The news has emerged after two reports published last week by the Commission for Health Improvement and public sector union Unison criticised the management and shortage of space in the hospital.
NHS trust project director Alan Davidson admitted that the hospital still suffers from overheating in the atrium and some internal rooms are without natural ventilation.
He said: "We have been given assurance by Amec that, prior to summer, action will be taken to reduce temperatures."
The NHS inspectors report relayed complaints from patients about the lack of space and privacy, particularly in the five-bedded bay areas in the 442-bed hospital.
The report listed complaints from patients about the lack of space and privacy
The report also criticised clutter in ward areas that compromised fire exits, the lack of space in ward areas, narrow corridors and insufficient storage space.
Amec has already carried out major remedial works to the roof covering and modifications to the fire dampers.