House Hold Heat

My 20 year old house follows some of Australia's building trends.
Its bigger than my previous small three bedroom home with more bedrooms and an open plan living area.
It is insulated in ceiling & walls but made with brick veneer.
We have roof vents to allow the heat to escape and the building has plenty of north facing windows, shaded from the rays of the sun in the summer.

A reasonable passive solar house design 20 years ago but not one that would pass muster for a 6-8 star energy design.This is how the house has functioned after two days of above 40 degrees C heat.

Day 1( Tuesday 14 Jan) & Day 3 (Thursday 16 Jan ) information:

Tuesday	14 Jan 2014	Melbourne	42 C Forecast
Time	Temp (ext) o C	Temp (int) o C	PV Output
6:00 am	19	22	0.0 kWh
8:30 am	26	23	0.06 kWh
9:30 am	33	24	0.26 kWh
12:45 pm	39	26.5	2.18 kWh
2:15 pm	40.6	27	3.38 kWh
4:04 pm	42	27.5	4.68kWh
6:10 pm	42	28	5.60 kWh
8:00 pm	38.6	27	5.78 kWh
Thursday	16 Jan 2014	Melbourne	44 C Forecast
Time	Temp (ext) o C	Temp (int) o C	PV Output
6:00 am	19	22	0.0 kWh
8:30 am	26	23	0.06 kWh
9:30 am	32.4	28	0.03 kWh
12:45 pm	40	30	1.70 kWh
2:15 pm	41.7	28.5	3.07 kWh
3:30 pm	43.9	29.5	3.90 kWh
6:10 pm	41 (approx)	30	? kWh
8:00 pm	41 (approx)	28	6 (approx) kWh