This thesis documents the usefulness and accuracy of uncalibrated simulations to determine for what end-uses these simulations should be used. The study was divided into three segments 1)comparison of the accuracy of two simulation models, massless and advanced, against measured data 2) comparison of the results from two simulations models, simplistic and massless, to determine the sensitivity of envelope shape and details for two weather conditions 3) identification of the parameters that have a significant impact on the simulation output. Five buildings were selected as the test sample. Four of the buildings were multi story commercial buildings. The fifth was a single-family residential house. For the first segment of the study two simulation models were created for all the buildings; the massless model with emphasis on the envelope using massless construction and typical values for system parameters and the advanced model with the inclusion of thermal mass and extensive as-built details of the systems. For the second part of the research the simplistic model was created having a single floor one-zone with glazing and conditioned areas equivalent to the massless model. The sensitivity analysis was done using the massless model and selected variables from the loads and systems as sensitivity parameters. By following the procedure mentioned, it was found that uncalibrated simulation models do not depict the real operating conditions of a building. For some cases the simulated values are higher than the measured data while for others they are significantly lower. The CV (RMSE) between the measured and simulated values ranges from 30 to 150%. From the comparison of the simplistic and massless model, it was concluded that the outer envelope shape and details have an impact on the heating and cooling energy use irrespective of the weather conditions. For internally load dominated buildings this impact is more on the heating loads than on the cooling loads. The conclusions from the sensitivity analysis were that outside air fraction and the total supply air have the most significant impact on the simulation output while thermal mass has a small impact.

The need for efficient, sustainable, and planned utilization of resources is ever more critical. In the U.S. alone, buildings consume 34.8 Quadrillion (1015) BTU of energy annually at a cost of $1.4 Trillion. Of this energy 58% is utilized for heating and air conditioning. Several building energy analysis tools have been developed to assess energy demands and lifecycle energy costs in buildings. Such analyses are also essential for an efficient HVAC design that overcomes the pitfalls of an under/over-designed system. DOE-2 is among the most widely known full building energy analysis models. It also constitutes the simulation engine of other prominent software such as eQUEST, EnergyPro, PowerDOE. Therefore, it is essential that DOE-2 energy simulations be characterized by high accuracy. Infiltration is an uncontrolled process through which outside air leaks into a building. Studies have estimated infiltration to account for up to 50% of a building’s energy demand. This, considered alongside the annual cost of buildings energy consumption, reveals the costs of air infiltration. It also stresses the need that prominent building energy simulation engines accurately account for its impact. In this research the relative accuracy of current air infiltration calculation methods is evaluated against an intricate Multiphysics Hygrothermal CFD building envelope analysis. The full-scale CFD analysis is based on a meticulous representation of cracking in building envelopes and on real-life conditions. The research found that even the most advanced current infiltration methods, including in DOE-2, are at up to 96.13% relative error versus CFD analysis. An Enhanced Model for Combined Heat and Air Infiltration Simulation was developed. The model resulted in 91.6% improvement in relative accuracy over current models. It reduces error versus CFD analysis to less than 4.5% while requiring less than 1% of the time required for such a complex hygrothermal analysis. The algorithm used in our model was demonstrated to be easy to integrate into DOE-2 and other engines as a standalone method for evaluating infiltration heat loads. This will vastly increase the accuracy of such simulation engines while maintaining their speed and ease of use characteristics that make them very widely used in building design.

A procedure has been developed for the preliminary selection of high-performance systems for office buildings in hot and humid climates. High-performance building systems and components were surveyed for buildings in the U.S., which were applicable for office buildings in hot and humid climates. This research developed a calibrated DOE-2.1e simulation model of a prototypical large office building. In addition, a Simplified Geometry DOE-2.1e (SGDOE-2.1e) model, was also developed, which used a simplified geometry to demonstrate the use of a proposed easy-to-use tool. The calibrated DOE-2.1e simulation model and the SGDOE-2.1e were compared and showed a good match with each. The SGDOE-2.1e model was then further modified based on the ASHRAE Standard 90.1-1999 commercial building energy code. A code-compliant (ASHRAE Standard 90.1-1999) SGDOE-2.1e simulation model was then used as a baseline for the evaluation of the high-performance measures. A total of 14 high-performance measures were implemented including the energy savings, while the comfort level was maintained based on the ASHRAE comfort zone. In addition to the 14 high-performance measures, solar thermal and solar PV system analysis were integrated with the SGDOE-2.1e simulation model to further reduce the annual energy use. Finally, specifications of the proposed easy-to-use simulation tool were developed. This tool includes options to choose systems from the 14 high-performance measures and solar systems. The proposed easy-to-use systems selection tool can be used for new building practitioners and existing building owners as well to evaluate the performance of their new buildings compared to the ASHRAE Standard 90.1-1999 code-compliant building, and to assess the feasibility of implementing high-performance measures to their existing buildings in terms of energy and cost savings.

The commercial buildings sector in the United States used 18 percent (17.93 Quads) of the U.S. primary energy in 2006. Office buildings are the largest single energy consumption category in the commercial buildings sector of the United States with annual energy consumption around 1.1 Quads. Traditional approaches used in commercial building designs are not adequate to save energy in both depth and scale. One of the most effective ways to reduce energy consumption is to improve energy performance of HVAC systems. High-performance HVAC systems and components, as well as application of renewable energy sources, were surveyed for buildings in hot and humid climates. An analysis of performance and energy saving potential estimation for selected HVAC systems in hot and humid climates was developed based on energy consumption simulation models in DOE-2.1E. A calibrated energy consumption model of an existing office building located in the hot and humid climate conditions of Texas was developed. Based on this model, the energy saving potential of the building was estimated. In addition, energy consumption simulation models were developed for a new office building, including simulation of energy saving measures that could be achieved with further improvements of HVAC system above the energy conservation codes requirements. The theoretical minimum energy consumption level for the same office building was estimated for the purpose of evaluating the whole building energy efficiency level. The theoretical minimum energy consumption model of the office building was designed to provide the same level of comfort and services to the building occupants as provided in the actual building simulation model. Finally, the energy efficiency of the building that satisfies valid energy conservation codes and the building with an improved HVAC system was estimated based on theoretically minimum energy consumption level. The analysis provided herein can be used for new building practitioners and existing building owners to evaluate energy reduction potential and the performance of innovative technologies such as dedicated outdoor air system, displacement ventilation, improved cooling system efficiency, air source heat pumps and natural gas heat pumps.