Designers of energy-efficient homes — especially homes aiming for net-zero energy use — must inevitably grapple with the question of simplicity versus complexity.
Residential designers can choose from an array of sophisticated appliances that improve comfort and help homeowners reduce energy use. Examples include heat-recovery ventilators (HRVs), condensing boilers, ground-source heat pumps, solar hot water systems, on-demand water heaters, heat-pump water heaters, photovoltaic modules, and co-generation systems.
Most of these devices perform well. However, designers who specify sophisticated appliances need to consider the trade-offs that accompany such hardware:
- Higher upfront costs;
- The need for proper commissioning; and
- The need for proper maintenance.
Commissioning? What’s commissioning?
Builders often underestimate the importance of commissioning all HVAC equipment after installation. (“Commissioning” simply means making final adjustments and tuning up equipment to verify that it functions properly.)
Unfortunately, most new homes are imperfectly commissioned, leading to one or more of the following errors:
- The air conditioner has the wrong refrigerant charge.
- The airflow over the cooling coils has not been verified.
- Duct systems haven’t been checked for leaks.
- The airflow through forced-air registers hasn’t been adjusted to meet specifications.
- Pressure imbalances between bedrooms with closed doors and adjacent hallways have not been remedied.
- Exhaust fan airflow hasn’t been tested.
- Heat-recovery ventilators have not been balanced.
- Atmospherically vented appliances haven’t been checked for backdrafting during exhaust fan operation.
- The temperature set-points on the solar hot water system controller are improperly set.
HVAC commissioning errors almost always result in needless increases in energy costs. Many HVAC specialists can share horror stories about commissioning errors, running the gamut from irritating to outrageous (for example, air-source heat pumps with electric resistance elements that operate for most of the winter).
You mean I have to change the filters?
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