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Re: [EnergyPlus_Support] The meaning of weather data

Those are design conditions as described in Chapter 14 of the ASHRAE 2009 Handbook of Fundamentals.
99% means that for the period of record (usually 20-30 years), the temperature is likely to be higher 99%.  (Similarly 99.6% means the temps higher 99.6% of the time.)  Combine that 99% with 'Ann Htg conds DB' and you have 8672 hours or about 128 hours of the year it will be colder. 
These values are used for sizing equipment (heating and cooling) automatically in EnergyPlus.

On Wed, Dec 15, 2010 at 1:33 PM, vicentina_0350024 <vicentina_0350024@xxxxxxxxxxxx> wrote:

Hi E+ Support~

When I input weather data to IDF, I could find there are several objects pop up in "SizingPeriod:DesignDay", Objects' Name: e.g. Chicago Ohare Intl Ap Ann Htg 99.6% conds DB, Chicago Ohare Intl Ap Ann Htg 99% conds DB.
What does the percentage "99.6%" and "99%" means?
Where could I get these information to understand it?

Thank you so much



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