Radiant-based-HVAC #

Radiant based HVAC systems by its implied definition, integrates the [interior surface temperatures](Mean%20Radiant_pg2.htm#Surface temp) of the building enclosure for the purposes of evaluating the mean radiant temperature for establishing thermal comfort based on human factor design. Background: The control over surface temperatures for thermal comfort is not new; to set the bookends as it were, are two quotes one from 1857 and another 2010 - both from internationally recognized authorities on health and buildings advising us to focus on the enclosure to control heat transfer by radiation: 1857 - “the Commissioners of the General Board of Health advocated as one of the requirements for comfort that the walls of a room be at least as high in temperature as the general temperature of the room, while they included cold walls or floors amongst the conditions which make for discomfort.”1 2010 - National Building Code of Canada v2010: Section A-5.3.1.2. (1) Use of Thermal Insulation or Mechanical Systems for Environmental Control states, “In addition to controlling condensation, interior surface temperatures must be warm enough to avoid occupant discomfort due to excessive heat loss by radiation.” Furthermore, recognized authorities in human factor design and thermal comfort are in agreement with the UK’s Health and Safety Executive which states, “The most commonly used indicator of thermal comfort is air temperature – it is easy to use and most people can relate to it. Mechanical solutions, like low temperature radiant heating and high temperature radiant cooling can then be applied if necessary to compensate for the buildings short comings. As illustrated below, low performing buildings using traditional heating systems need high fluid temperatures in heating (and low temperatures in cooling) but only a high performance building can use low temperatures in heating and high temperatures in cooling (applies to all systems). In fact with high performing buildings, using radiant cooling and heating, conductive floors and close tube spacing, fluid and surface temperatures operate close to the core body temperature and enable maximum efficiency from the heating and cooling plant. So you win when you improve the building and you win when you use low temperature radiant heating and high temperature radiant cooling.