Any project submitted to a court on this date (1 January 2021) must comply with the new 2020 Code. In our third part of a blog series that aims to explore these code changes, we look at notable changes in mechanical code. Natural ventilation depends on uncontrolled air movements or infiltrations that cannot be relied upon to evenly ventilate the house. It also brings unwanted moisture. Natural ventilation is largely based on the opening of windows and doors. However, when people do not open their windows and doors, natural ventilation is more or less infiltration through cracks and small holes in the house. This type of ventilation is generally not recommended for homes in Florida. If the building leaks, it can cost up to 30-40% more to heat or cool as air conditioning escapes and outside air seeps in. [1] Indoor air generally contains more types and higher concentrations of pollutants than outdoor air, even in industrialized areas. Common indoor air pollutants include biological pollutants (mold spores, dust mites, bacteria, viruses, pollen, animal hair); combustion pollutants (including carbon monoxide); lead from old paint or lead-containing soil; volatile organic compounds (VOCs) emitted by many paints, adhesives and other building materials (this is called “outgassing”); and in parts of Florida, radon. The other contributing factor to poor indoor air quality in Florida is humidity. When done properly, proper ventilation will help remove and control pollutants and moisture. In summary, all homes need ventilation to remove stale indoor air, pollutants and excessive moisture.
Researchers recommend mechanical ventilation systems for the whole house for all buildings. The amount of ventilation required depends on a number of variables, including: Whole-house ventilation systems can provide fresh, filtered outdoor air in controlled quantities using the existing HVAC distribution system for uniform distribution and mixing. Some of the most common systems include: In the past, air leaks were used to provide ventilation. However, a leaky building does not guarantee good indoor air quality. What for? Air leaks often lead to air quality problems in attics, crawl spaces and outdoors. These may include: Infiltration of buildings may vary depending on conditions. During cold and windy periods, penetration into the building can be accelerated, while very little air exchange can occur in calm and hot weather.2 To ensure adequate indoor air quality, mechanical or natural ventilation should be considered when planning and maintaining any home. The Ministry of Energy recommends the integration of mechanical ventilation into the heating, ventilation and air conditioning (HVAC) system. The 5th edition of the Florida Building Code (2014), energy conservation requires mechanical ventilation in new buildings using ASHRAE 62.2 and acceptable indoor air quality in low-rise residential buildings.
The minimum air exchange requirements per hour for residential buildings are the maximum permitted rates for residential use according to ASHRAE 62.2. Ventilation or auxiliary air should NOT be provided for air-conditioned rooms in attics, crawl spaces, attached enclosed garages or outdoor areas adjacent to swimming pools or spas. Air intakes and outdoor air outlets must be equipped with automatic shutters or gravity flaps that close when the ventilation system is not operating. To ensure a healthy indoor climate, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) recommends that a home have 0.35 air changes per hour (ACH). [2] An older home may have infiltration rates in the range of 2.5 ACH or higher, while a building built to today`s standards and practices typically has infiltration rates of 0.5 to 1.0 ACH.2 An energy-efficient new home can have significantly less than 0.35 air changes per hour. Improved point ventilation helps control specific humidity issues, but does not provide adequate ventilation of the entire building. Another type of ventilation – the whole house – can evacuate air from the kitchen, bathrooms, living room and bedrooms. Whole-house ventilation systems are generally classified as exhaust air when the mechanical system forces indoor air out of the house, supply ventilation when the mechanical system forces outside air into the home, or balanced ventilation when the mechanical system forces equal amounts of air inside and outside the house.
Each system has advantages and disadvantages, must be properly dimensioned and its presence must be taken into account when determining the cooling / heating needs of the house as well as filtration or dehumidification needs. Further information can be found in the Ganzhauslüftungssysteme data sheet and on the Energy.gov Ganzhausventilung website. More research is needed in the field of mechanical ventilation in buildings located in hot and humid climates such as Florida. We know that buildings are built with tighter building envelopes (less unwanted infiltration) and that air exchange is necessary to ensure a healthy and safe indoor climate. The amount required is set out in the ASHRAE standard and must be calculated by a CCV professional. “Ventilation” is defined as “the natural or mechanical process of providing conditioned or unconditioned air to a room.” “Infiltration” can be defined as the uncontrolled leakage of air inward through cracks and holes in the building envelope, particularly around windows and doors. Note that infiltration deals with uncontrolled situations. In our homes, we want to be able to control the movement of air. Point ventilation in bathrooms and kitchens is another approach to controlling humidity and odors. Many exhaust fans installed in standard constructions are inefficient – a major cause of indoor humidity problems for buildings in hot and humid climates.
