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A difficult challenge: poorly insulated, leaky, sprawling, shaded, dilapidated old oil heating system, and rural location.

Home

Location: Mendocino County, rural northern California coastal climate
Year built: 1978
Floor area: 2,500 square feet
Construction: Light construction (minimal insulation), only 2x4 walls, high ceilings, U-shape creates lots surface for heat loss
Solar access: Considerable shading by redwood trees on all sides; on-site solar not possible.
Occupancy: Two adults and three children through mid-2019, 2+2 through mid-2023, and two adults thereafter
Utilization: Both adults work at home, so “operating hours” are higher than in a typical home
Base-year carbon footprint: 27 Tons CO₂ = 15 Prius @ 60mpg, or 5 Ford F150s @ 20mpg

Cars

Initially: Minivan and sedan. Converted in 2019 and 2011 to electric vehicles

Petro-company Executive and President of the COP28 climate conference said that eliminating fossil fuels will “take the world back into caves”. Here’s my cave.

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Key Takeaways

It is possible to eliminate the carbon footprint of an entire household – even an energy hog – plus associated vehicles while significantly reducing energy bills.

Over 15 years, our home and vehicles have been fully electrified and carbon footprint reduced to zero.
After this work, our energy bills for home and cars are $11,000/year (67%) lower than if we had made no effort to cut carbon, paying back the added cost of the improvements in 9 years or a simple tax-free return of 11%, which is substantially better than a diversified 60/40 blend of stocks and bonds and more than twice that of similarly safe municipal bonds.
The corresponding energy savings are 88%, reducing carbon emissions by 97% assuming a standard grid. Remaining electricity needs are fully met with carbon-free renewable energy from Sonoma Clean Power.
Our home is far more comfortable, indoor air quality is vastly improved, and the cars are better.

Technology availability is not a significant obstacle. The obstacles are human, and are significant.

Repurposing an old saying, “The best time to start decarbonizing was 15 years ago. The second-best time is today.”

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One-third of US greenhouse-gas emissions are homes & passenger vehicles

6.3 billion metric tonnes CO₂-equivalent

https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-and-sinks-1990-2021

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Where did our home’s emissions originally come from: 2008?

Equals the Annual emissions of 15 top-efficiency hybrids**

** 11,100 miles/year-car * 1 gallon/59 miles * 19.37 pounds CO2/gallon gas * 1 ton/2000 pounds = 1.82 tons/car => 27.0 tons/1.8 = 14.8 cars

27 tons CO₂ per year

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Evolution of energy types and uses

19% decrease

100% decrease

88% decrease

Electricity counted at 3412 BTU/kWh

Original home (2008) heated with oil; all other uses electric (inefficient equipment). Oil initially switched to propane, with space- and-water converted to high-efficiency “condensing” boiler. Cooking also converted to propane. Later, all uses converted back to electricity, but using ultra-high-efficiency equipment. Original gas-powered cars later converted to electric.

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We achieved zero carbon along with increased energy services

We achieved net zero carbon emissions, while enjoying the following improvements in amenity and service levels potentially driving energy use higher:

2008-2019: Children growing from ages 4 and 8 to 15 and 19
2008: Significant increase in daylight thanks to 12 new skylights
2020: Second full-sized fridge added
2021: Hot tub added
2020-2022: five people home most times throughout the Covid pandemic

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Upgrades generally done at replacement time: light bulb replacement, appliance change-out, end of life for furnaces

We achieved $11,000 per year energy bill savings on home and cars vs. had we done nothing !

Cost of associated improvements was $103,000 over and above business-as-usual replacements (including sur-costs on two EVs, equipment, windows, insulation, etc.)

=> 9 year payback = 11% ROI

OTHER BENEFITS!:

reduced indoor air pollution, better comfort, better control,

fewer light bulb purchases, quieter fridge, better cars

67% decrease

(est.)

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$16,600

$5,400

Note: Hot water is such a large percentage of “before” cost because there were two electric water heaters and electricity was very substantially more expensive than heating oil

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2009:

• Install efficient

dishwasher

2010:

• Convert 1st-generation

fluorescent tubes to high-efficiency

2011:

• Improve boiler efficiency

• Insulate floor to R-22

Heat

(oil)

Cars (gasoline)

Space heating, water heating, cooking (propane)

Appliances, lighting, and changing uses over time (electricity)*

*Utility-provided 100% solar+geothermal mix after 2019

Zero emissions achieved

2017:

• Replace most windows and

patio doors: double-glazed to

triple-glazed

• Change fluorescent tubes to

LEDs

2008:

• Switch from oil to propane for space and water heat

• Replace oil furnace with high-efficiency LPG boiler

• Upgrade duct insulation to R-8; air sealing

• Convert electric cooktop to propane gas

• Change incandescent bulbs to compact fluorescents

• Install 12 skylights and two light tubes

• Install efficient refrigerator; eliminate second one.

2023:

• Install efficient washer-dryer

• Replace propane boiler with

high-efficiency combined space-� and water-heating heat pump

• Replace gas cooktop with

induction

2021:

• Insulate roof to R-35

• Upgrade remaining windows

• Install hot tub

• Second electric car

2020:

• Second fridge

• Upgrade electrical panel

Tons CO₂per

2018:

• First electric car

• Purchase 100%

solar+geothermal

power from utility

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*Delivered electricity: 3412 BTU/kWh

(est.)

Space heating, water heating, cooking (propane)

Appliances, lighting, and changing uses over time (electricity)*

Heat

(oil)

2009:

• Install efficient

dishwasher

2010:

• Convert 1st-generation

fluorescent tubes to high-efficiency

2011:

• Improve boiler efficiency

• Insulate floor to R-22

2008:

• Switch from oil to propane for space and water heat

• Replace oil furnace with high-efficiency LPG boiler

• Upgrade duct insulation to R-8; air sealing

• Convert electric cooktop to propane gas

• Change incandescent bulbs to compact fluorescents

• Install 12 skylights and two light tubes

• Install efficient refrigerator; eliminate second one.

88% energy savings achieved

2017:

• Replace most windows and

patio doors: double-glazed to

triple-glazed

• Change fluorescent tubes to

LEDs

2023:

• Install efficient washer-dryer

• Replace propane boiler with

high-efficiency combined space-� and water-heating heat pump

• Replace gas cooktop with

induction

2021:

• Insulate roof to R-35

• Upgrade remaining windows

• Install hot tub

• Second electric car

2020:

• Second fridge

• Upgrade electrical panel

Cars (gasoline)

Millions of BTUs

2018:

• First electric car

• Purchase 100%

solar+geothermal

power from utility

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Removing big trees for solar access didn’t “pencil”

Tree Biomass (kg) = 10^(-0.8252+2.2607*LOG10(dbh*2.54)+0.0054)

Removing this group of second-growth redwood trees (the largest of which is five-feet in diameter) to provide solar access would have resulted in the release of about 39 tons of CO₂.

That is 45 years of emissions from our home+cars after all efficiency upgrades were done and all uses switched to grid electricity … instead grid solar+geothermal now cuts our emissions to zero, while saving these trees.

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But, enlarged and south windows provide valuable solar gains

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Lighting: Progressive efficiency upgrades for >90% savings

First converted from incandescent to compact fluorescent bulbs, then some years latest LED bulbs

Ultra-low-wattage under-cabinet LED lighting in kitchen

Ultra-low-wattage LED display lighting

First changed first-generation fluorescent tube cove lighting to high-efficiency fluorescent, then some years later t LED tubes.

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Appliances: Replaced all with EnergyStar at time of natural turnover

c. 2009

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Induction cooking (heating)

Not radiation, convection, or conduction! Cooks faster, easier cleanup.

Any pot that a magnet sticks to will work

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When it was time for re-roofing, we took the opportunity to upgrade the insulation

Added panels with 4” of foam, bringing entire roof to around R-38. Similar to current building code for this 1979 house.

Poor workmanship resulting in air leakage and heat loss. Many corrections required to avoid energy waste and moisture issues.

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Ecological crimes in the crawlspace!

Poor workmanship for upgraded ductwork and piping. Failed to insulate key joints. Hot-water piping insulation overlooked.

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More crimes: Air leakage and heat losses by installers

Failure to seal around penetrations provides pathways for heat loss moisture problems, as well as pests and insects.

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Yet more crimes? Failure to properly insulate subfloor with foam for a total of about R-22

Poor workmanship. We contracted for 2”, but many areas had much less.

Installer returned to correct mistake.

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Superwindows

Two glass panes with a rugged plastic film between them, creating the thermal profile of an otherwise heavier and costlier triple-pane window. Layers are treated with invisible heat-retaining “low-e” coatings. Gaps are filled with gas such as Argon to further reduce heat flow. Frames are insulated and air gaps sealed.

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Upgraded old dual-pane to high-efficiency triple-pane windows

Infrared camera revealed heat losses around frame of old windows and cold glass (left). New windows performed much better. Thin blue line (cold) for windows n the right reflects failure to properly caulk and air seal around new windows (despite that being called for in the spec, not to mention modern professional standards of care.

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Integrated heating, cooling, and water-heating system

Controller

Heat pump

Outside air ductable to the house for cooling or indoor air quality

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The innovative heating system includes the world’s most efficient heat pump – and lowest GWP refrigerant – which fills a “thermal battery” with hot water made during off-peak times when power is cheap and the sun is powering the grid.

Lower panel: First month’s electricity use. Peak hot water production during low-carbon time of day, but lack of nighttime temperature setback meant unnecessary energy use in those hours – since corrected.

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Three key components of the high-efficiency heating system

Premium-efficiency

heat pumps, with ultra-low-GWP refrigerant. Works down to -26F below zero

Air handler where hot water us used to heat air for to be blown into the duct system

Water tank serves as a “thermal battery” to store many hours worth of hot water that can be used for heating when on-peak power would be more expensive and more polluting

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Trust but Verify: The role of measurement

Top row: Whole-house air leakage test using a blower door.

=> Result 6ach at 50Pa (very roughly equates to 0.3 air changes per hour under natural conditions), considered reasonably tight, and not requiring mechanical ventilation to ensure air quality.

Bottom row: Duct leakage using “ductblaster”.

=> Result ~6% leakage = “pass”

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Key Obstacles

The greatest obstacle is finding tradespeople who have the interest, skill, and commitment to help implement home improvements.

Problems with design, workmanship, and soft skills (particularly communication) are common, leading to higher costs and underachievement of carbon reductions.
Product manufacturers often have inscrutable documentation, and unskilled technical support staff.
Information understandable by the general public is hard to locate.
Financial incentives are abundant but also hard to find, confusing, and time-consuming to apply for.

Read more than you ever wanted to know about the obstacles here.

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