Factors in building out air conditioning across the public school system


As the state's cooling tradewinds continue to decline and the heat index continues to rise due to climate change, HIDOE is challenged by the need to install air conditioning at all public schools. This involves more than installing AC units — there are budget and infrastructure hurdles to overcome. And we must approach it with an eye to sustainability so we aren't adding to the problem of escalating energy use.

​​​​​​​The challenge​​​​​​

Hawaii's cooling tradewinds ​are faltering​ and ocean temperatures are rising​. As this climate change trend continues and the Islands get hotter, focus once again turns to installing air conditioning in classrooms. HIDOE is not against installing AC — in 2015 there are 17 AC-related projects on Oahu alone being installed, from a new school (Hookele Elementary in Kapolei) to a new classroom building at Ewa Elementary to a series of building retrofittings. As funding is released by the state for these projects, we will continue to whittle away our lengthy project list.

However, our goal is to make all classrooms thermally comfortable in a sustainable fashion — using fact-based, data-driven methodologies that lead to effective solutions. Here are the challenges we face in addressing classroom cooling.

​​What it costs to install​ AC​

Challenge 1: Our Budget
The estimated cost of installing air conditioning and related infrastructure improvements at the schools that don’t have campus-wide AC was determined by using both the estimated and actual cost (where available) of recent projects and includes both design and construction costs.

For example, the cost of air conditioning and related infrastructure upgrades at Pohakea Elementary School was $4.3 million when bids opened for the project in 2010. That equals about $110,000/classroom. Pohakea is one of our smaller elementary schools with an enrollment of 573 students in 2014. By comparison, August Ahrens in Waipahu, which is one of our largest elementary schools, has over 1,400 students. Based on this actual bid result, accounting for inflation since 2010, and adjusting for the various school sizes, we have estimated that the cost to air condition the average elementary school is $5 million.

The cost estimates for both middle and high schools were calculated in a similar fashion across the number and type of schools that need cooling.

  • 153 elementary schools X $5 million = $765 million
  • 33 middle schools X $10 million = $330 million
  • 40 high schools X $15 million = $600 million

Total = $1.695 billion

(Note: Combination elementary/intermediate schools were classified as middle schools; combination elementary/high schools were classified as high schools. We do have a cost estimate for Campbell High from 2010 which came in at over $13 million.)

HIDOE has been piloting newer technology that could bring down the costs. Of the most promising is photovoltaic air conditioning (PV/AC). A portable classroom at Waianae High School is into its second year running a system using three PV panels for each air conditioning unit. (Profiled here on Hawaii News Now.) However, there are limitations to how widespread PV/AC may be deployed — it's not a good fit for many multi-story buildings, and new funds will be needed to lease/purchase and install them. HIDOE's Facilities office is analyzing how many more could be added to our schools.

We are also running pilots around portable classrooms with sustainable design. There are more upfront costs in the materials and construction related to standard portables, but can save more in the long run thanks to "grid free" energy production and use.

Challenge 2: Infrastructure/Electrical Systems
The majority of Hawaii’s schools are more than 50 years old. As a result, many buildings do not have adequate electrical capacity to accommodate the increasing use of electronics including computers, and other high demand infrastructure such as air conditioning. HIDOE tackles a number of projects every year to upgrade the electrical supply and infrastructure at various schools. 

Because of the age of many of our schools, their electrical systems reflect a bygone era — they weren't designed to support today's high level of energy demand, requiring major upgrades. In many neighborhoods, even the supply from the utility is inadequate.

An elementary school recently bought air conditioners without the proper electrical upgrades and blew a circuit. Electricians, electrical engineers and knowledgeable contractors will tell you it is important to ensure you have the correct infrastructure before adding more than the system can handle.

Challenge 3: Building Improvements
Just as our older schools were not built to meet current levels of electrical use, the buildings were also not designed to be airtight. This stems from the fact that it was important for air to move through the buildings in a naturally ventilated environment. However, for an air conditioning system to function effectively, the building envelope needs to be sealed, requiring replacement of windows (typically jalousies) and doors, among other things.​

What it costs to run AC

While the initial cost of the air conditioning itself is substantial, there are other continuing costs to operate the system that must be taken into account.

Factor 1: Cost of Electricity
Even if you don’t factor in the cost of the units and installation there is the cost that air conditioning adds to the Department’s electricity bill. When AC was installed at Pohakea Elementary School, the power bill more than doubled.

Currently, the Department is expected to face an electricity bill of $47.6 million this year.​ The chart below shows ongoing costs of all HIDOE utilities, including electricity; we have a number of initiatives that encourage reducing and softening our usage and that keeps costs relatively flat. However, year-over-year funding of utilities from the Legislature is dropping. That makes it that difficult to run the utilities we have, let alone add to the bill.

There are some promising technologies that we have mentioned that can help reduce the cost of our electricity bill. Photovoltaic air conditioning draws most of its power for use from the PV panels. Some systems can be purchased with batteries. Those system are being considered, but there are some potential concerns regarding hazardous materials. HIDOE Facilities representatives have held discussions with several local PV companies to look at a pilot project for PV/AC with batteries.

Factor 2: Ongoing maintenance
Just like a car or any other major piece of equipment, an air conditioning system needs ongoing maintenance. This maintenance cost can be substantial and, if not done, can lead to early replacement of air conditioning equipment. No matter what type of system would be installed, this would be an additional cost and must be factored into the long-term plan. Also, there is a lifecycle to any machine. These initial expenses could be back once the units fail. That means buying replacement systems.​

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