Affordable Housing Toward Zero Energy

Affordable Housing

Betsy Pettit, AIA Building Science Corporation

PR-0507: Toward Zero Energy www.buildingscience.com Why Zero Energy Homes? © buildingscience.com

PR-0507: Toward Zero Energy 2 What makes an affordable home? © buildingscience.com • Someone who makes the median income in the area can afford to – Purchase – Operate © buildingscience.com – Maintain • Long Term Durability

PR-0507: Toward Zero Energy 3 Maintain shelter to current high standards in hostile environments© buildingscience.com without stored energy consumption?

– No oil, gas, or ‘net” off-site electricity use? • Aggressive © buildingscience.com conservation methods • More site generated energy

Site Energy Consumption = Site Energy© buildingscience.com Collection

PR-0507: Toward Zero Energy 4 Insuring Affordability © buildingscience.com

•Comfort of occupants • Indoor air quality © buildingscience.com • Energy efficiency • Durability © buildingscience.com

PR-0507: Toward Zero Energy 5 Comfort © buildingscience.com • Leak-free homes with high r-value enclosures © buildingscience.com • Deliver heated and cooled air in consistent manner © buildingscience.com to living space

PR-0507: Toward Zero Energy 6 © buildingscience.comIndoor Air Quality • Control water entry • Control interior pollution – Source control © buildingscience.com – Combustion appliances – Interior finishes – Things brought into the house © buildingscience.com • Provide air change

PR-0507: Toward Zero Energy 7 Energy Efficiency © buildingscience.com Leakfree Construction – Reducing the air leakage into and out of the building enclosure is critical for energy conservation and building durability © buildingscience.com

Airtight drywall – Drywall typically provides the primary air barrier from inside to outside of the enclosure © buildingscience.com

PR-0507: Toward Zero Energy 8 Energy Efficiency © buildingscience.com Thermally Efficient Assemblies • Structure only where needed • Insulating sheathing© buildingscience.com

• Blown insulations that fill the entire void © buildingscience.com

PR-0507: Toward Zero Energy 9 Energy Efficiency © buildingscience.com Control of electric load – Energy Star Lights – Energy Star © buildingscience.com Appliances

PR-0507: Toward Zero Energy 10 Plug Loads © buildingscience.com Common Large plug loads: Items with internal heaters –Cookers – Hair dryers © buildingscience.com Items with large-ish motors – Dehumidifiers – Vacuums Duty Cycle is important!!!! © buildingscience.com

PR-0507: Toward Zero Energy 11 Energy Efficiency © buildingscience.comHeating/Cooling - Gas/Electric Condensing furnaces yield efficiencies over 90% AFUE – Typically © sealed buildingscience.com combustion – Ducted system facilitates installation of ventilation system – Get ECM motors – Use High SEER ©AC buildingscience.com units

PR-0507: Toward Zero Energy 12 Energy Efficiency © buildingscience.comHeating/Cooling - Electric

High efficiency air source heat pump (ASHP) – Available © up buildingscience.com to 18 SEER & ~9 HSPF – Simple & cheap installation (relatively speaking) © buildingscience.com – No combustion risks

PR-0507: Toward Zero Energy 13 Energy Efficiency © buildingscience.comHeating/Cooling - Electric High efficiency ground source heat pump (GSHP) © buildingscience.com – Moves heat to & from the ground, instead of burning stuff – Year ‘round heating and cooling at high efficiency – No combustion risks © buildingscience.com – Option of de-superheater hot water system

PR-0507: Toward Zero Energy 14 Energy Efficiency - Ventilation © buildingscience.com Plan for ventilation: – Air tight houses need controlled air change – ERV’s can © deliverbuildingscience.com savings, but watch out for their electricity consumption – Central Fan integrated system among the © buildingscience.com simplest

PR-0507: Toward Zero Energy 15 Energy Efficiency - Hot Water, Gas © buildingscience.com Sealed combustion gas, located in insulated space – Efficiency of standard tanks reaches © only buildingscience.com ~62% – Hard to justify in a ZEH, since solar collection system would more than pay for an upgrade © buildingscience.com

PR-0507: Toward Zero Energy 16 Energy Efficiency © buildingscience.comHot Water - Gas, Tankless

• Tankless hot water heater eliminates standby losses • Efficiencies in© ~83% buildingscience.com range – a ~30% increase in hot water efficiency over gas tanks • Locate hot water heater central to fixtures to create short piping runs © buildingscience.com • Put piping in walls, not ground

PR-0507: Toward Zero Energy 17 Energy Efficiency - Hot Water, Electric © buildingscience.com Electric resistance – High efficiencies available, up to 94% – However, © it’s buildingscience.com more expensive than gas – Simple installation – No combustion risks © buildingscience.com

PR-0507: Toward Zero Energy 18 Integration © buildingscience.com

PR-0507: Toward Zero Energy 19 Integration © buildingscience.com

PR-0507: Toward Zero Energy 20 Integration © buildingscience.com

Foundations Walls © buildingscience.com Roofs

PR-0507: Toward Zero Energy 21 How much can we conserve © buildingscience.comfrom our current levels?

Building enclosure savings: 20% Mechanical © Savings: buildingscience.com25% Lights/Appliances/Plug: 10% Conservation savings: 55%

Left to offset by site © generation:buildingscience.com 45% Total savings: 100%

PR-0507: Toward Zero Energy 22 Solar Energy Collection © buildingscience.com • Only after loads have been reduced and mechanicals downsized should solar collection equipment be considered © buildingscience.com • Solar hot water better payback – should be considered first • Solar PV system © last buildingscience.com piece of the whole

PR-0507: Toward Zero Energy 23 Solar Technologies Solar© buildingscience.com hot water (SHW): – Consider appropriate location for system components (ideally, south roof for panels, insulated or protected interior space for tank) © buildingscience.com – Consider how system interacts with back-up heating source (electric tank, or gas boiler)

– Consider control strategy© buildingscience.com (PV panel, differential control, or thermosiphon)

PR-0507: Toward Zero Energy 24 Site Generated Energy - Hot Water © buildingscience.com

PR-0507: Toward Zero Energy 25 SHW System - Not Simple!

• SHW systems can get to quite high temperatures – (180F at tank, over 200F between collector & tank) under normal operation • Stagnation is when the solar collector is in full sun, but heat is not being moved to the storage tank – Leads to very high collector temperatures, and therefore elevated pressures in an antifreeze system – Result of low hot water usage, or times of high solar gains • Verify all piping components can handle temperatures and pressures developed in SHW system under stagnation

All SHW systems must have a tempering valve

PR-0507: Toward Zero Energy 26 Freeze protected © buildingscience.comSolar Hot Water System Options

Anti-freeze loop Drain Back

PR-0507: Toward Zero Energy 27 Freeze Tolerant © buildingscience.comSolar Hot Water System Options

• ICS (Integrated Collector Storage) • Storage ©tank buildingscience.com in the collector, water warms up when sun shines in • Water can cool overnight • Simplest type • Hybrid systems © buildingscience.com

PR-0507: Toward Zero Energy 28 Site Generated Energy - Hot Water © buildingscience.com

Tank and piping Panels on south roof

PR-0507: Toward Zero Energy 29 Solar Hot Water Savings © buildingscience.com

• Solar Hot water will contribute about 10% of the remaining total © buildingscience.com • Hot water use can vary widely, where space conditioning is more climate dependent © buildingscience.com • Other site generation for remaining 35%

PR-0507: Toward Zero Energy 30 ©Site buildingscience.com Generated Energy - Electricity

PR-0507: Toward Zero Energy 31 And the last step for the remaining 35%…PV panels

• Most costly component in getting to ZEH – Still, costs are half what they were 10 yrs ago • Unfortunately, also one of the most visible • Simple principle, no moving parts • Generally low collection efficiency (less than ~15% of available solar energy) • System loss reduces peak output by 10-20% • Still the simplest, cheapest method for generating electricity from the sun directly

PR-0507: Toward Zero Energy 32 Photovoltaic effect: some theory

• Sun’s rays (photons) strike semi-conductor PV panel • Electrons are ‘bumped up’ to a higher energy state, leaving an electron hole and a high energy electron • Electrons pass through house circuit on way back to electron hole

Ok, it’s magic…but it works repeatably, and it looks cool…

PR-0507: Toward Zero Energy 33 PV system layout: grid tied

• PV panels in sun • DC wiring to disconnect • DC disconnect • Inverter • AC wiring to main electric panel • Utility meter & grid

PR-0507: Toward Zero Energy 34 PV system layout: stand alone

• PV panels • DC wiring to charge controller • Charge controller • Battery bank • Backup generator, etc

PR-0507: Toward Zero Energy 35 © buildingscience.com Site Generated Energy - Integration •PV - back-up batteries or grid © buildingscience.com connection •Solar water - passive system drawn down © buildingscience.com with demand •Passive Solar Gain - awnings to protect from overheating

PR-0507: Toward Zero Energy 36 Heating© buildingscience.com / Cooling Trade-off

Space Conditioning Loads: Identical AK Benchmark House Moved Around the US

140.0 © buildingscience.com

120.0 Actual Cooling 100.0 Actual Heating Actual Heating load 80.0 includes heat from furnace, hot water

Btu/yr © buildingscience.com 60.0 heater, appliances, lights, and plug load

40.0 Actual Cooling load includes internal and external gains in 20.0 BTU's prior to A/C removal 0.0 Juneau, AK: CO Springs, Pontiac, MI: Cleveland, Richmond, N. Orleans, Hilo, HI: 0 San Diego, 9113 HDD CO: 6353 6228 HDD OH: 6154 VA: 3939 LA: 1437 HDD CA: 1507 HDD HDD HDD HDD HDD

PR-0507: Toward Zero Energy 37 © buildingscience.com Extreme Home -Very Cold, Haidaburg, AK

PR-0507: Toward Zero Energy 38 © buildingscience.com Extreme Cold: Haida Tribe, Juneau, AK Extreme Cold: Haida Tribe, Juneau, AK Heating Degree Days: 9113 250.0 Project Highlights (1190 sf House)

Building Enclosure R-28 rigid foam with interior frame 200.0 R-42 cathedral ceiling © buildingscience.com Low E windows (U-0.33, SHGC-0.45) 15.2 R-33 Floor insulation on pier foundation 150.0 BSC BA Airtightness (2.5 ins/100 sf) 33% Savings 43.8 46% Savings 7.4 Mechanical Combo System 100.0 28.5 85% AFUE Hot Water Heater 41.3 6.1

Baseboard heaters © buildingscience.comEnergy Use (MMBtu/yr) 33.6 ASHRAE 62.2 ventilation by HRV 50.0 19.5 14.6 Flourescent lighting 78.7 43.9 35.8 Solar Site Collection 40 sf glycol SHW system (3% Savings) 0.0 2.0 kW Peak PV system (10% Savings) Benchmark Prototype With PV & SHW

Space Heating Space Cooling DHW Appliances + Plug Lighting

PR-0507: Toward Zero Energy 39 Extreme© buildingscience.com Home -Extreme Details

PR-0507: Toward Zero Energy 40 © buildingscience.com Very Cold - Colorado Springs, Colorado

PR-0507: Toward Zero Energy 41 © buildingscience.com

Cold: CORE H3, Colorado Springs, CO Cold: CORE H3, Colorado Springs, CO Heating Degree Days: 6353 250.0 Project Highlights (1190 sf House) © buildingscience.com Building Enclosure R-19 + R-5 Walls 200.0 R-38 attic / R-35 Cathedral ceiling Low E windows (U-0.33, SHGC-0.28) 15.2 R-23 walls on conditioned crawl 150.0 43.8 BSC BA Airtightness (2.5 ins/100 sf) 36% Savings 7.4 Mechanical 92% AFUE Gas Furnace 100.0 27.5 Ducts in conditioned space © buildingscience.com 41.3 60% Savings 5.1 0.82EF Tankless Hot Water Heater Energy Use (MMBtu/yr) ASHRAE 62.2 ventilation by HRV 50.0 18.8 28.2 Flourescent lighting 84.3 7.3 45.6 31.1 Solar Site Collection 64 sf glycol SHW system (7% Savings) 0.0 2.0 kW Peak PV system (17% Savings) Benchmark Prototype With PV & SHW

Space Heating Space Cooling DHW Appliances + Plug Lighting

PR-0507: Toward Zero Energy 42 Very© buildingscience.com Cold - Details

PR-0507: Toward Zero Energy 43 Very© buildingscience.com Cold - Details

PR-0507: Toward Zero Energy 44 Very© buildingscience.com Cold - Details

PR-0507: Toward Zero Energy 45 Very© buildingscience.com Cold - Details

PR-0507: Toward Zero Energy 46 HRV© vs.Supplybuildingscience.com Ventilation

Yearly Energy Use: HRV vs Fan Cycling Ventilation Air Heating O. Airflow % Heat Climate Yearly Energy Cost @ CFM Recovery 92% AFUE $1.20/therm Efficient HRV Fan only (40w) 40 70% 7500 HDD 25.6 therms 30.71 $ Fan Cycling Rightsized © buildingscience.com40 0 7500 HDD 85.3 therms 102.37 $ Fan Cycling RS+HRV 40 70% 7500 HDD 25.6 therms 30.71 $ Inefficient HRV Fan (150w) 40 70% 7500 HDD 25.6 therms 30.71 $ Fan Cycling Oversized 40 0 7500 HDD 85.3 therms 102.37 $ Constant RS Fan + HRV 40 70% 7500 HDD 25.6 therms 30.71 $ Fan Energy Duty Unit % Heating Continuous Yearly Cost @ Cycle watts Calls Watts Energy Use $0.12/kWh Efficient HRV Fan only ( 100% 40 40 350 kWh 42.05 $ Fan Cycling Rightsized 33% 250 13% © 72 buildingscience.com 632 kWh 75.83 $ Fan Cycling RS+HRV 33% 250 13% 112 982 kWh 117.88 $ Inefficient HRV Fan (15 0 100% 150 150 1314 kWh 157.68 $ Fan Cycling Oversized 33% 500 6% 156 1363 kWh 163.55 $ Constant RS Fan + HR V 100% 250 13% 259 2265 kWh 271.85 $ Yearly Energy Yearly Cost Efficient HRV Fan only (40w) 1.2 MMBtu 72.76$ Fan Cycling Rightsized 2.2 MMBtu 178.20$ Fan Cycling RS+HRV 3.4 MMBtu 148.59$ Inefficient HRV Fan (150w) 4.5 MMBtu 188.39$ Fan Cycling Oversized 4.7 MMBtu 265.91$ Constant RS Fan + HRV 7.7 MMBtu 302.56$

PR-0507: Toward Zero Energy 47 HRV vs. Supply Ventilation 9.0 MMBtu 8.0 MMBtu 7.0 MMBtu Yearly Energy use of HRV vs Fan Cycling 6.0 MMBtu 40 CFM, 7500 HDD, 70% HRV, 92% AFUE, $0.12/kWh, $1.20/therm 5.0 MMBtu 4.0 MMBtu Efficient HRV Fan Cycling Fan Cycling Inefficient HRV Fan Cycling Constant RS 3.0 MMBtu Fan only (40w) Rightsized RS+HRV Fan (150w) Oversized Fan + HRV 2.0 MMBtu 1.0 MMBtu 0.0 MMBtu

PR-0507: Toward Zero Energy 48 HRV vs. Supply Ventilation

$350.00 $300.00 Yearly Cost of HRV vs Fan Cycling 40 CFM, 7500 HDD, 70% HRV, 92% AFUE, $0.12/kWh, $1.20/therm $250.00

$200.00

$150.00 Efficient HRV Fan Cycling Fan Cycling Inefficient HRV Fan Cycling Constant RS Fan only (40w) Rightsized RS+HRV Fan (150w) Oversized Fan + HRV $100.00 $50.00 $-

PR-0507: Toward Zero Energy 49 © buildingscience.com Slab on Grade Options © buildingscience.com

PR-0507: Toward Zero Energy 50 © buildingscience.com Cold - Pontiac, Michigan © buildingscience.com

PR-0507: Toward Zero Energy 51 © buildingscience.com

Cold: Venture Inc, Pontiac, MI Cold: Venture Inc, Pontiac, MI

Heating Degree Days: 6228 250.0 Project Highlights (1190 sf House) © buildingscience.com22.7 Building Enclosure R-19 + R-5 Walls 200.0 R-38 attic / R-35 Cathedral ceiling 43.8 Low E windows (U-0.33, SHGC-0.28) R-23 walls on conditioned basement 150.0 27.1 42% Savings BSC BA Airtightness (2.5 ins/100 sf) 7.4 55% Savings Mechanical 92% AFUE Gas Furnace 100.0 41.3 5.9 Ducts in conditioned space 32.7 18.4 0.82EF Tankless Hot Water Heater Energy Use (MMBtu/yr) © buildingscience.com124.2 11.8 ASHRAE 62.2 ventilation by FanCycler 50.0 Flourescent lighting 63.5 50.2

Solar Site Collection 40 sf glycol SHW system (3% Savings) 0.0 2.0 kW Peak PV system (10% Savings) Benchmark Prototype With PV & SHW

Space Heating Space Cooling DHW Appliances + Plug Lighting

PR-0507: Toward Zero Energy 52 © buildingscience.com Cold - Details © buildingscience.com

PR-0507: Toward Zero Energy 53 © buildingscience.com Cold - Cleveland, Ohio © buildingscience.com

PR-0507: Toward Zero Energy 54 © buildingscience.com

Cold: 71st St House, Cleveland, OH Cold: 71st St House, Cleveland, OH Heating Degree Days: 6154 250.0 Project Highlights (1190 sf House)

Building Enclosure© R-19buildingscience.com + R-5 Walls 200.0 R-38 attic / R-35 Cathedral ceiling 15.2 Low E windows (U-0.33, SHGC-0.45) 21% Savings 43.8 R-8 walls on conditioned crawl 150.0 7.4 BSC BA Airtightness (2.5 ins/100 sf) 36% Savings 27.1 41.3 6.1 Mechanical 0.75EF CA Combo System Heat 100.0 9.0 33.9 10 SEER Cooling System 25.1 5.7 19.1 Ducts in conditioned space (MMBtu/yr) Use Energy © buildingscience.com 4.7 0.59EF Tank Hot Water Heater 50.0 95.8 ASHRAE 62.2 ventilation by FanCycler 72.1 59.2 Flourescent lighting 0.0 Solar Site Collection 40 sf glycol SHW system (3% Savings) Benchmark Prototype With PV & SHW 2.0 kW Peak PV system (12% Savings)

Space Heating Space Cooling DHW Appliances + Plug Lighting

Regional© standardbuildingscience.com (2000) Infill prototype (2000) heating $613 heating $262 cooling $189 cooling $144 hot© water buildingscience.com $148 hot water $135 total $950 ($80 mo) total $541 ($45mo)

HERS rating 82 HERS rating 90

Mixed Humid: Haymount, VA Mixed Humid: Haymount, VA

Heating Degree Days: 3939 250.0 Project Highlights© (1190 buildingscience.com sf House) Building Enclosure R-19 + R-5 Walls 200.0 R-38 attic / R-35 Cathedral ceiling Low E windows (U-0.33, SHGC-0.28) 15.2 R-23 walls on conditioned crawl 150.0 BSC BA Airtightness (2.5 ins/100 sf) 43.8 36% Savings 7.4 Mechanical 92% AFUE Gas Furnace 24.5 100.0 55% Savings 14 SEER Cooling System 41.3 27.0 5.4

Ducts in conditioned space (MMBtu/yr) Use Energy © buildingscience.com 30.2 0.82EF Tankless Hot Water Heater 50.0 16.1 9.9 9.0 ASHRAE 62.2 ventilation by FanCycler 65.7 7.3 Flourescent lighting 37.2 27.2 0.0 Solar Site Collection 40 sf glycol SHW system (4% Savings) Benchmark Prototype With PV & SHW 2.0 kW Peak PV system (15% Savings)

Space Heating Space Cooling DHW Appliances + Plug Lighting

Building America Zero Energy Home Plan 1644 Building envelope

Ceiling R-38 blown cellulose at ceiling ©Walls buildingscience.com R-19 + R-3 insulating sheathing Foundation Slab, R-4 interior insulation Windows Double Glazed Vinyl Frame LowE2 U=0.39, SHGC=0.31 Infiltration 2.5 sq in leakage area per 100 sf envelope

Mechanical systems © buildingscience.com Heat 4.3 COP Ground Source heat pump Cooling 20 EER ground source heat pump DHW Rinnai Tankless HWH 0.82EF AHU location in conditioned space Ducts In vented attic, R-6 insulation Duct Leakage 5% or less Ventilation ERV with 70% energy recovery 46 CFM continuous average flow Lighting 90% compact fluorescent lighting Appliances & Plug Energy Star Appliances, 20% reduction in plug loads PV System 5.3 kWp array & 5 kW Inverter

0 Benchmark Envelope Mechanical Light-Appl ERV 53.4% PV Panels Upgrade Upgrade Upgrade Overall (5.3 kW) 18.4% Overall 42.6% Overall 50.5% Overall Savings 89.1% Overall Savings Savings Savings Savings

Cooling Heating Hot Water Lighting Appl & Other

Total Source Energy Savings (H/C/DHW/Lights/Appliances/Plug) Estimated Estimated Savings Change Annual Simple Payback Parametric Individual Cumulative over From Energy Item Payback of Change Run ID Description of change Cost Cost BA BM Previous Cost Savings (yr) (yr) © buildingscience.com 0 Benchmark n/a n/a n/a n/a $1,659 n/a n/a n/a 1 0 + Envelope Upgrade $1,000 $1,000 18.4% 18.4% $1,348 $311 3 3 2 1 + Mechanical Upgrade $4,000 $5,000 42.6% 24.1% $951 $397 7 10 3 2 + Light-Appl Upgrade $1,000 $6,000 50.5% 7.9% $818 $134 7 7 4 3 + ERV $700 $6,700 53.4% 2.9% $769 $48 8 15 5 4 + PV Panels (5.3 kW) $31,000 $37,700 89.1% 35.8% $168 $601 25 52

Table© 1. Summary buildingscience.com of End-Use Site-Energy Table 2. Summary of End-Use Source-Energy and Savings Annual Est. Annual Source Energy Savings Annual Site Energy Site Energy Source Energy % of End-Use % of Total BA Benchmark Standard BA Benchmark Standard Prototype 1 Prototype 1 End-Use kWh therms kWh therms End-Use 106 BTU/yr 106 BTU/yr Savings Savings Space Heating 8232 0 2617 0 Space Heating 84 27 68% 25% Space Cooling 4740 0 1199 0 Space Cooling 49 12 75% 16% DHW 0 228 0 145 DHW 27 17 36% 4% Lighting* 2085 693 Lighting* 21 7 67% 6% Appliances + Plug 4779 0 4368 0 Appliances + Plug 49 45 9% 2% Total Usage 19835 228 8877 145 Total Usage 230 108 53% 53% Site Generation 0 0 8051 0 Site Generation 0 -82 36% Net Energy Use 19835 228 826 145 Net Energy Use 230 26 89% 89%

Hot Humid: New Orleans, LA Hot-Humid: New Orleans, LA Heating Degree Days: 1437 250.0 Project Highlights (1260 sf House)

R-20 Foam over roof deck 15.6 Low E windows (U-0.33, SHGC-0.3) 150.0 R-10 Foam under floor framing 49.0 BSC BA Airtightness (2.5 ins/100 sf) 44% Savings Mechanical 8.5 HSPF ASHP 100.0 31.3 7.9 14 SEER Cooling System 27.2

Ducts in conditioned space Energy Use (MMBtu/yr) 70% Savings © buildingscience.com0.94EF Electric Hot water Tank 71.6 28.9 5.1 50.0 ASHRAE 62.2 ventilation by FanCycler 17.4 28.2 7.6 Flourescent lighting 18.1 17.0 11.2 7.2 0.0 Solar Site Collection 40 sf glycol SHW system (12% Savings) Benchmark Prototype With PV & SHW 2.0 kW Peak PV system (15% Savings)

Space Heating Space Cooling DHW Appliances + Plug Lighting

PR-0507: Toward Zero Energy 69 © buildingscience.com Utility Savings across the US ©250.0 buildingscience.comTotal Yearly Energy Use 200.0

150.0

MMBtu/ Proto w/solar 100.0

50.0

Juneau, AK: CO Springs, CO: Pontiac, MI: Cleveland, OH: Richmond, VA: New Orleans, 9113 HDD 6353 HDD 6228 HDD 6154 HDD 3939 HDD LA: 1437 HDD 0.0

PR-0507: Toward Zero Energy 70