The most recent cost estimates for replacing the Bromfield School’s problem-plagued heating, ventilation, and air conditioning system are substantially higher than expected. The School Committee discussed that unwelcome news at its Monday meeting this week. Superintendent Dana Labb had prepared a request for the Capital Planning and Investment Committee, asking for nearly $28.3 million for the project in fiscal years 2028 and 2029. That amount is roughly double last year’s estimate, mainly because the new figures include the cost of replacing Bromfield’s roof as well as the cost of the new HVAC equipment itself. The new cost figures came from…