A new purpose-built prison hall is too noisy and overheated, according to an inspection report.
Glenochil prison is currently being rebuilt
However, Her Majesty's chief inspector of prisons, Dr Andrew McLellan, said conditions at Glenochil Prison, Clackmannanshire, were improving.
Dr McLellan said he was generally happy with the way staff and prisoners at Glenochil were coping with change caused by rebuilding work.
Some prisoners were unhappy about sharing cells in the new facility.
But Dr McLellan said nothing could be done as long as prison numbers kept rising.
A new building, Harvieston House, is already occupied and another is under construction.
It was found that the size of the new hall had led to ventilation problems, resulting in the blocks becoming very hot.
The report said the size also contributed to the noise problem as it was difficult for staff and prisoners to avoid shouting.