At the turn of the 20th century, the zeitgeist of building technology in the US was utilizing handcrafted terracotta ceramic tiles mounted on structural steel framing. There were dozens of companies in the United States alone employing thousands of workers making each tile from custom built moulds interpreted from architects’ drawings. As pressure on the architecture, engineering and construction industry increased the size and speed of how buildings were built, building technology evolved to meet the needs of the changing market, and handcrafted time-intensive building systems fell by the wayside of the mainstream industry. Today, few such terra cotta companies remain, and most are primarily involved in the historic preservation of old buildings. Yet, the natural process of erosion of the Earth’s crust likely produces clay faster than we could ever hope to use it. While terracotta has many desirable properties as a building material; durable vitrified (glazed) finishes, thermal mass characteristics (energy efficiency), humidity controlling properties (environmental control), and plasticity of form (structural stability), modern building techniques require an efficient and resilient construction system with a streamlined design and manufacturing process. While modern terra cotta products are by-and-large globally available and developed from a mature and efficient industry, the bridge between the energy manipulation of the material and the product types available has not been built.
To be of significant value, a new building industry product must contribute to energy efficiency, utilize abundant or recyclable materials and encourage local economic development through appropriate available technologies. Ceramic building materials meet these requirements. To reintroduce architectural ceramics more widely to the high performance design and construction industry, traditional terracotta must be
expanded. In this time of diminishing energy resources, it is desirable to use the properties of ceramics to support the thermal management of energy transfer across the building envelope.
1.1.3
Thermo Active Building System as a Building Envelope
When considering the active transfer of energy across the building envelope, there are two broad categories of systems: active and adaptive. Mike Davies’ characterization of the polyvalent wall, as shown in Figure 1.1 is the cornerstone of the development of Adaptive Building Envelopes and paved the way as the primary instigation towards the development of multiple functioning building envelope systems. The contemporary work being developed at TU Delft in the Architectural Engineering + Technology Department and specifically the development of the integrated wall strategy by Professor Ulrich Knaack, as illustrated in Figure 1.2, has been used to inform advances in the characterization of Adaptive Building Envelopes as a multivalent wall that engages the building envelope construction with bioclimatic forces lowering reliance on energy intensive mechanical systems (Knaack, 2007). The research in this dissertation focuses on the thermal adaptability of the building envelope because this is the most extensive system that has yet to widely develop any paradigm shifting advances in the state of the art and that also has the most opportunity to have the most substantial impact on energy use in the building sector.
The ability to control energy transfer rates for heat loss and heat gain through the building envelope can be developed by storing and releasing sensible heat as latent heat. This effect has traditionally been accomplished with the application of thermal mass as a building system. As illustrated in Figure 1.4 and Table 1.1, the drawback of using these types of systems (e.g., terra cotta, clay brick, concrete, etc.) in simple terms (detailed in Section 1.4) are: 1) the unmanageable time lags of energy transfer; 2) the significant mass required to store the quantities of energy; 3) requirements of modern building envelopes largely isolate mass systems to either the interior (i.e., passive thermal or Trombe type) or exterior (i.e., rainscreen type) of the weather barrier which is the demarcation of the building envelope as either interior or exterior. One solution that makes the qualities of thermal mass more effective in modern building operation is to integrate a controllable countercurrent energy exchanger design into a thermal mass building system.
1 Silica weather skin and deposition substrate 2 Sensor and control logic layer — external 3 Photo electric grid
4 Thermal sheet radiatior/ selective absorber 5 Electro reflective deposition
6 Micropore gas flow layers 7 Electro reflective deposition
8 Sensor and control logic layer — internal 9 Silica deposition substrate and inner skin 1 8 4 5 6 7 3 9 2
FIG. 1.1 Mike Davies’ vision for the Polyvalent wall where each distinctive layer has a specific use . Redrawn (Davies, 1981).
In modern building envelopes, this could allow the capacitive storage of mass systems to transgress the weather barrier demarcation line if the exchange systems are deployed as an array to move energy between the inside and outside. By controlling the transfer, storage and release of thermal energy across the building envelope, a thermal mass-based system can achieve the same balancing effects, without the unmanageable time lag and the required quantities of materials used in traditional thermal mass strategies.
1 eterior energy collector functional element 2 Reflective functional element
3 Insulation functional element 4 energy storage funtional element 5 Integrated structural element 6 Interior energy transfer element 1 4 5 3 2 6
FIG. 1.2 The multivalent wall as envisioned by Ulrich Knaack where the layers have both specific uses and recombinant interactions. Redrawn (Knaack, 2007).
Thermo-Active Building Systems (TABS), as exemplified in Figure 1.3, are considered to be active systems where a working fluid is used to heat or cool the thermal mass, typically an interior floor slab or mass based wall, through integrated piping (Olesen, 2012). TABS have typically, though not exclusively, relied on an active energy source (e.g., boiler, chiller, etc.) to charge the mass. An alternative to using an active energy source is to use locally available energy sources (e.g., ground or water temperature, ambient air temperature, insolation, etc.). While not a high quality of power, a system relying on locally available energy resources uses significantly less input energy. Unlike systems that use energy intensive energy sources, this approach is not a brute force system. Available resources are often low grade or fluctuate and may not be able to be used based on weather, climate and building energy demand profiles; the system ‘adapts’ to the conditions to best use the resources available at the times where this is effective.
FIG. 1.3 Installation of the Thermo Active Building System in the form of a radiant slab in the Balanced Office Building (BOB) engineered by VIKA Ingenieur GmbH in Aachen. (VIKA Ingenieur, 2005)
Developed as the main body of the research of this dissertation, the Thermal Adaptive Ceramic Envelope (TACE) is one instance within the broader typology of TABS. The TACE system integrates a working fluid to assist in the heating and cooling of the interior of the building using a scalable form of countercurrent energy exchange. It operates by adapting its thermal characteristics, depending on the local energy resource and demand conditions, that are being managed (e.g., heating vs cooling, night time radiation, diurnal energy storage, etc.). The system is active because it deliberately and mechanically transfers energy to achieve desired results. The differentiating quality, however, is that the system adapts to the local conditions of energy resource and demand with minimal external energy inputs.
Stone wall Mono-Assembly Layered-Assembly Insulative active Rainscreen wall Combined Wall System exterior Insulation Finish system aerated autoclaved Concrete Frame wall Integrated Concrete
Formwork wall adaptive
Integrated (Polyvalent) Thermal Mass sandwich wall M1 M2 L1 L2 L3 C1 C2 C3 A1 A2 Assembly Type -
Mono, Layered, Combined Drawbacks of Energy Transfer Control Strategies -Various Envelope Assemblies Assembly Type - Integrated Potential Design Solution - Active/Adaptive Envelope
Structural Insulated Panel system
FIG. 1.4 Taxonomy of wall assemblies showing the flows of energy across the building envelope and categorizing the drawbacks and potential solutions of the various broad categories of envelope types: Mono-Assembly (M), Layered-Assembly (L), Combined-Assembly (C). The area of focus of the dissertation is in the Layered-Assembly, Integrated, Adaptive Typology (A).
TabLe 1.1 Corresponding table of aassembly types, drawbacks, and solutions to Fig. 1.4.
Assembly Type Drawbacks of Energy Transfer Control Assembly Type Potential Design Solution (M), (L), (C) Various Envelope Assemblies (A) Active/Adaptive Envelope
M1 M2 C1 C2
Lag Time: useful energy release is out of sync with demand or does not adjust to dynamic space needs
A1 A2 Active circulation with adjustable flowrate moving energy held in both material, working fluid and storage bank MI M2
L1 L2 L 3 C1 C2 C3
Flow Direction: lack of control strategy for useful energy flow in or out of space
A2 Bi-directional active energy flows for
heating and cooling of space L1 L2 L 3
C1 C2 C3
Interior/Exterior Separation: useful energy is relegated to inside or outside.9 cm
A1 A2 Energy is captured transformed, stored
and redistributed across the building envelop demarcation line