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4/24/2018 1 Save Water . . . Save Energy With Efficient Hot Water Delivery © Steven Winter Associates, Inc. 2017 Getting to Zero National Forum 2018 Steven Winter Associates Since 1972, SWA has been providing research, consulting, and advisory services to improve the built environment for private and public sector clients. Our services for new and existing commercial and residential properties include: • Green Building Consulting Services • Energy Efficiency Consulting Services • Building Enclosure Design and Consulting • Accessibility Compliance and Consulting
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4/24/2018
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Save Water . . . Save Energy With Efficient Hot Water Delivery
© S
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Getting to Zero National Forum 2018
Steven Winter Associates Since 1972, SWA has been providing research, consulting, and advisory services to improve the built environment for private and public sector clients.
Our services for new and existing commercial and residential properties include:
• Green Building Consulting Services• Energy Efficiency Consulting Services• Building Enclosure Design and Consulting • Accessibility Compliance and Consulting
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Presentation Overview
• Domestic hot water design options– Generation, distribution, & storage– Common in multifamily?
• Efficient recirculation design strategies• Energy demand and cost implications• Water heating in a carbon-free future?• Electrification
“Domestic Hot Water”
• Hot water used for drinking, food prep, sanitation, and personal hygiene
• Not for heating, swimming pools, commercial cooking, etc.
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SYSTEM TYPESMultifamily Domestic Hot Water: How Can We Do Better?
System Types• Heat Generation
– Gas boiler– Electric resistance– Heat pump– Combined Heat & Power– Solar Thermal
• Distribution– Recirculation– Partial recirculation– No recirculation
• Storage vs. Instantaneous
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System Types• Heat Generation
– Gas boiler– Electric resistance– Heat pump– Combined Heat & Power– Solar Thermal
• Distribution– Recirculation– Partial recirculation– No recirculation
• Storage vs. Instantaneous
What’s Typical in Unit
Electric Storage
Gas Tankless
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Not So Typical in Unit
Gas w/ Indirect Storage
Electric Tankless
Common in Mid & High-rise
Central Gas w/ Recirculation
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Gas Boiler(s) with Recirculation• Common in multifamily • 24/7 operation
TAP TAP TAP
HWH~40°F
~120°F
~100°FRECIRCULATION PUMPFROM
STREET
EFFICIENT RECIRCULATION DESIGNMultifamily Domestic Hot Water: How Can We Do Better?
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Central Recirculation
Central RecirculationTAP TAP TAP
HWH40°F
120°F
100°F
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Central Recirculation
Design Optimization – Recirc.• Reduce # of risers
– Cluster plumbing locations when feasible
– Optimize HWR loop location• Insulation
– R-4 minimum on all pipes– 1.5-2” of insulation on pipes
over 1.5” in diameter
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Design Optimization – Central Recirc.
Recirc. Pipe Length
Pipe Heat Loss
Cooling Energy
Water Heating Energy
Design Optimization – Central Recirc.
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Central Recirculation
Source: SWA PH Modeled Data
Recirculation Controls• Control Options
– Timer Control – Temperature Control– Temperature Modulation Control– Demand Recirculation Control– Demand + Temperature Modulation
Control• Balance the System
– Include DHW balancing specs – Include a detail for the riser
balancing valves including a check valve
– Show balancing valves on the riser diagram
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Recirculation Controls
DOE Report: Conway Street Apartments: A Multifamily Deep Energy Retrofit November 2014
Recirculation Controls
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Recirculation Controls
IMPACTS ON BUILDING ENERGY DEMAND & COST
Multifamily Domestic Hot Water: How Can We Do Better?
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Modeled Building Site Energy Demand©
Ste
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Win
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• 25 stories• 274 units• Affordable
housing• Gas fired w/
recirculation
Passive House High Rise - NYC
Building Energy Demand & Cost
• Site energy demand– 20-40% of total building demand– How efficient are we building?
• Code, Energy Star, Zero Energy Ready, Passive House, etc.
• How much $$?– Gas or electric? Location?
• Gas - ~$50-$120 per unit/year– Costly to do in-unit required gas water heaters
• Electric resistance - ~$250-$500 per unit/year
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HOW DO WE GET TO NET ZERO? – THE FUTURE IS NOW
Multifamily Domestic Hot Water: How Can We Do Better?
Carbon-Free Future?
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Carbon-Free Future?
Carbon-Free Future?
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Electrification
• Electric Options– Direct electric w/ (a
lot of) photovoltaic– Heat pump water
heaters• CO2 refrigerant
– Global warming potential = 1
– Carbon capture?• First step = reduce
the load
Heat Pump Water Heaters
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Heat Pumps – Smaller Scale Systems
• Many indoor options readily available in US market
• Must get the design right!
• Volume of air (~1,000 ft3)• Warm air, above ~50°F• BIGGER is better• HOTTER is better (with tempering valve)• Drain condensate• Locate where noise and cool air won’t cause discomfort• Doesn’t “steal” much space heat
– Don’t heat space with electric resistance!
If all this is done right, they can use 50-70% less energy than resistance.
Heat Pumps – Smaller Scale Systems
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Impacts on DHW DemandPassive House High Rise - NYC
Large Scale HPWH• Commercial grade for modular engineered solutions• Little to no market penetration in the USA in multifamily• Widely used in Asia and Europe for DHW• In USA, used in commercial/industrial applications
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Large Scale HPWH
Down to 14F
R‐744
Up to 194F
Down to 40F
R‐410A
Up to 150F
Down to 10F
R‐410A
Up to 150F
Down to ‐4F
R‐410A
Up to 150F
Ambient Temp
Refrigerant
Max H2O Supply
Heat Pumps – Designing ProperlyCold Weather Performance
36% efficiency drop in colder temps
38% capacity drop in colder temps
Impacts energy costs and savings Impacts sizing of storage
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# of units # of bedroomsExterior Air Wet‐Bulb Temp (°F)
Rated Heating Capacity of HPWH # of HPWH
Storage Volume (gallons)1
274 416 45 25 tons 2 10,000
274 416 80 ‐ 100 25 tons 2 3,400
150 228 45 25 tons 1 2,800
150 228 80‐100 25 tons 1 1,800
50 90 45 25 tons 1 1,000
50 90 80‐100 25 tons 1 300
Storage Sizing Scenarios
• Accounting for cold weather performance matters
1. Does not include water volume in recirculation lines* Based on ASHRAE DHW sizing method** Assumes recirculation in all 3 scenarios
+194%
+55%
+233%
Heat Pumps – Designing Properly
Passive House → Net Zero
New York City Block: 40th–23rd St & 5th–6th AveRoof Area of PV + → PH Site EUI (22 kBtu/sf.yr)
for Net Zero: + + → Current Site EUI (~82 kBtu/sf.yr)
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• Designing efficiently– Insulate pipes to minimum of R-4– Optimize HWR loops in recirculation systems– Incorporate recirculation controls w/ proper installation– Avoid electric resistance heating, if possible
• A carbon-free future?– Reduce the load first– Heat pump water heaters
• Smaller units– Give them space to breathe– Don’t heat space with electric resistance
• Larger units are on the horizon• Cold weather performance matters
Solutions Are Everywhere
In Summary
This concludes The American Institute of Architects Continuing Education Systems Course
Contact Us:
Dylan MartelloBuilding Systems Analyst | CPHD
203.857.0200 x231
