Structures that breathe
Since installations have become a fundamental aspect of projects, with a significant presence in the overall budget, and volume of the building, designers have tried to integrate them as much as possible with the building, making them coincide with other architectural elements such as structure and envelope.
This integration not only offers a large field of design possibilities, but it allows a considerable reduction of the total height per storey , and environmental impact of the building during its construction process, As the energy required is lower during the usage stage of the building, , it adapts to nZEB requirements and facilitates the implementation of sustainable strategies such as thermal activation and ventilation by heat recovery devices.
The evolution of the integration of structure and facilities
Romans already heated their hot spring Caldarium by a hypocaust, an underfloor heating system, but it was not until the appearance of mechanical air-conditioning systems and electrical wiring that the horizontal distribution of facilities began to occupy an important space of the building.
The integration of installations and floors were first put into practice in ships and airplanes, where the control of mechanical elements is a fundamental aspect of its operation. Also, examples can be seen in nature where the spongy structure of bones is traversed by "facilities" such as nerves and blood vessels.
The most interesting examples in the twentieth century refer to buildings of great spans and depth. When adopting solutions in large structures with a high load of facilities, lightweight solutions, such as triangular steel structures (Rogers and Piano Pompidou Center, General Motors by Eero Saarinen, Lake Grove Village in Michigan). Other technologies in concrete can be developed such as the Art Gallery of Yale by Louis Kahn.
In the current panorama, there are solutions for the integration of installations such as perforated steel beams, slabs with longitudinal registers (cast-in-place and pre-cast hollow core) or the HOLEDECK patented system consisting of concrete voided slab. Works are also being done with triangulated wooden solutions that allow the passage of installations.
nZEB advantages during the construction of the building resulting from integration
By integrating structures and installations, which are normally superimposed, the total section of the building is significantly reduced (in office buildings between 35 and 70 cm. representing about 15 and 25% of the total section of the building). The resulting economic advantages also become nZEB advantages.
Height and vertical constructions reduction
By reducing the height of each floor with the same volume of concrete, more floors can be obtained, which also results in a reduction of vertical building elements such as facades, walls, columns or partition walls.
Elimination of suspended ceilings and raised floors
With a system where installations are accessible from the top or bottom of the structure the additional layers of floor and ceiling can be completely eliminated, favoring the hygiene, registrability and transformability of all the facilities of the building.
Optimization or reduction of the structural material
Since more depth can be attributed to the structure as it can be shared with the facilities, increasing structural inertia, there is a significant reduction in the use of material for steel, concrete, or wood solutions.
nZEB integration advantages over the life of the building
Reduction in the volume to be air-conditioned
As the height of each floor is reduced, less volume of air needs to be heated. The reduction in the energy required is proportional to the reduction of the building’s height.
Thermal activation of the structure and thermal inertia
For high thermal inertia structures, such as concrete slabs with perforations, the surface in contact with the air is larger than a conventional slab, therefore the thermal exchange between the mass of the structure and the air develops more efficiently, especially when air circulation is performed by plenum.
The integration of structure with ventilation systems and recuperators
In nZEB or Passivhauss, for housing or tertiary uses, the use of heat recovery devices has been imposed as an energy optimization system, being necessary the implementation of a network for air supply and air return thus requiring the installation of suspended ceilings. In an integrated solution, these ducts can be arranged within the perforations of the slab, achieving substantial savings in height and facilitating the assembly and transformation of its layout.
The transformation of the building’s use and the arrangement of its facilities can be performed faster and more efficiently, significantly increasing the useful life of the building.
Design recommendations to integrate structure and facilities
Even though the integration of structure and facilities can be done at any point of the design process, below are some design recommendations.
- The integration of structure and facilities is more efficient if taken into account at early stages of the design process, allowing many of these facilities to be left exposed.
- The incorporation of new floors or the reduction of the total volume of the building is possible by configuring its geometry and appearance.
- Considering from the beginning the layout of both vertical and horizontal installations. In large buildings, it is advisable to horizontally zonify the air installations in order to avoid the suspension of main ducts.
- Even when the integration is performed with a finished design, in a modified version that integrates structures and facilities, advantages such as the increase of the useful height, simpler layout of the installations or reduction of constructive elements and structural materials can be achieved.
Quantifying the reduction of energy consumption of the building
The advantages of integrating structure and facilities will depend on various parameters, such as the use of the building, spans between column, initial structural solution and facilities’ requirements. Therefore, an individual study is necessary in order to determine the most appropriate solution.
In general, it can be said that the integration of structure and facilities will always pose sustainability advantages regardless of the starting conditions. In order to asses the reduction of energy consumption of an integrated building it must be compared with one that does not employ such integration.
As an example, a comparison between a conventional office building with a structure of beams and slabs, and an integrated structure is performed employing HOLEDECK 45.
Prices from Itec’s database are considered, which also allows to value carbon emissions.
Results concluded that for a conventional office building it is possible to accomplish a height saving of 12%. Height savings can be achieved in office buildings with more structural depth and installations, which are represent 20%.
Many of the CO2 emissions of the building occur during its construction. The conventional building has a C-type rating, which suggests that energy savings are most important during its useful life. more energy-efficient nZEB buildings, major savings of CO2 emissions occur during the construction process.
The most sustainable building is that which is not built, and if it is, it employs the less built volume and raw materials and energy in order to function.
Integrating structure and facilities is a very efficient way to reduce the impact of the building, especially when conceived from the beginning of the design process. The reduction of carbon emissions obtained by integrating structure and facilities can be between 10 and 25% , depending on the conditions established for the non-integrated building.