The integration of building and landscape in a highway proximal environment through the smart use of earth berm sound barriers Maria Kaskareli Department of Architecture, Technical University of Delft, Delft, The Netherlands 14 January 2014 ABSTRACT This paper is investigating the possibility of merging building and landscape in a highway proximal environment in the Netherlands. Green in urban areas is under constant pressure and adding green in cities is a contemporary challenge. This merging is approached by examining how to make smarter use of the earth berm sound barriers that are commonly used on the sides of highways by making them multifunctional. This approach can fit under the earth sheltering technique. Five aspects are identified and studied individually. First, the technique of earth sheltered construction is studied including considerations such as structural loading, the application of thermal insulation, moisture and humidity. Secondly, lighting conditions for earth covered or underground spaces are presented. Next, the acoustic performance of the earthen sound barriers is studied, including general principles, geometry, surface cover and the influence of vegetation. The fourth aspect studied is the greening part, which is comparable to intensive green roof design, taking into consideration the slope. The final aspect studied is the thermal properties of soil, the potentials that are presented with its high thermal mass and the thermal energy storage that is possible in it. Moreover, some references are presented as examples for the study. Finally, it is concluded that such integration, however complex, is a possible task that can have very positive effects of the dense urban environment of present cities. Keywords: Earth sheltering; Earth berms; Sound barriers; Building - landscape integration; Underground building; Green roof; Thermal mass; Heat storage; Building with soil; Highway environment 1. Introduction around cities. “More trees are still being chopped down than planted, and more green areas are being It is a fact that world population is growing and that replaced by buildings and paving than are being [1] urbanisation is increasing. As a result, cities are added.” It is a fact that almost 40% of the Dutch growing, in their need to accommodate more population lives in districts with insufficient green people. It is frequent that a city is surrounded by recreational facilities. The shortages are greatest in [2] major transportation infrastructure belts, which the Randstad urban conglomerate. This is while acting as connections in one direction, are especially true of the increasing urban density in great barriers on the other direction (perpendicular the Groene Hart zone of the Netherlands. The need to their axis of movement). Such transport for more buildings means that green is undervalued channels, whether highways or railways, are and construction is preferred over parks and green creating several problems to the areas they pass public areas, also because it brings higher profit. through. Mainly the sound pollution that they are a source of, has as a result that the proximal areas 1 Heat. More Urban Green Keeps the City Cooler 2 remain unused or are used but with low occupant “The monitor of the National Spatial Strategy and a study conducted by Alterra (2005) show that a great deal needs to be satisfaction. Architecture can take the role of done to bring Dutch towns and cities back to the level where reconnecting separated components of a city and they should be: almost two-thirds of the fifty largest Dutch physically absorbing infrastructure. municipalities offer less than 75 m2 of green within a radius of 500 metres of a given home. Forecasts predict that the pressure on urban vegetation will increase further, since the population One other issue that appears with the growing cities is growing and policy dictates that the density of existing built- is the pressure that green areas are subject to in and up areas be increased.” - The social and economic importance of green and blue areas 1 Adding green public space in a tight environment is more common in the United States than in Europe, a great contemporary challenge. A current where – as the name indicates – buildings are movement that is calling for more green in cities is covered by soil and thus can be made to blend in taking the form of green roofs and facades. with the natural landscape. However, even more important is the retention of existing green areas at ground level in order to have an essential impact on the urban living conditions.[3] Green has been proven to have numerous benefits and is much desired and even necessary in urban areas. In recent years, more information is becoming available about the benefits of green in cities. The fact that vegetation enhances the quality of life is something that urban planners have been aware of since the start of the profession. “Most people prefer living in green districts. House prices Fig.1.1 in green districts or along water or areas of vegetation are relatively higher than elsewhere. To draw citizens with higher levels of education, towns and cities need to be attractive and offer green and culture. Highly educated engineers, in particular, 2. Methodology prefer to remain close to green areas: both for where they live and for their holiday This earth sheltering technique is simple in its destinations.”[4] It is also a fact that vegetation principle and brings several benefits. One is the reduces stress levels and helps people to recover integration with the landscape. The building can be faster from illnesses. made to blend in with its surroundings and almost disappear. Another is the stabilization of internal Nature is being burdened and threatened constantly thermal environment due to the thermal mass of by the building sector. The solution is clearly not to soil. With around 40% of the total energy stop building, but ways must be found to continue consumed by the building sector being used for construction in agreement with nature. The term space conditioning, this aspect of earth sheltering is “nature” is used here in two ways, meaning first particularly important. As this paper will further nature as the natural landscape (green areas, explain, a building designed with this technique can vegetation, biodiversity etc.) and on the other hand present great energy savings from the respect of the natural resources (minimising energy space heating and cooling. It is interesting to see consumption, renewable resources, low emissions). that in the past, people used earth sheltering to It seems inevitable that we must learn how to better protect from the environment, while today, people overlap architecture and green space in smart ways. use it to protect the environment. In this specific case, a benefit of the technique is also its ability to be formed into a sound barrier and the sound In a dense urban centre, the increasing lack of insulation properties of soil. If not taken into space and the increasing land values often forfeit consideration, lighting in such semi-underground the luxury of autonomous building typologies, and buildings can become a great disadvantage. quite often, disparate programs are forced to be Therefore this also needs to be given the combined. This paper will be dealing with the importance that it deserves. In order to study how specific case of an environment surrounding a busy the technique can be used as a solution to the highway in the Netherlands, with all the problems problem posed, it has been broken down to five it introduces, as above discussed. In order to aspects: achieve the merging of landscape and building in such an environment, the problem can be approached as making the typical earthen sound constructing an earth shelter barriers smart, by integrating functions in them and light conditions & comfort in earth turning them into usable green areas, doing this in a sheltered buildings sustainable way and including energy earth berm sound barriers & acoustic considerations [Fig.1.1]. The technical solution of properties of soil this approach can be fitted under the construction green over earth sheltered buildings technique known as “earth sheltering”, a technique thermal properties of soil & heat storage in the soil 3 Pötz, p. 247 4 The social and economic importance of green and blue areas In order to research this broad topic, each of the five aspects, forming a distinct topic, has been 2 approached separately. To avoid presenting houses of Iceland being one of the most irrelevant research for the five separate topics and characteristic [Fig.3.1.1]. including excess information, the results for each topic have been limited to the information that could be directly relevant to the specific research, with all its limitations. Most of the research has been carried out by literature study. Books were usually a source of broader information, while focused articles on the specific topics provided the more detailed information. Moreover, some references were studied. Finally, professional experience has been taken into account by having direct contact with experts in each field within the academic environment. In order to make the results of this multifaceted research clearer, they have been translated into a diagrammatic form. In this Fig. 3.1.1 way (and as this paper is mainly directed at architects, and architects have a more visual Earth sheltered construction can be categorised in perception) the results can be easily read, three basic construction methods: appreciated and can inform a design in a more direct way than plain text would. Sometimes earth berming: where earth is packed against the underground buildings were used as reference walls of a building and over its roof and let to slope when the conditions studied were similar. down to the ground level, in-hill construction: where a building is set into a sloping hillside, and fully recessed construction: where a building is set below ground and is arranged around a central 3.