Mechanical System Selection
Significant contribution of the passive design elements of the building (quantified through Energy Modeling) allowed a sizable decrease in the size and type of mechanical systems required to heat and cool the building.
Additionally, energy systems constraints, as well as the owner/occupant values and comfort needs, also helped determine the final mechanical system selection.
As an environmental organization attuned to outdoor experience, neither the executive director nor support staff of the organization required, (or desired) refrigerant cooling, for example.
The design-to temperature for the winter heating season was a modest 68°, with a summer design-to cooling temperature of 78°.
This less-demanding comfort zone requirement, combined with the passive energy contributions of the building itself, pointed towards variable-speed control evaporative cooling, and in-floor radiant heating as the appropriate heating and cooling system options for the James Learning Center.
Life Cycle Considerations
Life cycle cost considerations relative to the mechanical system choices for the building are consistent with the values of the organization for choosing high durability, low-replacement cost systems. The selected boiler’s lifespan (between 25-40 years), combined with the life span of the PEX in-floor radiant tubing (between 50-100 years) is higher than comparable forced air systems.
On the cooling side, evaporative cooling boasts one of the more favorable life cycle cost scenarios, as both first cost and annual operating cost are much lower compared to a typical refrigerant cooling system.