In the last few weeks, we’ve been discussing broad ideas in the context of sustainability. In this post, I’d like to share a more detailed case study on a specific project we’ve been working on.

It’s human nature to resist change. As an advocate of green building, believe me when I say that I am very used to people resisting the change we try to push even though it’s a change for the better.

When it comes to air conditioning in the Philippines, the most common method is either the box type window mounted units or split units (including inverters). This type of air conditioning focuses on cooling down a space and does not usually ventilate an area. Most occupants rely on infiltration for fresh air which leads to poor energy performance.

We’ve recently been working on a hotel project and the question of the appropriate building systems came up. The project team had indicated that the plan was to either use box type ACs or variable refrigerant flow units to save energy. Both strategies would have individual AC units in each hotel room which can be switched on or off by the guests. The units will focus on cooling down the space without any direct fresh air ducting. Ventilation will then come from either operable windows, the undercut of the room door, or infiltration.

Surely there’s a better way to cool a space and provide adequate ventilation to its guests. We then suggested using centralized air conditioning in order to provide both air conditioning and mechanical ventilation to each space. Air-cooled chillers have roughly the same efficiency as split units, and are more expensive. Even more expensive are water-cooled chillers, however, they operate at twice the efficiency of the other options.

As with any strategy, the most important thing to do is to quantify energy savings and compare them against one another. After our calculations, we found that while the water-cooled chiller was the most expensive system by far, it also had a simple payback of 4.3 years. The air-cooled chiller and the VRF systems, while being cheaper to purchase, did not provide any environmental and economical benefit during operation.

It was then quite obvious that the most sustainable strategy was to use the water-cooled chillers. Using the triple bottom line, we can see that the strategy addresses all three factors. The social benefit is providing the appropriate amount of fresh air to all the guests. Environmentally, we consume less than half of the energy we otherwise would use for cooling thus a reduction in carbon emissions. The payback period makes it so that after 5 years of operation, the project would be saving more money than it would have had it used a different strategy which makes the solution economically viable.

We came up with an even better strategy which would shorten the payback however would require additional capital. Can you think outside the box and figure it out?