2016 ASHRAE Annual Conference

Buildings account for roughly 40 percent of all energy consumption in the United States, according to the U.S. Department of Energy (DOE).  As a result, improving the energy efficiency of buildings should be a top priority for building owners, design professionals, utility companies, allied industries, the federal government, and cities across the country. These diverse groups are working not just to build efficient new construction, but also to improve aging properties through energy retrofits.

Energy retrofits for commercial buildings focus on installing high-efficiency boilers, motors, and lighting.  However, efficiency gains from equipment can be offset by occupant discomfort due to inefficient windows, which can account for 25 percent of a typical building’s heating load in cold climates and 50 percent of the cooling load in warm climates, according to the U.S. Environmental Protection Agency.  Because equipment is sized to service a specific building’s needs, improving a building’s envelope should be addressed first, so that smaller equipment can be specified, saving on the upfront and ongoing costs.

A variety of options exist for improving the energy performance of existing commercial glazing systems including: Application of interior window films – solar heat gain. Complete window rip-out and replacement – solar heat gain and improved U-factor. Interior commercial storm windows - improved U-factor. Interior installed Low-E retrofit insulating glass unit - solar heat gain and improved U-factor

Each alternative has specific performance benefits and associated cost and convenience implications.  Solar heat gain is a primary problem with most commercial buildings having lower performance, single-glazing, regardless of climate zone.  This leads to increased cooling loads, larger sizing of HVAC equipment, higher energy costs and lower occupancy comfort levels.  Any improvement in the glazing system should incorporate technology to reduce the impact of solar heat gain through the use of high performance low-e coatings.  Concurrently for heating dominant climate zones, a substantial reduction in U-factor acts in parallel to reduce HVAC demand for heating, reduces energy costs and improve occupancy comfort levels.

This paper compares the performance benefits, cost implications and occupancy comfort factors for each of these systems with a focus on the advantages of an interior installed low-e retrofit insulating glass unit.  Such a system has been demonstrated to provide the full benefits of a rip-out and replacement at approximately 40% of the installed cost.  It includes independent case study energy analysis, installation and cost comparison, testimonial on occupancy comfort and sustainability attributes.

As a result of architectural trends, technological advances and increasing focus on energy efficiency, buildings with high performance envelope and HVAC systems, large window-to-wall ratio, motorized window shades, smart lighting controls and Building Automation Systems (BAS) have found their way into the market. With a focus on this building type and dynamic environments such as offices in perimeter zones, this paper presents results of a long-term field study with a large number of human test-subjects, aiming to advance our understanding of (a) occupants’ interactions with shading and electric lighting control systems; and (b) their preferences and satisfaction with the visual environment.

To investigate the impact of  environmental control on occupants’ comfort, satisfaction level and subjective productivity, four identical side-by-side offices with different control setups and interfaces, ranging from fully automated to fully manual and from low-level of accessibility (wall switches) to high-level of accessibility (remote controllers or modular web interfaces) were selected for the purpose of this study. The experimental study includes monitoring of physical variables, actuation and operating status of building systems and online surveys of occupants’ perception of environmental variables as well as their personal characteristics and attributes.

Compared to previous studies conducted in buildings with non-motorized blinds and artificial lights without dimming options, our results show substantial differences in dynamics and frequency of human-shading and –electric lighting interactions for buildings equipped with this advanced technology. Moreover, it was found that comfort with amount of light and visual conditions, satisfaction with window view, and subjective productivity are all maximized in offices with manual control setups and occupants are comfortable with a wide range of indoor illuminance when they have control over their environment. These results also demonstrate occupants’ strong preference for customized indoor climate and the outcomes support the development of personalized controls, which will be discussed in the paper.