Sawney Beane wrote:
My windows have horizontal mini blinds as well as curtains
with valence boxes. The windows have two layer of glass.

On a cold night, what's a good way to reduce heat loss through
the windows? Do the blinds make much difference?

Neither my nets nor my blinds do anything for heat. My biggest mistake was
taking down my beautiful full length wall to wall curtaining that had
separate thermal linings and replacing with the more modern lightweight
ones. My house used to be SO cosy. Then come summer off would come the
linings for a lighter look.

In summer it can pay to reflect sunlight hitting east and west
windows. Vinyl blinds let some light through and probably
absorb some. Is there a better way to reduce solar heating
through windows?
You could try black out curtains. They can be especially handy when you
wish to have an afternoon nap and don't want heat and light in the room.
They can also stop people peeping in at you when you're about your everyday
business. HTHs Mr Beane.