Net Zero Energy. Summary. Renovating an Existing Home. Mary Kraus AIA, LEED BD&C

Transcription

1 Net Zero Energy Renovating an Existing Home Mary Kraus AIA, LEED BD&C KRAUS-FITCH ARCHITECTS, INC. Home Community Planet Kraus-Fitch Architects, Inc Summary What / why net zero? Steps for a net zero renovation Case study Other examples Conclusion

2 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?

3 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

4 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

5 What Was Our Starting Point? Context: Cohousing, walk & bike commute Small, energy-efficient home

6 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?

7 Analyzing Existing Conditions Utility Bills Analyzing Existing Conditions Specific electric loads

8 Analyzing Existing Conditions Energy audit: blower door test Modeling Energy Usage Input for engineer

9 Modeling Energy Usage Engineer s modeling of existing conditions Modeling Energy Usage Engineer s modeling of existing conditions

10 Modeling Energy Usage Engineer s modeling of existing conditions Modeling Energy Usage Engineer s modeling of existing conditions

11 Modeling Energy Usage Relative impact of different building components Modeling Energy Usage Comparing different strategies

12 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.

13 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

14 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

15 Strategy 1 Air Sealing Setting up the blower door Strategy 1 Air Sealing Feeling for leakage

16 Strategy 1 Air Sealing Removing and sealing around cathedral ceiling penetrations Strategy 1 Air Sealing Stairwell light in cathedral ceiling

17 Strategy 1 Air Sealing Caulking perimeter of second floor Strategy 1 Air Sealing Some tight areas The joy of air sealing!

18 Strategy 1 Air Sealing Interior door connecting to ceiling - an unlikely air path? Strategy 1 Air Sealing Leaks at range hood chase

19 Strategy 1 Air Sealing A closeup. (Duct needs sealing, too!) Strategy 1 Air Sealing Weatherstripping exterior doors

20 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.

21 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

22 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)

23 Strategy 4 Minisplit heat pump Increases occupant comfort Strategy 5 Superinsulated electric water tank to back up solar hot water

24 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???

25 Results Energy Data Month BEFORE: BEFORE AFTER Difference Electric Propane Propane TOTAL TOTAL kwh gal kwh equiv kwh kwh kwh Dec Jan Feb Mar Apr May Jun ]ul Aug Sep Oct Nov Totals Monthly averages 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/ start data 1138 data 1354 start data 1/1/ /1/ /4/ /4/ /3/ /4/ /5/ /3/ /4/ /1/ /5/ /3/ Totals

26 Results Cost Cost of Renovation Item Cost Rebates Tax Credit (Fed) Tax Credit (MA) PV $48, $(10,500.00) $(14,580.30) $(1,000.00) SDHW changes $3, Electric assoc. w/ PV & SDHW $ Heat pumps $6, $(1,000.00) HRV $3, Sale of old boiler $(2,300.00) Misc carpentry $ Gas disconnect $45.00 New refrigerator $ Air sealing $ Weatherstripping (by owner) $13.70 Total Cost $62, Totals: Rebates & Tax Credits $(11,500.00) $14,580.30) $(1,000.00) Net Total Cost $35, Note: A SF addition would cost the same. Results Cost Payback for Renovation kwh or gal Cost per unit Savings/year Electricity Savings 3748 $0.17 $ Propane Savings 334 $2.70 $ SRECs $2, Total Revenues $3, Years to Payback: 9

27 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

28 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

29 2 Further reduce electric usage Change over to induction range Graphics: GE 3 More Air Sealing

30 4 Improved Monitoring 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

31 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)

32 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

33 Northampton Residence Gut Renovation Before & After

34 Before & After Complete Gut Renovation

35 Interior Note: Gas cooktop & open fireplace door not recommended Interior Note thick walls

36 Interior Mechanical System Ground-source heat pump fueled by PVs

37 New Leverett Home Attempting net zero for heating, cooling, hot water & electric loads; appear to be at 50%+. Interior

38 Interior Mechanical System Ground-source heat pump fueled by PVs

39 New Community in Berlin, MA Simple massing simplifies air sealing and insulation details

40 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.

41 What makes a tight, well-insulated building envelope? (Some general information) Wall Construction Double stud wall for thicker insulation

42 High-Performance Windows Triple-glazed window w/insulated fiberglass frame & sash And don t forget air sealing!

43 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

44 What does a hero look like? (You know, the kind of person who is helping to save the world...)

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46 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.

47 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

48 KRAUS-FITCH ARCHITECTS, INC. Home Community Planet Mary Kraus, AIA, LEED 110 Pulpit Hill Road Amherst, MA Resources Center for Ecological Technology (CET), energy audit & air sealing, (413) , Solar Store of Greenfield, (413) , Energy Federation, Inc., North Quabbin Energy, Winserts interior storm windows, Northeast Solar Design Associates (PV), Kraus-Fitch Architects, Inc., (413) ,