DRY stands for Design Reference Year

http://www.byg.dtu.dk/upload/institutter/byg/software/bruger...

´Programmet er opbygget i et Excel regneark og beregner hvornår der optræder kondens på vinduesruder afhængig af rudens U-værdi, hældning og orientering samt rudens vinkel¬strålingsforhold til himlen. Beregningerne foretages ud fra timeværdier af klimadata fra det danske Design Reference Year, DRY.´

´An average year in normal Danish outdoor conditions´ or one of the other suggestions.


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Note added at 23 hrs (2008-10-29 08:06:55 GMT)
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Typical Danish weather conditions here.

Under typical Danish weather conditions the total energy performance of glazing and windows is characterized by their net energy gain which is defined as the solar heat transmitted in, minus the heat loss transmitted out through the window during
the heating season corresponding with the Design Reference
Year.
-- This comes on page 19 of the reference below, in the Introduction after the English abstract.

http://www.tc.cz/old/soubory/pdf/SessionB.pdf

DRY seems to be an expression originally defined and used by the Technical University of Denmark, DTU.

There is also a TRY - Test Reference Year.