04 energy and matter part 1 slides

CliC Climate Construction in Architecture Lecture 4.

Energy and Matter Sustainable Design Principles in Architecture Part 1.

Relative comfort, universal strategy‌

Although thermal comfort is relative (basically personal) issue, the architectural strategy that can aid to reach our goal may be more general in terms of strategy and approach.

Relative comfort, universal strategy‌

Technological solutions however vary from place to place, because some system may be better for one place than another. There may be a general strategy, but there is no universal solution.

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.

Thermal comfort

Energy losses are: -human body energy loss
 (natural convection, radiation, exhalation) -external energy losses
 (forced convection, conduction, evaporation)

Thermal comfort

Energy gains are: -metabolism (human body energy production - internal gain) -external energy gains
 (i.e. insolation, air temperature, surfaces, radiation, etc.)

Thermal comfort

Example 1 (cold environment): In case the ambient temperature is lower, the heater’s energy input has to balance the heat loss of the body.

Human body loses energy in 4 basic ways: Perspiration, Radiation, Conduction and Convection.

Thermal comfort

Example 1 (cold environment): Perspiration is the only cooling effect of the human body that takes place even if the environment temperature is lower than 37 Celsius (our body temperature).
 The loss is about 17 Watts/sec (about 600 g of water/day).

Thermal comfort

Example 1 (cold environment): Convection occurs when the human body comes in physical contact with an colder/warmer object. The energy exchange depends on the insulation and the temperature difference.

Convection loss is usually small (unless we are barefoot) and therefore we calculate it together with conduction.

Thermal comfort

Example 1 (cold environment): Just like in case of convection, conduction occurs between human body and a colder object, but this case the other object is the surrounding air (5 cm thick layer).

P=k*A*(Tskin-Tamb)/d=5.67⋅10^−5W/ m2K^4∗1.7m2∗(296K-310K)

P≈8.92W

Thermal comfort

Example 1 (cold environment): Warmer objects do not loose energy only through physical contact, but also through radiation. This is the highest part of the total energy loss. Human skin has emissivity about 1.0 (0.96), 1.7 sq. m surface area and 310 Kelvin (36.85 C): P=e*σ*A*T^4=0.97∗5.67⋅10^−8W/m2K^4∗1.7m2∗(310K)^4

P≈860W (14 lightbulbs!)

Thermal comfort

Example 1 (cold environment): Radiation however depends on temperature difference, therefore the surrounding surfaces lower energy loss significantly (surface temperature: 23 C): ΔP≈(5.67⋅10^−8W/m2K^4)*(1.7m2)*((310K)^4−(296K)^4) ΔP=112.95W

Thermal comfort

Example 1 (cold environment): The net energy loss is therefore only 138.87W. This can be further lowered with lowering conductivity or increasing the temperature of surrounding surfaces (floor, ceiling, wall).

Thermal comfort

Example 1 (heating): The net energy loss is therefore only 180 W. This can be further lowered with lowering conductivity or increasing the temperature of surrounding surfaces (floor, ceiling, wall).

Thermal comfort

Example 1 (heating): The net energy loss is therefore only 180 W. This can be further lowered with lowering conductivity or increasing the temperature of surrounding surfaces (floor, ceiling, wall).

Thermal comfort

Example 1 (heating): The net energy loss is therefore only 180 W. This can be further lowered with lowering conductivity or increasing the temperature of surrounding surfaces (floor, ceiling, wall).

Thermal comfort Conclusion:
 In terms of heating, the emphasis is on the temperature of the surrounding surfaces and not the temperature of the air.
 The first example therefore is not sufficient, because the heating capacity (100W) is not enough.

The 2nd and 3rd can work, but to assure thermal comfort, the heater needs to warm up both the air and surrounding surfaces.

If the room is sufficiently insulated, the difference between the two systems is therefore only the necessary time to achieve Since buildings (just like human body) loose energy towards the environment, the heating capacity/1 sec of the heater needs to balance both at the same time.

Thermal comfort

Example 2 (warm environment): In case of cooling, the case is reversed: the energy gain needs to be kept at a lower (or equal level) than the heat loss demand of the body (resulted by metabolism) Human body loses energy in 4 basic ways: Perspiration, Radiation, Conduction and Convection.

Thermal comfort

Example 2 (warm environment): Perspiration is the only cooling effect of the human body that takes place even if the environment temperature is lower than 37 Celsius (our body temperature).

Thermal comfort

Example 2 (warm environment): In case of higher temperatures however, perspiration increases significantly., up to 1.5 liter / hour (1500g/hour), which is about 1 kW. Maximum level can be as high as 3.5 liter / hour (tropical climate) and 2.4 kW.

Thermal comfort

Conclusion: Technically, human body can generate cooling at a much higher rate than needed (because of metabolism) through perspiration. This may be often still insufficient because: -large heat gain because of surrounding objects (radiation) -humid environment (low perspiration)

Thermal comfort

Beduin traditional clothing Black color may seem inefficient, still works because the clothes are light (low heat mass) and loose (high ventilation).
 https://www.theguardian.com/science/2012/aug/19/mostimprobable-scientific-research-abrahams

Nicholas Grimshaw: UK Sevilla Pavilion

The building utilizes several cooling solutions simultaneously to combat the hot summer of Seville, Spain. The south faรงade that is exposed to the Sun has a waterfall, north side has water drums to increase the thermal mass of this temporary building.

Nicholas Grimshaw: UK Sevilla Pavilion

The building utilizes several cooling solutions simultaneously to combat the hot summer of Seville, Spain. The south faรงade that is exposed to the Sun has a waterfall, north side has water drums to increase the thermal mass of this temporary building.

Nicholas Grimshaw: UK Sevilla Pavilion

The building utilizes several cooling solutions simultaneously to combat the hot summer of Seville, Spain. The south faรงade that is exposed to the Sun has a waterfall, north side has water drums to increase the thermal mass of this temporary building.

Nicholas Grimshaw: UK Sevilla Pavilion

The building utilizes several cooling solutions simultaneously to combat the hot summer of Seville, Spain.

The south faรงade that is exposed to the Sun has a waterfall, north side has water drums to increase the thermal mass of this temporary building.

Norman Foster: 30th Street Tower, London

The building is an attempt to rethink working conditions in modern office environments. Instead of relying on ‘total control’ of temperature and ventilation, the building introduces gardens and natural ventilation for the building.

The layout of the garden follows the wind pattern of the site.

Norman Foster: 30th Street Tower, London

The building is an attempt to rethink working conditions in modern office environments. Instead of relying on ‘total control’ of temperature and ventilation, the building introduces gardens and natural ventilation for the building.

The layout of the garden follows the wind pattern of the site.

Helmut Jahn Architects: Post Tower, Bonn

Post Tower is a redesign of a former Ministry of the German Democratic Republic. After unification, German Post services became a company that is the largest courier company. Transparency was an important keyword to this transformation and an important environmental challenge.

Helmut Jahn Architects: Post Tower, Bonn

Just like in case of 30th Street, natural ventilation was an important goal of the concept. To achieve that even in case of strong winds, the building was designed with large internal courtyard that is open only at the bottom and the top.

Helmut Jahn Architects: Post Tower, Bonn

Just like in case of 30th Street, natural ventilation was an important goal of the concept. To achieve that even in case of strong winds, the building was designed with large internal courtyard that is open only at the bottom and the top.

Helmut Jahn Architects: Post Tower, Bonn

Just like in case of 30th Street, natural ventilation was an important goal of the concept. To achieve that even in case of strong winds, the building was designed with large internal courtyard that is open only at the bottom and the top.

Helmut Jahn Architects: Post Tower, Bonn

The faรงade was designed with operable windows that allowed natural ventilation even for the highest floors. The two layers of glass protect indoors from strong winds.

Helmut Jahn Architects: Post Tower, Bonn

The building is located next to the river. This was an important asset because the building had to be transparent which resulted a high solar gain in the summer.

The tower is cooled by heat exchangers in that period to avoid excessive air-conditioning.

Helmut Jahn Architects: Post Tower, Bonn

Cold air from the river cools the faรงade zones to protect indoors from overheating. Later, when temperature is lower, the water cools a generator on site (that produces electric power). The heated water does not return to the river directly (to protect environment) but enters a pond first to cool down.