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LEED v4
Homes
Energy and Atmosphere
Efficient hot water distribution system

LEED CREDIT

Homes-v4 EAc2: Efficient hot water distribution system 2-5 points

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© Copyright U.S. Green Building Council, Inc. All rights reserved.

Requirements

Credit available for all projects, whether they are using the EA performance or EA prescriptive path
Option 1. Efficient hot water distribution (2 points)
Design and install an energy-efficient hot water distribution system, based on either maximum pipe length requirements (Path 1) or maximum pipe volume limits (Path 2). The source of hot water is assumed to be a water heater, boiler, circulation loop piping, or electric heat-traced piping. Multiple water heaters and multiple distribution systems may be used to comply with this credit. Systems that use heat traces that serve a single unit or house are awarded only half credit. All heat traced piping must be insulated.
Path 1. Maximum Allowable Pipe Length
Do not exceed the maximum allowable pipe length from the source of hot water to the termination of the fixture supply pipe, as listed in Table 1a or Table 1b. If a branch consists of more than one size of pipe, use the largest size when determining the maximum allowable length. Branch length requirements do not apply to cold water demand loads (e.g., toilets), tubs without showerheads, or stovetop pot-fillers.
Table 1a. Maximum length of pipe (IP)
Nominal pipe size (inch) Maximum pipe or tube length
Hot water source is a water heater or boiler with no circulation loop or heat traced pipe or in multifamily buildings a central circulation loop or heat traced pipe (feet) Hot water source is a circulation loop or heat traced pipe serving a single unit or house (feet)
1/4 50 16
5/16 50 16
3/8 50 16
½ 43 16
5/8 32 12
¾ 21 8
7/8 16 6
1 13 5
1 ¼ 8 3
1 ½ 6 2
2 or larger 4 1
Table 1b. Maximum length of pipe (SI)

Nominal pipe size (mm)

Maximum pipe or tube length

Hot water source is a water heater or boiler with no circulation loop or heat traced pipe or in multifamily buildings a central circulation loop or heat traced pipe (meters)

Hot water source is a circulation loop or heat traced pipe serving a single unit or house (meters)

6

15

5

8

15

5

9

15

5

13

13

5

16

10

4

19

6

2

22

5

2

25

4

2

32

2

1

38

2

1

50 or larger

1

0.3

OR

Path 2. Maximum allowable pipe volume
Do not exceed a maximum volume of hot or tempered water of 64 ounces (1.89 L) for hot water from a water heater or boiler with no circulation loop or heat traced pipe; or in multifamily buildings a central circulation loop or heat traced pipe or in multifamily buildings a central circulation loop or heat traced pipe to the fixture; or 24 ounces (0.71 L) for hot water from a circulation loop pipe or an electric heat-traced pipe serving a single unit or house to the fixture. Pipe volume is the sum of the internal volumes of pipe, fittings, valves, meters, and manifolds between the source of hot water and the termination of the fixture supply pipe. To determine the volume, refer to Table 2, which lists the volumes for specific types of tubing. Branch volume requirements do not apply to cold water demand loads (e.g., toilets), tubs without showerheads, or stovetop pot-fillers.
Table 2. Volume of water distribution pipes, by tubing type
Ounces of water per foot length of hot water tubing
Normal size (inches) Copper
M
Copper
L
Copper
K
CPVC CTS SDR 11 CPVC SCH 40 PEX-AI-PEX ASTM F 1281 PE-AL-PE PEX CTS SDR 9
0.375 1.06 0.97 0.84 N/A 1.17 0.63 0.63 0.64
0.500 1.69 1.55 1.45 1.25 1.89 1.31 1.21 1.18
0.750 3.43 3.22 2.9 2.67 3.38 3.39 3.39 2.35
1.000 5.81 5.49 5.17 4.43 5.53 5.56 5.56 3.91
1.250 8.7 8.36 8.09 6.61 9.66 8.49 8.49 5.81
1.500 12.18 11.83 11.45 9.22 13.2 13.88 13.88 8.09
2.000 21.08 20.58 20.04 15.79 21.88 21.48 21.48 13.86
Source: Modified from 2009 International Plumbing Code Table E202.1 International Code Council. Conversions: 1 gallon (3.8 liters) = 128 ounces 1 ounce = 0.00781 gallons (0.0296 liters) 0.5 gallons (1.9 liters) = 64 ounces 0.6 gallons (2.3 liters) = 76.8 ounces
Paths 1 and 2, Pumps and Controls for Hot Water Circulation Loops
Circulating systems must meet the following requirements.
  1. Circulating pump may not operate continuously, on a timer control, or on a water temperature (aquastat) sensors. Gravity and thermo-syphon circulation systems are prohibited.
  2. Circulating pump must be demand activated by a momentary contact switch, motion sensor, flow switch, door switch or voice command.
  3. After the pump starts, the controls shall allow the pump to operate until the water temperature in the return pipe rises not more than 10ºF (6 ºC) above the initial temperature of the water in the pipe. Controls shall further limit the water temperature to a maximum of 105ºF (40 ºC). Controls shall limit pump operation to not more than 5 minutes per activation in the event that both means of shutting off the pump have failed.
  4. Circulating hot water systems must be provided with an automatic or readily accessible manual switch to turn off the hot water circulating pump when not in use.

OR

Option 2. Performance test (3 points)
Case 1. Hot water source is a water heater or boiler with no circulation loop or heat traced pipe: or in multifamily buildings a central circulation loop or heat traced pipe.
To minimize wasted water before hot water is delivered, using EPA WaterSense testing procedures, verify that no more than 0.5 gallons (1.9 liters) of water is stored in any piping between the hot water source and any fixture, and that no more than 0.6 gallons (2.3 liters) of water is collected from the hot water fixture before hot water is delivered. Heat traces are only allowed in situations to prevent freezing. Projects that meet WaterSense Labeled New Homes requirements automatically achieve this credit.
Case 2. Hot water source is a circulation loop or heat traced pipe serving a single unit or house
To minimize wasted water before hot water is delivered, using EPA WaterSense testing procedures, verify that no more than 0.25 gallons (1 liter) of water can be collected from the hot water fixture furthest from the recirculation loop. Systems that use heat traces that serve a single unit or house are awarded only half credit. All heat traced piping must be insulated.

AND/OR

Option 3. Pipe insulation (2 points)
Install at least R-4 insulation on all domestic hot water piping, including subslab pipes. Insulation on all piping elbows and tees must adequately insulate changes in direction. Run buried piping in a slab or below grade through a protective, waterproof raceway, channel, sleeve, or path whose internal dimensions and changes of direction are large enough that the piping and insulation can be removed and replaced without damaging the piping’s dimensional integrity. The waterproof sleeve is not required for below-grade piping if the insulation manufacturer stipulates that the pipe insulation will maintain its insulating value in underground applications in damp soil when installed according to the manufacturer's instructions. This exception does not apply to piping that runs through or under building slabs. See all forum discussions about this credit »

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Addenda

1/1/2015Updated: 2/14/2015
Reference Guide Correction
Description of change:
Step-By-Step Guidance
Step 1. Select System
Remove the last sentence in the last bullet. The sentence to delete reads "Each unit must be able to control the demand pump that provides hot water when needed."
Step 2. Design System
Remove the following bullets under 'Demand circulation loop design':
Bullet two, which starts with "Confirm that the actual installed..."
Bullet four, which starts with "Provide controls (e.g. switches, motion sensors)..."

Replace the last bullet with the following language:
"Circulating pumps may not operate continuously. Gravity and thermo-syphon circulation systems are prohibited. The controls shall allow the pump to operate if the water temperature at the end of the supply portion of the recirculation loop is less than 105ºF (40 ºC) and shall not allow the pump to operate if the water temperature is greater than 115ºF (46ºC)."

Add in new bullet after bullet four:
"Pumps and controls, including temperature sensors shall be accessible. Sensors shall be accurate within +/- 2ºF (1ºC) and shall be able to respond to changes in water temperature within 15 seconds."

Add in new bullet after bullet five (Multifamily buildings can use multiple...."
"Each circulation loop shall be controlled independently. The minimum diameter in the circulation loop (both supply and return) shall not be less than 3/4 inch nominal diameter."

Further Explanation
Multifamily Midrise Options
Add the following directly below the header:
"Circulating pumps may not operate continuously. Gravity and thermo-syphon circulation systems are prohibited. The controls shall allow the pump to operate if the water temperature at the end of the supply portion of the recirculation loop is less than 105ºF (40 ºC) and shall not allow the pump to operate if the water temperature is greater than 115ºF (46ºC). Pumps and controls, including temperature sensors shall be accessible. Sensors shall be accurate within +/- 2ºF (1ºC) and shall be able to respond to changes in water temperature within 15 seconds. Pumps shall be installed above the drain on the water heater. There shall be full-port flow isolation valves around the pump. There shall be a check valve between the pump and the the water heater. There shall be a method of flushing the circulation loop to remove air and particles."

Delete the following language from bullet one "and controllers at each use point to operate the pump when hot water is needed (Figure 10)."
Delete the following from bullet two "and controllers at each use point to operate the local pump when hot water is needed."
Delete the following from bullet three "and controllers at each use point to operate pumps when hot water is needed."


Campus Applicable
No
Internationally Applicable:
Yes
4/5/2016
LEED Interpretation
Inquiry:

According to the US DOE “Zero Energy Ready Homes are at least 40%-50% more energy efficient than a typical new home. This generally corresponds to a Home Energy Rating System (HERS) Index Score in the low- to mid-50s, depending on the size of the home and region in which it is built.”

Interpretation 10398 states that projects that receive ENERGY STAR for Homes v3 certification may automatically earn a HERS 70. Can projects that earn the DOE Zero Energy Ready Home label also receive a HERS equivalency?

Ruling:

Projects that earn the DOE Zero Energy Ready Home certificate may automatically earn a 15 points in EA credit Annual Energy Use.

In addition, projects that earn the DOE Zero Energy Ready Home certificate meet the following credits and prerequisites:

EA prerequisite Minimum energy performance (Required)
EA prerequisite Education of homeowner, tenant, or building manager (Required)
EA credit Efficient hot water distribution system Option 2. Performance test (3 points)
EA credit Active solar-ready design (1 point)
EA credit HVAC Start-up credentialing (1 point)
EA credit Annual energy use (15 points)
IN credit Innovation ZERH (1 point)

Projects also meet the requirements of all credits and prerequisites deemed equivalent to the EPA Indoor airPLUS program.

Update 7/25/19: This interpretation does not apply to projects that include pools or other major energy users not covered by the energy model.

Campus Applicable
No
Internationally Applicable:
No
See all forum discussions about this credit »

Documentation toolkit

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USGBC logo

© Copyright U.S. Green Building Council, Inc. All rights reserved.

Requirements

Credit available for all projects, whether they are using the EA performance or EA prescriptive path
Option 1. Efficient hot water distribution (2 points)
Design and install an energy-efficient hot water distribution system, based on either maximum pipe length requirements (Path 1) or maximum pipe volume limits (Path 2). The source of hot water is assumed to be a water heater, boiler, circulation loop piping, or electric heat-traced piping. Multiple water heaters and multiple distribution systems may be used to comply with this credit. Systems that use heat traces that serve a single unit or house are awarded only half credit. All heat traced piping must be insulated.
Path 1. Maximum Allowable Pipe Length
Do not exceed the maximum allowable pipe length from the source of hot water to the termination of the fixture supply pipe, as listed in Table 1a or Table 1b. If a branch consists of more than one size of pipe, use the largest size when determining the maximum allowable length. Branch length requirements do not apply to cold water demand loads (e.g., toilets), tubs without showerheads, or stovetop pot-fillers.
Table 1a. Maximum length of pipe (IP)
Nominal pipe size (inch) Maximum pipe or tube length
Hot water source is a water heater or boiler with no circulation loop or heat traced pipe or in multifamily buildings a central circulation loop or heat traced pipe (feet) Hot water source is a circulation loop or heat traced pipe serving a single unit or house (feet)
1/4 50 16
5/16 50 16
3/8 50 16
½ 43 16
5/8 32 12
¾ 21 8
7/8 16 6
1 13 5
1 ¼ 8 3
1 ½ 6 2
2 or larger 4 1
Table 1b. Maximum length of pipe (SI)

Nominal pipe size (mm)

Maximum pipe or tube length

Hot water source is a water heater or boiler with no circulation loop or heat traced pipe or in multifamily buildings a central circulation loop or heat traced pipe (meters)

Hot water source is a circulation loop or heat traced pipe serving a single unit or house (meters)

6

15

5

8

15

5

9

15

5

13

13

5

16

10

4

19

6

2

22

5

2

25

4

2

32

2

1

38

2

1

50 or larger

1

0.3

OR

Path 2. Maximum allowable pipe volume
Do not exceed a maximum volume of hot or tempered water of 64 ounces (1.89 L) for hot water from a water heater or boiler with no circulation loop or heat traced pipe; or in multifamily buildings a central circulation loop or heat traced pipe or in multifamily buildings a central circulation loop or heat traced pipe to the fixture; or 24 ounces (0.71 L) for hot water from a circulation loop pipe or an electric heat-traced pipe serving a single unit or house to the fixture. Pipe volume is the sum of the internal volumes of pipe, fittings, valves, meters, and manifolds between the source of hot water and the termination of the fixture supply pipe. To determine the volume, refer to Table 2, which lists the volumes for specific types of tubing. Branch volume requirements do not apply to cold water demand loads (e.g., toilets), tubs without showerheads, or stovetop pot-fillers.
Table 2. Volume of water distribution pipes, by tubing type
Ounces of water per foot length of hot water tubing
Normal size (inches) Copper
M
Copper
L
Copper
K
CPVC CTS SDR 11 CPVC SCH 40 PEX-AI-PEX ASTM F 1281 PE-AL-PE PEX CTS SDR 9
0.375 1.06 0.97 0.84 N/A 1.17 0.63 0.63 0.64
0.500 1.69 1.55 1.45 1.25 1.89 1.31 1.21 1.18
0.750 3.43 3.22 2.9 2.67 3.38 3.39 3.39 2.35
1.000 5.81 5.49 5.17 4.43 5.53 5.56 5.56 3.91
1.250 8.7 8.36 8.09 6.61 9.66 8.49 8.49 5.81
1.500 12.18 11.83 11.45 9.22 13.2 13.88 13.88 8.09
2.000 21.08 20.58 20.04 15.79 21.88 21.48 21.48 13.86
Source: Modified from 2009 International Plumbing Code Table E202.1 International Code Council. Conversions: 1 gallon (3.8 liters) = 128 ounces 1 ounce = 0.00781 gallons (0.0296 liters) 0.5 gallons (1.9 liters) = 64 ounces 0.6 gallons (2.3 liters) = 76.8 ounces
Paths 1 and 2, Pumps and Controls for Hot Water Circulation Loops
Circulating systems must meet the following requirements.
  1. Circulating pump may not operate continuously, on a timer control, or on a water temperature (aquastat) sensors. Gravity and thermo-syphon circulation systems are prohibited.
  2. Circulating pump must be demand activated by a momentary contact switch, motion sensor, flow switch, door switch or voice command.
  3. After the pump starts, the controls shall allow the pump to operate until the water temperature in the return pipe rises not more than 10ºF (6 ºC) above the initial temperature of the water in the pipe. Controls shall further limit the water temperature to a maximum of 105ºF (40 ºC). Controls shall limit pump operation to not more than 5 minutes per activation in the event that both means of shutting off the pump have failed.
  4. Circulating hot water systems must be provided with an automatic or readily accessible manual switch to turn off the hot water circulating pump when not in use.

OR

Option 2. Performance test (3 points)
Case 1. Hot water source is a water heater or boiler with no circulation loop or heat traced pipe: or in multifamily buildings a central circulation loop or heat traced pipe.
To minimize wasted water before hot water is delivered, using EPA WaterSense testing procedures, verify that no more than 0.5 gallons (1.9 liters) of water is stored in any piping between the hot water source and any fixture, and that no more than 0.6 gallons (2.3 liters) of water is collected from the hot water fixture before hot water is delivered. Heat traces are only allowed in situations to prevent freezing. Projects that meet WaterSense Labeled New Homes requirements automatically achieve this credit.
Case 2. Hot water source is a circulation loop or heat traced pipe serving a single unit or house
To minimize wasted water before hot water is delivered, using EPA WaterSense testing procedures, verify that no more than 0.25 gallons (1 liter) of water can be collected from the hot water fixture furthest from the recirculation loop. Systems that use heat traces that serve a single unit or house are awarded only half credit. All heat traced piping must be insulated.

AND/OR

Option 3. Pipe insulation (2 points)
Install at least R-4 insulation on all domestic hot water piping, including subslab pipes. Insulation on all piping elbows and tees must adequately insulate changes in direction. Run buried piping in a slab or below grade through a protective, waterproof raceway, channel, sleeve, or path whose internal dimensions and changes of direction are large enough that the piping and insulation can be removed and replaced without damaging the piping’s dimensional integrity. The waterproof sleeve is not required for below-grade piping if the insulation manufacturer stipulates that the pipe insulation will maintain its insulating value in underground applications in damp soil when installed according to the manufacturer's instructions. This exception does not apply to piping that runs through or under building slabs.
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