Soaking in the Sun

Passive and active solar heating, combined with energy efficient building materials, give this Colorado-based aquatic center an edge on energy savings and long-term sustainability.

The difficulties of renting pool time to practice aquatic therapy originally motivated Watsu practitioners Greg and Debbie Ching to consider constructing their own pool house on their 2.5-acre home site in Nederland, Colorado. But their commitment to solar energy—and the energy and financial savings it offers—brought them to the doorstep of Solar Works Construction, my solar and general contracting business.

The Chings dreamed of having a facility where they could practice Watsu (aquatic massage) themselves, hold classes, and open it to other practitioners and their clients. To do so, they needed a pool about 20 feet square and 4 feet deep, with water that could be maintained near body temperature. They also wanted an office, a bathroom, and a room for table massage. As a designer and builder promoting sustainability, what was most compelling to me was the Chings’ interest in extending their philosophy of caring for people to caring for the environment.

Efficiency in the Details

Debbie and Greg were already committed to and familiar with using renewable energy, and wanted to use solar energy to heat the new building and the pool water. Correctly siting the building to take advantage of passive and active solar heating opportunities was key. The building’s roof ridge runs east and west, providing a large south-facing surface for an array of solar hot water collectors. A large bank of double-paned windows on the building’s south face allows sunlight in, and the thermal mass of the concrete floors captures, stores, and reradiates this solar-made heat into interior spaces. A special film in the Heat Mirror windows slows heat transfer back through the south-facing windows, especially when outdoor temperatures drop into the single digits. These windows allow more solar heat to enter than ones with other low-emissivity (low-E) coatings.

Insulating concrete forms (ICFs), large polystyrene foam forms that are stacked and filled with steel-reinforced concrete, make up the pool house walls. This system produces a fire-resistant, sound-dampening shell with low air infiltration and an R-33 performance rating. For even more fire-resistance, plus low maintenance, the Chings chose a fiber-cement panel siding for the exterior finish that could be stained to match their house. Ten-inch-thick structural insulated panels (SIPs)—styrene foam faced with oriented strand board—comprise the roof and ceiling system, and insulate to about R-38. Like the ICFs, this product provides a tight, well-insulated roof that is little affected by the humidity created by the warm pool water.

The concrete-and-plaster in-ground pool risked losing a substantial amount of heat to the earth. To slow heat loss, 2- to 4-inch-thick extruded polystyrene rigid insulation was added to the inside of the foundation wall, underneath the slab, and to the outside of the pool shell, insulating the pool and foundation walls to R-20, and the concrete slab to R-10.