Chapter 8 Overview

Office heating, ventilating and air-conditioning (HVAC) systems are responsible for controlling office temperature and humidity as well as circulating fresh air throughout a building. HVAC systems are relatively energy intensive and represent a significant portion of an office’s energy consumption—51% on average in office buildings in the U.S. (35% heating, 6% ventilating, 10% cooling).1

The annual breakdown of HVAC energy draw among heating, ventilating and cooling enduses can vary widely depending on the geographic location of an office. It is not uncommon for larger office buildings to require cooling year-round because of the substantial heating effect of office equipment, lighting, water heaters and people within the building. Additionally, HVAC systems often operate at high levels during

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periods of regional peak load (for example, hot summer days) when electricity prices are highest, which can significantly increase a company’s power costs.

HVAC designs vary widely across building types. Standard HVAC systems are considered "active" technologies, which require energy input to drive mechanical equipment. A typical HVAC system involves components including chillers, boilers, air ducts, fans and heat exchangers. Alternative "passive" cooling technologies are rarer, but typically much more energy efficient. These technologies include: natural ventilation, evaporative cooling systems and radiative heating and cooling systems.

A range of methods can be used to decrease the energy draw of an HVAC system, but one of the easiest is reducing a building’s cooling load by reducing waste heat generated by inefficient lighting systems, office equipment and water heating systems. These measures are extremely cost effective and should be undertaken before any upgrade to HVAC equipment is considered. If HVAC equipment has recently been upgraded to an efficient model, maintaining system performance at the proper level of efficiency should be a primary consideration.

Like lighting quality, HVAC performance is key to the comfort and productivity of office occupants. In fact, many HVAC efficiency upgrades have the added benefit of improving air quality and comfort throughout an office (e.g., precise tuning of thermostat controls or installation of outside air economizers). An HVAC engineer should ensure that efficiency upgrades to an office HVAC system do not cause any reduction in the quality of an office environment.

The recommended efficiency improvement strategies for HVAC are presented in the order in which they should be undertaken: 1) ensure that proper maintenance is being performed; 2) investigate possibilities for reducing heating/cooling load; 3) calibrate and tune system controls; and 4) consider upgrading HVAC equipment.

Note: Costs and energy savings for HVAC efficiency measures vary widely depending on building characteristics. In this section, examples of costs and savings potential are presented through financial case studies.

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