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Chapter 7: Heating, Ventilation, Air Conditioning To be used with the Guide to Building Energy Efficient Homes in Kentucky.

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Presentation on theme: "Chapter 7: Heating, Ventilation, Air Conditioning To be used with the Guide to Building Energy Efficient Homes in Kentucky."— Presentation transcript:

1 Chapter 7: Heating, Ventilation, Air Conditioning To be used with the Guide to Building Energy Efficient Homes in Kentucky

2 Decisions Type of HVAC System First-rate Contractor Energy Efficient Home

3 HVAC Efficiency Keys to obtaining design efficiency include: Sizing the system Proper selection and proper installation of controls Correctly charging the unit with proper amount of refrigerant Sizing and designing the layout of the ductwork Insulating and sealing all ductwork

4 Heating Systems Types of heating systems Forced-air Radiant Heat source Furnace (gas) Electric heat pump

5 Components of Horizontal Flow Forced-air System

6 Choices for Central, Forced-air Systems Fuel-fired furnaces with electric air conditioning units Electric heat pumps or Dual fuel system Best choice depends upon: ―Cost ―Efficiency ―Annual energy use ―Local price ―Availability of energy sources

7 Radiant Heating Systems

8 Advantages: Quieter operation Increased personal comfort at lower air temperatures Better zoning of heat Increased comfort from the heat

9 Radiant Heating Systems Disadvantages: Higher installation costs No provision for cooling the home No filtering of the air Difficulty in locating parts

10 Heat Pumps Heat pumps move heat from one fluid to another. Air (air-source) Water (geothermal) Inside Air

11 Heat Pumps

12 Air-source Heat Pumps Most heat pumps operate: Twice as efficiently as conventional electric resistance heating systems Have a 15 year life compared to 20 years for furnaces

13 Air Conditioner Vapor Compression Cycle

14 Compressor

15 Air Conditioner Vapor Compression Cycle Fan/Condensing Coil

16 Air Conditioner Vapor Compression Cycle Refrigerant

17 Air Conditioner Vapor Compression Cycle Evaporator Coil

18 Air Conditioner Vapor Compression Cycle Duct Heater

19 Heat Pumps Balance point = temperature at which heat pumps can no longer meet the heating load – Outside temperatures of 25° to 35°F Supplemental heat needed

20 Heat Pumps Some homes use a dual-fuel system. Heat Pump Gas Furnace

21 Heat Pumps Air-source heat pumps need outdoor thermostats. – This prevents operation of the strip heater at temperatures above 35°F. Many mechanical and energy codes require controls to prevent strip heater operation during weather when the heat pump alone could provide adequate heating.

22 Efficiency Heating efficiency of a heat pump is measured by its Heating Season Performance Factor (HSPF). HSPF = ratio of heat provided in Btu per hour to watts of electricity used

23 HSPF Minimum efficiency = 7.7 HSPF Medium efficiency = 8.0 HSPF High efficiency = 8.2 HSPF Variable speed heat pumps = 9.0 HSPF Geothermal heat pumps > 10.0 HSPF

24 HSPF HSPF and specific climates In colder climates, the HSPF declines In warmer climates, the HSPF increases In Climate Zone 4, in the winter, the predicted HSPF is approximately 15% less than the reported HSPF

25 Geothermal Heat Pumps A geothermal heat pump relies on fluid- filled pipes, buried, as a source of heating in winter and cooling in summer ~54°F

26 Geothermal Heat Pump

27 Deep well systems: Piping loop extends several hundred feet underground Closed Loop Designs ~54°F

28 Closed Loop Designs Shallow loops are placed in long trenches, like a “slinky”

29 Closed Loop Designs

30 Geothermal Heat Pumps Proper installation is essential for high performance Longer service than air-source units Cost is $1,300 to $2,300 more per ton than conventional air-source heat pumps

31 Geothermal Heat Pump Efficiency Coefficient of Performance (COP) = heating efficiency of a geothermal heat pump COP measures the number of units of heating or cooling produced by a unit of electricity

32 Geothermal Heat Pump Efficiency COP is a more direct measure of efficiency than the HSPF COPs are provided for different supply water temperatures – If COP = 3.0, the system would be operating at 300% efficiency

33 Furnace Equipment Which is more economical? heat pump or furnace Variables: Type of fuel burned Its price Home’s design Outdoor climate

34 Furnace Operation Furnaces require Oxygen (for combustion) Extra air (to vent exhaust gases)

35 Furnace Operation


37 New furnaces have forced draft exhaust systems – A blower propels exhaust gases out the flue to the outdoors Atmospheric furnaces have no forced draft fan ―Must be isolated from conditioned space

38 Sealed Mechanical Room Design

39 Measures of Efficiency AFUE = efficiency of a gas furnace Annual Fuel Utilization Efficiency (AFUE) = a rating which takes into consideration losses from pilot lights, start-up and stopping

40 AFUE The AFUE does not consider the unit’s electricity use for fans and blowers 78% = minimum AFUE for most furnaces 97% = AFUE for furnaces with condensing heat exchangers


42 Efficiency is highest if the furnace operates for longer periods Oversized units run intermittently and reduce operating efficiencies

43 AFUE 78% to 87% AFUE units have: electronic ignitions efficient heat exchangers, better intake air controls induced draft blowers 90% AFUE units have: special secondary heat exchangers that cool flue gases until they partially condense heat losses up the flue are virtually eliminated

44 AFUE Condensing furnaces A drain line must be connected to the flue to catch condensate With cooler exhaust gas, the flue can be made of plastic pipe

45 Condensing Furnaces Secondary heat exchanger – Increases efficiency Pulse furnace – Achieves efficiencies over 90% using a spark plug to explode gases, sending a shock wave out an exhaust tailpipe – Noisy

46 Economic Analysis Economic Analysis of Gas Furnaces Type of Treatment AFUE 0.95 Energy Savings*($/yr) Compared to AFUE 0.80 Break-even Investment ($) Code Home42477 ENERGY STAR ® Home31352 *For a system in Lexington, KY

47 Electric Integrated Systems A central heat pump that provides water heating, space heating and air conditioning should: Have a proven track record Have comparable price Have a 5 year warranty Be properly sized for both the heating and hot water load

48 Unvented Fuel-fired Heaters Malfunction could be life threatening Can cause serious moisture problems

49 Unvented Heater

50 Direct Vent Heater

51 Air Conditioning In summer, air conditioners and heat pumps work the same way to provide cooling and dehumidification.

52 Air Conditioner System: Air-handling unit houses – Evaporator coil – Indoor blower – Expansion or throttling valve Controls Ductwork

53 Air Conditioner Vapor Compression Cycle

54 Compressor

55 Air Conditioner Vapor Compression Cycle Fans

56 Air Conditioner Vapor Compression Cycle Pressurized Liquid piped to Air-Handling Unit

57 Air Conditioner Vapor Compression Cycle Evaporator Coils

58 Air Conditioners Homeowners will frequently lower the thermostat if a/c units are not providing sufficient dehumidification. – Every degree the thermostat is lowered will increase cooling bills 3% to 7%

59 SEER Rating The cooling efficiency of a heat pump or an air conditioner is rated by the Seasonal Energy Efficiency Ratio (SEER). SEER = a ratio of the average amount of cooling provided during the cooling season to the amount of electricity used.

60 SEER National legislation mandates: A minimum SEER 13.0 for most residential air conditioners Efficiencies can exceed SEER 19.0

61 SEER SEER and specific climates In warmer climates, the SEER declines In Climate Zone 4, the predicted SEER is approximately 5% less than the reported SEER

62 Economics Air Conditioner Economics Type of TreatmentEnergy Savings* ($/yr)Break-even Investment ($) SEER 14 (3 tons) - compared to SEER SEER 15 (3 tons) - compared to SEER *For a system in Lexington, KY

63 Variable Speed Units Advantages Save energy Quiet Dehumidify

64 Proper Installation How much lower is the operating efficiency, in hot weather, of a SEER 13 air conditioning system, with leaky ductwork?  1% to 4% lower  10% to 20% lower  25% to 40% lower  Over 50%

65 Proper Installation How much lower is the operating efficiency, in hot weather, of a SEER 13 air conditioning system, with leaky ductwork?  1% to 4% lower  10% to 20% lower  25% to 40% lower  Over 50%

66 Variable Speed Units Typical installation problems : Improper charging of the system – For new construction, the refrigerant should be weighed in

67 Variable Speed Units Typical installation problems : Improper charging of the system Reduced air flow – A 20% reduced air flow can drop the operating efficiency of the unit by 1.7 SEER points

68 Variable Speed Units Typical installation problems : Improper charging of the system Reduced air flow Inadequate air flow to the outdoor unit – Air temperatures around the unit rise, making it more difficult for the unit to cool the circulating refrigerant

69 HVAC Proper Design and Size Proper Installation Proper Operation

70 Sizing Energy efficient and passive solar homes have less demand for heating and cooling – Install smaller units that are properly sized – High efficiency systems will not provide as much annual savings on energy bills May not be as cost effective as in less efficient homes

71 Sizing Oversized equipment Costs more Wastes energy May decrease comfort – Inadequate dehumidification

72 Sizing Rule of thumb 600 square feet of cooled area per ton of air conditioning

73 Sizing Heating and cooling load calculations rely on: Outside winter and summer design temperatures Size and type of construction for each component of the building envelope Heat given off by the lights, people and equipment inside the house

74 Sizing Equipment Sizing Comparison Type of HouseCode Home HERS = 98ENERGY STAR ® Home HERS = 85 Exceeds ENERGY STAR ® Home HERS = 70 HVAC System Sizing Heating (BTU/hour)52,20038,80025,700 Cooling (BTU/hour)31,70025,70019,800 Estimated tons of cooling* Square feet/ton ,000 *Estimated at 110% of calculated size. There are 12,000 Btu/hour in a ton of cooling.

75 Sizing Latent load = amount of dehumidification needed for the home Sensible Heating Fraction (SHF) = portion of the cooling load for reducing indoor temperatures

76 Sensible Heating Fraction

77 SHF Many homes in Climate Zone 4 have design SHFs of 0.7 – 70% sensible cooling – 30% latent

78 Temperature Controls Thermostat Programmable (setback) thermostat – Energy saver – Automatically adjust – Must be designed for the particular heating and cooling equipment it will be controlling

79 Thermostat Centrally located Should not receive direct sunlight or be near a heat-producing appliance A good location is 4 to 5 feet above the floor in an interior hallway near a return Interior wall on which it is installed should be well sealed at the top and bottom

80 Zoned HVAC Systems Larger homes often use 2 or more separate heating and air conditioning units

81 Zoned HVAC Systems A single system with damper control over the ductwork 1.Install a manufactured system that uses a dampered bypass duct connecting the supply plenum to the return ductwork

82 Automatic Zones System

83 Zoned HVAC Systems 2.Create two zones and oversize the ductwork 3.Use a variable speed HVAC system with a variable speed fan for the duct system

84 Cooling Equipment Selection Sample Cooling System A Data, SEER 15 Total Air Volume (cfm) Total Cooling Capacity (Btu/h) Sensible Heating Fraction (SHF) Dry Bulb (°F) 75°F80°F85°F 95035, ,20037, ,45038, Sample Cooling System B Data, SEER 13 Total Air Volume (cfm) Total Cooling Capacity (Btu/h) Sensible Heating Fraction (SHF) Dry Bulb (°F) 75°F80°F85°F 95032, ,20034, ,45035, Consider dehumidification !

85 Ventilation and Indoor Air Quality Ventilation Removes stale interior air Removes excessive moisture Provides oxygen

86 Ventilation

87 Amount 7.5 natural cubic feet per minute of fresh air per bedroom + 1, plus additional air flow equal to (in cubic feet per minute) 1% of the house conditioned area, measured in square feet

88 Ventilation 7.5 cfm x (3 + 1)+ 1% of floor area (2,000) = 30 cfm + 20 cfm = 50 cfm 2,000 square foot home 3 bedrooms + 1

89 Leaks

90 Ventilation with Spot Fan

91 91 Spot Ventilation Bathroom fans Range hoods Choose low sone fans rated for continuous use

92 In-Line Ventilation with Spot Fan

93 93 Central Ventilation System “Pick-up” ducts connected to bedrooms and bathrooms 3-speed blower

94 Spot Ventilation

95 Whole House Fan Images courtesy of U.S. EPA

96 Supplying Outside Air from Air Leaks Where are the air leaks?

97 Supplying Outside Air from Inlet Vents Provide fresh outside air through inlet vents Purchased from energy specialty outlets Located in exterior walls Control either manually or with humidity sensors Locate in bedroom closets with louvered doors or high on exterior walls

98 Supplying Outside Air via Ducted Make-up Air Provide fresh outside air through the ducts for a forced-air heating and cooling system Automatically controlled outside air damper in the return duct system Blower – either the air handler or a smaller unit specifically designed to provide ventilation air

99 Fresh Air and Dehumidification Strategies

100 Heat Recovery Ventilators

101 101 Stale room air return ducts Heat recovery ventilator (not part of HVAC system) Exhaust air outlet Fresh air inlet Heat Recovery Ventilators (HRV)

102 Sample Ventilation Plans Mechanical ventilation system plans are routine for commercial buildings

103 Upgraded Exhaust Ventilation

104 Whole House Ventilation System DESIGN 2

105 Heat Recovery Ventilation System

106 Radon Cancer-causing, radioactive gas Found in soils Is not visible Has no odor Has no taste

107 Radon Highest potential Moderate potential Low potential

108 Removing Radon Ventilate under the foundation to help remove radon and other soil gases More cost-effective to include any radon resistant techniques while building a home

109 Radon Resistant Construction


111 SLAB-ON-GRADE OR BASEMENT Use a 4 to 6 inch gravel base Install continuous layer of 6-mil polyethylene Stub in “T” below polyethylene that protrudes through polyethylene and extends above poured floor height Pour slab or basement floor Seal slab joints with caulk

112 Radon Resistant Construction CRAWL SPACE Install sealed, continuous layer of 6-mil polyethylene Install “T” below polyethylene that protrudes through polyethylene

113 Radon Resistant Construction ALL FOUNDATIONS Install a vertical 3-inch PVC pipe from the foundation to the roof through an interior wall Connect the “T” to the vertical 3- inch PVC pipe for passive mitigation Have electrician stub-in junction box in attic Label PVC pipe “RADON” so that future plumbing work will not be tied into the stack

114 Testing for Radon Test for elevated radon levels Do-it-yourself radon test kits are available If high: – Easy and inexpensive to make an active system from an existing passive system – Add an in-line fan

115 Summary

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