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• A comprehensive analysis of data from commercial buildings in United States to identify operational problems and opportunities. • These opportunities were not strongly correlated with building vintage, size, or building type, but were reflective of how the buildings are operated. • This analysis showed that opportunities to improve building operations exist in almost every building. • There was wide variation in whole building energy savings, ranging from 0 to 50% and 0 to 18 $/m2 with median percent annual whole building savings of 12% and median normalized annual cost savings of $1.75/m2. In the United States, as much as 30% of the 19 EJ that commercial buildings consume is considered excess. Much of the excess energy is due to the inability to manage building operations efficiently. Because almost 20% of the total primary energy consumption is associated with commercial buildings, significant energy reductions in this sector are needed to mitigate climate change. Therefore, many cities and states are mandating periodic "tune-ups" of these buildings to eliminate excess energy consumption. Although the benefits of tune-ups and retro -commissioning are clear, focusing these mandates to look for specific opportunities has been a challenge because of the lack of studies that document the prevalence of opportunities. Therefore, we analyzed building automation system data from 151 buildings across the United States to document common operational problems and opportunities to improve building operations. This analysis showed that opportunities to improve building operations exist in almost every building. These opportunities were not strongly correlated with building vintage or size, but were reflective of how the buildings are operated. The prevalence of the top 20 opportunities ranged between 74% and 23%, with 40% of these associated with air-handling units. The rest of the opportunities are associated with schedules, chilled and hot-water distribution, and zone controls. Of the 151 buildings, 69 of them implemented corrective actions of some or all opportunities that were identified. Implementation varied across the Re-tuning categories, with 60% for schedule opportunities, 50% for zone opportunities, over 40% for the air-handling unit and hot-water opportunities, and 35% of the chilled-water opportunities. There was wide variation in whole building energy savings, ranging from 0 to 50% and 0 to 18 $/m2 with median percent annual whole building savings of 12% and median normalized annual cost savings of $1.75/m2. In addition to documenting these key findings, the paper provides a list of opportunities that can be automatically and continuously identified and corrected and offers a list of those opportunities that should be the focus of the mandates. [ABSTRACT FROM AUTHOR]

The origin, structure and continuing development of a model of time-varying energy consumption in the US commercial building stock is described. The model is based on a flexible structure that disaggregates the stock into various categories (e.g. by building type, climate, vintage and life cycle stage) and with attributes assigned to each of these (e.g. floor area and energy-use intensity by fuel type and end use) based on historical data and user-defined scenarios for future projections. In addition to supporting the interactive exploration of building stock dynamics, the model has been used to study the likely outcomes of specific policy and innovation scenarios targeting very low future energy consumption in the building stock. Model use has highlighted the scale of the challenge of meeting targets stated by various government and professional bodies, and the importance of considering both new construction and existing buildings. Sont decrits l'origine, la structure et le developpement continu d'un modele de consommation d'energie variable dans le temps pour le parc bati commercial americain. Le modele est base sur une structure souple qui decompose le parc en differentes categories (par ex. selon le type de batiment, le climat, l'anciennete et le stade dans le cycle de vie) et avec des attributs assigne a chacune de celles-ci (par ex. surface au plancher et intensite d'utilisation de l'energie selon le type de combustible et l'utilisation finale) en se basant sur les donnees historiques et les scenarios definis par l'utilisateur pour de futures previsions. Outre le soutien apporte a l'exploration interactive de la dynamique du parc bati, le modele a ete utilise pour etudier les resultats probables d'une politique specifique et de scenarios innovants visant a une tres faible consommation energetique future dans le parc bati. L'utilisation du modele a mis en evidence l'ampleur de la difficulte a atteindre les objectifs fixes par les differents organismes publics et les diverses organisations professionnelles, et l'importance qu'il y a a prendre en compte a la fois les constructions neuves et les batiments existants. Mots cles: parc bati, changement climatique, rendement energetique, emissions, energie, basse energie, constructions neuves, planification, renovation, postcablage/solarisation [ABSTRACT FROM AUTHOR]