Publications and Documents

Publications and documents of interest on weather data for building simulations.

Published papers

Which Weather Data Should You Use for Energy Simulations of Commercial Buildings, Crawley, 1998, ASHRAE Transactions.


  • Users of energy simulation programs have a wide variety of weather data from which to choose–from locally recorded weather data to preselected ‘typical’ years, often a bewildering range of options. In the last five years, several organizations have developed new typical weather data sets including WYEC2, TMY2, CWEC, and CTZ2. Unfortunately, neither how these new data influence energy simulation results nor how they compare to recorded weather data is well documented.
  • This paper presents results from the DOE-2.1E hourly energy simulation program for a prototype office building as influenced by local measured weather data for multiple years and several weather data sets for eight U.S. locations. We compare the influence of the various weather data sets on simulated annual energy use and costs and annual peak electrical demand, heating load, and cooling load. Statistics for temperature, heating and cooling degree-days, and solar radiation for the different locations and data sets are also presented. Where possible, the author explains the variation relative to the different designs used in developing each data set. The variation inherent in actual weather data and how it influences simulation results is also shown. Finally, based on these results, the question is answered: which weather data should you use?

Improving the Weather Information Available to Building Simulation Programs, Crawley et al, 1999, Building Simulation 1999.


  • Developers of building simulation tools have been continuously improving their programs and adding new capabilities over the last thirty years. Time steps of less than an hour are now common and even necessary to properly simulate the complex interactions of building components and systems. For example, some control issues, such as daylighting, require much shorter time steps of minutes— more traditional hourly time steps have been shown to introduce errors as large as 40% in illumination calculations.
  • Despite these increased capabilities, many simulation programs are still using the same limited set of hourly climatic/weather data they started with— temperature, humidity, wind speed and cloud cover or solar radiation. This often forces users to find or calculate missing weather data such as illuminance, solar radiation, and ground temperature from other sources or developers to calculate it within their program.
  • In this paper, we describe a generalized weather data format developed for use with two energy simulation programs. We also compare the new format with previous data sets in use in the US and UK.


  • Current format is shown at the document link below and here.

Estimating the impacts of climate change and urbanization on building performance, Crawley, 2008, Journal of Building Performance Simulation.


  • Over the past 15 years, much scientific work has been published on the potential human impacts on climates. For their Third Assessment Report in 2001, the United Nations International Programme on Climate Change developed a set of economic development scenarios, which were then run with the four major general circulation models (GCM) to estimate the anthropogenesis-forced climate change. These GCMs produce worldwide grids of predicted monthly temperature, cloud, and precipitation deviations from the period 1961–1990. As this period is the same used for several major typical meteorological year data sets, these typical data sets can be used as a starting point for modifying weather files to represent predicted climate change. Over the past 50 years, studies of urban heat islands (UHI) or urbanization have provided detailed measurements of the diurnal and seasonal patterns and differences between urban and rural climatic conditions. While heat islands have been shown to be a function of both population and microclimatic and site conditions, they can be generalized into a predictable diurnal and seasonal pattern. Although the scientific literature is full of studies looking at the impact of climate change driven by human activity, there is very little research on the impact of climate change or urban heat islands on building operation and performance across the world. This article presents the methodology used to create weather files which represent climate change scenarios in 2100 and heat island impacts today. For this study, typical and extreme meteorological weather data were created for 25 locations (20 climate regions) to represent a range of predicted climate change and heat island scenarios for building simulation. Then prototypical small office buildings were created to represent typical, good, and low-energy practices around the world. The simulation results for these prototype buildings provide a snapshot view of the potential impacts of the set of climate scenarios on building performance. This includes location-specific building response, such as fuel swapping as heating and cooling ratios change, impacts on environmental emissions, impacts on equipment use and longevity comfort issues, and how low-energy building design incorporating renewables can significantly mitigate any potential climate variation. In this article, examples of how heat island and climate change scenarios affect diurnal patterns are presented as well as the annual energy performance impacts for three of the 25 locations. In cold climates, the net change to annual energy use due to climate change will be positive – reducing energy use on the order of 10% or more. For tropical climates, buildings will see an increase in overall energy use due to climate change, with some months increasing by more than 20% from current conditions. Temperate, mid-latitude climates will see the largest change but it will be a swapping from heating to cooling, including a significant reduction of 25% or more in heating energy and up to 15% increase in cooling energy. Buildings which are built to current standards such as ASHRAE/IESNA Standard 90.1-2004 will still see significant increases in energy demand over the twenty-first century. Low-energy buildings designed to minimize energy use will be the least affected, with impacts in the range of 5–10%. Unless the way buildings are designed, built, and operated changes significantly over the next decades, buildings will see substantial operating cost increases and possible disruptions in an already strained energy supply system.

Rethinking the TMY: Is the 'Typical' Meteorological Year Best for Building Performance Simulation, Crawley, Lawrie, 2015, 14th Conference of IBPSA 2015


  • Historically, building simulation users have used a single typical year or a constructed typical meteorological year to represent climatic conditions for a location or region. With advent of increasingly powerful computers, it is no longer necessary to represent climatic conditions with a single year of data. Prior studies have shown that a single year of data often do not well represent the range of climate conditions over a period.
  • This paper proposes a new regime for climatic data representation in buildings—an XMY or eXtreme Meteorological Year—building on a paper from Building Simulation 1999 that called for a common format for building simulation representation. We demonstrate how several sets of international typical meteorological data sets compare to the actual period of record that they represent. Then using an example prototype building, we show that the climatic response of the building would be better served by a range of building climatic data, investigating high and low cases of temperature, humidity, solar radiation and wind conditions.


EnergyPlus Weather File Format

  • The EPW format in quick data dictionary style along with descriptions of fields.