Knowledge Centre – Passive Strategies

Form & Orientation
Introduction
Recommendations
Resources & Tools
Energy & Cost Savings

Introduction

Form & Orientation Introduction

Buildings must be responsive to solar orientation on the site. The sun is at a low angle during the winters and to the south of east-west axis. During summer, its path is at a high angle and slightly north to the east west axis. The alteration in path affects solar radiation penetration patterns during different seasons and consequently, heat gain and loss in a building.

Form and orientation constitute two of the most important passive design strategies for reducing energy consumption and improving thermal comfort for occupants of a building. It affects the amount of sun falling on surfaces, daylighting and direction of winds. Towards net zero energy goals, form and orientation have significant impact on building’s energy efficiency, by harnessing sun and prevailing winds to our advantage. Thus they play a pivotal role in NZEB design approach as these strategies are one time interventions and their potential benefits should not be missed.

Building designs vary according to context of its location and climate. However, the underlying principle remains the same, maximising amount of solar radiation in winter and minimizing the amount in summers. In predominantly hot regions, buildings should be ideally oriented to minimize solar gains, the reverse is applicable for cold regions. Orientation also plays an important role with regard to wind direction.

The building form determines the volume of space inside a building that needs to be heated or cooled. Thus, more compact the shape, the less wasteful it is in gaining/losing heat. In hot & dry regions and cold climates, building’s  shape needs to be compact to reduce heat gain and losses, respectively.

Recommendations

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Orient buildings to take advantage of prevailing wind. In case of multiple buildings on a site, they must be arranged to avoid built forms falling in the wind shadows created by other buildings on the site.

Cooling for hot regions

  1. In tropical climate like India, long facades of buildings oriented towards north- south are preferred.
  2. Buildings should be oriented with their longer axis (north –south) aligned perpendicular to the prevailing winds to facilitate maximum air-flow and cross ventilation through the building. (Buildings can be oriented at an angle between 0° to 30° with respect to the prevailing wind direction (http://envitrans.com/windrose.php) in your city)
  3. Buildings that feature a courtyard (in climates where cooling is desired), orienting the courtyard 45° from the prevailing wind maximizes wind flow into the courtyard and enhances cross ventilation in the building.
  4. In hot & dry climates, the surface to volume(S/V) ratio of the building should be as low as possible to minimize heat gain (compact plans have greater thermal efficiency, e.g. a square plan is more thermally efficient than a rectangular one).
  5. Recommendation for composite climate (e.g. Delhi and  Gurgaon) :
    1. Compact form with low S/V ratio is recommended.
    2. A square plan with a courtyard would be very effective.
    3. A rectangular form with a longer axis along the north-south is the preferred orientation.
    4. East and west orientation should be protected by buffer spaces, shaded walls, etc.
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Mutual shading of built forms and compact forms i.e. forms with low surface area to volume (S/V) ratio and low perimeter to area (P/A) ratio are ideal for extreme climates.  Compact forms gain less heat during daytime and lose less heat at nighttime.

Heating for cold regions

  1. Surface area to volume ratio of a building should be low to avoid unwanted heat loss (approaching a cube or a hemisphere).
  2. For cold climates, orientation slightly east of south is favoured (especially 15° east of south), exposing the unit to morning and afternoon sun and enabling the building to heat during the day.
  3. Buildings with a ‘rectangular form’ should ideally orient their longer axes towards north-south direction rather than east-west direction. Greater the perimeter to area ratio, greater is the heat gain of the building.
  4. Greater the perimeter to area ratio, greater is the heat gain of the building.
  5. Building form for energy efficiency should consider the floor area, perimeter, building height and surface to volume ratio.
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Service cores can act as thermal buffers against heat gain and loss. Optimal locations for building service cores are in the east and west.

Resources & Tools

Online Resources

Publications

  • Sustainable Building Design Manual – Volume 1 and 2
  • Geetha , N., & Velraj, R. (2012). Passive cooling methods for energy efficient buildings with and without thermal energy storage – A review. Energy Education Science and Technology Part A: Energy Science and Research, Vol 29- 913 – 946.
  • Energy Efficiency Buildings in India- TERI

Tools

Autodesk Ecotect Analysis
Autodesk Ecotect Analysis is an environmental analysis tool that allows designers to simulate building performance from the earliest stages of conceptual design. It combines analysis functions with an interactive display that presents analytical results directly within the context of the building model.
http://usa.autodesk.com/ecotect-analysis/

Climate Consultant
A graphic-based computer program that displays climate data in dozens of ways useful to architects, builders, contractors, and homeowners, including temperatures, humidity, wind velocity, sky cover, and solar radiation in both 2-D and 3-D graphics for every hour of the year in either Metric or Imperial units.

Energy & Cost Savings

  • The form of the building and orientation of the spaces determine the thermal and visual comfort to a large extent.
  • Appropriate building orientation can result in reducing cooling demand and energy use compared to a wrongly oriented building.