There are different opinions about this.
Here is [u]an experiment[/u]:
You will need two thermometers one to put inside and one to put outside. Get a sheet of paper and draw up a chart.
Over one week record the temperature inside and the temperature outside 3-5 times a day starting early in the morning and finishing about sunset. Make sure the thermometers are not in direct sunlight.
You will notice that at some times of the day it is warmer outside and at other times it is warmer inside.
[u]Method for controlling temperature in the home in summer[/u]:
Once you have got an idea of the time of day when the temperature outside is hotter than the temperature inside start closing the windows and curtains/blinds as soon as it starts to warm up outside. This will usually be first thing in the morning.
Leave them closed all day. Then once the temperature outside starts to be cooler than the temperature inside open the blinds and windows wide. Leave them open all night (you will need to attend to security) to let the house cool down thoroughly overnight.
[u]
Method for controlling temperature in the home in winter[/u]:
Closing curtains and windows when the temperature is colder outside than inside will help warm your home in winter.
Sometimes during the day it will be warmer outside so consider opening the curtains and windows to let in the warmer air.
Take the opportunity to let in morning sunlight to warm things up.
Remember warm air rises.
Do you have a high-set or two storey home? It will usually be much cooler downstairs in summer and warmer upstairs in winter.