Toward Assessing the Sensitivity of Buildings to Changes in Climate

A building is designed for one set of typical climatic conditions. In the context of expected climate change, substantial numbers of existing and new buildings are expected to survive long enough to experience perceptible shifts in climate ‘normals’ (averages). This is problematic for predicting building performance, largely because the exact nature of climate change is hard to predict with certainty. Thus an optimal design is not only tuned to the original design conditions, but is also robust to changes in climatic conditions in the sense of a low sensitivity of its performance. To predict a building’s response to changes in typical weather, two inputs are required: weather data representing this change, and suitable metrics to compare building performance across different climate normals. This report presents initial work on a proposed method for assessing the sensitivity of new or existing buildings to climate change. This method begins with a selection of weather files to represent climate change, then quantifies a building’s passive performance in those climates using an enthalpy-based metric, and ends with a graphical analysis of the performance of the building in different climates to assess its robustness. In this report, we propose an objective performance metric based on the extent to which a building creates indoor conditions passively, i.e. without auxiliary systems. Initial work suggests that the performance assessment carried out here is reproducible and applicable for indoor environment design and evaluation in different ranges of climate change. This approach enables a comparison of building performance without the bias introduced by inherent differences in climatic conditions.

Marilyne Andersen, Sönke Frederik Horn, Parag Rastogi

Substantial numbers of existing and new buildings are expected to survive long enough to experience perceptible shifts in climate ‘normals’ (averages). To predict a building's response to changes in typical weather, two inputs are required: weather data representing this change, and suitable metrics to compare building performance across different climate normals. This paper presents initial work on a proposed method for assessing the sensitivity of new or existing buildings to climate change. This method begins with a selection of weather files to represent climate change, then quantities a building's passive performance in those climates using an enthalpy-based metric, and ends with a graphical analysis of the performance of the building in different climates to assess its robustness. In this paper, we propose an objective performance metric based on the extent to which a building creates indoor conditions passively, i.e. without auxiliary systems. Initial work suggests that the performance assessment carried out here is reproducible and applicable for indoor environment design and evaluation in different ranges of climate change. This approach enables a comparison of building performance without the bias introduced by inherent differences in climatic conditions.

2013

Prevention of forest fires in a changing climatic context in Ticino, southern Switzerland

Michael Reinhard

Switzerland is not a place commonly associated with forest fires, unlike many areas of the nearby Mediterranean Basin. However, in this Alpine country, forest fires occur every year and destroy forests that fulfil various functions, the most socially and economically important of which is protection from natural hazards. Canton Ticino is the most affected by forest fires. The protective function is of vital importance for local communities. Most of Ticino's population lives in valley bottoms, where most transportation infrastructures are built, and without forests these are vulnerable to mass flows. In Ticino, forest fires occur mostly during the winter/spring season when dry conditions occur due to low precipitation and strong Foehn events. At this time, deciduous trees have shed their leaves and there is an important seasonal accumulation of dry litter on the forest floor. Fuel load has also increased over recent decades due to the abandonment, since about 1960, of traditional agro-forestry activities that removed dead wood, dry leaves and forage grass from the forest. Fuel in the forest is particularly flammable during the dry winter and leads to very high fire risks. Climate change has contributed to increasingly fire-prone conditions over the past decades and may also have had an effect on forest composition. Most Ticinese forest fires are anthropogenically triggered and negligence is the primary cause of fires. The only natural cause of fire is lightning, which affects forests particularly during summer, when heavy storms occur. This dissertation aimed at gaining a better scientific understanding of the interactions between landscapes, humans and forest fires in the context of climate change, in order to prescribe recommendations to achieve forest fire prevention and diminish fire related risks. We focused on the mechanisms leading to forest fires and adopted an integrated approach, which necessitated the use of a variety of methods: i) climate trend analyses, ii) flammability tests using a standardised ignition apparatus and a thermo-gravimetric analyser, iii) qualitative social science methods using focus groups and semi-structured interview techniques, iv) quantitative social science methods by means of a questionnaire. The results suggest that climate has changed in recent decades with more frequent and intense fire-prone conditions. Minimum and maximum temperatures have both increased significantly and relative humidity has decreased significantly for all daily measures during fire season. The present study suggests that fire-prone conditions are likely to become even more acute. Climate also has an important impact on the composition of the forests and the state of vegetation, as well as the condition of the fuel load. The most flammable species (Castanea sativa and some laurophyllous species) tend to occur near human settlements and this is of importance for management. Some of these species are expected to increase due to climate change. People involved with the forest fire prevention system perceived the actual fire policy as generally well working and well planned, and they perceive preparedness as strong, although discussions showed that the prevention of accidental fires is not addressed by the current fire policy. Effective prevention requires accurate information about the social aspects of forest fires, which until now has not been available in Ticino. Mechanisms leading to fires are not very well understood by locals, although many people identify correctly some technical aspects of forest fires. Depth of understanding is related to geography, gender, age, profession, marital status, income and life-style. Differences between these socio-demographic groups and geographical patterns suggest that prevention needs to be better targeted and that the population cannot be treated as a homogeneous entity. We conclude the dissertation with a series of recommendations for local authorities and people involved in the forest fire policy setting. These recommendations concern climate, vegetation flammability and forest fire prevention in Ticino.

EPFL2006

Subalpine Pasture-Woodlands in a Changing Climate

Konstantin Svetlozarov Gavazov

Climate change in temperate mountain systems and associated increase in temperature and decrease in precipitation are expected to have strong implications for vegetation productivity, species diversity and carbon turnover in subalpine grasslands. Little is known, however, about the interaction between the effects of climate change and those of local land use management and possible changes in landscape structure. Pasture woodlands in the Swiss Jura Mountains are a traditional landscape, resulting from a long-lived sustainable use of grasslands and woodlands, and as such provide a suite of important ecosystem services to human society. These range from carbon sequestration and biodiversity preservation, to provision of timber and forage for livestock, and last but not least an aesthetic value, much appreciated by tourism. In this thesis various aspects of ecosystem functioning have been studied, investigating the combined effects of experimental climate change and land use on structurally different wooded pastures. An altitudinal gradient method has been used to simulate future climate change conditions, by imposing warmer and drier climate on subalpine turfs transplanted at lower elevation. The resulting gradient in mean annual temperature and precipitation – ranging from cold and wet in the subalpine zone, to warm and dry in the colline zone – has allowed for the detection of tipping points and altered states of ecosystem functioning in response to the treatments. The method employed provided also the possibility for a direct comparison of three land use types: unwooded pastures, sparsely wooded pastures, and densely wooded pastures (the result of pasture management intensity), in their response to climate perturbation. During the four years of experimental work, a series of observations have been made at the plot scale (square metre) in terms of plant performance and biogeochemical cycles, as well as at the landscape scale (hectare) in terms of forage production. A general threshold level for ecosystem resistance to experimental climate change was detected between the moderate IPCC scenario (+2 K mean annual temperature; -20 % annual precipitation) and the intensive IPCC scenario (+4 K mean annual temperature; -40 % annual precipitation). A concomitant gradient in ecosystem response to climate change was observed across the three land use types. The intensively managed unwooded pasture type was consistently more affected by the experimental treatment and rarely exhibited signs of resistance, especially under the intense climate change scenario. A drastic loss of plant species diversity, reduction of herbaceous biomass, impaired litter decomposition and soil microbial metabolic activity have all contributed to the altered state of ecosystem functioning. In contrast, the two extensively managed wooded pasture types showed considerable resistance to climate perturbation in terms of both above and belowground ecosystem processes. The reported inter-annual variation in herbaceous diversity and biomass production within these land use types demonstrated their resilience (recovery) potential too. Using a modelling approach for upscaling these results to the heterogeneous landscape of pasture woodlands in the Swiss Jura Mountains, has proven that extensively used wooded pastures could grant sustainable ecosystem services in terms of forage provision for cattle under climate change. Considering that the two experimental climate change intensities implemented this study are the projected ‘best’ and ‘worst’ case scenarios for the coming decades, the reported resistance of wooded pastures to climate change has to be embraced, and sustainable land use set as a goal in high altitude mountain pastures.