Create and understand the building model’s geometry.
Building type
Dominant heat exchange
Buildings are often described as either envelope (skin) or internally loaded; these descriptions characterise the dominant heat exchange in the building.
Skin load dominated means that internal gains are low relative to fabric heat transfers Internal load dominated means that internal gains are high relative to fabric heat transfers
So …
Skin load dominated = gains < losses
Internal load dominated = gains >= losses
Where:
Gains = Internal gains + Solar gains
Losses = Conduction + Fresh air + Infiltration
And where:
Fresh air = Aux vent gain + Nat vent gain + Free cooling gain + MacroFlo ext vent gain
The method reports the sum over all occupied hours of the energy in each condition and the hours that each condition is dominant.
Similarly ventilation, casual, solar loads and how the building is used add detail and help in defining appropriate responses.
Building Use
Response limitations
Critical use or night occupied buildings limit responses e.g. night purge ventilation, relaxed summer design set points etc.
Building dimensions
Ceiling heights
Floor to ceiling heights of 3m or more promote stratification; with the right HVAC strategy this reduces cooling load. Ceiling heights lower than 3.5m can reduce HVAC system choice. Very tall spaces require special consideration
Building form
The overall form of the building can be a response to these characteristics and to the climate type; high surface area buildings lose heat faster and thus suit hot climates better than cold climates
Cross ventilation
Cross ventilation is more effective than single sided ventilation; cross ventilation can occur across the building plan form window to window, across corners, via windows and roof lights or chimneys. The importance of cross ventilation in naturally ventilated designs increases with higher occupancy, higher heat gains and as the climate becomes hotter. In hot and humid climates it is essential.
Glazing
For day lighting purposes glazing % (ext wall) is normally in the range of 15 - 40%; beyond 40% glare and solar gains are a problem. In hot climates lower than optimum glazing areas maybe chosen as heat gains are predominant
