Learning occupants’ indoor comfort temperature through a Bayesian inference approach for office buildings in United States

A carefully chosen indoor comfort temperature as the thermostat set-point is the key to optimizing building energy use and occupants’ comfort and well-being. ASHRAE Standard 55 or ISO Standard 7730 uses the PMV-PPD model or the adaptive comfort model that is based on small-sized or outdated sample data, which raises questions on whether and how ranges of occupant thermal comfort temperature should be revised using more recent larger-sized dataset. In this paper, a Bayesian inference approach has been used to derive new occupant comfort temperature ranges for U.S. office buildings using the ASHRAE Global Thermal Comfort Database. Bayesian inference can express uncertainty and incorporate prior knowledge. The comfort temperatures were found to be higher and less variable at cooling mode than at heating mode, and with significant overlapped variation ranges between the two modes. The comfort operative temperature of occupants varies between 21.9 and 25.4 °C for the cooling mode with a median of 23.7 °C, and between 20.5 and 24.9 °C for the heating mode with a median of 22.7 °C. These comfort temperature ranges are similar to the current ASHRAE standard 55 in the heating mode but 2–3 °C lower in the cooling mode. The results of this study could be adopted as more realistic thermostat set-points in building design, operation, control optimization, energy performance analysis, and policymaking

Computational Approach to Predict Thermal Comfort Levels at Summer Peak Conditions in Passive House Based on Natural Ventilation

The Passive House building concept has been widely-researched in relation to its performance, especially the aspects of energy consumption and thermal properties. Nevertheless, the design stages still do not present a dynamic thermal comfort predictive process that aids investigating the design performance. This research focuses on a methodology that calculates summer months peak conditions in a pilot Passive House dwelling in the United Kingdom, based on the natural ventilation plan effectiveness in maintaining sufficient airflows, while the mechanical ventilation-heat recovery summer bypass mode is on. The methodology’s technical aspect involves EnergyPlus dynamic simulations, Ansys computational fluid dynamics simulations, and the Centre for the Built Environment Thermal Comfort Tool. The results presented showed a  spectrum of predicted percentages of people dissatisfied ranging between 13.3-99.2% for different airspeeds. The majority were of uncomfortable levels at summer peak days. Results also presents the ranges of thermal comfort parameters simultaneously. The findings produced by the methodology may add a more comprehensive description to the thermal comfort status during design stages, employing the integrated software combination

Use of calibrated building simulation to investigate comfort conditions in a healthcare facility

Design activity regarding healthcare buildings must not only address the energy efficiency aspects but also account for the indoor thermal comfort conditions. Indeed, the occupants of this category of buildings are affected by different kinds of health issues. Thus, particular efforts are required in order to ensure conditions adequate for therapies and medical treatments. Simulation can be a helpful tool in designing new buildings, particularly in case of complex clinics and hospitals. When analyzing existing facilities, a proper calibration is a necessary step to reduce discrepancies between simulated and measured performance. This improves the reliability of the model itself and allows its use for many purposes, from the assessment of energy performance to the evaluation of indoor thermal comfort, under a broader range of operating conditions and use patterns. In the present contribution, a calibrated model of a healthcare facility in Vienna, Austria, was developed for the assessment of both thermal performance and comfort conditions. The facility, built in the early ‘90s with later expansions, consists of different rooms and spaces in which several therapeutic activities are performed. Long-term measurements of the air temperature were conducted every 10 minutes for the period between March and June 2015 and used for calibrating the model. During the same period, occupants were interviewed concerning their thermal comfort sensations and detailed shortterm measurements were collected to calculate thermal comfort indicators, including Fanger’s Predicted Mean Vote and Predicted Percentages of Dissatisfied. The same indices were also calculated through the calibrated simulation model and compared to experimental results and subjective evaluations. The resulting model is finally used to extrapolate the assessment of thermal comfort conditions beyond the measurement period

Out with the power outages: Peak load reduction in the developing world.

In developing economies with hot climates, the summer time peak load due to space cooling frequently results in power outages, as the outdated grid is not able to keep up with the demand. In this paper, computer simulation is carried out to develop and analyse a two-pronged strategy for peak load reduction, utilizing a relatively new thermal comfort model, together with variation in building fabric properties. The thermal comfort model is used to dynamically set the cooling setpoint temperature through implementation in MATLAB, with the building is simulated using EnergyPlus V8.8, both linked for co-simulation using the Buildings Control Virtual Test Best (BCVTB). Compared to the baseline with a typical fixed cooling setpoint of 24°C, the newly developed cooling setpoint control strategy resulted in a reduction of 20% and 41% in the peak load and monthly energy demand respectively. This came at the cost of increasing the average PPD% from 7.2% to 12.6%. This work may be of interest to practitioners wishing to address demand management at the building scale. Moreover, it may be readily extended to analyse a group of buildings towards demand management at a higher level of aggregation

Energy Performance and Comfort Level in High Rise and Highly Glazed Office Buildings

Thermal and visual comfort in buildings play a significant role on occupants' performance but on the other hand achieving energy savings and high comfort levels can be a quite difficult task especially in high rise buildings with highly glazed facades. Many studies suggest that the energy needed to keep the interior conditions at required comfort levels in buildings depends on several factors such as physical and optical properties of building elements, indoor and outdoor climate and behaviour of the occupants, etc. Moreover depending on the different orientation of building facade, the impact of these parameters might vary. The buildings are usually designed without paying much attention to this fact. The needs of each building zone might differ greatly and in order to achieve better indoor environment, different actions might be needed to taken considering the individual characteristics of each zone. In the proposed research the possibilities of evaluating building energy and comfort performance simultaneously taking into account the impact of facade orientation with use of whole building energy simulation tools are investigated through a case study

PREDICTIVE MODELING OF AUTOMATED BUILDING FACADE ELEMENTS TO ATTAIN THERMAL COMFORT IN PASSIVELY CONDITIONED BUILDINGS IN DIFFERENT CLIMATES

Climate change, along with corresponding weather extremes, are creating new and pressing problems for the built environment. Buildings are the largest contributor to climate change. The main hypothesis for this research work is that an automated dynamic façade can provide whole year thermal comfort in a passively heated and cooled building by using predictive modeling of short-term future weather conditions. The dynamic facade should be adaptable to different climates, weather extremes and climate change. Predictive simulation requires using a weather forecast to predict the performance of a building and then modify the shading and ventilation rate to optimize the building thermal comfort for a single day. The goal of the dissertation was to develop a method for designing dynamic predictive façades to maximize thermal comfort in most climates and weather conditions. The research for the dissertation was conducted through computer simulations in the 15 different climate zones of the United States (considering both historic climate data, as well as predicted climate change data for the years 2050 and 2080), and an experimental study. The computer simulations, using EnergyPlus and custom scripts, were used to optimize the façade for a scaled physical model of the façade and the individual building elements. EnergyPlus simulations were also used for the predictive modeling in the experimental study. A test cell with one of the designed façade systems and controls was studied during the winter, spring and summer and compared to simulation results. The results of both the simulation study and the test cell were similar so modifications to the predicted model and predicted control procedure can be studied further with simulation only. The simulations and the physical experiment results show that it is possible to achieve thermal comfort in a passively heated and cooled building in at least 10 of the 15 different climate zones in the United States

Short-Term Reduction of Peak Loads in Commercial Buildings in a Hot and Dry Climate

abstract: A major problem faced by electric utilities is the need to meet electric loads during certain times of peak demand. One of the widely adopted and promising programs is demand response (DR) where building owners are encouraged, by way of financial incentives, to reduce their electric loads during a few hours of the day when the electric utility is likely to encounter peak loads. In this thesis, we investigate the effect of various DR measures and their resulting indoor occupant comfort implications, on two prototype commercial buildings in the hot and dry climate of Phoenix, AZ. The focus of this study is commercial buildings during peak hours and peak days. Two types of office buildings are modeled using a detailed building energy simulation program (EnergyPlus V6.0.0): medium size office building (53,600 sq. ft.) and large size office building (498,600 sq. ft.). The two prototype buildings selected are those advocated by the Department of Energy and adopted by ASHRAE in the framework of ongoing work on ASHRAE standard 90.1 which reflect 80% of the commercial buildings in the US. After due diligence, the peak time window is selected to be 12:00-18:00 PM (6 hour window). The days when utility companies require demand reduction mostly fall during hot summer days. Therefore, two days, the summer high-peak (15th July) and the mid-peak (29th June) days are selected to perform our investigations. The impact of building thermal mass as well as several other measures such as reducing lighting levels, increasing thermostat set points, adjusting supply air temperature, resetting chilled water temperature are studied using the EnergyPlus building energy simulation program. Subsequently the simulation results are summarized in tabular form so as to provide practical guidance and recommendations of which DR measures are appropriate for different levels of DR reductions and the associated percentage values of people dissatisfied (PPD). This type of tabular recommendations is of direct usefulness to the building owners and operators contemplating DR response. The methodology can be extended to other building types and climates as needed.Dissertation/ThesisM.S. Architecture 201

An Experimental and Numerical Case Study of Passive Building Cooling with Foundation Pile Heat Exchangers in Denmark

Technologies for energy-efficient cooling of buildings are in high demand due to the heavy CO2 footprint of traditional air conditioning methods. The ground source heat pump system (GSHP) installed at the Rosborg Gymnasium in Vejle (Denmark) uses foundation pile heat exchangers (energy piles). Although designed for passive cooling, the GSHP is used exclusively for heating. In a five-week test during the summer of 2018, excess building heat was rejected passively to the energy piles and the ground. Measured energy efficiency ratios are 24–36 and the thermal comfort in conditioned rooms is improved significantly relative to unconditioned reference rooms. A simple model relating the available cooling power to conditioned room and ground temperatures is developed and calibrated to measured test data. Building energy simulation based estimates of the total cooling demand of the building are then compared to corresponding model calculations of the available cooling capacity. The comparison shows that passive cooling is able to meet the cooling demand of Rosborg Gymnasium except for 7–17 h per year, given that room temperatures are constrained to < 26 °C. The case study clearly demonstrates the potential for increasing thermal comfort during summer with highly efficient passive cooling by rejecting excess building heat to the ground