A Simplified Methodology to Estimate Energy Savings in Commercial Buildings from Improvements in Airtightness

Abstract

Air leakage through the envelope of commercial buildings in the United States accounts for approximately 6% of their energy use. Various simulation approaches have been proposed to estimate the impact of air leakage on building energy use. Although approaches that are based on detailed airflow modeling appear to be the most accurate to calculate infiltration heat transfer in simulation models, these approaches tend to require significant modeling expertise and effort. To make these energy savings estimates more readily available to building owners and designers, Oak Ridge National Laboratory, the National Institute of Standards and Technology, the Air Barrier Association of America, and the US Department of Energy (DOE) are developing a user-friendly online calculator that applies a detailed airflow modeling approach to examine energy savings due to airtightness in commercial buildings. The calculator, however, is limited to 52 US cities and a few cities in Canada and China. This paper describes the development of an alternative, simplified method to estimate energy savings from improved airtightness. The proposed method uses the same detailed approach for hourly infiltration calculations as the online calculator but it expands the ability to estimate energy savings to all US cities using hourly outdoor air temperature as the only input. The new simple regression model-based approach was developed and tested with DOE’s standalone retail prototype building model. Results from the new approach and the calculator show good agreement. Additionally, a simple approach to estimate percent energy savings for retrofitted buildings was also developed; results were within 5% of the energy saving estimates from the online calculator.

A Parametric Study and Performance Evaluation of Energy Retrofit Solutions for Buildings Located in the Hot-Humid Climate of Paraguay—Sensitivity Analysis

“…It is important to highlight that the simulations tools employed in this research are highly recommended by several international and renowned standards, which have been greatly used in several scientific investigations [41][42][43][44][45][46]. Accordingly, the simulation tools accuracy supports the results reliability of the energy efficiency of the building in its original state, without thermal insulation materials, and the results of the energy efficient version, demonstrating thus the effectiveness of the strategies implemented for the climate under analysis.…”

Airflow and indoor air quality models of DOE prototype commercial buildings

“…Another alternative approach is to utilize the CONTAM Results Export Tool [43] to convert CONTAM infiltration rates to schedules that can be used in EnergyPlus simulations, which have been applied in the development of an online airtightness savings calculator [23,24].…”

“…NIST has used the reference and prototype buildings to: perform airflow and IAQ analyses [1,17], develop weather-correlated infiltration inputs for the EnergyPlus models of the buildings [18][19][20][21][22], and develop an online airtightness savings calculator in collaboration with Air Barrier Association of America (ABAA) and Oak Ridge National Laboratory [23,24], for developing and exercising the CONTAM-EnergyPlus coupling capability [25,26] and CONTAM-TRNSYS coupling capability [27], and for studying the potential energy savings from air sealing of commercial buildings [28]. models, limitations of modeling airflow and energy separately, the implication for coupled airflow-energy modeling, and future work.…”

Energy Modelling and Calibration of Building Simulations: A Case Study of a Domestic Building with Natural Ventilation

“…Although studies indicate that heating energy demand derived from air infiltration can be considerable [6], the oversimplification of its treatment in modelling and analysis is recognized [1,[10][11][12]. In residential buildings where natural ventilation is not controlled, the prediction of air change rate is complicated by its dependence on temperature difference and wind speed.…”

“…In the assessment field, software programs for simulating the building energy performance have become essential tools, for example, Energy Plus, DOE-2, TRNSYS (TRaNsient SYstem Simulation program), or ESP-r (Environmental Systems Performance-Research) [1,[9][10][11][12][13][14][18][19][20][21], which typically assume constant air infiltration rates [12]. A number of assumptions need to be made and these can vary between buildings, hence model calibration is an important factor [19].…”