Pure Transparency

Designing a complete glass shelter for the temple of Apollo Epikourios at Bassae, Greece.

_OVERVIEW

The ancient Greek temple of Apollo Epikourios, isolated as it is in a mountainous rough ter- rain in Western Peloponnese, is one of the most important Greek votive sanctuaries of the Classic era.

It was built in the late 5th century BC (around 420 BC), mainly of local limestone and it is said by Pausanias (VIII 41.7-8) to have been designed by Iktinos, the same architect as Parthenon. The temple, famous for its internal Ionic frieze and the earliest known Corinthian Capital, was the first Greek monument to be listed by UNESCO as world heritage in 1986. At the present, it is difficult to appreciate the beauty of the temple, due to an opaque canopy which completely encases it and obstructs any exterior views of the monument, prohibiting visitors from realizing its unique architecture. This protec- tive canopy was erected in 1987 as a temporary solution since it was essential to protect the specific temple from further weathering. The reason was that the limestone that the temple is built of is a material vulnerable to the elements, espe- cially to rain and ice; the extreme weather conditions that prevail during wintertime in the area have caused the exten- sive deterioration of limestone, leading to severe erosion problems and structural damages of the temple. Since 2000, the temple is under extensive restoration works in order to repair and strengthen its foundation and restore the damage of the architectural members. Nonetheless, even after the completion of the restoration works, the monument, if uncovered and exposed, will remain subject to severe corrosion because of the combination of the building material and the environmen- tal conditions. This combination does not apply to the majority of the ancient Greek temples, which are built in friendlier Photograph of the temple before 1987 Current situation of the temple environments and are made of marble, a much more durable material.

In this work, a novel, completely transparent shelter is proposed so as to ensure the protec- tion of the monument from the elements, and at the same time, to make it publicly visible by following minimal intrusive architecture principles. In order to minimize the visual obstruc- tions, not only the cladding, but also the load bearing structure of the shelter, is proposed to be made of glass.

The design of such a protective shell is not only an architectural challenge, but also a challenge in terms of structure; since such a large glass beam span has not been realized in the past. Furthermore, it is a challenge in terms of thermal perfor- mance -regarding the high sun radiation intensity and temperature values that appear in Greece during summer. For these reasons, the need for an holistic assessment of the construction, taking into account all the relevant parameters, is crucial for a successful, sustainable and long-lasting, not only architectural, but also technologically innovative solution.

_ARCHITECTURAL DESIGN

The new shelter should be differentiated from the ancient temple, so that the visitor will conceive the architecture of the monument as one integral unit; on the other hand it should be incorporated into the environment to allow the temple’s con- nection with the surroundings unaffected. The presence of the shelter should actually be a form of absence. The key for this is minimal design and maximum transparency: the overall design takes advantage of the “keep it simple” principle, while not only the cladding but also the load bearing structure is suggested to be made of glass. Subsequently, a neutral design and a simple form were chosen for the shelter, in order to promote the ancient temple, without distracting the visitors’ focus from it but also for allowing for the use of glass as a load-bearing component.

Proposed Solution: An all glass shelter that re-connects the temple with its surroundings.

_STRUCTURAL DESIGN

The load-bearing structure of the shelter consists of reinforced glass beams and fins. The slender dimensions of the columns and beams are plausible if the clad- ding is part of the load bearing structure.

In the same way as in airplanes, the cladding is treated as a structural skin that ties together the load-bearing “rib” structure, turning the shelter into a strucutral whole that behaves as one rigid unit against loading. To make this structural scheme feasible, joints are needed that visually do not obstruct, allow force transfer and provide structural safety. The reinforced glass solution chosen will only be safe if the joints are at least as safe as the glass components. In order to minimize the connection surface of the joints, the steel reinforcement of the load-bearing elements, as well as the spacers of the façade and roof panes serve a multifunctional use: Besides their primary function, they are simultaneously used as connectors between the different elements. In “Skin” this way, a dry and demountable connection is accomplished that allows the glass units to remain intact. Regarding the structural performance, preliminary structural simulations and the results of the laboratory compression test indicate that the proposed structure should be able to withstand buckling due to its mono- lithic behavior. From the structural analysis it was also deducted that heat-strengthened glass is needed for the load-bearing structure components, while the structural skin can be made of annealed glass.

“Ribs”

_CLIMATIC DESIGN

The roof angle together with the natural venti- [Roof] High reflective coating (> 25%) lation helps to reduce hot air stagnation. The aim is to minimize the overall energy demand required to obtain thermal com- Natural Ventilation Outlet + 50% fritting (sun shading) fort through passive strategies: an optimum combination of glass properties, frit- [fritting] ting, utilization of the thermal mass and of natural ventilation.

The shelter functions as a protection shield from the nature’s elements and it can be described as a semi- 50% density outdoor space, an area which while ‘still being exposed to the outdoor environment in most respects, include man-made structures that moderate the effects of the outdoor conditions’. Accordingly, the temperature range, 30% density conceived as comfortable by the occupants is wider. It was determined that for the shelter this range lies be- tween 10-30 Celsius degrees. This range also enhances the further maintenance of the temple, since wide 15% density outdoor temperature fluctuations can damage the stone. The meteorological data of the temple’s specific location indicate a warm climate with many hours of sun ex- 0% density Natural Ventilation Inlet posure. Thus, the main measures concerning the shelter were taken towards reducing the risk of overheating. In short: - Sun-shading is applied in the form of gradient glass fritting. Fritting creates an effective UV shield that helps controlling solar gain and glare and enhances diffuse light, which is the most appropriate light for anaglyphs such as in the temple. - In order to further reduce the solar gain to the radiant transmittance, double glazing with an external high reflective pane (Pilkington Suncool Silver 50/30) was applied in the roof and with a low-e glass pane (Pilking- [Structure] Pilkington Optiwhite ton Optitherm) for the facades. - Stack ventilation is used for the recycling of air inside the shelter through natural ventilation. This is achieved by an inlet at the bottom of the west façade and an outlet on the top of the east façade. The air flow rate is [Facades] Double glazing with low-e coating on the outer pane further accelerated due to the roof slope. - A key factor for the thermal performance of the shelter is to acknowledge the fact that the temple itself + gradient fritting: 0 -50% serves as a very effective thermal mass. Since the shelter is located in South Greece (warm climate zone) the utilization of the temple’s thermal mass plays a critical role for the stabilization of the interior temperature, especially during summer when there is a large temperature difference between day and night.

Student: Faidra Oikonomopoulou_4120647_Track: Building Technology_Subtrack: Computation & Performance _ Topic: Pure Transparency _ Mentors: Dr. Fred Veer_Dr. Regina Bokel