Zero Carbon ® Client Case Studies

Homeowner earns 46% return on investment by cutting carbon footprint 38%.

The first client of David Green’s Zero Carbon® consulting practice, David Sguazzin, has cut the carbon footprint of his modest home on Long Island, NY by approximately 4 tons of carbon dioxide per year and is saving over $1,100 per year on heating and electric bills. David Sguazzin is earning a 46% return on his investments in insulation, air sealing and triple-glazed windows. The triple-glazed windows were made by David Sguazzin and fitted to the inside of his existing single-pane windows using a technique pioneered by David Green on his own home. 

Before engaging Zero Carbon® LLC, the approximately 1,000 square foot, single-story house’s heating and electric bills were about $3,500 per year. Today, they are about $2,400 per year saving David Sguazzin $1,100 per year.  The total investment was about $1,300 in materials. The fee paid to Zero Carbon® LLC was 1x the annual savings on the bills or $1,100. The 46% return on investment includes the fee.

“Working with David Green was an absolute pleasure, he guided me through the process with his experience in lowering my energy expenses and my overall carbon footprint.” Said David Sguazzin.

David Green said, “If every household in the U.S. did what David Sguazzin has done, the US would more than reach its goals under the Paris Climate Treaty. And it could do it within a year. Every household would be better off by over $1,000 a year. Each year, every year and forever. This would be a $300 billion dollar economic stimulus to the U.S. economy every year. Using the standard rate of 8.34 jobs per million dollars of construction spending, this would create 2.5 million new jobs every year, just what we need to pull us out of this recession.”

If you live in Massachusetts, MassSave would have paid for almost all of David’s insulation program and would have installed the insulation for him.

On David Green’s own home, the return on investment in a more comprehensive program of energy reduction, heat pumps and solar panels that cut the house’s carbon footprint and utility bills to zero, was 15%. 

David Green’s “fab four” recipe for making money by cutting your carbon footprint has now been proven on houses ranging from 1,000 square feet to 14,000 square feet and from 1810 colonial farmhouses to brand new construction.

Case Study: 1,300sf, 1934, colonial-style home with limited solar potential

Despite being a vintage home that did not allow for adding wall or basement insulation, and without changing any windows, this house’s bills and carbon emissions were both cut in half.

The house is in Arlington, MA with 5,600 heating degree days.

The program consisted of:

  1. Insulation was added in the attic, some air sealing was done in the attic (but neither insulation nor air sealing was done in the basement), 
  2. Air sourced heat pumps were added
  3. A fairly small solar array was added to the roof (which has considerable shade from nearby trees)
  4. The natural gas furnace was retained
  5. A wood-burning stove was added for both ambience and heating

Here are the details:

Congratulations are in order! You have cut your carbon emissions by 56% and your bills by 32%. The cut in the bills is despite the price of natural gas being 32% higher than it was when I measured your house back in 2019 and electricity having gone up 13% since 2019. Natural gas will soon have doubled in price from 2019 and electricity will soon be 50% more expensive so you have insulated yourself from those increases as well. You are also not funding Putin’s war in Ukraine.

In the year before I worked on your house your total bills were:
$2,632 for gas, $830 for electricity
$3,462 total
In the last 12 months they were:
$1,033 for gas, $722 for electricity net of solar, $600 for wood
$2,355 total

Your total carbon emissions before the “fab four” were 11.4 tons per year and after they were 5.8 tons, for a cut of 56%.

So I saved you $1,107 per year so that is what you owe me. This is 32% cut in your bills. And this is with the prices for both natural gas and electricity having gone up considerably since I started work on your house. If I recalculate your “before” costs at today’s prices for gas and electricity your “before” bills were $4,207, so you can think of your savings as having been more like $1,851 or a 44% cut compared to the recalculated costs before the Fab Four. So roughly roughly you can say you cut your carbon emissions in half and cut your bills in half too. I assumed you were using electricity from the grid at the average ISO NE emissions per kWh rather than the zero emissions from the “green” electricity you buy because you pay extra for that.

With the limited amount of sun available on your roof I think this is a very good outcome. You are absolutely right that it would be better for everyone if the utilities supplied more green electricity. In addition to the money savings and carbon emissions savings you have almost certainly increased the price of your adorable little house with both the heat pumps and solar panels.

Did you burn the entire cord of wood in the last 12 months? If not let me know how much you burned as I suspect I have overestimated your carbon emissions.

You can read more about the “fab four” by visiting where you can watch a 45-minute webinar, download the slides used in the webinar and download written Q&A from prior webinars, all for free.

David Green can be contacted at

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