05 energy and matter part 2

CliC Climate Construction in Architecture Lecture 5.

Energy and Matter Sustainable Design Principles in Architecture Part 2.

Thermal comfort

Norbert Lechner uses the analogy of a car to explain the principles of thermal comfort. Our body constantly produces heat (energy) while is exposed to microclimate around it, therefore loses/gains energy constantly. They key to thermal comfort is to balance heat losses and gains.

Radiation

Radiation is the most important element of thermal comfort.

The effect depends on surface area (A) and temperature (T).

Even if there is only a small temperature difference between user and surface, the impact on thermal comfort can be significant if the surface is large.

Radiation

In case of Climate Construction, manipulating the surfaces is a strong and efficient tool to create different climates. Basic rules of energy exchange and behavior of materials play a crucial role in this, therefore it is important to understand the basic aspects.

Heat

Heat is basically kinetic energy of small components in a material. The hotter the medium, the quicker the components move in the volume. Heat is in direct relation with mass and temperature: double mass or temperature represents double heat (Watt) of the object.

Energy flow

In our environment there is always temperature difference, therefore energy is always on the move. Heat always flows and radiates from hot to cold areas. In case the two object is in physical contact, the energy flow is called conduction. In case energy flows through the air, it is radiation.

Energy flow

In addition to temperature difference, energy also flows because of the change of density. Hotter gas/liquid is lighter than colder one, therefore it flows upwards. Norbert Lechner explains this idea with the analogy of height difference.

Energy flow

In case of architecture, spaces with large ceiling heights often took advantage of this to assure air movement and cold air indoors.

The floor area was usually heated by sunlight or human body, which flows upwards and is cooled by the colder ceiling’s radiation, which finally forces the cooled air down again.

Energy flow

Similar effect can be achieved with a static concentrated heat source. If it is well located in the room, the air can constantly flow around without any energy investment (like fan). The heated air flows upwards or towards cold areas and eventually returns to the heater after being cooled down.

Air flow

Movement is not only important because of ventilation but also because of cooling. Evaporation is much faster when air is on the move. Perspiration intensity depends on humidity and if the air does not move, the immediate air gets too humid and needs to be replaced.

Air flow

Generating temperature differences is one of the most effective way to move air around. Creating shadow is one way to move air, which is a typical strategy for hut-humid climates like Japan. Another way is to use water. Water surfaces have large surfaces that can absorb heat of the air.

More importantly, water has large thermal mass.

Thermal mass

Thermal mass is the heat storage capacity of a material. The higher the value, the more energy can be stored. Heat storage capacity is different for any material. For example, heat storage of water is 3000 times higher that that of air.

Thermal mass

Or 3 times higher than silicate materials. Heat storage capacity is one value for each material (intensive property).

Thermal mass is different for every structure, because it depends on capacity and material volume.

TM=C*V (Thermal Mass= Capacity * Volume)

Time-leg effect

Thermal mass is crucial when it comes to temperature of the surrounding surfaces. In case temperature is hot outside, the heat starts to flow in the building (from hot to cold). This however takes time, especially when the surface has a large heat mass.

Time-leg effect

The effect of thermal mass is similar to latent heat. Unlike sensible heat, in case of latent heat the material absorbs energy without increasing temperature.

Time-leg effect

In case of thermal mass the same happens. The energy is absorbed, without significant increase in temperature. Since in case of thermal comfort the interior surface temperature matters, the mass can effectively protect the environment indoors.

Time-leg effect

Naturally, the surface will eventually heat up, if the temperature outside remains hot for a long time. The intensity of heat flow depends on temperature difference and the material of the wall.

Time-leg effect

If thermal mass is high enough, this process may take more than 8-9 hours. If that is the case, outside temperature drops after sunset and heat turns back, which is called time-leg effect.

Thermal conductivity Thermal mass is only one element that slows the heat flow between outside and inside. Thermal conductivity shows the amount of energy that can flow through a material in a given time. The higher the value, the more energy can pass through at the same time.

Thermal conductivity is different for each material (intensive property), some have higher resistance than others. Wood for example is very good insulator, while steel is a very good conductor.

Thermal conductivity, resistance

The actual heat flow of a structure depends not only on conductivity but also on the thickness of the material. For example, the heat flow in a 1” wood is the same as in a 12” block of concrete, although the conductivity of the second is much higher (worse).

The actual heat flow in any structure therefore is calculated with thermal resistance, that depends on thickness and conductivity of the material.

R=d/λ (lambda) Or Resistance=thickness/conductivity

Energy flow

Finally, the total energy loss depends not only on the thermal resistance, but also on the total surface and the temperature difference. The higher the building surface or temperature difference, the more energy moves between inside and outside every second.

E=R*A*ΔT=d/Ν*A*ΔT Or

Heat =Resistance*Surface*Temp diff.

Norman Foster: Reichstag Berlin, Germany

The historical building of the German Parliament has been renovated after the unification of East- and West-Germany.

The project was symbolical both politically and architecturally as transparency met sustainability.

Norman Foster: Reichstag Berlin, Germany

The original opaque dome above the main chamber was destroyed during WWII. The architect proposed a new glass dome instead that allows visitors to look in the chambers without disturbing the work below.

Norman Foster: Reichstag Berlin, Germany

The glass dome included a reflecting structure that directs sunlight downwards into the chamber hall. Additionally, the structure also works as a ‘solar chimney’ that leads foul air upwards from the hall towards outside.

Norman Foster: Reichstag Berlin, Germany

Sunlight improved the working conditions inside since natural lighting is much more effective and healthy than artificial one. Additionally, it also saves operational energy.

Norman Foster: Reichstag Berlin, Germany

The shape of the reflecting structure has been designed according to the solar angles. The structure has also a shading net (left side of the picture) that blocs strong sunlight from the south to block glare effect.

Norman Foster: Reichstag Berlin, Germany

Additionally, the reflecting structure also enhances ventilation. Sunlight heats the reflecting structure that warms the air, that flows upwards and leave the building.

Norman Foster: Reichstag Berlin, Germany

Fresh air enters the building from the west side. This is the first characteristic of the building where thermal mass is a real asset: fresh air takes a long way to the chambers while tempered mass radiation warms it up/cools it down.

Norman Foster: Reichstag Berlin, Germany

Visitors can enjoy the view from the glass dome while the reflecting structure illuminates both chambers below and dome above.

Norman Foster: Reichstag Berlin, Germany

Normally, a building would receive additional insulation layers on the outside to increase the buildings’ energy performance. In case of historical building, this is not an option, because the ornaments are difficult to cover.

Norman Foster: Reichstag Berlin, Germany

Instead of insulation, the project is taking advantage of large thermal mass of the building itself and under it.

Tracks (6) transport biofuel to the site that feeds a generator (7) producing electric power for government district (5).

Norman Foster: Reichstag Berlin, Germany

The burning process of the generator produces a lot of heat and needs to be cooled. The water that is used to cool the generator heats up in the process. The warm water runs through the floors (3) and heats the spaces when needed.

Norman Foster: Reichstag Berlin, Germany

In case of cooling demand, the warm water goes underground (1) where it will be stored for later. Warm water returns by heat pump (2) and warms the floors like the one from the generator.

Norman Foster: Reichstag Berlin, Germany

The used water flows down to another underground storage (4) from where it can go to generator (7) to cool again.

Norman Foster: Free University Berlin, Germany

Free University of Berlin Library is a building that has a very simple energy concept that is similar to that of planet Earth.

The building has a heavy mass of floors that is surrounded by a light and thin structure and layer of air.

Norman Foster: Free University Berlin, Germany

The external skin is a steel frame that is clad by aluminum panels and glass openings. During summer the upper openings let used air pass through. Sunlight heats the air in the external layer that enhances the ventilation process.

Norman Foster: Free University Berlin, Germany

In case of winter, the same solar gain heats the air before reaching indoors. The openings let air in the skin at the bottom, air is running upwards as it is heated by the sun. A the top they enter the space below.

Norman Foster: Free University Berlin, Germany

Section shows the building with the thin layer of air (the same layer as the structure) that normally works as an insulation (air is a very good insulator). Fresh air enters this skin at the bottom and reaches the spaces passing through until the top or simply flowing through the floors.

Norman Foster: Free University Berlin, Germany

The floor+wall mass and the skin are not in physical contact, air-insulation is wrapped around the mass like in case of planet earth. Heating and cooling is provided by the mass (water channels running in ceiling and floor).

Norman Foster: Free University Berlin, Germany

The building is an extension of an orthogonal structure and is located inside the courtyard of the building. Its form, planning, structure and materials are all generated by the sustainable climate construction concept of the building.

Norman Foster: Free University Berlin, Germany

The original concept comes from Buckminster Fuller, who described Climatroffice as an architectural concept that focuses on generating climates inside the building based on properties of materials and their effect on microclimate.

Norman Foster: Free University Berlin, Germany

Detail of the upper layer of the building envelope, showing window opening and aluminium-clad insulation panels.

Norman Foster: Free University Berlin, Germany

Detail of lower layer of building envelope, showing translucent textile and steel structure. The textile keeps the air layer separated from indoors which enhances insulation (similar to clothes, that keep an air layer between exterior and body). Textile also disperses sunlight to avoid glare.