Occupancy settings
To allow fair comparisons between buildings, NatHERS defines the conditions whereby occupants are most likely to be thermally comfortable. The comfort rules vary according to many factors including acclimatisation to the local climate, the impact of the RMY climate on the room, the primary function or functions of the room, and the time of day a room is expected to be used.
Occupancy hours
Every house is operated in a unique way every day of every year and therefore it would be impossible to assess a dwelling according to its actual use. To allow residential buildings to be fairly compared according to the intrinsic value of the design for that local climate, a standard occupancy pattern is applied to represent a reasonable expectation of space use.
For the purpose of assessing a building under the Scheme each room (space) is allocated a function or functions and is allocated a period of time whereby that space is to be maintained at a thermal comfort range appropriate to its likely use.
- For living spaces - thermal comfort is maintained from 0700 to 2400.
- For sleeping spaces - thermal comfort is maintained from 1600 to 0900.
Comfort range
For the purpose of assessing a building under NatHERS each room (space) is maintained within a thermal comfort range appropriate to its likely use. NatHERS requires that all spaces be considered for thermal comfort: firstly, by natural means (e.g. open windows); secondly, in the case of cooling via mechanical air movement (e.g. ceiling fans); and finally, by adding or extracting an amount of energy to that space (artificial heating and cooling).
NatHERS requires that all external openings (e.g. windows) are considered operable at all hours, although a factor restricting the operation of external and internal openings may be incorporated to reduce the number of operations to one per each three hour period.
- For sleeping spaces (including bedrooms and other spaces closely associated with bedrooms): a minimum heating thermostat setting of 18 deg. C is used from 0700 to 0900 and from 1600 to 2400; and a heating setting of 15 deg. C from 2400 to 0700.
- For living spaces (including kitchens and other spaces typically used during waking hours): a minimum heating thermostat setting of 20 deg. C is applied.
The heating thermostat setting varies according to the expected activity type (function) and therefore the expected clothing level in that space during a particular time period. For example: a lower minimum heating thermostat setting is used during designated sleeping hours to reflect the likelihood of bedding (sheets, blankets, quilt, etc) being available.
Cooling thermostat settings
The cooling thermostat setting varies according to the climate region to take into account acclimatisation, and varies from room to room according to the effect of air movement, air temperature and humidity level in that space. The cooling methodology is based on the Effective Temperature method of calculating thermal comfort.