Best Practices Guide for residential HVAC retrofits
This best practices guide for residential HVAC system retrofits is aimed at contractors who want guidance on delivering energy efficient, cost effective and innovative products. It has been developed around the idea of having packages of changes to the building HVAC system and building envelope that are climate and house construction dependent. These packages include materials, procedures and equipment and are designed to remove some of the guesswork from a builder, contractor, installer or homeowner decisions about how best to carry out HVAC changes. The packages are not meant to be taken as rigid requirements – instead they are systems engineered guidelines that form the basis for energy efficient retrofits. Similar approaches have been taken previously for new construction to develop extremely energy efficient homes that are comfortable safe and durable, and often cost less than standard construction. This is best epitomized by the Building America program whose partners have built thousands of residences throughout the U.S. using these principles. The differences between retrofitting and new construction tend to limit the changes one can make to a building, so these packages rely on relatively simple and non-intrusive technologies and techniques. The retrofits also focus on changes to a building that will give many years of service to the occupants.
Another key aspect of these best practices is that we need to know how a house is working so that we know what parts have the potential for improvement. To do this we have put together a set of diagnostic tools that combine physical measurements and checklists/questionnaires. The measured test results, observations and homeowner answers to questions are used to direct us towards the best retrofits applicable to each individual house. The retrofits will depend on the current condition of the building envelope and HVAC system, the local climate, the construction methods used for the house, and the presence of various energy saving systems (e.g., a Heat Recovery Ventilator) and/or materials. This is just like a doctor referring a patient for blood tests or x-rays before actually performing surgery. This way the doctor can be sure that he does the right thing. To take this analogy further — we can borrow from the medical profession and say that the first thought when retrofitting a house is to do no harm, i.e., do not make changes that could make the house worse to live in.
This guide was developed in conjunction with input from many members of the HVAC industry and research community. Thanks to all those who participated.
When the HVAC system is not working is usually the first time a homeowner has any interest or awareness of the HVAC system in the house. Because of the catastrophic nature of repair calls and the short time allowed for repair (particularly unheated homes in cold winter climates) — prepared packages are essential because there is little time to analyze an individual home to determine optimum retrofits. Often equipment is broken and this is an ideal time to suggest replacement, together with other related upgrades from the retrofit packages.
Some homeowners will have consistent maintenance programs for their HVAC systems (e.g., spring tune-ups for air conditioners) and will be aware that it is better to replace equipment before it fails in an emergency situation. Homeowners may also want to upgrade/improve their HVAC systems, in some cases to increase energy efficiency if they have high bills or if their utility offers rebate programs. When equipment is replaced, this is another key time to use the systems engineering approach to look at building and HVAC components beyond the furnace or compressor.
When homes are remodeled, HVAC systems are often upgraded so that they can better condition the house and changing use of rooms, or their capacity is increased if the remodel includes the addition of rooms. Because remodeling often includes removal of floors and walls this allows more extensive retrofits — like replacing all ducts or completely redesigning the duct system to make it smaller or run inside conditioned space. Because of the high disruption level associated with remodeling, location of air handlers, outdoor condensers and installation of economizers will also be easier.