PART 5: HVAC & DHW SYSTEMSBuilding Science Review
Learn more at energy.gov/betterbuildings
• This document will help you:• Correctly answer all parts of the “HVAC Systems” section in the Home Energy Score
Tool• Calculate equipment efficiency based on type and manufacture year• Identify Heating Equipment – 9 Types• Identify Water Heating Equipment – 5 Types• Identify Cooling Equipment – 3 Types• Determine impact of multiple HVAC systems within a home• Identify Duct Quality
Learn more at energy.gov/betterbuildings
Building Science Review: HVAC & DHW Systems
To address this issue, the Dept. of Energy (DOE) has developed an efficiency calculator to help determine the efficiency. It is based upon the age of the equipment, whether it is routinely maintained and its initial efficiency.
Link for the downloadable excel efficiency calculator. http://homeenergyscore3dtraining.com/course/hvacefficiency.php?id=3
Link to find the age of equipment (more detail on next page): http://www.buildingcenter.org/
Learn more at energy.gov/betterbuildings
HVAC Systems: Equipment Efficiency
When using the Assessor Calculator, always use the current year when determining the equipment age.
In practice, the actual energy efficiency of a piece of equipment is rarely known. Even if it is known, age and wear and tear tend to decrease the efficiency.
If you downloaded the Sim Calculator prior to January, 2016, it is out-of-date. Download the current Calculator.
The Assessor Calculator is easy to use. Simply input the 4 data items:1. System Type. Determine through visual inspection.2. Is it well maintained? Determine through visual inspection and/or homeowner interview.
If you don’t know or can’t tell, answer “no”.3. System age. Determined from the equipment label & building center website.4. Installed efficiency. Determined through the table found in the Assessor Calculator /
given below:
Learn more at energy.gov/betterbuildings
HVAC Systems: Equipment Efficiency
If the date of manufacture is not clearly printed on the data plate, visit www.buildingcenter.org to learn how the manufacture year is coded into the to the serial number.
Learn more at energy.gov/betterbuildings
HVAC Systems: Date of Manufacture
Example of the manufacture date coded in the serial
number on a Trane furnace. This unit was manufactured in 1991. (For Sim calculations, please disregard the month.)
When using the Assessor Calculator always use the current year when determining the equipment age.
Heating Equipment – 9 Types:• Central Gas Furnace• Room (through-the-wall) Gas Furnace• Propane (LPG) Furnace• Oil Furnace• Electric Furnace• Electric Heat Pump• Electric Baseboard Heater• Gas Boiler• Oil Boiler
Cooling Equipment – 3 Types:• Central Air Conditioner• Room Air Conditioner• Electric Heat Pump
Water Heating Equipment – 5 Types: • Electric Storage• Natural Gas Storage• LPG Storage• Oil Storage• Electric Heat Pump
Learn more at energy.gov/betterbuildings
HVAC & DWH Systems: Types in the Scoring Tool
Learn more at energy.gov/betterbuildings
Heating: 9 Equipment Types
1. Central Gas Furnace• High Efficiency (Condensing)• Mid-Level Efficiency (Induced Draft)• Low Efficiency (Natural Draft)
2. Oil Furnace• Condensing (High Efficiency)• Flame-Retention Head Burner (Mid-Level Efficiency)• Conventional Burner (Low Efficiency)
3. Room (through-the-wall) Gas Furnace4. Propane (LPG) Furnace5. Electric Furnace6. Electric Heat Pump7. Electric Baseboard Heater8. Gas Boiler9. Oil Boiler
Learn more at energy.gov/betterbuildings
Heating: Central Gas FurnacesCentral Gas Furnaces – 3 Types:
Type Condensing HE Induced Draft Natural Draft
Defining Features
• White PVC flue pipe connected to the outside, often paired with PVC intake pipe
• Metal exhaust flue pipe, often connected to the chimney• Inducer fan
• Draft diverter or hood for air intake below the metal exhaust flue pipe
Starting Efficiency 0.90 AFUE 0.82 AFUE 0.78 AFUE
Example
Learn more at energy.gov/betterbuildings
Heating: Oil FurnacesOil Furnace features: Barometric damper (except condensing), injection controller, oil tank.
Type Condensing Flame-Retention Head Conventional
Defining Features
• PVC pipe exhaust venting • Motor RPM 3450• Standard since mid 1980’s• Natural draft exhaust venting
• Motor RPM 1725• Phased out in 1980’s• Natural draft exhaust venting
Starting Efficiency 0.90 AFUE 0.80 AFUE 0.72 AFUE
Example photo missing?
Learn more at energy.gov/betterbuildings
Heating: Other Furnaces
Type Through-the-Wall Propane / LPG
Defining Features
• Gas furnace• No ductwork• Temperate regions
• Identical to natural gas furnace in house• Also has propane tank – sometimes buried in yard• Typically found in rural areas• Boiler plate on equipment will indicate type of fuel
Starting Efficiency 0.78 AFUE Same as natural gas
Example
Learn more at energy.gov/betterbuildings
Heating: BoilersGas and Oil Boilers are used to heat homes with hot water or steam pumped through radiators.
Type Gas Boiler Oil Boiler Tankless Coil
Defining Features
• Open draft diverter• Large pipes attached to the system• Lack of ducts
• Barometric damper (top circle)• Outside oil injection controller (bottom circle)• Flue
• A tankless coil has an additional controller on the outside. • no DHW heater or storage tank present
Starting Efficiency 0.75 - 0.84 AFUE 0.75 - 0.84 AFUE 0.75 - 0.84 AFUE
Example
Learn more at energy.gov/betterbuildings
Heating: Electric
Type Electric Baseboard Electric Heat Pump Electric Furnace
Defining Features
• Wiring• No pipes• No Combustion
• Thermostat has Emer Heat setting / light• Turn up thermostat on heat mode until system comes on. If outside unit is running, then it is a heat pump.
• Large electric breaker in front• Heavy wiring• No flue
Efficiency 0.99 AFUE 6.6 – 9 HSPF 0.99 AFUE
Example
Learn more at energy.gov/betterbuildings
Cooling Equipment: Distinguishing TypesCooling Equipment – 3 Types:
Type Central Air Conditioner Room Air Conditioner Electric Heat Pump
Defining Features
• Outdoor compressor unit• Two copper pipes, one insulated• Evaporator coil
• window mounted or through-the-wall• No central / outdoor unit
• Thermostat has Emer Heat setting / light • Looks and functions like central A/C compressor
Starting Efficiency 9 - 20 SEER 8 - 12 EER 9 - 20 SEER
Example
The Home Energy Score Tool is able to account for 2 heating or cooling systems within a home.
If there are more than two systems, then the two largest system characteristics should be entered.
Learn more at energy.gov/betterbuildings
HVAC Systems: Multiple Furnaces
The Scoring Tool requires data on the ducts. If the ducts are in more than one floor/location you must estimate the % in each location.
Learn more at energy.gov/betterbuildings
HVAC Systems: Ducts
In this diagram, 50% of the ducts are in unconditioned attic and 50% are in an unconditioned basement and unvented crawlspace. (Note: the basement is unconditioned as per the Home Energy Score definition of conditioned areas, because there are no supply registers located there.
• Determining duct locations in a multi-story home: • If supply vents on the top floor are in the floor, you can assume the vents are in a conditioned area - the floor joist space of the living space. • If they are in the ceiling of the top floor the ducts are in the attic. • Use the floor area ratios as an approximation for duct % in these difficult cases.
Learn more at energy.gov/betterbuildings
Ducts: Schematic
Learn more at energy.gov/betterbuildings
Ducts: Exterior Insulation
Duct insulation is usually indicated on the exterior of the ducts with a foil or plastic covering. Rigid insulated ducts will often have the insulation R-value printed on the outside.
Interior duct insulation can usually be determined by knocking on the ducts. A hollow sound indicates no insulation. You should be able to see the insulation through the duct register. There is a material called duct board that is pressed fiberglass with a reinforced foil-like covering. It will give if you poke it, unlike metal ducts, but not as much as exterior insulation.
Learn more at energy.gov/betterbuildings
Ducts: Interior Insulation
A common duct sealant is mastic, shown in these photos. If the duct joints are “sealed” with duct tape, this is not considered sealed as the tape tends to deteriorate quickly.
Learn more at energy.gov/betterbuildings
Ducts: Sealing
Look for presence of sealing at the return of the furnace/ac unit and/or at joints in the duct work.
Learn more at energy.gov/betterbuildings
Domestic Hot Water: Distinguishing TypesWater Heating Equipment – 5 Types:
Type Natural Gas Storage LPG Storage Oil Storage Electric
Storage
Electric Heat Pump
Storage
Defining Features
• Open draft diverter• Large pipes attached to the system, no ducts
• Looks like natural gas but with storage tank outside.• Boiler plate says LPG.
• Barometric damper• Oil injection controller• Flue
• Heavy wiring • No exhaust flue
• Compressor attached to top of water heater• Heavy wiring• No exhaust flue
Starting Efficiency 0.55 EF 0.55 EF 0.53 EF 0.87 EF Assume 2.5 EF
Example