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Manuela Sarnuk, Student of Architecture and Slavcho Filipov, Student of Architecture

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The simplest definition of green building,or sustainable design, is to build in a way that minimizes environmental impact and creates a healthy indoor environment for occupants. It is practice of increasing the efficiency with which buildings and their sites use energy, water, and materials, and reducing building impacts on human health and the environment over the entire life cycle of the building. As energy prices continue to climb and more people become aware of their personal impact on the environment, green building has moved from the fringe to the mainstream of the construction industry. Sustainable, passive or green architecture concepts extend beyond the walls of buildings and can include site planning, community and land use planning issues as well.
Straw is a renewable resource that acts as excellent insulation and is fairly easy to build with, but it is mostly wasted. Each year millions of tons of straw are burnt or left to rot. In Bulgaria building with straw is not very common, although there are enormous resources of it.
Straw bales are a highly insulative, low-embodied-energy, natural building material made from an agricultural waste product. For many, they are locally available and affordable. Straw is easy to work with for people new to construction as they are flexible and can be very forgiving. Strawbale walls can be organic, rustic and hand-made, or precise, neat, flat and ultra modern.
A typical straw bale wall is roughly three times as efficient as conventional framing. Over the life of a typical thirty year mortgage, this superior insulation can reduce energy costs by up to 75%, saving money and vital natural resources. The straw bale structure wall has proven to be exceptionally resistant to fire. It also provides good sound insulation and contrary to the belief pests are no real threat. Once the walls are properly plastered or sided, there is no way for bugs or rodents to get into the bales.
Using the characteristics of passive house standard as a basis we are proposing a design that is not only energy efficient and providing high quality living environment but it combines various sustainable features.
First of all the unspecified situation, the flat terrain and the possibility of choosing the north direction focus our attention to propose a passive house that will fit any situation, and will both suit an urban environment, small town, village or even uninhabited place.
Most important for the passive house is the shape. It should be as compact as possible and have low external surface. That provides the minimal thermal transition through the walls and the roof.
The materials used for the insolation of the house are the next basic feature in the concept of the sustainable building. Using a recycled, secondary or wasted material not only saves resources but have smaller impact on the environment. We choose the straw as a natural building material with high isolative efficiency and low embodied energy. It is used for generations and recently is a very popular technique for building green houses in other countries. Fortunately building with straw bales is not very common in our country even though we have huge resources of it. Because of the structure of the bales the walls become very thick and provide excellent sound, thermal and moisture insulation. We can say that here in Bulgaria it is very cheap; even if you have friends in the agriculture business it is for free. The building does not require special skills.
The next basic characteristic of a passive house is the orientation. The north elevation is closed. It has only one opening for the front door. The south elevation is entirely glassed. On the other hand to avoid overheating in summer we extend the south eave. So in summer when the sun is high the eave stops the rays and shades the house, and in winter when the sun is low in illuminates the living space.
The building is raised on pillars so that it has less impact on the situation, less digging expenses and adds some universality of the house as it is not engaged with the terrain levels. This also results in less expenses for hydro insulation.
Having the compact passive house volume as a basis we add some modifications so that the building gains natural resources more easily which is a basic feature of its design. The distortion of the simple shape is deeply related with the concept of collecting resources as much as possible throughout the year. The curved roof acts as a funnel for rainwater which is lead to a water tank under a patio. Further the water is being filtered and used for flushing toilet water, irrigating, washing clothes etc.
The annual change of the angle of the sunrays makes the static photovoltaic panels optimally positioned to the sun only for a few weeks. Due to the curvature of the roof there are always perpendicular to the sun rays panels. The south face of the funnel roof which is used as a surface for the panes is not only curved but trapezoidally cut so that in the lower part which is perpendicular to the winter sun has less area than the upper part which is perpendicular to the summer sun.
The healthy environment is maintained by draught free supply of fresh air. The system uses the energy of the exhaust air which is lead out of the house after exchanging heat in an air/air exchanger.
Having no constraints from the contest task such as north position, particular lot and surrounding environment we assume that the task of the competition to produce a general passive house design that is suitable for various situations. This is the aim we are trying to achieve with our design proposal.