Controlling moisture entry into buildings and preventing condensation are critical in protecting buildings from mold and other moisture-related problems, including damage to building components.

Designing for Efficient Operations and Maintenance

  • Ensure that all system components, including air handling units, controls, and exhaust fans are easily accessible.

To help ensure that proper operation and maintenance of HVAC system components will be performed, it is critical that the designer makes the components easily accessible. AHUs, controls, and exhaust fans should not require a ladder, the removal of ceiling tiles, or crawling to gain access. Rooftop equipment should be accessible by way of stairs and a full-sized door, not a fixed ladder and a hatch.

  • Label HVAC system components to facilitate operations and maintenance.

Labeling of HVAC components is an inexpensive and effective method for helping facilities personnel properly operate and maintain the HVAC systems. The labels should be easy to read when standing next to the equipment, and durable to match the life of the equipment to which they are attached. At a minimum, the following components should be labeled in each ventilation zone of the school and should correspond with the HVAC diagrams and drawings. “AHU” refers to any air handling unit that is associated with outdoor air supply.

  • The number or name of the AHU (e.g., AHU ##, or AHU for West Wing)
  • The outdoor air (OA), supply air (SA), return air (RA), and exhaust or relief air (EA) connections to the AHU, each with arrows noting proper airflow direction
  • The access door(s) for the air filters and the minimum filter dust-spot (or MERV) efficiency (Air Filters, minimum xx% dust spot efficiency)
  • The filter pressure gauge and the recommended filter change pressure (Filter Pressure, max 0.x in. w.g.)
  • The access door(s) for the condensate drain pan (Drain Pan)
  • Other pertinent access doors such as to energy recovery ventilation wheels or plates (Energy Recovery Ventilation Unit)
  • The minimum amount of outdoor air for each AHU (### CFM minimum during occupied times)
  • The outdoor air damper (OA Damper), with special marks noting when the damper is in the fully closed (Closed), fully opened (open), and minimum designed position (Min)
  • If a motorized relief damper is installed (EA Damper), note the same positions as above.
  • The access door to any outdoor air controls (OA Control(s)) such as damper position adjustments, outdoor airflow measuring stations, resets, fuses, and switches)
  • Breakers for exhaust fans (Exhaust Fan ##), AHU, unit ventilators
  • Access doors for inspection and maintenance of air ducts
  • Any dampers and controls for air side economizers (as appropriate)
  • The number or name of all exhaust fans, including the air quantity exhausted (EF##, ###CFM)