The results of CFD numerical simulations show that the stairwell can have a fundamental role in the natural ventilation of low-rise multifamily buildings (three to five levels) in winter. The natural ventilation system here presented is characterized by low installation costs, quite easy operation and inexpensive management.

In this case-study, the main design rules to obtain an effective natural ventilation system are: location and size of inlet and outlet (to move upward the neutral pressure level above the upper extraction grille device) and the aerodynamic characteristics of the openings (to equalize the flow rates). CFD simulations showed effective behaviour of the above mentioned ventilation system.

The well known stack effect simplified model [2] cannot be used in the case studied because the stairwell was characterized by complex geometry and boundary conditions. So, CFD codes are an invaluable tool in the design and verification of the behaviour of the stairwell performing as a chimney.

The behaviour of the system studied is influenced by a great number of parameters depending on the external micro-climate (such as air temperature and solar radiation), the stairwell (such as the morphology and the geometry of the stairwell, the location and the aerodynamic characteristics of the openings, the thermal properties of the envelope), the dwellings (heating temperature, pressure losses along the internal flow path), the users (the control of the natural ventilation system and the heating scheduling/operation).

The results shown only concern a certain number of the typical boundary conditions. However, these results can be useful for the design of other similar natural ventilation systems.

Future research projects will concern the evaluation of different boundary conditions. The further aim is the definition of the most relevant parameters for the designing of similar systems.

Further CFD simulations will be run to test different boundary conditions and different scenarios (such as higher external air temperatures, one or more flats unheated, no ventilation in one or more units).

Different technical solutions of the stairwell envelope (such as a photovoltaic facade or solar wall) will be tested in order to enhance diurnal ventilation in winter and/or nocturnal ventilation in summer, especially in new buildings. In energy retrofitting, generally speaking, the design opportunities are reduced by inadequate building orientation, solar shadowing of neighbouring buildings and payback of intervention costs.

Ventilation rate varies depending on adjustment of air-inlets, windows and doors as perceived necessary by occupants. So, further models with different resistance and with partial use of the single-unit ventilation system will be run. The control system design

needs further study, especially into the automatic adaptation to external micro-climatic conditions (master) and to the partial extraction rate of one or more units.

REFERENCES

1. ASHRAE Standard 62: "Ventilation for acceptable indoor air quality”, American Society of Heating Refrigerating and Air-conditioning Engineers, Atlanta, GA, 1999.

2. Awbi H. B. "Ventilation of Buildings”, E. & F. N. Spon, London, UK, 1991.

3. Flomerics Ltd. "Flovent version 4.2 User Guide”. Flomerics Limited, UK, 2003.

4. lannone F. "Natural ventilation and sustainability: designing with Computational Fluid Dynamics”. Sharing Knowledge on Sustainable Buildings, Bari, Italy, 16-17/12/1999.

CONTRIBUTORS

M. Catalano planned and supervised the study, G. R. Dell’Osso codesigned the study and wrote the background (par.1), F. lannone codesigned the study, executed the CFD simulations, analysed the data (paragraphes 2.1 and 2.2) and wrote the conclusions.

Lichtblau Florian, Lichtblau Architects BDA

The estate with solid-brick terrace housing was built in 1956. One house was thoroughly renovated, using highly efficient vacuum insulation panels and ecologically high-quality materials, while still essentially retaining the original substance. These renovation measures, together with the integrated solar and heating ventilation system, are the components promising a sustainable future for this renovation prototype. The heating energy demand for space heating and domestic hot water was reduced to about 10 % of the original value and the indoor conditions can now be considered ideal.

A natural ventilated building must be designed to get air in and out as well as to support a natural airflow through the interiors. The main architectural consequences are in short:

o Ventilation openings for inlet(s) and outlet(s) in the building envelope o An internal layout, both in plan and section, that provide a low pressure drop air path from the inlet(s) to the outlet(s).

To elaborate on these two points, we have used a "checklist of architectural aspects” to structure the architectural consequences of natural ventilation in the three case buildings. The checklist consists of the following points: Site, Orientation and shape, Plan, Section, Fagade, Ventilation elements, and Interior spaces.

Site

A natural ventilation concept is based on the characteristics and potentials of the site. The most dominating driving force on the site (wind or buoyancy) is selected and utilised as effectively as possible. The ventilation concept is thus designed for the primary driving force (buoyancy in the case of Media School) or for both wind and buoyancy (like in the GSW Headquarters). The climatic conditions on the site also influence the design of the natural ventilation concept. Cold climates favour central ventilation inlets and outlets, as that is advantageous with regard to heat recovery and pre-heating of the ventilation air (e. g. Media Primary School). Local inlets and outlets may be applied in temperate climates (e. g. GSW and B&O Headquarters) where the risk of draught is lower. The investigation on the three case-study buildings indicated that their urban/rural response (to neighbouring buildings, streets/roads, the building typology at the site and so forth) and laws and regulations governed the design of their natural ventilation concepts to a great degree, especially in the initial design stages.

The architectural design of contemporary houses (post 1970) in Cyprus is mostly based on the educational experience of local architects. As most Cypriot architects were educated abroad, their designs are profoundly influenced by western architecture and there exists a tendency to recreate an international architectural style without considering the advantages of traditional architecture and the distinctive climatic conditions and social life.

Materials used for the construction of contemporary houses in Cyprus are reinforced concrete, hollow clay bricks for the house structure, glass, wood, steel and aluminium profiles for doors and windows, smooth or granulated ordinary Portland cement plaster and paints for wall finishes, in site concrete, ceramic tiles and linoleum for floor finishes. The roof is mostly erected with a thin layer of reinforced concrete of about 12 cm and topped with two layers of hessian damped with mastic asphalt. These materials are normally incorporated in semi-heavy-weight constructions inappropriately designed. The roof and external walls are seldom provided with sufficient thermal insulation. They are also not thick enough to compensate for such loss of insulation by having high thermal capacity.

Assoc. Prof. Dr. Demet IRKLIERYILDIZ

Gazi University, FacultyofEngineering andArchitecture, irkli@gazi. edu. tr Prof. Dr. Semih ERYILDIZ

University ofBahgegehir, Faculty of Architecture, seryildiz@bahcesehir. edu. tr

In this study, our recent buildings and projects, which are the products of natural thought and sustainability are analyzed and discussed. Planning and architecture, which are aware of environmental requirements, develop and implement energy­saving technologies and use renewable energy wherever possible.

In the framework of ecological architecture principles, use of renewable energy, harvesting rainwater and its reuse, purification of gray water and compost toilets for natural cycles, natural building materials and edible landscape are subjects of our design studies. Green roofs, sky gardens, edible landscape, waste cycles, biologic diversity etc. are also discussed besides passive heating and natural ventilation on the sample projects.

Sample buildings are;

• Adobe house in Hasandede (passive solar energy, thermal storage wall),

• Durudeniz dwellings in Mugla (natural acclimatization, earth insulation),

• Bodrum Ikizada Turkcell base Station: Natural material, renewable energy; (PV panels, wind turbines),

• Super insulation material: Straw-bale house in Hasandede.

• “Econovation”: ecological renovation of a social housing unit in Batikent.

The projects; chosen as samples in this study are;

• Bio-climatic house for 5 house-holders, A

• Metropolitan Istanbul Municipality; Headquarter.

For decades to come, the energy consumption of the existing building stock will offer our greatest potential to save energy. However, neither the quality nor the quantity of the efforts made to date adequately reflect the enormous challenge we are facing. Against this background, a demonstration project was planned within a research project on highly efficient thermal insulation with vacuum insulation panels, or "VIP" for short.

The orientation and overall shape of buildings utilising natural ventilation is less influenced/dictated by the natural ventilation concept than initially expected. Considerations related to the urban context and laws and regulations decided the orientation of the buildings to a far greater extent than did considerations to the natural ventilation concept.

Furthermore, the buildings investigated in this study show that the form of naturally ventilated buildings need not be shaped more aerodynamically than mechanically ventilated buildings. The greatest difference in terms of shape appears to be that the majority of naturally ventilated buildings are rather narrow (even though there are examples showing that naturally ventilated buildings can be designed as deep plan buildings). It can therefore not be said that natural ventilation dictates the shape of buildings; they can evolve into "any” shape.

Most characteristic ventilation elements associated with natural ventilation do influence the shape of the building, however. Characteristic ventilation elements located on the roof (chimneys, wind scoops and wind towers) influence the silhouette of the building like e. g. the wing on the GSW Headquarters. Solar chimneys as well as double facades and ventilation openings in the fagade (GSW Headquarters) also influence the appearance of facades.

The proportion of the plan of a naturally ventilated building must be shaped to facilitate natural airflow. This results most often in linear plans or in various atrium designs that can be effectively cross-ventilated (GSW and B&O Headquarters). The plan layout must further accommodate natural airflow from the inlet(s) to outlet(s) when stack and cross-ventilation are the applied ventilation principles. This is best achieved with an open plan layout, or a layout with fewest possible internal walls. Such layouts coincide well with utilisation of daylight and view to the outside, but may conflict with flexibility/use, as well as with fire and acoustics issues.

Section

Utilisation of natural ventilation does not have any obvious architectural consequences in the section of buildings other than those associated with vertical air paths in stack-ventilation principles. Such a vertical air path with architectural consequences can typically be interior spaces stretching over several stories, like e. g. a lobby or a reception, or stairwells that are used as exhaust air paths and therefore must be connected openly with the spaces/stories served (like in the B&O Headquarters). Other examples of vertical air paths are chimneys and double fagades serving all (or some) stories in a building (like in the GSW Headquarters). The roofs of low-rise buildings (or the top floor of taller buildings) utilising the stack ventilation principle can be sloped to accommodate a natural airflow up and out of the room, like in the classrooms of Media School.

Facade

Ventilation openings constitute the greatest architectural consequences of natural ventilation in the fagade. Local inlets and outlets, rather than central, affects the fagade expression to the greatest extent, as they are distributed over the entire fagade and need to cover a rather large area to avoid large pressure drops. The east fagade of the GSW Headquarters, which has a lot of ventilation inlets, is a prime example of that. Centralised ventilation inlets are typically located in towers away from the building, and outlets are located on the roof and do consequently not affect the facades. The Media School is a representative example of that. Characteristic ventilation elements like chimneys (Lanchester Library, UK), solar chimneys (The Environmental Building, BRE, UK), and double facades (Deutsch Post Headquarters, Germany) are all integrated in the fagade and therefore influence the fagade expression.

Advances in design and technology have also provided many means by which the shortcomings of contemporary houses may be overcome, and much improved new houses incorporating the design advantages of both traditional and contemporary houses may be created-such as creation of the experimental solar house.

Thermal mass may not be restricted in the exterior walls. Exterior walls may be insulated and lightweight and interior separating walls can be made with blocks or with concrete, which has a high thermal effusivity. The thermal mass can be located on the floor or on the roof. A thickness of 10cm of a massive material (concrete or brick) is quite suitable for providing coolness for the span of one day or for storing passive heat during a winter day.

In order to progress to the ultimate level the theory of the Cypriot solar house, the process of construction was commenced. The principle of design and construction of the solar

house is based on the theories and findings on passive solar architecture in Cyprus2, in and inevitable compromise with local house codes and town planning regulations.

The construction was decided to be a concrete frame and floors and roof (constructed as the typical Cypriot contemporary house, 250mm brick work and plaster on the interior and

exterior of the walls3. 70mm expanded polystyrene was used to cover the whole house, including walls concrete beams, columns and roof. In this way thermal bridges are excluded.

Winter indoor temperatures have also been successful4. Enough solar heat storage was collected and stored during daytime and released with the appropriate rate in order to maintain pleasant nightly temperature. The fireplace was used to top up the heat on occasions when winter evening temperatures dropped below the norms. In the winter of 2000 these occured only 8 times and the winter of 2001 these occured 10 times. The fireplace was lit on average three to four hours per night and the warmth was retained until well into the next morning.

The contractor has 21-acre site area decided to build 14 earth-sheltered dwellings. By this decision, it has been shown importance of the earth sheltered building energy gains: Energy Consumption, Noise Reduction, Aesthetics and Land use. One of the more common motivations for building an earth sheltered structure, like Durudeniz is to blend the building in with its natural surroundings. This is often the case on rural sites where the owner wishes to build a dwelling but also retain the ‘untouched’ beauty of the natural landscape.

Double use of the land, house underneath, garden on top, means earth sheltered houses can be built on smaller blocks than conventional houses and still have sufficient space for outdoor living. This makes earth sheltered housing particularly useful for low or medium — density housing developments, an area of construction that will no doubt increase in the future as the world population grows and cities become larger and larger.

The main ecological criteria considered in the Settlement are: Green roofs, Sky gardens, Edible landscape, Waste cycles, Passive heating and Natural ventilation, Biologic diversity etc.

A comparative study has been conducted for the earth-sheltered building and four sides on the land cases for same building conditions. (Eryildiz, 2002) Heat losses and auxiliary energy loads are calculated as:

Annual heat losses Auxiliary heat load (annual)

Earthsheltered 5.050 kWh(Q1) 43.24 kWh/m3

Ontheland 9.210kWh(Q2 78.85 kWh/m3

Only one design criterion taken into consideration changes the results in very large scale Q1 annual / Q2 annual = 5050 kWh / 9210 kWh = 0 .5483

The ratio shows the big difference on the heat gains and the importance of the energy efficient design.

A terrace house from 1956 was chosen as an example for the renovation. To implement it, we developed a completely new type of facade construction, which achieves the u values of a passive house with a thickness of only 9 cm. In addition, a thermal solar absorber was fully integrated into the southern facade, which heats the domestic hot water, assists the space heating, and reduces the thermal losses of the facade practically to zero. The new windows, which open outward, were constructed in the plane of the insulating envelope and all thermal bridges were eliminated.