I

Illuminance
The illuminance at a particular point of a surface is the quantity of luminous flux uniformly distributed over the surface, divided by the area of the surface. The unit of illuminance is the lux, i.e. the illuminance produced on a square metre of surface by a luminous flux of one lumen uniformly distributed over that surface.

Incidence angle
The angle between the centre of the solar disc and a line normal to the surface being considered.

Indirect storage
When a building component is heated up by absorption of heat radiated from other, warmer, components (such as walls and floors) or by convection from the surrounding air, this is known as indirect storage.

Indirect storage through radiation is influenced by the temperature difference between the components, their location and emissivity. Unlike visible radiation, the emission of infra-red radiation is not affected by the colour of the surface. It is, however, influenced by surface condition, as rough or dirty surfaces inhibit emission.

Indirect storage through convection is influenced by the temperature difference between the air and the component, by the speed of the air and the roughness of the component surface. Rough surfaces have a greater area and therefore assist convective heat transfer.

Heat exchange between masses at different temperatures is spontaneous because it obeys the second law of thermodynamics concerning thermal equilibrium between masses.

Infiltration
The uncontrolled inward air leakage through cracks and interstices in any building element and around windows and doors of a building, caused by pressure effects of the wind and/or the effect of differences in the indoor and outdoor air density, measured as an air change rate.

Integration in the site
Integration in the site essentially concerns two aspects:

• integrate the characteristics and constraints on the installation site,
• minimize the impact of the project on the environment.

Consequently, preliminary studies for the project are recommended to identify constraints and advantages related to the local context and the site. These studies concern:

• weather conditions (sunshine, wind, precipitations, etc.)
• specific characteristics of the immediate environment: proximity services (transport, energy, etc.), noise sources, etc.
• specific characteristics of the site : soil pollution, topography, hydrology, fauna, flora, etc.

The results of these studies control the general layout, the orientation of each building, architectural choices, the treatment of external and common spaces, the production of a good mineral-vegetation ratio, management of rain water, and the use of renewable energy resources on and around the site.

Internal heat gains (kWh or GJ)
Heat generated inside a building by occupant activities (body heat, household appliances, artificial lighting).