A new study by the National Institute of Standards and Technology in the United States is the first in the country to quantify energy efficiency losses due to installation errors in HVAC systems.
The push for more efficient air conditioners and heat pumps aims to significantly reduce the 30 per cent share of residential electrical energy use devoted to cooling and heating, but the benefits of improved energy efficiency ratings count for nothing if the equipment is not installed properly, the report says.
“Our measurements indicate that improper installation could increase household energy use for space heating and cooling in the order of 30 per cent over what it should be,” said Piotr Domanski, who leads NIST research on the performance of HVAC (heating, ventilation, and air conditioning) and refrigeration equipment.
The three-year measurement and modeling study was undertaken in response to surveys and other field evidence indicating that, as “typically installed,” HVAC equipment may waste considerable energy. Common installation errors and faults include leaky ducts, improper refrigerant charge, oversizing of systems, and restricted air flow.
Under controlled environmental conditions, the team measured the performance of a heat pump while operating with any one of seven commonly encountered faults and how they might impact energy use in two types of houses—one with a basement, the other built on a concrete slab—and in five different climate zones.
Leaky air ducts emerged as the “dominant fault.” Refrigerant undercharge and incorrect indoor airflow due to improperly sized ductwork followed as the most significant cause of increased energy use.
For six of the seven faults studied, associated increases in energy use are similar for slab-on-grade and basement houses. However, leaky air ducts installed in unconditioned attic space can cause the greatest increase in energy use in slab-on-grade houses.
In hot and humid climates, duct leakage substantially increases indoor relative humidity, reducing human comfort. Occupants will typically lower the thermostat to compensate, which significantly increases energy use.
The energy consumption and energy efficiency of air conditioning and heat pumps is an equally, increasingly important issue in Australia. Residential cooling and heating accounts for significant energy consumption, and importantly is also pushing peak electricity demands higher on many networks.
“Higher efficiency equipment is part of the solution. Best-practice energy-efficient design and installation is the second piece in the puzzle. Energy-efficient operation and maintenance completes the best-practice residential air conditioning picture,” said Australian Institute of Refrigeration Air-conditioning and Heating (AIRAH) CEO Phil Wilkinson.
“AIRAH strongly support the development and publication of best-practice guides to cover the energy-efficiency aspects for the design and installation of residential air conditioning.”
In 2010, AIRAH proposed that a new Australian Standard be developed to outline industry best practice in the area. The purpose of the Standard would be to specify minimum requirements for the selection and installation of air conditioning systems for residential applications to address operating energy efficiency, and also include requirements to address system design and installation quality.
The new Standard would underpin several energy-efficiency initiatives in the sector, including the MEPS and Star Rating programs, and recent developments in electrical demand management technology for residential cooling and heating applications.
“There is considerable support in industry and government for the development of an energy-efficiency-based standard for residential air conditioning,” Wilkinson said. “The proposed project was accepted by Standards Australia, and a new technical committee EE-01 has been formed to undertake the work, with a current project to develop the new Standard already in place.”
Wilkinson said that, once completed, the new Standard could be enacted voluntarily through consumer contracts and supply agreements.
Additionally, it could be used as a condition of any future government or utility funded energy efficiency incentives such as air conditioner buy-back/upgrade schemes. Installers and equipment suppliers could operate a voluntary accreditation scheme based on the Standard to create a quality point in the supply chain.
“At the very least the new Standard would be a publically available record of what is considered good practice in the residential heating and cooling sector,” Wilkinson said.