MAH_2019

MAH 2019 Companion Guidance Section C Understanding HVAC System Designs 5 MAH Companion Guidance Section C UNDERSTANDING HVAC SYSTEM DESIGNS AND INFLUENCE ON TEST RESULTS For comfort, indoor temperatures are kept between 65˚and 80˚ F (18˚ - 27˚ C). When outdoor temperatures go below about 65˚(18˚C), buoyant indoor air rises upward to drive radon entry from soil. As outdoor air grows colder, heating systems activate to result in consistent upward stack effect that drives radon entry. Whenever and wherever air handlers are active, radon is distributed around the building. Group 1: BASIC HEATING AND COOLING (HAC) Dedicated system(s) that do not supply additional outdoor air for ventilation. HAC Systems: Most homes have forced-air heating and air conditioning (HAC) systems. Supply and return ducts distribute air around the building. Ductless Systems: Some homes do not have ducted forced-air distribution. • Hot and Cold-Water Circulation (sometimes referred to as “radiator" systems). • Window Air Conditioners. • Wall or Baseboard Heating/Cooling Systems. • Ductless Split Systems with one unit for cooling and another unit for heat (i.e. Window AC for cooling and Baseboard or Wall units for heat). Group 2: MULTI-ZONE SYSTEMS Multi-zone systems are those where different air handlers or systems are employed and independently controlled for different areas within the same dwelling or common use area of a building. Radon concentrations can vary from room to room based upon variances in system operations.