Impact of Urban Context on Built Form

05 THE URBAN CONTEXT ANALYTICAL WORK

5.1 Impact of Urban Context on Built Form

Environmental conditions are different for urban microclimates and surrounding rural areas. These varying microclimates within an urban area result from its heat and mass transfer balances (Yannas 2000). The energy balance is a result of several energy and heat inputs and outputs, including the incoming shortwave radiation (incident and reflected), the outgoing long-wave radiation from the surfaces to the sky, the heat stored within the fabric, the heat loss or gain through convection, and the generated heat from people, cars and machinery (Dib 2013). These energy balances can be influenced by careful urban design strategies to create a desired urban context. In their juxtaposition, geometrical configuration, and materiality, buildings can modify the microclimate, which eventually impacts their indoor environments.

Thermal Balance of Buildings

Since urban microclimates and the indoor environment of a building are a result of heat inputs and outputs; therefore, they can be considered as “thermal systems” which can be analyzed in steady state-conditions (Szokolay 2017):

Buildings Thermal Balance: Qi + Qc + Qs + Qv + Qe = delta S

Where Qi = internal heat gain,

Qc = conduction heat gain or loss,

Qs = solar heat gain, Qv = ventilation heat gain or loss,

Qe = evaporative heat loss.

This thermal balance is only achieved when all the heat outputs are equal to the heat inputs. If the sum is positive, the indoor temperature of the building will increase, and if the sum is negative, the building will cool down (Szokolay 2017). Furthermore, heat flow within a building is typically driven by two external climatic factors: air temperature and solar radiation (Szokolay 2017), which, as mentioned earlier, can be modified by careful microclimatic design.

Heat Inputs by Period

As the indoors’ preferred temperatures vary throughout the year depending on the outdoor conditions, it is crucial to define when and what environmental parameters affect the building’s thermal balance. This will allow creating a microclimatic design to control those specific parameters.

The environmental parameters illustrated by Table 5.1 were used to determine the steady state of heat flows through the envelope of one of the labor rooms, as laid out in Chapter 2. The investigation was done for the mild, warm, and hot periods. Each period is represented by a single day with an average dry bulb temperature for the whole period. The comparative analysis specifies the unit’s parameters (area, U-values, and window-to-wall ratio) as specified in the Estidama (It is a building design methodology for constructing and operating

Table 5.1 Building thermal balance input data

Figure 5.1 Heat gains and losses of an abstract unit in the mild, warm and hot period in Sharjah