A measure (in percentage) of the partial shading effect on a surface caused by for instance trees, shrubs or vines over a pergola.

Design of the jointing and fixing etc. of building materials and elements.

The temperature at or below which condensation will occur on a surface by condensing out of a gas (eg air) at a certain relative humidity (see Psychrometric Chart).

The portion of solar radiation scattered (up to about 25% of the direct radiation); it is non-directional.

That portion of solar radiation which is not scattered on its path from sun to earth; it is directional, and at ground level on a clear day is about 1000 W/m² on a surface perpendicular to its rays. 

A method of calculating costs or returns on investments which takes into account the changes on the value of money over time eg due to inflation, and the availability and rate of interest, so as to relate all expenditure and income at the same point in time; used to assess the cost/benefit ratio of thermal improvements.

The temperature difference (‘swing’) over a day - between daily minimum and daily maximum;  greater in inland regions than near the coast, due to the greater thermal inertia of the sea than that of the land.

Glazing whose U-value is reduced from the level of standard single glazing by the installation of two panes. ‘Evacuated’ double glazing is factory-constructed hermetically sealed with a near vacuum between the panes; if air is allowed between the panes, condensation may occur, so glazing should be constructed to allow access to the air space. (In higher latitudes of the Northern Hemisphere, triple glazing is common).

The difference in temperature across a building element which causes heat flow from the hotter to the colder side.

The temperature of still air measured by a standard thermometer protected from sources of radiation.

In the tropics, the season of minimal rain

An enclosed channel, usually horizontal or vertical, and larger than a pipe, provided to carry air, pipework or service cables etc.