The Value of Optimisation in Faรงade Engineering and Design An Overview of the Multiple Variables of Sustainable and Environmental Design of Building Facades
Perspective and Approach to Sustainable Design of Facades Real Estate, and Architectural Design Developers
and
Faรงade Specialists and Engineers
What is a Building Faรงade?
The Façade is one of the components of the Building Envelope
A Building Envelope – is the group of components which separate the indoor spaces from the outdoors. These components include all ‘physical’ barriers such as walls, roofs, windows, doors and foundations.
Building Envelope or / Shell or / Enclosure
Building Structure, Foundations, Internal Walls, Services‌etc.
Exploded View of a One-story house
Source: Building Construction Illustrated - Ching
Conventionally; the Main Functions of a Building Envelope – or ‘Enclosure’– have been: 1.Structural support and load-bearing. 2.Control of inward and outward flow of energy and matter. 3.Aesthetic element of interior and exterior.
Source: J.F. Straube and E.F.P. Burnett. Building science for building enclosures. Building Science Press, 2005.
The Façade is essentially the External Wall Component of a Building Envelope…
Source: Visual Dictionary of Architecture - Ching
What are the Functions of a Building Faรงade?
The Architects / Developer Conventional View
Source: Façade Construction Manual – Birkhauser – 2004
What are the Sustainability Aspects of Faรงade Design and Construction?
The Architects / Developer Conventional View
Heating, Ventilation and Air Conditioning (HVAC) Efficiency In cold climates, such as that of the UK, Energy Consumption % for Domestic Space Heating = 25% of total Domestic energy consumption In other countries with hotter climates such as the UAE, specifically Abu Dhabi, buildings cooling energy consumption had risen from 1625 MW to 4750 MW of power from 1990 to 2007 (= avg. increase 11.3% per year)
The Architects / Developer Conventional View
Heating, Ventilation and Air Conditioning (HVAC) Efficiency …The Energy Conservation Aspects Become Obvious Through Façade Control of Heat Transfer, HVAC Efficiency, and accordingly, Energy Consumption Efficiency can be achieved.
The Architects / Developer Conventional View
Façade Control Technique: Passive Solar Design
Passive solar design refers to the use of the sun’s energy for the heating and cooling of living spaces. In this approach, the building itself or some element of it takes advantage of natural energy characteristics in materials and air created by exposure to the sun
The Architects / Developer Conventional View
Façade Control Technique: Passive Solar Design
Passivhaus Design (Example from Hassan Fathy’s Architecture)
The Architects / Developer Conventional View
Faรงade Control Technique: Passive Solar Design
Multiple Variables Specific to Faรงade/Envelope Design
The Architects / Developer Conventional View
Façade Control Technique: Passive Solar Design Due to the complete dependence of Passive Solar Design Techniques on the Unique conditions of each building site; its success necessitates Optimisation‌ Passive Solar Design methods will usually achieve 15% reduction in HVAC energy costs; but usually does not exceed 45%, and anything beyond would be considered a rare success.
The Architects / Developer Conventional View
Is the Undertaking of an optimum Sustainable Faรงade subject only to Passive Design Theories?
Faรงade Design and Engineering Principles
Façade Design and Engineering Principles
1. Functional Criteria
Source: Façade Construction Manual – Birkhauser – 2004
Façade Design and Engineering Principles
1. Functional Criteria Heat gains are the obvious functional criterion related to sustainability (thus the use of passive design)…
Source: Façade Construction Manual – Birkhauser – 2004
Façade Design and Engineering Principles
1. Functional Criteria … but natural ventilation, and natural lighting are also a significant factors in the buildings Energy Conservation scheme…
Source: Façade Construction Manual – Birkhauser – 2004
Façade Design and Engineering Principles
1. Functional Criteria Again… the concept of multi-variable optimisation is evoked to produce an integrated solution
INTEGRATED SOLUTION
Source: Façade Construction Manual – Birkhauser – 2004
Faรงade Design and Engineering Principles
Is Energy Conservation the only Sustainability aspect to Faรงade Design? What other Principles Guide the design process that can impact Sustainability?
Façade Design and Engineering Principles
How about… •Economy of fabrication and construction? •Value Engineering and Conservation of Material? •Health and Wellbeing of Factory Workers, Site Labour, or Construction Site Neighbours?
Façade Design and Engineering Principles
2. Constructional Criteria (i.e. Fundamental Criteria)
Integrated Solution
Source: Façade Construction Manual – Birkhauser – 2004
Façade Design and Engineering Principles
At some point in history, all facades were load-bearers and part of the main building structure‌
A Cavity Wall Faรงade
Façade Design and Engineering Principles
Loadbearing vs. Nonloadbearing
The systematic separation of loadbearing structure and façade structure
a- External Cladding Leave b- Air cavity c- Main Loadbearing Structure d- Insulation
Vertical Section Showing Façade Leaves Source: Stone Cladding Engineering – Springer
Façade Design and Engineering Principles
Loadbearing vs. Nonloadbearing
This separation is an efficient load transfer mechanism that ultimately simplifies façade structure design and reduces material requirements …an economic and material conserving design.
Vertical Section Showing Façade Leaves Source: Stone Cladding Engineering – Springer
Façade Design and Engineering Principles
Multi-leafed /Multi-layered Design
This separation also allows for multi-layered or multi-leafed construction; which can include: 1.Insulation layers 2.Building Services 3.Air cavities
Source: Façade Construction Manual – Birkhauser – 2004
Faรงade Design and Engineering Principles
Ventilated Cavity
vs.
Non-Ventilated
Façade Design and Engineering Principles
Ventilated and Nonventilated Cavities The Cooling Effect of Ventilated Cavity Walls will result in minimization of HVAC / Mechanical cooling costs…
Ventilated Cavity Source: Guide for the design, construction and maintenance of natural stone facades - Centro Tecnológico del Granito
Façade Design and Engineering Principles
Ventilated and Nonventilated Cavities Non-ventilated facades will retain energy in internal heated spaces in cold climates (air is a natural insulator)‌ ‌ thus reducing heating costs
Non-ventilated Cavity
Faรงade Design and Engineering Principles
Prefabrication
Stick-systems
vs.
Panelised Source: CMHC - Glass and Metal Curtain Walls, Best Practice Guide
Façade Design and Engineering Principles
Prefabrication In Stick systems (in the case of aluminium curtain walls) all elements are fabricated separately and assembled, installed, and sealed at the construction site‌
Source: Building Construction Illustrated - Ching
Façade Design and Engineering Principles
Prefabrication In Stick systems (in the case of aluminium curtain walls) all elements are fabricated separately and assembled, installed, and sealed at the construction site…
These systems can be more cost-effective in low-rise or mid-rise buildings… however: 1.Construction is longer, and carbon footprint can be relatively high 2.Health and safety of worker, and residents of nearby buildings, are harder to control and maintain. Source: Building Construction Illustrated - Ching
Façade Design and Engineering Principles
Prefabrication In Panelised / Unitised systems all elements are fabricated and assembled at factories / fabrication facilities‌
Source: Building Construction Illustrated - Ching
Façade Design and Engineering Principles
Prefabrication In Panelised / Unitised systems all elements are fabricated and assembled at factories / fabrication facilities‌
These systems can be technically demanding, however: 1.Construction is much shorter, and carbon footprint is minimized 2.In the controlled environment of a factory, Health and safety of workers is easily maintained, and impact at construction site is minimized. Source: Building Construction Illustrated - Ching
Façade Design and Engineering Principles
Non-loadbearing facades do not transfer weight of the main building, but they have to carry their own weight, and weight of incident loads (wind, earthquakes‌)
Faรงade Design and Engineering Principles
Structural Steel, Stainless Steel and Aluminium Alloys Framing and Brackets, are almost exclusively used for the Faรงade's structure
Faรงade Design and Engineering Principles
Structural Steel, Stainless Steel and Aluminium Alloys Framing and Brackets, are almost exclusively used for the Faรงade's structure
Faรงade Design and Engineering Principles
Structural Steel, Stainless Steel and Aluminium Alloys Framing and Brackets, are almost exclusively used for the Faรงade's structure
Faรงade Design and Engineering Principles
Structural Steel, Stainless Steel and Aluminium Alloys Framing and Brackets, are almost exclusively used for the Faรงade's structure
Façade Design and Engineering Principles
3- Structural Principles
Source: Façade Construction Manual – Birkhauser – 2004
Façade Design and Engineering Principles
3- Structural Principles How is the Façade Material ‘coupled’ to the main structure? What are the structural considerations? What are the methods of fixation?
Integrated Solution Source: Façade Construction Manual – Birkhauser – 2004
Façade Design and Engineering Principles
The geometry / configuration of fixing elements:
Which is the safest and most cost-efficient, and least material consuming? a. b. c. d. e. f.
Over entire surface Linear, vertical framing Linear, horizontal framing Linear, Peripheral framing Discrete (brackets) Multiple Discrete
Source: Façade Construction Manual – Birkhauser – 2004
Façade Design and Engineering Principles
How will the façade structure react to different loads? Source: Façade Construction Manual – Birkhauser – 2004
Façade Design and Engineering Principles
Stresses Induced:
A 10 mm diameter steel wire rope has a breaking load of 5 tons of force when loaded in Pure Tension
A much larger section will be required to carry the same forces in Compound Loading (bending, torsion‌etc.)
Façade Design and Engineering Principles
Stresses Induced: Optimised Solutions can reduce the section size by carefully studying and adjusting the loading mechanism… Thus, creating design with minimal material consumption…
Façade Design and Engineering Principles
The Movement of Fixing Elements:
Source: Façade Construction Manual – Birkhauser – 2004
Façade Design and Engineering Principles
The Movement of Fixing Elements:
Sliding
Fixed
Fixed
Sliding
Facades must allow for vertical movement, to account for earthquakes, or thermal expansion… The location of movement might seem logical in the top (Standing Façade) and the other solution (Suspended Façade) will seem counter-intuitive.
Source: Façade Construction Manual – Birkhauser – 2004
Façade Design and Engineering Principles
The standing façade creates what is called a column effect, which induces additional loads in compression (buckling loads) and requires bigger sections, therefore more material is consumed The suspended façade is loaded in tension only, requires a smaller section, less material, and is more efficient…
Sliding
Fixed
Fixed
Sliding
Source: Façade Construction Manual – Birkhauser – 2004
An Example of Combined Principles / Multiple Variable Optimisation
Thermal Bridging of Brackets/Supports
Visualization of Thermal Loss Computer Simulation of the Bracket
Thermal Loss Rate Differentials Graph of the Bracket
Structural Thermal Bridging occurs when structural elements penetrate the envelope creating discontinuities in the thermal insulation creating a path for heat loss (in case of heated internal spaces), or heat gain (in case of cooled internal spaces) Sources: www.halfen.de
An Optimised design is made to: 1.Prevent thermal bridging 2.Improve structural performance 3.Reduce cost and material consumption
Sustainability of Steel
How does Steel fare against other construction materials in terms of Sustainability?
Sustainability of Steel
Metals / Alloys in general have high Strength-toWeight Ratios, in comparison to other construction materials Example: Concrete = Steel =
This means less material for the same structural performance Steel is also one of the cheapest metals for its strength
Sustainability of Steel
Steel is completely Reusable or Recyclable after the end of a building's life-cycle And almost 0% waste in fabrication, with all scrap being recyclable.
Sustainability of Steel
Steel is fabricated, treated, coated, welded, assembled offsite in controlled factory conditions, with minimal risk of impact in terms of Health and Safety to the workers
The Value of Optimisation
The Value of Optimisation
Design By Routine
vs.
Optimum Design
Source: Optimum Design of Steel Structures
The Value of Optimisation
Design By Routine Design without goals, objective functions Fulfilling design constraints can only be approximate Minimum material consumption or cost is not reached It is impossible to develop new, innovative structural types
vs.
Optimum Design Exact formulation of Design Problem and goals or constraints Inclusion of all engineering aspects Consideration for fabrication/cost aspects Can achieve significant cost savings in design stage Allowing designers to innovate, and create competitive designs
Source: Optimum Design of Steel Structures
Thank you‌