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Chapter 7: HVAC for Smaller Buildings (skin dominated) 7.1 The need for mechanical equipment

Chapter 7: HVAC for Smaller Buildings (skin dominated) 7.1 The need for mechanical equipment cold climates – solar heating not sufficient hot climates – air motion and relative humidity control air quality

patrick-barrett
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Chapter 7: HVAC for Smaller Buildings (skin dominated) 7.1 The need for mechanical equipment

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  1. Chapter 7: HVAC for Smaller Buildings (skin dominated) 7.1 The need for mechanical equipment cold climates – solar heating not sufficient hot climates – air motion and relative humidity control air quality Is the mechanical system an occasional modifier, permanent interpreter or permanent excluder? Design decision: sealed vs operable openings

  2. Chapter 7: HVAC for Smaller Buildings (skin dominated) 7.2 Design process determine comfort needs ( related to activities) and climate characteristics In small buildings this process in done by the architect. At the design development stage, the mechanical engineer proposes a system. Typically: interior plus perimeter mechanical room need sizes distribution trees – vertical chase, horizontal runs in space components Coordination – vertical clearances, possibility of integration with structure, plumbing, electrical

  3. Chapter 7: HVAC for Smaller Buildings (skin dominated) 7.3 Equipment location and service distribution a) Central (equipment contained - easy maintenance) vs. Local (quick response to individual room needs, esp. in skin loaded building, south vs north walls) Mechanical/furnace room space required or not. c) Distribution trees – water (more easily integrated) vs. air ( bulky air ducts) both have noise issues Expressed (how? on the interior or exterior) vs. Hidden (how?) How is the final delivery achieved? Grill, slot, perforated surface?

  4. Chapter 7: HVAC for Smaller Buildings (skin dominated) 7.4 Controls (automated systems that learn) Building management systems (BMS) 7.5 Refrigeration cycles Unlike passive systems, mechanical systems can rapidly concentrate heating and cooling on demand. a) compressive refrigeration fig. 7.1 b) alternative refrigerants that do not contain CFC’s (green) fig. 7.2 7.6 Cooling only systems a) fans – individual, whole house b) unit air conditioners con: noisy, ugly no chance to conserve energy pro: only used when needed c) evaporative cooling

  5. Chapter 7: HVAC for Smaller Buildings (skin dominated) 7.7 Heat only systems Locating heat next to exterior walls increases heat loss (Δ T) Less need because of better insulation and windows. a) wood stove with catalytic converter (less pollution) temperature swings radiant effect you must see the stove add thermal mass wood storage b) electric heaters - high grade energy for low grade task low first cost individual control no distribution problems

  6. Chapter 7: HVAC for Smaller Buildings (skin dominated) 7.7 Heat only systems e) hot water boilers whole building systems f) hot water baseboard and radiator systems fig. 7.19 a) series loop system b) one pipe system c) two pipe reverse return equal heat to all pipe expansion noise

  7. Chapter 7: HVAC for Smaller Buildings (skin dominated) 7.7 Heat only systems g) radiant panels, floors don’t heat floors where you want to collect solar energy new polyethylene tubing Fig.7.24 radiator styles Fig. 7.26 high efficiency furnaces no longer require big chimneys

  8. Chapter 7: HVAC for Smaller Buildings (skin dominated) 7.7 Heat only systems k) warm air heating systems comfort, good air circulation, quick, filter and air conditioning and humidification possibilities return air ducting can be minimized ducts can be lined with sound absorbing material Coordination – duct sizes, dampers, registers with vanes

  9. Chapter 7: HVAC for Smaller Buildings (skin dominated) 7.8 Heating/Cooling systems c) air to air heat pumps fig. 7.38 uses the refrigeration cycle to both heat and cool. heat is pumped from in to out in summer, out to in in winter. single package (out) – on roof – noisy split package (in/out) per room – motels – noise (masking?) can be combined with solar collection

  10. Chapter 7: HVAC for Smaller Buildings (skin dominated) 7.8 Heating/Cooling systems c) air to air heat pumps In the heating mode, the heat pump can give more energy than it receives (electrically). Electric energy is used to run the cycle but the pump draws free heat from a source such as outdoor air or water souces, solar heat storage, ground sources, etc. Ceases to be efficient at low temperatures. Fig. 7.44

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