Traditional prison window bars will be phased out in England and Wales under Ministry of Justice plans.
New jails are instead to be fitted with toughened glass and air vents.
The department has promised to replace old and expensive accommodation with 10,000 “modern and safe” prison spaces.
The first new prisons are expected to be built on the site of former jails at Wellingborough, Northamptonshire and Glen Parva, Leicestershire in 2021 and 2022 respectively.
Ministers also want to build new prisons in south Wales and near HMP Full Sutton, Yorkshire, in addition to redeveloping existing prisons at Hindley, Greater Manchester and Rochester, Kent.
A Prison Service spokesperson said: “Secure, sealed windows with toughened glass and narrow vents will be used in all cells in future prisons.
“These windows are difficult to break, making them more effective in stopping prisoners from accessing contraband.”
Bars on prison cell windows are used in most jails, including the most modern buildings such as Berwyn, north Wales and Oakwood, Wolverhampton.
Peter Dawson, director of the Prison Reform Trust said: “A normal environment in which people take responsibility for as much of their own lives as possible is preparation for successful release.
“Bars in windows is yesterday’s technology.”
But ex-prisoner turned charity worker and Out of the Box author Leroy Smith described the changes as “a pointless gesture” – adding that prisoners needed better education and training.
“Otherwise nothing is going to change,” he said.
The move comes as researchers begin a study to examine the impact of a more relaxed and humane prison by examining changes at HMP Berwyn.
There, prisoners are referred to as men, housed in communities rather than blocks, and locked up in “rooms” rather than cells.
There have also been attempts at the prison to fill empty wall space with photos of the local Welsh landscape.
Professor Yvonne Jewkes from the University of Bath said the changes were “relatively simple” but could have “an important effect when it comes to making prisoners feel that they are treated with respect and dignity”.
The £600,000 study has been funded by the Economic and Social Research Council.