Natatoriums and Aquatic Facilities: Working for a Triple Bottom Line

Jun 7, 2018

Picture an indoor pool: feel the warm air and humidity, see a slide, maybe a bubbling hot tub, kids splashing in the shallow water, maybe some retirees doing water aerobics. Then it hits you—the “chlorine.” Your eyes start itching and you squint. What is that? Why can’t it go away? Is there anything we can do about this? The short answer is yes. But first I’m going to tell you why as an energy engineer I’ve been focused almost single mindedly on pool projects since the start of 2017.

Why pools?

It started with a search to find projects in the commercial building sector with large natural gas savings potential. As it turns out, natatoriums are highly energy intensive; it is not uncommon to find facilities with Energy Use Intensity (EUI) above 300 kBtu/sqft. This large energy consumption base-load means we have more to work with on each measure. What is more, many natatorium facilities were value engineered from the start and have a wide gap between what is possible, and what was done. There are real (and large) opportunities to help pool customers save on energy costs. But this is not the only reason.

As I’ve partnered with key players in the pool industry, my viewpoint has expanded. I now appreciate that these projects can play a much larger role. We can make a real impact on the comfort and health of pool patrons while driving revenue to small businesses. Wouldn’t you be more inclined to frequent your local swimming pool if the water was clean and the air was fresh? With energy efficiency efforts in natatorium spaces we can fully impact the triple bottom line—people, planet, and profits.

Helping pools and their swimmers save energy

Pools and Buildings Don’t Naturally Mix

Starting with the basics, “natatorium” is a fancy word for a pool enclosed by a building. So what’s the problem? Knowingly putting a large volume of water inside of an enclosed space does not work within the original intent of a building- historically structures have been made to stay dry. Since buildings are typically designed and built to keep moisture out— on their own they don’t fare well with heavy internal latent loads —this heavy presence of moisture can and does lead to premature structural decay, mold build-up, and health issues such as asthma. Buildings (and pool patrons) are especially prone to moisture laden with chemicals as can be found in many pool facilities. Natatoriums are thus difficult to design and difficult to manage. But it is possible.


Before we talk about HVAC and plumbing, we need to talk about chemistry—very lightly. That chlorine smell you detected? It’s not strictly speaking “chlorine”. It’s actually a sign chlorine did its job by reacting with contaminates in the pool. Hair, skin, fluids, the chlorine is attacking the stuff we leave behind. Chlorine reacts with these contaminates to give us what we want —disinfected water— but we now have to deal with disinfection by-products called “combined chlorines” or “chloramines” for short. Moist air is especially eager to hold onto the off-gassed chloramines, giving us the chemical laden air mentioned earlier. There are three common chloramine formulations we need to consider:

  1. Monochloramine - This one is always present when you have chlorine in contact with ammonia but it’s not too bad. In fact, municipal water systems actually use monochloramines to treat drinking water.
  2. Dichloramine - Dichloramine is more volatile than monochloramine, meaning it leaves the water faster than monochloramine. But it breaks down quickly in air, so is generally ignored.
  3. Trichloramine - Trichloramine is very volatile and is easily swept out of water when it’s disturbed by kicking, splashing, air going across it, etc. Trichloramine is the big baddie that is most responsible for indoor pool air quality problems and the only species of combined chlorine that causes eyes to tear. It’s generally accepted as bad for us.

One of the primary goals for both water-side and air-side systems is to manage these trichloramines. While some natatoriums have a full arsenal of equipment ready to handle chloramines, others may need some capital upgrades to adequately address the issue (UV, source capture exhaust, chemical controllers, etc.), but in all cases, the natatorium needs to be managed by skilled hands to make the most of what is available.

It’s a Balancing Act

Natatoriums require continuous balancing of occupant comfort and operational costs. Managing pool heating, pumping, filtration, and sanitation systems in addition to the building's heating, ventilation, and dehumidification systems requires significant effort, skill, and diligence. When one or more of these systems goes out of alignment with the functions of the others, it can create issues with air quality, water quality, and occupant comfort, and can lead to unnecessary overhead in terms of labor, energy, water, and chemical costs.

To combat these challenges, sophisticated building controls have been successfully introduced at natatoriums here in Oregon* and across the United States. Building controls can now seamlessly connect and optimize the vast majority of natatorium equipment. For example, a UV system can now increase or decrease its output (dosage) as directed by the chemical controller, a relatively new capability in the marketplace. For natatoriums with independently controlled equipment, integrating these new control systems presents significant opportunity to improve building performance. In fact, natatoriums that have installed system-wide controls systems have seen their operating costs go down while creating a healthier space for their pool patrons.

But, that is not the end of the story. While advanced controls can help unify equipment operation, care must still be taken to ensure the equipment and control systems are maintained, scheduled, and operated correctly. Therefore, natatoriums that already have fully or partially integrated building control systems can also benefit and save through retrocommissioning** and/or expansion of their control systems.

We will explore technical details in a future post, but if you can’t wait, I’d recommend reading one or both of these excellent natatorium design guides:


*Energy Trust of Oregon provides energy savings analyses to evaluate facilities for optimization opportunities and offers cash incentives to offset the cost of completing capital and O&M projects, including natatorium control systems.


**Retrocommissioning involves improving the use of old equipment or systems in an existing building to energy efficient (sometimes ENERGY STAR) equipment/systems. (This work is referred to as commissioning if it is new construction.) It usually requires the help/expertise of engineers and experienced trade allies. Nexant manages retrocommissioning programs for many utilities across the country.


Jacob James is an Engineer and Certified Energy Manager with Nexant’s Utility Services business unit.  He was recently asked to speak on pool system basics and efficiency opportunities at an Association of Energy Engineers Event that included a tour of the Chehalem Parks & Recreation Aquatic Center in Oregon.


Chehalem Aquatic Center is an excellent example of what is possible in a natatorium space. Care was taken when selecting equipment that is both efficient and capable. Heat pumps provide chilled water for space dehumidification while simultaneously heating the pool water. High efficiency condensing boilers were installed as backup to the heat pumps. Every recirculation pump was installed with variable speed drives programmed to meet the desired flow rates. Regenerative filters were used to lower head on the recirculation pumps while simultaneously increasing water quality. Chemical storage rooms were installed separately from the mechanical rooms. Water level dedicated exhausts were incorporated beneath the lower return ducting to evacuate low-lying contaminated air.