Lisø PhD Dissertation Manuscript - NTNU

A frost decay exposure index for porous, mineral building materials
Kim Robert Lisø *, a, c , Tore Kvande b , Hans Olav Hygen d , Jan Vincent Thue c and
Knut Harstveit d
a Norwegian Building Research Institute (NBI), P.O. Box 123 Blindern, N-0314 Oslo
E-mail: kim.robert.liso@byggforsk.no, fax +47 22 96 57 25
b Norwegian Building Research Institute (NBI), Høgskoleringen 7B, N-7491 Trondheim
c Department of Civil and Transport Engineering, Norwegian University of Science and Technology (NTNU),
Høgskoleringen 7A, N-7491 Trondheim
d Norwegian Meteorological Institute, P.O. Box 43 Blindern, NO-0313 Oslo, Norway
Abstract
The disintegrative process of freezing and thawing of porous, mineral materials represents
a significant challenge in the design and construction of building enclosures. In this paper
we present a simple method for assessing the relative potential of a climate to accelerate
frost decay based on multi-year records of daily air temperatures and rainfall, with special
emphasis on masonry. Distributions of 4-day rainfall prior to days with freezing events
provide quantitative information on the geographically dependent frost decay risk in
porous, mineral building materials in a given climate. Data from 168 weather stations in
Norway are analysed, using weather data from the reference 30-year period 1961 - 1990.
Keywords: building defects, building enclosure performance, building materials, climate
adaptation, climatic impact, decay, freezing, Norway.
1. Introduction
Norway’s climate is extremely varied. From its southernmost point (Lindesnes) to its
northernmost (North Cape) there is a span of 13 degrees of latitude, or the same as from
Lindesnes to the Mediterranean Sea. Furthermore there are large variations in received
solar energy during the year. The largest differences are found in Northern Norway, having
midnight sun in the summer months and no sunshine at all during winter. The rugged
topography of Norway is one of the main reasons for large local differences over short
distances. Norway is often regarded as a cold and wet country. The country shares the
same latitude as Alaska, Greenland and Siberia, but has a rather pleasant climate compared
to these areas. Thanks to its westerly location, on the east side of a vast ocean, with a huge,
warm and steady ocean current near its shores and a dominating southwesterly air flow
from the Atlantic Ocean, Norway has a much friendlier climate than the latitude indicates.
The highest annual temperatures can be found in the coastal areas of the southern and
western part of Norway. Skudeneshavn (Rogaland County) on the southwest coast has an
annual normal temperature of 7.7°C. In 1994, Lindesnes lighthouse (Vest-Agder County)
recorded the highest annual temperature ever, with 9.4°C. When excluding uninhabited
mountain areas, the coldest area throughout the year is the Finnmark Plateau. One of the
stations there, Sihccajavri, has an annual normal temperature of -3.1°C. The coldest year
ever was in 1893, when Kautokeino (Finnmark County) recorded an annual temperature of
-5.1°C. Sihccajavri equalled this in 1985. In the mountains, large areas have an annual
* Corresponding Author
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