Net Zero Energy Renovating an Existing Home Mary Kraus AIA, LEED BD&C KRAUS-FITCH ARCHITECTS, INC. Home Community Planet Kraus-Fitch Architects, Inc. 2012 Summary What / why net zero? Steps for a net zero renovation Case study Other examples Conclusion
Net Zero Energy What does it mean? Net zero operational energy Net zero including embodied energy / lifecycle Ecological footprint Remember to look at the whole context! Why Net Zero Energy?
4 Examples: Renovation of small duplex home in Amherst Renovation of historic home in Northampton New home in Leverett New community in Berlin, MA Steps for a Net Zero Home Renovation 1. Define your goals 2. Analyze existing conditions 3. Run energy modeling to evaluate different strategies 4. Identify solutions 5. Implement your chosen strategies 6. Evaluate performance and refine over time
A Note of Caution: A house is a system, with many interrelated parts. Be sure to get expert advice before insulating, air sealing, etc., to avoid possible moisture and/or air quality problems. My Home
What Was Our Starting Point? Context: Cohousing, walk & bike commute Small, energy-efficient home
Small, energy-efficient home Defining Our Goals 1. Net zero operational energy or net energy producing heating, ventilation, hot water, electric plug loads 2. Learning: What would we do differently if building new?
Analyzing Existing Conditions Utility Bills Analyzing Existing Conditions Specific electric loads
Analyzing Existing Conditions Energy audit: blower door test Modeling Energy Usage Input for engineer
Modeling Energy Usage Engineer s modeling of existing conditions Modeling Energy Usage Engineer s modeling of existing conditions
Modeling Energy Usage Engineer s modeling of existing conditions Modeling Energy Usage Engineer s modeling of existing conditions
Modeling Energy Usage Relative impact of different building components Modeling Energy Usage Comparing different strategies
Modeling Energy Usage Comparing different strategies Findings Air tightness: Good, but can be improved. Insulation levels: Already good, adding exterior foam would improve further but may not be best bang for buck. Windows: Double-glazed, low-e, need improvement.
Findings Ventilation: Exhaust-only ventilation has no heat recovery (and is ineffective) Heating system: Efficient, but fueled by non-renewable propane Hot water: Solar hot water system already in place, backed up with propane Electricity: Low usage, but can be improved (dehumidification of basement causing disproportionate use) Details Air leakage: 500 CFM 50 ( 0.2 air changes / hour) Insulation levels: R/24 walls w/ thermal break, R/34 roof Windows: Double-glazed, low-e (~R/3) Electric usage: 300 kwh/month Propane usage: 300 gal/year
Solution: One Way to Get to Zero Consultant s Recommendations 1. Targeted air sealing to reduce leakage ~15% EDIT 2. High-grade interior storm windows 3. Reduce electricity use from 300 to 200 kwh/month 4. Replace exhaust-only ventilation with heat recovery ventilation 5. Replace gas boiler with minisplit heat pump 6. Install solar electric: 5 kw of photovoltaics Solution: One Way to Get to Zero What We Did: 1. Targeted air sealing to reduce leakage ~15% - 20% 2. Reduce electricity use (moderately) 3. Replace exhaust-only ventilation with heat recovery ventilation 4. Replace gas boiler with minisplit heat pump 5. Super insulated hot water tank 6. Install solar electric: 5.9 kw of photovoltaics
Strategy 1 Air Sealing Setting up the blower door Strategy 1 Air Sealing Feeling for leakage
Strategy 1 Air Sealing Removing and sealing around cathedral ceiling penetrations Strategy 1 Air Sealing Stairwell light in cathedral ceiling
Strategy 1 Air Sealing Caulking perimeter of second floor Strategy 1 Air Sealing Some tight areas The joy of air sealing!
Strategy 1 Air Sealing Interior door connecting to ceiling - an unlikely air path? Strategy 1 Air Sealing Leaks at range hood chase
Strategy 1 Air Sealing A closeup. (Duct needs sealing, too!) Strategy 1 Air Sealing Weatherstripping exterior doors
Strategy 2 Reduce electric usage Replace existing refrigerator with Energy Star model Old refrigerator: 648 kwh/yr. New refrigerator: 383 kwh/yr. Strategy 2 Reduce electric usage Electricity Usage: Already using compact fluorescent bulbs & fixtures. Next step is to replace with LEDs.
Strategy 2 Reduce electric usage Efficient appliances and conserving behaviors Strategy 3 Heat recovery ventilation Replace exhaust-only with heat recovery ventilation Graphic: Popular Mechanics
Strategy 3 Heat recovery ventilation Replace exhaust-only with heat recovery ventilation Strategy 4 Minisplit heat pump Driven by PV; eliminates carbon fuel Interior unit (above) Exterior units (left)
Strategy 4 Minisplit heat pump Increases occupant comfort Strategy 5 Superinsulated electric water tank to back up solar hot water
Strategy 6 Photovoltaics PV-ready roof 5.9 kw system powers both electric loads & heat pump Grid-tied Results Air Sealing Initial air leakage: 500 CFM 50 ( 0.2 air changes / hour) Reduction in air leakage: 110 CFM 50 ~20% improvement BUT- Subsequent test after heating system renovations: 640 CFM 50 HMM WHAT HAPPENED???
Results Energy Data Month BEFORE: BEFORE AFTER Difference Electric Propane Propane TOTAL TOTAL kwh gal kwh equiv kwh kwh kwh Dec 391 55 1485 1876 1090-786 Jan 357 53.2 1436.4 1793.4 1347-446.4 Feb 358 74.3 2006.1 2364.1 1053-1311.1 Mar 346 52.3 1412.1 1758.1 751-1007.1 Apr 313 33 891 1204 441-763 May 218 8.3 224.1 442.1 247-195.1 Jun 222 8.3 224.1 446.1 185-261.1 ]ul 367 8.3 224.1 591.1 187-404.1 Aug 292 8.3 224.1 516.1 197-319.1 Sep 253 0 0 253 166-87 Oct 241 8.3 224.1 465.1 305-160.1 Nov 390 24.8 669.6 1059.6 623-436.6 Totals 3748 334 9021 12769 6592-6176.7 Monthly averages 312 28 752 1064 549-515 Results Energy Data Total "10" on net "4" on Net Meter meter - PV to Electric Net Usage from Grid Usage (Grid Date -Usage from Grid Grid PV production (#4 - #10) + PV) (date of usage for for for net usage net usage reading) reading period reading period reading period for period to date for period start 12/3/2010 1534 start data 1138 data 1354 start data 1/1/2011 2428 894 1354 216 1766 412 678 678 1090 2/1/2011 3557 1129 1545 191 2175 409 938 1616 1347 3/4/2011 4393 836 1977 432 2824 649 404 2020 1053 4/4/2011 4961 568 2450 473 3480 656 95 2115 751 5/3/2011 5288 327 2903 453 4047 567-126 1989 441 6/4/2011 5456 168 3478 575 4701 654-407 1582 247 7/5/2011 5576 120 4129 651 5417 716-531 1051 185 8/3/2011 5665 89 4783 654 6169 752-565 486 187 9/4/2011 5778 113 5423 640 6893 724-527 -41 197 10/1/2011 5886 108 5865 442 7393 500-334 -375 166 11/5/2011 6129 243 6319 454 7909 516-211 -586 305 12/3/2011 6650 521 6685 366 8377 468 155-431 623 Totals 5116 5547 7023-431 6592
Results Cost Cost of Renovation Item Cost Rebates Tax Credit (Fed) Tax Credit (MA) PV $48,6010.00 $(10,500.00) $(14,580.30) $(1,000.00) SDHW changes $3,818.40 Electric assoc. w/ PV & SDHW $750.00 Heat pumps $6,619.00 $(1,000.00) HRV $3,125.00 Sale of old boiler $(2,300.00) Misc carpentry $545.00 Gas disconnect $45.00 New refrigerator $736.40 Air sealing $135.00 Weatherstripping (by owner) $13.70 Total Cost $62,088.50 Totals: Rebates & Tax Credits $(11,500.00) $14,580.30) $(1,000.00) Net Total Cost $35,008.20 Note: A 150-200 SF addition would cost the same. Results Cost Payback for Renovation kwh or gal Cost per unit Savings/year Electricity Savings 3748 $0.17 $618.42 Propane Savings 334 $2.70 $901.80 SRECs $2,357.76 Total Revenues $3,877.98 Years to Payback: 9
Next Steps Next Steps: 1. High-grade interior storm windows 2. Further reduction to electrical usage 1. LED 2. Induction Range 3. More air sealing 4. Improved monitoring 1 Interior Storm Windows
2 Further reduce electric usage Power strip to control vampire loads Graphic: Energy Federation, Inc. 2 Further reduce electric usage Change over to LED light bulbs Graphics (l-r): GE, Switch, Philips
2 Further reduce electric usage Change over to induction range Graphics: GE 3 More Air Sealing
4 Improved Monitoring http://www.brultech.com ECM-1240 Home Monitor Starting Point A Review Small, energy-efficient duplex home Built in1994 for approximately $56/SF Compact fluorescent lighting Exhaust-only ventilation Spacious feeling in a compact floor plan Solar hot water already installed
A Review Strategies Careful modeling to determine strategies Targeted air sealing Reducing plug loads (old refrigerator and dehumidifier were energy hogs) New air-source heat pumps to replace propane boiler New HRV to replace exhaust-only ventilation Super-insulated electric water tank as new backup for solar hot water 5.9 kw PV array to cover all energy uses A Review Results Exceeded zero net: net energy producing by 430 kwh/year Total energy use reduced by 23% New refrigerator alone saved ~40 kwh/month Original tight construction (improved, then undermined) Basement dehumidification using heat pump is more efficient & effective Comfort improved (pleasant heating system)
A Review Costs: Total cost before rebates: $62,100 Cost after rebates & tax credits: $35,000 Yearly revenue from SRECs: $2,400 Yearly cost savings on utilities: $1,500 Payback: 9 years A Review Next Steps Interior storm windows More air sealing LED lighting Magnetic induction range Further reduction in plug loads Improved monitoring
Northampton Residence Gut Renovation Before & After
Before & After Complete Gut Renovation
Interior Note: Gas cooktop & open fireplace door not recommended Interior Note thick walls
Interior Mechanical System Ground-source heat pump fueled by PVs
New Leverett Home Attempting net zero for heating, cooling, hot water & electric loads; appear to be at 50%+. Interior
Interior Mechanical System Ground-source heat pump fueled by PVs
New Community in Berlin, MA Simple massing simplifies air sealing and insulation details
Wall Section 14 TJI roof rafters provide for 14 of dense packed cellulose insulation Penetrations for bathroom, kitchen and plumbing vents need to be detailed to ensure air tightness Exterior walls are 2x6 construction with 2 layers of 1 rigid foam on the outside, further enhanced with a rain screen detail under the siding. Exterior sheathing is the air barrier so it is taped at all seams and sealed at all edges and rough openings. Insulated rim joists and window headers Triple glazed windows are detailed carefully for air tightness with prefabricated corner flashing. Fully insulated slab and slab edge Detailing OSB sheathing is taped for air sealing prior to the installation of rigid exterior insulation, strapping (right) and exterior siding.
What makes a tight, well-insulated building envelope? (Some general information) Wall Construction Double stud wall for thicker insulation
High-Performance Windows Triple-glazed window w/insulated fiberglass frame & sash And don t forget air sealing!
Insulation & Air Tightness Levels Comparison of a 1,400 SF home (2,700 SF including conditioned basement & attic) in New England with four levels of insulation & air-tightness: Base case (better than Energy Star) R-16 walls, R-35 roof, R-3 windows, R-5 foundation walls, 0.30 CFM50 infiltration 39,000 BTU / hour design heat loss Annual heat load of 71 million BTU ~640 gallons of fuel at 80% efficiency. Well insulated & very tight (equal to that at Mosaic Commons Cohousing) R-31 walls, R-48 roof, R-5 windows, R-10 foundation walls, 0.18 CFM50 infiltration 24,600 BTU / hour design heat loss Annual heat load of 44 million BTU ~400 gallons of fuel at 80% efficiency. 62% of base case Super insulation & even tighter R-40 walls, R-55 roof, R-5 windows, R-30 foundation walls, 0.10 CFM50 infiltration 15,500 BTU / hour design heat loss Annual heat load of 20 million BTU ~185 gallons of fuel at 80% efficiency. 29% of base case German passivhaus Estimated at approximately 15% of base case Calculations provided by Marc Rosenbaum, Energysmiths Closing Thoughts
What does a hero look like? (You know, the kind of person who is helping to save the world...)
YOU Net Zero? Whether you go all the way to net zero, or substantially improve your home s performance, whatever you do will reduce your footprint and help us all learn more. The strategies you select will depend upon your home and your personal goals.
Remember It s not just the house, it s how you live there! Technical Credits: Mary Kraus Laura Fitch Photo Credits: Mike April Janice Doyama John Fabel Laura Fitch Mary Kraus Jen Luck Rebecca Reid Kraus-Fitch Architects, Inc. 2006
KRAUS-FITCH ARCHITECTS, INC. Home Community Planet Mary Kraus, AIA, LEED mkraus@krausfitch.com 110 Pulpit Hill Road Amherst, MA 01002 413-549-5799 www.krausfitch.com Resources Center for Ecological Technology (CET), energy audit & air sealing, (413) 586-7350, www.cetonline.org Solar Store of Greenfield, (413) 772-3122, http://solarstoreofgreenfield.com/ Energy Federation, Inc., www.efi.org North Quabbin Energy, Winserts interior storm windows, www.northquabbinenergy.org/wordpress/ Northeast Solar Design Associates (PV), www.nesolardesign.com Kraus-Fitch Architects, Inc., (413) 549-5799,