Compactness

This principle is to minimize the external wall area while planning the arrangement of dwelling units -whether as a single unit on its plot of land or as a group of units. Lesser the area of exposure of the external envelope to the outside, for a given floor area, lesser will be the heat transfer into the building. Simple rectangular shapes are more efficient.

Compactness of Building -

Compactness depends on the geometry of the building and it varies with the building typology. In this figure the surface to volume ratio increases from A to C as the built form gets more complicated, the compactness reduces.

Building Orientation

Orientation affects the amount of sun falling on surfaces, daylighting and direction of winds and constitutes one of the most important passive design strategies for reducing energy consumption and improving thermal comfort for occupants of a building. Even while the building designs vary based on their location and climate, however, the underlying principle of, maximizing amount of solar radiation in winter and minimize the amount in summers remains the same. Additionally, orientation also allows the building to take advantage of prevailing winds and improves ventilation in the building.

Sun path for ideal building orientation -

The alteration in sun path affects solar radiation penetration patterns during different seasons and consequently, heat gain and loss in a building.

Thermal Insulation

The roof of the building receives the hottest rays of the sun for most of the day. The sun’s rays heat up the roof. If the roof is of a dark finish it will absorb the heat of the sun’s rays and become extremely hot. The hotter the surface of the roof the more heat will travel to the room below and make it unbearably hot. In order to reduce this effect:

• Use a light-colored roof finish such as China mosaic, or limewash, or a heat reflective paint so as to reflect the sun’s rays.
• Use and insulating material such as extruded polystyrene under the roofing finish so as to reduce the conduction of heat through the roof.
• Build the roof structure with something heavy such as RCC so as to delay and to reduce the effect of the afternoon sun.

The above cross -

Section depicts an ideal roof construction to protect the roof from long exposure to heat and cold during different seasons

Thermal Comfort

a) Degree Discomfort Hours

The difference in temperature between the indoor air temperature and the IMAC – R comfort temperature over 8760 hours (365 days * 24 hours).Lower the DDH better the performance.

UNITS : Hours

b) Building Envelope Efficiency

Indicated by-

(i)- ‘Residential Envelope Transmittance Value (RETV)’

RETV - Is the net heat gain rate (over the cooling period) through the building envelope (excluding roof) of the dwelling units divided by the area of the building envelope (excluding roof) of the dwelling units. (W/sqm)

STANDARD : All type designs to meet an RETV < 15 watts /sqm/deg.C

UNITS : W/sq m/deg C

(ii)- ‘U-Value’

It refers to the rate of heat transfer through matter. Lower U-values of the external envelope are desirable for keeping the home thermally comfortable.

UNITS : W/m²K

Cost Analysis

Cost of construction / Unit Sqm of Carpet Area

Typically,70% of the cost of construction is attributable to the structure of the building, its walls, wall plasters, roofing and doors and windows. In the cost reported for each type design paints, tiling, flooring, electrical and plumbing installation are not included, since these are usually decided according to the preferences of developers and buyers

STANDARD : Cost of civil works + doors & windows + finishing (only plaster & roofing) + insulation

UNITS : Cost / Sqm of Carpet area

Variation in Climate zone

The performance of the Type Designs is evaluated for different climatic zones. The warm climate set serves the 4 warm Climate Zones : Hot & dry, Warm & Humid, Composite and Temperate with variations in openings and materials as required for each climate. The cold climate set, where the predominant need is for heating rather than for cooling, is specially designed to suit cold climate conditions.

Variation in Unit Position in the Block

The differences in performance due to the positioning or placement of a dwelling unit – middle floor or top floor , middle unit, end unit etc. is reported by simulation.