MASTER PLANNING
‘In all climates, site layouts and building massing strategies should aim to capture the beneficial environmental effects of the local weather systems and minimise the heat island effect.’
radiation, humidity and air temperature is then defined as the air temperature of the reference environment which produces the same strain index value (
UTCI.ORG). Most of the work done for external spaces
relates to supporting the design of public realm spaces. The Lawson criteria and other indices such as PET, PT and UTCI can be used for this. A detailed description of all indices is perhaps beyond the scope of this paper. However, we have covered the most relevant aspects of these types of studies. The public realm final design is likely to be influenced by the application of the techniques and methodologies mentioned previously. Guidance regarding the use of the above
indices is dependent on the particular application or geographical zone for which they were created. Newly developed indices like the UTCI have been designed for worldwide applications.
Case study The following case study shows positive and
negative microclimate features. It involves the assessment of the impact of a proposed new
building on the environmental conditions within the site and immediate surrounds. The microclimate affecting the
Pinderfields Hospital in the north of England site was simulated to study the urban airflow regime and assess the impact of proposed new buildings on the outdoor environment of the courtyard and surrounding areas. The study provided a context for reporting building performance as issues arose throughout the design process. A full 3D CFD model of the development was constructed to investigate the particular effects of sun exposure, the most onerous wind directions and the combined effect of wind, air temperature, solar exposure and humidity. Locations within the model can be
assessed for comfort and safety. Both are related to the pedestrian, the former relates to the activity and the second to the level of distress experienced. The methodology developed at BRE, and the UTCI has been used here. These criteria have been widely accepted for this type of study and are comparable with international guidance. In all climates, site layouts and building massing strategies should aim to capture the
beneficial environmental effects of the local weather systems and minimise the heat island effect. This is achieved by optimising solar gain and wind air flows, as well as the combined effect of other external environmental conditions, the primary drivers that will affect the environment and ultimately the patients, visitors and hospital staff.
Minimising solar gains Simulations were carried out to determine
shadow cast and the solar exposure of the Wakefield Hospital for a whole year. Figure 1 shows the predicted and actual shadows produced by the hospital building. The predicted shadows for the whole year are shown in the three images below and to the left, and the picture to the top right shows the shadows on a particular day. The agreement between the model and the real situation is very good increasing the confidence of the methodology to assess the outdoor microclimate. Solar studies are also used with Dynamic Thermal Modelling (DTM) to assess energy consumptions and comfort of internal spaces. The areas in the surroundings are likely to be better suited for patients taking the sun, to the deep location of the courtyard which reduces the time these can be used for the same objective. A roof garden could serve the same purpose.
Optimising air flow Figure 2 shows the wind vectors for the
prevailing wind moving around the massing Extreme heat stress
Very strong heat stress Strong heat stress Moderate heat stress
No thermal stress
Slight cold stress Moderate cold stress
Strong cold stress Very strong cold stress
60 58 56 54 52 50 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0
-2 -4 -6 -8
-10 -12 -14 -16 -18 -20 -22 -24 -26 -28 -30 -32 -34 -36 -38 -40
heat stress
Very strong heat stress
Strong heat stress
Moderate heat stress
No thermal stress Slight
cold stress
Moderate cold stress
0 10 20 30 40 50 60 %
Extreme heat stress
Very strong heat stress Strong heat stress Moderate heat stress No thermal stress Slight cold stress
Moderate cold stress Strong cold stress
Very strong cold stress Figure 3: Courtyard area Equivalent Temperature. 92 IFHE DIGEST 2015
0.00 0.00 0.00 0.04
73.48 24.92 0.75 0.00 0.00
Extreme
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