He was pleased to find the honeycomb blinds topped the test having put them in his own home about nine years ago.
He said the hexagonal cells in the curtain, which when extended trap the air in the cells, "acting like a down jacket; trapping still air".
"It was good for me seeing this because anecdotally I thought 'oh these are doing a great job' because when you open the curtains in the morning you can see all the cold air fall out from behind the window."
In the test, the honeycomb blinds retained more than 60 per cent of the heat lost through a bare window.
Roman blinds were the second best performing blind, followed by roller blinds.
As for wooden or aluminium venetians, wooden were proven the better insulator, he said.
If curtains were preferred, people were urged to go "heavy" and long.
Heavy-lined curtains were ones which had two layers which again acted as an air trap. To get the best result, they needed to go down to the ground, no matter the size of the window, to keep the cold air out.
It was best to keep the gap between the curtain or blind and the frame of the window as small as possible.
Thermal curtains - a curtain which has a thermal layer stitched to the back - did not perform as well as the heavy-lined curtains, he said.
However, Dr Smith had come up with a few cheap hacks for people not bothered about what there lounge or particular room looks like for a few cold nights over winter.
One was hanging a blanket over the top of your curtains.
"It is less convenient because you've got to hang a blanket and take it down each time.
"We pinned it up where the railing was, so we just pinned it up above the window and just let it hang down and cover the whole window."
The other option was to roll up towels and sit them above your window railing which again prevented cold air circulating around the room.
"It stops the air being sucked in to the top. So when the hot air rises up to the ceiling. If the curtains aren't well-fitted, that warm air falls behind the window.
"They call it the reverse chimney so it's like the air coming down past the window and all the heat being lost, so if you put something across the top it stops that from happening."
TOP TIPS FOR HEAT RETENTION
• Mount curtains as close as possible to the window frame,
• Position nets as close to the window as possible,
• Use floor length curtains and ensure they touch the floor,
• Make curtains a generous width so they overlap the window frames at the sides,
• Using net curtains help with heat retention, especially on wooden frame windows,
• Using a fan "significantly" reduces heat loss.
