Buildings erected today will have to withstand the environmental actions of the future, not those of the past. And most of the buildings erected the next few decades must be expected to be still in use in 2100
The standards are based upon distributions of past years and no longer constitute the safe basis everyone assumes.
My suggestion, put forward in 2006: the load basis of the standards should be changed so it is based upon the most unfavourable supportable/probable weather projections.
Stricter standard requirements cost little, whereas the insufficient standard requirements may have incalculable consequences, both for each individual and for society.
It should be noted that increasingly stricter insulation requirements lead to thicker roofs which makes it easier and cheaper to build stronger roofs that may withstand stronger winds and deeper snow.
And it should be noted that removal of snow from roofs under extraordinary weather conditions may prove to be a considerable maintenance cost, and maybe impossible when it is really needed, which would seem evident as based on the experience from Bornholm in December 2010.
The consequences of the abundant snowfall in recent years seem to confirm the need for stricter standard requirements, including higher values of snow load.
It should be noted that it is impossible to establish the snow load on the basis of the snow depth alone: with temperatures about, and especially shifts above and below, 0°C, as has been the case in recent years, the density may be increased considerably, leading to an underestimation of the real snow load.
One rather doubtful assumption, included in the basis for the decision to keep the hitherto values of snow load, has been that the changes in weather would lead to warmer winters with more rain and less snow.
This assumption seems to have been disproved: on the contrary, in recent years the frequent shifts above and below 0°C, and the higher frequency of easterly and northerly winds have led to increased snowfall.
We have yet to see wind speeds clearly exceeding those which have occured in the past here, and which form the basis of the present standards, but in a changing world with increasing wind speeds elsewhere it can only be a matter of time.
It should be noted that every 5% increase in the wind speed leads to a 10% increase in the destructive force of the wind.
Apart from the immediate visible effects, flooding and higher sea and groundwater levels may actually undermine buildings.
It is important to realize that the safety of buildings rely on the combination of different relevant standards, the load standard being the crucial one applying to all cases.
Each standard has an inbuilt safety and contributes to the total safety of the combination.
This means that a building may fail if it does not meet the requirements of one or more of the standards, but it may also be able to withstand loads beyond the current values according the present load standard if it more than meets the requirements of other standards.
Therefore it is a fallacy to claim, as has been done in both 2010 and 2011, that there is no reason to reconsider the standard values of snow loads because the only structures to fail in the latest winters were specific kinds of buildings that did not meet one or more other relevant standards, for the simple reason that there may be countless buildings that have withstood loads beyond the standard values of snow loads because they more than met the requirements of other standards.
The only way to uphold the safety of buildings is to ensure that the values and requirements of each and every standard corresponds to the real conditions, now and in the future, completely independent of compliance with other standards.
Unfortunately, the unique opportunity to establish the actual snow loads in the latest winters was forfeited, in favour of irrelevant considerations about non compliance with other standards, which may be interpreted as a bad excuse for failing to reconsider the standard values of snow loads.
It is also important to realize that foresight and due diligence is crucial, above all in connexion with events and conditions still to be experienced, as is the case with future weather, and as was the case with the recent earthquake and the following tsunami in Japan.
A persistent refusal to incorporate the expectable increasingly violent weather conditions in the standards, can hardly be seen as anything but an irresponsible and inexcusable failure, especially by the authority which everyone relies upon, namely Danish Standard, but also by other experts with the sufficient background knowledge.
The effects of such a failure may appear manageable and increase gradually, but since most of the buildings erected in the next few decades must be expected to be still in use in 2100, the long term effects may be incalculable.
The beginning of 2011 seemed to bring a new hope for a more responsible approach, but so far it seems to remain a hope.