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Calculation of heat transfer from building foundations is a computationally intensive three-dimensional problem that can require several weeks to solve using current computing hardware. The Kiva numerical framework was developed to compare foundation heat transfer calculation methods and determine approaches that reduce computation time without sacrificing a balance of capability, ease-of-use, and accuracy. This paper demonstrates the application of the Kiva framework to determine an accurate method of approximating three-dimensional heat transfer effects using two-dimensional coordinate systems. In two-dimensions, problems that would otherwise take days or weeks to solve can be solved in less than a minute. Three existing two-dimensional approximation methods along with a new boundary layer adjustment method are tested across a range of foundation types, shapes, and insulation configurations. The boundary layer adjustment method is shown to provide results within 3% mean absolute deviation from the three-dimensional solution. [ABSTRACT FROM PUBLISHER]

KivaTMwas developed to evaluate the energy performance of building foundation designs. This free, open-source tool can be integrated into existing annual building energy simulation software tools. This article describes the verification of Kiva's six numerical solution methods against the International Energy Agency Building Energy Simulation Test and Diagnostic Method test cases for slab-on-grade heat conduction. Comparisons of accuracy, computation time and stability between the numerical solution methods revealed their advantages and disadvantages. While each solution method satisfactorily approximates slab heat loss, many methods exhibited stability issues or required substantially longer computation time. The method least affected by these two challenges was the alternating-direction implicit (ADI) method. Kiva features four approaches of initializing the soil temperatures for an annual simulation. A new accelerated initialization approach is shown to reduce the required years of pre-simulation. The combination of the ADI method and accelerated initialization reduces the total computation time by 95% relative to the traditional implicit solutions. [ABSTRACT FROM PUBLISHER]

This study evaluates the energy savings resulting from the remediation of coil and filter fouling in constant air volume HVAC systems in residential and small commercial buildings. A computer model was developed to simulate the behavior of buildings and their duct systems under various levels of fouling. The model was verified through laboratory and field testing. Parametric simulation and sensitivity analysis results suggest that although fouling can have an impact on both air conditioner and furnace energy use, for the levels of fouling found in the literature, energy savings will be negligible for residential buildings and negative for small commercial buildings. [ABSTRACT FROM PUBLISHER]

The potential for natural ventilation in building design to reduce associated building cooling and fan energy consumption makes it an area of great interest. However, its increased use is dependent on the availability of accurate modeling tools to predict its impact on a given building design. Network airflow models have been developed to predict airflows within buildings and between indoor and outdoor, which usually require user-supplied thermal conditions in a space. Because of the dependency between airflow and space temperature in naturally ventilated buildings, network airflow models need to be incorporated into whole building energy simulation models. This study reviews existing network models that may be used for natural ventilation design and investigates the capability and accuracy of four prevalent network airflow models to simulate a wide range of natural ventilation scenarios, with varying combinations of geometry and natural ventilation driving forces. Comparison of predictions with measurements obtained from literature shows that the tools are generally able to predict natural ventilation rates within 35% except for the wind-driven single-sided ventilation case. The article indicates some significant needs for improvement of the network airflow model for natural ventilation applications. [ABSTRACT FROM AUTHOR]

In this article, the Interzone Temperature Profile Estimation solutions are first utilized to carry out a frequency analysis for the foundation heat transfer to determine the effect of indoor air and ambient air temperature fluctuations on the variation of the foundation heat loss/gain. Then, a frequency-domain regression-based method is used to develop transfer functions for ground-coupled surfaces. The regression frequency-domain method is tested and validated using one-dimensional heat transfer for above-grade walls. It is found that the proposed method provides a more effective alternative than numerical methods to estimate conduction transfer function coefficients for building foundations and thus can be easily implemented in whole-building simulation programs. [ABSTRACT FROM AUTHOR]

In this article, a two-dimensional transient ground-coupled numerical model for slab-on-grade foundation is developed and integrated into EnergyPlus. A verification analysis is first presented to ensure that the developed building foundation heat transfer module is properly implemented within EnergyPlus. Then, predictions from the developed model are compared with those obtained from a simplified building foundation model currently used in EnergyPlus. Finally, the impact of several foundation insulation configurations on the annual variation of both heating and cooling loads is investigated for a one-storey single-family ranch house. The results show that the developed foundation heat transfer module accounts more accurately for the effects of the ground thermal mass than the foundation model currently used in EnergyPlus. In particular, it was found that annual heating and cooling loads can be overestimated by over 20% for a typical residential building if ground-coupled heat transfer calculations are not fully integrated in EnergyPlus. [ABSTRACT FROM AUTHOR]