National Defence is quietly spending $50 million to upgrade giant air conditioning units aboard the navy's frigates after discovering sophisticated new electronics and weapons systems — installed as part of a recent $4.3 billion mid-life refit — could overheat.

Documents obtained by CBC News show the problem was pointed out five years ago as contractors inspected the ventilation system, an exercise that turned up significant issues involving mould and condensation in all 12 warships.

A report by Bronswerk Engineering, which examined HMCS St. John's and other ships, found the heating, ventilation and air conditioning controls and the four ship-wide "chilling units" were not working properly.

I don't want to get into any guesswork on what could go wrong. — Capt. (Navy) Craig Skjerpen, commander Maritime Operations Group 5.

The problem becomes acute when the frigates operate in equatorial waters where the outside temperature hits 29 C and above. The inspection found, with air conditioning blasting and the combat systems switched off, the warship was still warm inside.

"Should HMCS St. John's have to operate at the maximum design conditions, using its combat suite, it is unlikely to be able to maintain the design conditions," said the report, written in the fall of 2011 and presented to National Defence Headquarters shortly thereafter.

Capt. (Navy) Craig Skjerpen, the commander Maritime Operations Group 5 — based on the East Coast — said three of the frigates have since undergone the air conditioning retrofit and the remaining nine will be scheduled over the next three and a half years.

Four of the warships, which have not had the air conditioning systems modified, have been deployed in the Caribbean and elsewhere off the U.S. without experiencing problems, Skjerpen said.

He downplayed any threat to their combat systems and ability to deploy in hot climates, and even made it sound almost routine.

"It's just upgrading a system that needs to be upgraded," Skjerpen said. "I don't want to get into any guesswork on what could go wrong."

'No cooling. No radar'

But the engineers who did the initial inspection painted a more stark picture. They pointed to "the poor state of the (air conditioning) plant" and warned that overheating "would also likely lead to numerous failures of equipment."

A separate slide deck presentation by the engineers, obtained by CBC News, shows the air conditioning units, which are known as chillers, were at the time of the inspection operating at "69 per cent of the required capacity."

It warned a failure of the system would "put sailors' lives at risk," particularly if the ship was called upon to operate in areas contaminated by nuclear, chemical or biological materials.

The scenarios didn't necessarily involve full war. The international response to the 2011 nuclear accident in Japan could pose such a risk, the presentation said.

But on a more day-to-day level, the inspection cautioned: "No cooling. No radar."

Analysis not understood?

The engineering analysis was done to help inform the multi-billion dollar facelift of the combat fleet, a program recently completed and deemed an unmitigated success by the navy.

Led by Rear-Admiral Gilles Couturier, followed by Defence Minister Harjit Sajjan, officials board HMCS Regina at CFB Esquimalt last spring. The ship, one of 12 Halifax-class frigates, was recently part of the modernization project. (Chad Hipolito/Canadian Press)

Unlike some procurement disasters that have plagued National Defence, the frigate life extension was delivered on time and under budget on both the east and west coasts.

'Financial limits meant they couldn't do everything they wanted to.' — Dave Perry, analyst, Canadian Global Affairs Institute.

Yet, the warning about the air conditioning system was not incorporated into the original work plan, and the navy will have to pay for the upgrades out of its annual maintenance budget.

Skjerpen says that was not an oversight. With the timing of the retrofit, "that's the way it works" sometimes.

"I would say the modernization program was a success," he told CBC News.

"What we wanted to get done got done. So, it wasn't a thing that anything was left out. It is: This is when we had the information. That information is used to be able to put in a program and that program is progressing."

Nonetheless, Skjerpen said, "the navy remains responsive, globally deployable, and we're able to conduct operations in very warm environments and maintain operational capability."

Prioritizing projects

A defence source with knowledge of the file said the defence planner responsible for the refit "did not understand the implications" of the Bronswerk assessment when the work plan was drawn up.

A dockyard worker walks past HMCS Halifax in Halifax. (Andrew Vaughan/Canadian Press)

The source, who was not authorized to speak publicly, said once the extent of the problem was realized there was considerable internal debate about how to proceed and where the money for the chiller retrofit would come from.

Dave Perry, a defence analyst at the Canadian Global Affairs Institute, says he was also aware of the tough choices and debate that went on within the overall modernization program.

"Financial limits meant they couldn't do everything they wanted to," he said. "So, they prioritized the most important things, with the understanding that there'd have to be some follow-on projects."

Just how many projects were excluded and what it might mean for future maintenance budgets is unclear.