Conference Agenda

In 2018, commercial building space cooling alone consumed 9% of the world’s electricity, and the median age of the U.S. commercial building stock was 37 years. Heating, Ventilation, and Air Conditioning (HVAC) systems in older buildings often have limited controls and are expensive to upgrade. Current HVAC operational rules of thumb are outdated and do not prioritize energy efficiency. Here, we explore opportunities to reduce energy consumption in existing commercial buildings by explicitly considering both indoor and outdoor relative humidity (RH) in HVAC operational decision making through real-world experiments.

Air handling unit (AHU) set point temperatures are generally very low (50-55°F/10-12.8°C), to condense excess water from the outside air to maintain indoor RH below 50-60%, well below the maximum RH limits set by ASHRAE Standard 55 for occupant comfort. The air is then often reheated to maintain a comfortable indoor temperature. Relaxing indoor space RH constraints is thus expected to save energy. To quantify these energy savings, experiments were conducted in a commercial building at a corporate campus in Texas (IECC climate zone 2A, Hot Humid). Over the course of three weeks, the AHU Supply Air Temperature (SAT) set point was repeatedly increased from a baseline of 55°F (12.8°C) or 57°F (13.9°C) to 59°F (15°C). There are three main findings from these experiments: indoor RH increased from 55% to 65%, cooling load was reduced by up to 10%, and zone-level temperatures were minimally impacted (+0.45°F/0.25°C). Experimental conditions met ASHRAE Standard 55 comfort levels and maintained no risk of mold growth. We also measured secondary system effects, including the impacts on total air flow and reheat activity. The system was modeled using enthalpy calculations and good agreement was found between measured and calculated chilled water loads. This indicates that a simple model for estimating chilled water load can be created to understand how demand responds to changes in set points if accurate air flow estimates through the system are available. Our results indicate that relaxing RH constraints could significantly reduce cooling loads and provide a lever for demand flexibility, applicable in existing buildings with limited HVAC controls across the U.S.

Next-generation high-performance building technologies are envisioned where buildings are assembled on-site from factory manufactured modular elements, which would lead to better quality control, less material waste, more predictable schedules, and consequent savings in cost and energy consumption. Prefabricated building elements would enable the cost-effective integration of climate-responsive building envelopes, localized thermal comfort delivery systems, and decentralized heating and cooling technologies such as wall-embedded micro-heat pumps, sensors, embedded intelligence, and networking, lowering the cost of resilient and decarbonizing technologies. These modular elements can integrate the smart technology needed to provide scalable and cost-effective solutions with autonomous, occupant-responsive, healthy, and sustainable features.

To explore and evaluate these new high-performance building technologies and study novel interfaces for their interaction with occupants, a new test facility has been designed and constructed. The facility has a modular construction layout utilizing reconfigurable thermally active panels for walls, floor, and ceiling. The interior surface temperature of each 3.05m × 1.22m (4 ft. x 10 ft.) panel can be controlled individually by using a hot and cold water hydronic system. This allows for formulating different climate zones, building type conditions, and novel heating/cooling systems such as wall-embedded micro-heat pumps, and enables studies on localized comfort delivery, occupant comfort control, active building materials, and surface treatments, among others. This paper presents the overall design of the facility, modular building elements assembly, commissioning, and experimental results.

This paper discusses challenges that were overcome during seven technology demonstration projects in 50 occupied homes and businesses as part of an applied research and deployment program in Northern California. All technologies were commercially available but underutilized due to insufficient market awareness or lack of demonstrated energy savings in retrofit applications. These technologies included ducted mini-split heat pumps, grid-interactive heat pump water heaters, aerosol envelope sealing, phase change materials, induction cooktops, heat recovery dish machines, and night ventilation cooling.

Each of these projects included a field test component to quantify energy savings, cost-effectiveness, and measure durability. Many challenges were encountered and addressed along the way. Most significant was the outbreak of the COVID-19 pandemic during the program, severely complicating the analysis of energy savings because of the impact on usage patterns for both residential and commercial buildings. Other complications included modifications to HVAC systems during the test period, electrical and structural issues, health and comfort concerns, permitting requirements, selling of homes and businesses during the test period, and changes required to address occupant dissatisfaction with certain measures.

The results of the study provided a wealth of lessons learned for future researchers seeking to evaluate emerging technologies in occupied buildings. Valuable knowledge about technology performance was gained at all 50 sites, but accurate energy savings estimates were not always possible. This paper documents the challenges encountered and the range of creative solutions developed by the project team to overcome these challenges and maximize the knowledge gained from the program.

Burying your ventilation ducts inside attic insulation can save you money. Yet, this installation approach is not very common. Traditionally, and most commonly, ducts are suspended from the roof trusses and therefore located in the attic space. However, when ducts are partially or fully buried within loose fill insulation, the overall thermal resistance between the air inside the ducts and that attic increases significantly, resulting in less energy losses. There is also an expected increase in service-life of buried ducts since, when buried, they are not as exposed to extreme attic temperatures as suspended ducts.

Some of the previous work on buried ducts has underestimated the thermal benefits of buried ducts. This paper presents how the thermal performance of buried ducts can be more accurately assessed depending on various variables such as duct diameter, duct insulation value, attic insulation level and material, as well temperature boundary conditions.

In addition, this paper investigates reasons for a currently lower adoption rate of buried ducts and also identifies potential market barriers, installations issues, and any other industry concerns. Further, other reasons are considered related to the complexity of the compliance and enforcement process, and any other regulatory context which complicates the adoption of buried ducts.

Data centers are growing exponentially, and their power demand is increasing significantly owing to its important role in data processing and storage. Recently, the free cooling method through an economizer has been used to reduce power consumption in data centers. However, studies on achieving high energy efficiency and reducing power consumption for data center operations are limited. Moreover, owing to the weather-dependent nature of free cooling methods, a regional analysis is essential. The objective of this study is to compare and optimize the free cooling method using an economizer according to the region. TRNSYS was used to model data center systems. Two types of economizers including air-side economizer (ASE) and water-source economizer (WSE) systems were modeled with three weather data sets including Ottawa, Seoul, and Cairo. As a result, at a server room temperature of 27 °C, power usage effectiveness (PUE) was 0.11 lower in the WSE than in the ASE. However, the lower the room temperature, the greater the decrease in the PUE of the WSE. In Ottawa, ASE had an advantage owing to low temperature. However, in Cairo, WSE had an advantage owing to high temperature and dry air.