Here ‘thermal capacitance’ excludes the external walls of the zone and so covers the internal furnishings including floor cov- erings, furniture, curtains and any internal walls。 A search of the literature did not identify any measurement data for this parame- ter, though several authors [30–32] have considered values in the range 1–15 times the thermal capacitance of the air within the zone。

Table 1

Building parameters and parameter values considered。 Variable Parameter values

Thermal  capacitance 360, 1080 kJ/K

Infiltration rate 0。5,2。0 a/hr

Internal  load multiplier 0。5×, 1。0× (see Fig。 3)

Building aspect ratio 1:1, 2:1

Orientation (degrees from Nth) 0, 45, 90, 135, 180, 225, 270, 315◦ Roof ventilation Natural, forced

Ceiling insulation None, R3

Roof solar absorptivity 0。3, 0。9

Wall insulation None, R2

Wall construction Light (weatherboard), Medium (brick veneer),

Heavy (double-brick)

Wall solar absorptivity 0。3, 0。75

Window area 2。5 m2 , 5 m2

Window type Single glazed, double glazed

Fig。 5。 Schematic showing building orientation, window location and aspect ratio cases。

Since we assume the zone to be occupied and  hence furnished, here we have chosen values equivalent to 5× and 15× the thermal capacitance of the air to cover plausible above and below average values。

Rates of natural infiltration are highly variable not only amongst different building construction styles, build quality and features, but also over the course of the day for a given building。 This is due to both the driving weather effects (i。e。 the temperature dif- ference and the wind driven pressure) and the occupant behaviour (i。e。 opening of windows and doors)。 Australian standards [33] rec- ommend a minimum fresh air amount of 10L/s per person for residential buildings, which, based on a single person occupancy of the conditioned room, corresponds to an air-change rate of approx- imately 0。5 air-changes per hour。 Here we use this as the minimum assumed natural infiltration rate。 A study of 10 brick veneer and concrete clad buildings in Melbourne, Australia reported natural infiltration rates up to 1。2/ach, although these houses were all built after 2010 and these rates did not include occupant opening of windows[34]。 Hence, here was have selected 2 air-changes/h as a plausible ‘above average’ infiltration rate。

Internal loads due to people, equipment and lighting were assumed to follow a daily pattern with morning and evening peaks as shown in Fig。 3。 This pattern had contributions from up to 3 occu- pants combined with equipment loads up to 300W and a lighting

radiative  load  of  5 W/m2ˆ。  Here  occupant  sensible  and  latent  heat

loads were taken from [35] according to the assumed activities。 For the ‘below average’ profile sensible, latent and radiative loads were set equal to half of the values shown in this   figure。

M。J。 Goldsworthy / Energy and Buildings 135 (2017) 176–186 181

For the building aspect ratio square and rectangular rooms were considered with all possible building orientations chosen at 45◦ increments。 The influence of roof cavity ventilation was assessed by comparing a naturally ventilated space with a forced ventilated space using ASHRAE recommended heat transfer resistances [36]。 The influence of wall and ceiling insulation was investigated by comparing uninsulated walls and ceilings (as is common for many existing Australian residential buildings [6]) with those with an R2 (walls) and R3 (ceiling) level of insulation equivalent to or exceed- ing the minimum requirement for new constructions as outlined