Purpose
Properly sized mechanical systems greatly effects efficiency, performance, comfort, system life, and could help save on installed and operational costs. Properly sizing mechanical systems requires detailed information determined by the results of step 2. Balanced whole building mechanical ventilation strategies often utilize the same ducting as the heating and cooling system so identifying opportunities for ventilation, filtration, and heat / energy recovery are prudent at this stage. Because water heating is often the 2nd largest energy use in buildings after space heating it’s important to carve out a space in the electric panel for heat pump water heating at this stage. Consider low Global Warming Potential refrigerant heat pumps which can also play a role in the overall efficiency of the system.
Strategies
Prioritize heat pump technology for space heating and water heating. Semiconditioned spaces like unfinished basements and attached garages are ideal locations for heat pump water heaters.
Work with an HVAC professional experienced in high performance buildings to properly size and design the space heating system using software tools.
Ductwork is ideally located inside conditioned space or ductless mechanical equipment is utilized. Ductwork that cannot located inside should be air sealed and insulated.
Consider smart thermostats that suggest and learn efficient behavior.
Whole building, balanced mechanical ventilation with heat recovery provides comfort in addition to energy efficiency.
Design for the highest level of filtration practical.
The highest levels of filtration can negatively effect airflows in HVAC systems and should be always be accounted for in system design with an HVAC professional.
Consider replacing exhaust fans with high efficiency DC brushless fans.