“What’s the use of a fine house if you haven’t got a tolerable planet to put it on?”

— Henry David Thoreau, “Familiar Letters” (1895)

As reports pour in of intolerable climate change – with Maine now leading the nation for the fastest rise in annual average temperature over recent decades – we clearly need to rethink what constitutes a “fine house” or even just a pretty good one.

It must be one that uses minimal energy to stay warm in winter and cool in summer, is close to carbon-neutral, and relies primarily on local and renewable resources.

Whether called green, sustainable, or energy-efficient, this approach to building and retrofitting is hardly new. What’s novel is how technology is making it far easier and cheaper to achieve “high performance” (builder-speak for a healthy and comfortable living environment with a low input of energy and a minimal outflow of money and pollution).

The first requirement for a more sustainable house is to “reduce before you produce” – sealing up the structure so energy is not wasted.

Many Maine residents are now taking advantage of Efficiency Maine loan programs to retrofit old, drafty buildings – adding insulation and high-performance windows to reduce cold infiltration.

Those doing new construction have even greater options to design a house in ways that minimize the need for mechanical heating and cooling – like adding south-facing windows with overhangs, and building directly on slab.

Our house has these features and is toasty in winter using just two cords of wood in a high-efficiency wood stove, with no other heat source besides passive solar gain.

It also stays relatively cool on hot days without need of air conditioning – just opening windows at night and closing and shading them in the day.

When it comes to increasing home efficiency, “There’s so much low-hanging fruit,” says Richard Riegel Burbank of Evergreen Home Performance. “For an investment of $10,000, a common first step for many households, it’s possible to realize a 20-25 percent reduction in energy use.”

Those who choose more substantial retrofits (typically costing $40,000 to $50,000) can achieve much higher reductions – in the range of 50-60 percent.

Homeowners not ready for a whole-house investment can still cut carbon emissions and electricity costs by upgrading to LED light bulbs and Energy Star appliances.

The payback on an LED light bulb is measured in months, and the collective impact of this small change is significant. Light bulb upgrades that Americans made in 2012 removed greenhouse gas emissions equal to taking 2 million cars off the road.

For those willing to invest more in efficiency, upgrading the home’s central heat source can yield great dividends (and qualify for financial incentives through Efficiency Maine’s Home Energy Savings Program). Burbank counsels his clients to think out two decades over the lifetime of the system they’re considering – trying to anticipate what the cost and availability will be of different fuel sources.

Two carbon-neutral options that rely on a local resource – wood stoves and wood pellet boilers – are near the top of Efficiency Maine’s list for heating systems with the least annual expense.

Surprisingly, electricity – long dismissed as exorbitant in the years of wasteful baseboard heat – is now a credible option.

Electrically powered ductless (air source) heat pumps top even the wood-based heaters on Efficiency Maine’s list. These pumps (known as mini-splits) move heat, rather than generating it, and can reverse direction to provide summer cooling as well as winter warmth.

While fossil fuel combustion can never exceed 100 percent efficiency, heat pumps draw “free” energy from the air to lift efficiency levels up over 300 percent.

A friend who installed a ductless heat pump two years ago reports that it eliminated his family’s $2,000 oil bill entirely, while adding about $700 a year to their electric bill.

For those enrolled in the Maine Green Power Program (choosing local, renewable electricity sources), that conversion can cut greenhouse emissions as well as annual energy expenses.

Some homeowners opt to power heat pumps with electricity from their own solar photovoltaic panels. Robert Howe, who runs the Maine Association of Building Efficiency Professionals, will soon make the move from a 1789 farmhouse to a home he hopes will achieve a “net-zero” ideal – producing as much energy as it consumes.

Its solar panels will power both an air source heat pump and a heat pump water heater.

The cost of solar panels has plummeted in recent years, increasing their appeal as a means to cut both carbon emissions and electricity bills.

“You’re not getting penalized to do the right thing anymore: that’s a real game changer,” says David Foley, of Holland and Foley Architecture (which designed our home a decade ago).

Two years ago, he had a dozen 250-watt solar panels installed on the roof of an office outbuilding, which produce electricity for the office and his adjoining home. The panels have been generating a surplus throughout the year, drawing from the grid only between late November and mid-January.

He sees the initial expenditure on solar panels as a “low-risk prudent investment with a 5.4 percent annual rate of return that’s risk-free and tax-free: ‘What’s not to like?’ ”

With energy costs rising faster than returns on traditional investments, and help from Efficiency Maine programs and federal solar incentives, more Maine residents are opting to invest in efficiency upgrades.

Saving money, cutting carbon emissions, and being more self-reliant are all strong draws. But what really moves people to action? “Comfort,” says Burbank: “That is the prime motivator – totally.”