Zero Carbon Zero Bills – free talk, free book

We have cut our home’s carbon footprint and energy bills to zero. David Green is doing a 40 minute presentation via Zoom, sponsored by Upper Charles Climate Action (part of 350.MA), on how to do it. It is free. Click below to register. All attendees get a free copy of my book Zero Carbon Home – the brand new 2020 edition. 

Zero Carbon, Zero Bills

A presentation by David Green

Please join us on Tuesday, June 2nd at 7 PM or Saturday, June 20 at 10:00 AM
for a 40 minute Zoom presentation (followed by Q&A) 
on how to reduce your house’s carbon footprint while saving money doing it.

David Green, a local resident, will explain how he retrofitted his 1970s home to achieve net zero emissions while realizing a 15% return on the investment.  As David says, “My zero energy retrofit beats my 401(k)”.  He is the author of Zero Carbon Home and Zero Carbon Pool. David is a physicist by training and has a solid understanding of technologies like solar panels, heat pumps, and low-E, triple-glazed windows.  He also has an MBA from Harvard Business School and spent 20 years as President or CEO of private and public companies.  He has kept detailed records of his heating oil use and his electricity use in order to measure the effect of each improvement made to his home.  His results are based on his own experience rather than generalized claims made by manufacturers or installers. 

David will explain his decisions to use certain technologies and avoid others.  He will focus on both reducing emissions and the financial benefits of the technologies he chose (as well as the reasons he did not choose other available technologies).

Join us to hear about his experiences and how you can reduce your carbon footprint while making money doing it!


Sponsored by Upper Charles Climate Action, a node of 350MA   

Cosponsored by our Sustainability Coordinators, Matt Zettek (Holliston), Dorothea Von Herder and Gino Carlucci (Sherborn) 

To register for this event,  Click Here 
                                            or enter in your browser and search  “Zero Carbon Zero Bills”.

Green in Quarantine – “Stuck-at-Home” COVID19 Special Edition of Zero Carbon Home Available for Free

We are all trapped at home and probably going a little stir-crazy during the pandemic. Why not use the spare time to cut your carbon footprint? Here are three ideas proven to cut your bills and carbon footprint that are all easy to do. I have used them myself. They are discussed in more detail in the special “Stuck-at-Home” COVID19 Edition of Zero Carbon Home that you can download from my store for free by clicking here. Use coupon code COVID19 at the checkout.

  1. Insulate the hot water pipes in your basement. This usually pays for itself in months. You can order this pipe insulation online from Loewe’s or Home Depot (or other hardware stores), have it delivered to your house (hence avoiding any COVID-19 risk) and install it in minutes. 
  2. Insulate the ceiling of your basement with 12” of fiberglass. This usually pays for itself in less than a year. You can order this online from Loewe’s or Home Depot (or other hardware stores), have it delivered to your house (hence avoiding any COVID-19 risk) and install it in a day or two. Wear gloves and a face mask – it does not need to be an N95 respirator – a cloth mask (like a ski mask) will do. This is the insulation I used myself. It has a high recycled glass content.
  3. Add “fit from the inside” windows to your double-glazed windows to make them triple-glazed. These windows usually pay for themselves in a few years. You can order them to the exact size of your windows from any of several companies. Read my review of four different companies’ windows in the mini book which you can download by clicking here.

Why does a T-shirt made with organic cotton grown in the U.S.A. have a low carbon footprint?

U.S.A.-grown organic cotton has the lowest carbon footprint of all the major fibers (cotton, hemp and polyester) used for making shirts.  Its carbon footprint is 61% lower than conventionally grown cotton, 35% lower than imported organic cotton and 76% lower than polyester1. However, even U.S.A.-grown organic cotton still generates a small carbon footprint. This carbon footprint is offset completely by Zero Carbon®LLC by purchasing verified, incremental carbon offsets2. The total lifetime carbon footprint of a T-shirt is about twice that of making it. This extra carbon footprint is caused by washing and drying the shirt over its lifetime3. This entire lifetime carbon footprint is completely offset by the carbon offsets purchased by Zero Carbon®LLC.

So you can feel great about buying this T-shirt because it has a zero carbon footprint over its entire lifetime! We believe it is the world’s first zero carbon clothing.

Zero dyes. Zero bleach. Zero carbon.

All cotton. All organic. All made in the USA.

Soft on your skin

Soft on your planet™

Zero Carbon®Clothing Co.

1. Ecological Footprint and Water Analysis of Cotton, Hemp and Polyester. Nia Cherrett, John Barrett, Alexandra Clemett, Matthew Chadwick, and M.J. Chadwick, 2005. Study conducted by the Stockholm Environmental Institut.

2. These carbon offsets fund a project to capture methane gas that would otherwise leak into the atmosphere from exposed coal seams on the Southern Ute Indian reservations in Utah. Even the carbon offsets support American jobs and communities! Methane gas is 25 times stronger than carbon dioxide in causing global warming. These carbon offsets are audited and verified to be real and incremental by Cool Effects™.  Verified incremental means that the carbon offset would not have happened without this program. This is in contrast to many carbon offsets that rely on planting trees in rainforests to capture carbon dioxide out of the atmosphere. Reforestation programs are often not truly incremental because trees naturally seed and regrow, especially in a rainforest. So planting trees does not necessarily result in capturing more carbon dioxide from the atmosphere than would happen naturally. The Southern Ute Indian methane capture project is 100% incremental because if the Tribe did not capture the methane it would leak into the atmosphere and cause global warming.

3.  Mapping of Evidence on Sustainable Development Impacts that Occur in the Lifecycles of Clothing.Carbon Trust and BCG Analysis, DEFRA, 2007. Institute for Sustainable Resources, Queensland University of Technology. 

What is a secondary carbon footprint?

How to cut your secondary carbon footprint.

If you want to reduce your secondary carbon footprint (in other words the carbon footprint caused by the products you buy rather than the carbon footprint caused by heating your home or driving your car) then you need to start buying products with a zero-carbon footprint, or at least ones with the lowest possible carbon footprint that still get the job done for you. 

The secondary footprint comes in two parts: 

  • Part 1 is the carbon footprint of making, selling and delivering the product to you, and
  • Part 2 is the carbon footprint of using the product over its lifetime

You may think that part 2 is so small as to be ignored. Surely the biggest carbon footprint is in making the product, right? Sometimes yes, but often no. For instance, building a house is expensive and it creates a high carbon footprint from making concrete for the foundation, glass for the windows and copper for the wiring. Building scientists have estimated that the embodied carbon footprint of a house (i.e., how much carbon dioxide is emitted by building the house) is approximately equal to the carbon footprint caused by heating and cooling the house over its lifetime. At the other end of the spectrum, scientists have estimated that the carbon footprint caused by washing and drying a T-shirt over its lifetime is approximately equal to that of making the T-shirt. What we really care about is the lifetime carbon footprint.

There are very few products today that have a zero-carbon footprint. Zero Carbon LLC has introduced one, a T-shirt with a lifetime carbon footprint of zero. Since everyone needs T-shirts, buying one of these instead of buying a “fast-fashion” T-shirt is a great way to reduce your secondary carbon footprint. However, the first priority is to cut your primary carbon footprint and the best way to do that is to implement the fab four on your house. I.e., install 12” of fiberglass insulation in your attic and in the ceiling of your basement, replace your AC units with heat pumps, install single or double-glazed windows with triple-glazed windows when you are replacing your windows and install solar panels on your roof. 

You can see the Zero Carbon™ T-shirt by clicking here

Zero Carbon(R) T-shirt

Zero carbon footprint all organic cotton made in USA T shirt

Strut your zero carbon credentials with a T-shirt with a lifetime carbon footprint of zero! This T-shirt is made from wonderfully soft organic cotton. The cotton was grown on a family farm in Texas and the T-shirt was sewn in South Carolina. Domestic organic cotton has the lowest carbon footprint of all major fibers used in making T-shirts. The small remaining carbon footprint (including that of washing and drying it over its lifetime) is completely offset by us buying carbon offsets. These carbon offsets are independently verified to be both real and incremental (i.e., the carbon reduction would not have happened without the offset). The Zero Carbon(R) T-shirt – soft on your skin, soft on your planet.

This shirt is popular with companies for use as a corporate T-shirt printed with their logo. Substantial discounts are available for quantities of more than 1,000 shirts. If you are interested in this please email me at

You can see it by clicking here: Zero Carbon™ T-shirt

Green New Deal

Email to Senator Markey 8thFebruary 2019.

Hello Senator MArkey, 

I believe I can help sell your Green New Deal to skeptics, especially Republicans who control the Senate. We have cut the carbon emissions of our home in Dover by almost 90% in the last four years. We did this by retrofitting our 1970s house with heat pumps, insulation, triple-glazed windows and solar panels. All installed by local, hard-working plumbers, electricians and carpenters.

The best part of “going zero” is that we are saving about $9,000 a year in heating and electric bills. The savings will pay for the retrofit in about eight years. Our return on investment is about 11% per year after tax, which sure beats my 401k! We are saving money by saving the planet.

I believe this is the inflection point, the turning point, the point of no return. You said it yourself, “The sun is setting on the dirty energy of the past.” You can now make money by “going zero”. Making money is possible because the technologies of heat pumps, triple-glazed windows and solar panels have improved greatly and have tumbled in price. It is also because Massachusetts has smart policies such as: net metering for electricity, the MassSave program for subsidizing insulation, incentives for heat pumps and the new SMART solar subsidy. Massachusetts has led the way for your Green New Deal.

As you say in your Senate Resolution, we need to, “upgrade all existing U.S. buildings…to achieve maximum energy efficiency.” It is now possible to massively scale-up “going zero” because every home or business owner would make money. “Going zero” is no longer being driven by a hippy environmentalism, it is being driven by cold, hard cash in your pocket. 

To move from the inspiring language of the Green New Deal resolution to the action needed to deliver on its promises you will need concrete plans. Making money by going zero on your home, office or factory should be one of them. 

I know this might sound like it is unreal or that I am exaggerating. But I assure you it is very real. If you would like to send an aide to see my house, my electric bills that say, “No payment due” and my very carefully recorded results I would be happy to accommodate them.

Yes, and my family name really is Green. I am not making that up either.

Make money by going zero on your pool too

Today, Zero Energy Project, an authority on how to cut your carbon footprint, published an article on the advice on going zero on your swimming pool. This is based on my new book, Zero Carbon (TM) Pool. The article by Bruce Sullivan, is below:

Woot! Look What I Can Do!

Great news! Making money by cutting your carbon footprint to zero is a new reality. I own a large house built in the 1970s. I’ve already cut its energy bills and carbon footprint to zero, making a 15% return on investment in the process (see my previous Zero Energy Project blog post for details). Now I’ve done the same on my swimming pool. It was quicker, cheaper, and made a higher return on investment to “go zero” on our pool than it did on our house.

By “going zero” on our pool I saved about $3,000 a year and cut about 9 tons of carbon dioxide emissions a year. We did this by installing energy saving devices that I call the “pool fab four”: a new variable-speed pool-water circulating pump, an electric-powered pool vacuum/cleaner, a heat pump pool heater and about five solar panels to power it all. Going zero on our house saved us about $11,000 a year and cut our carbon footprint about 43 tons per year, so the savings on the pool made a significant addition to my total gain from going zero in the first place.

I am a physicist by training so I have a solid understanding of technologies like solar panels, heat pumps, and pool-water circulating pumps. I also have an MBA from Harvard Business School and spent 20 years as President or CEO of private and public companies. So I also understand how to use discounted cash flow analysis (the standard way companies analyze investments) to make financial calculations like internal rate of return (IRR, a measure of return on investment) and payback period (how long it takes to get your investment back). I keep detailed records of my pool’s propane and electricity use in order to measure the effect of each improvement we made to our pool. My results are based on my own experience rather than generalized claims made by manufacturers or installers.

In going zero, I only took measures that made financial sense, i.e., upgrades that paid for themselves with the savings on heating and electricity bills. This excluded doing many things typically done in deep-energy retrofits for swimming pools:

  • I replaced my old fixed-speed pool-water circulating pump with a variable-speed pool-water circulating pump and set its speed to the lowest setting needed to circulate all the pool water once each day, the rate of exchange required to keep the water clean. This reduced the pump speed from 3,450 rpm for about 12 hours a day to about 2,000 rpm for 24 hours per day. The laws of physics state that the electricity used by a pump goes up as the cube of the rpm, so slowing the pump down more than compensates for the doubling of the time that the pump is on. This effect is so powerful that it cut the electricity used to circulate the water by 87%, saving us over $2,000 a year. The new pump paid for itself in the first year with a return on investment of 100% a year. I wish I could invest my 401k in pool pumps!
  • I installed an electric-powered Dolphin™ pool vacuum/cleaner to replace the old pump-driven pool vacuum cleaner. This is safe because it is connected to a GFCI (ground-fault circuit interrupter) electrical socket and because we take it out of the pool and disconnect it whenever anyone is in the water. This alone saved us about 2,000 kilowatt-hours of electricity per year or over $400 worth. It pays for itself in about 3 years with a return on investment of 55% per year. This keeps the pool cleaner too, which eliminates the dreaded summer rite of scrubbing algae off the walls of the pool.
  • We use the pool only in summer, so an air-source heat pump pool heater is appropriate. My pool heat pump is about four to six times as efficient as my old propane-fired heater. In many areas, electricity is also less expensive than propane as a fuel in dollars per btu delivered, if you use the electricity to run a heat pump. We installed a single heat pump, one designed especially for pools, at a total installed cost of $6,000. The savings on the propane bills, after accounting for the extra electricity the heat pump uses, will pay for the heat pump in about 16 years. That’s a return on investment of about 4% per year after tax.
  • I did not add a pool bubble blanket to insulate the pool. This is because with the heat pump and solar panels, the cost of heating our pool is very low, just over $100 a year. This is using the highest measure of the cost of electricity from my solar panels (7 cents per kilowatt-hour) and was calculated as the total installed cost of the panels divided by the guaranteed electricity output of the panels. The running cost of my solar panels is zero. Including the storage rack, a pool bubble blanket for our pool would cost about $1,000 and might last ten years (the warranty is eight years) for an annual cost of about $100 a year. Spending $100 a year on a pool blanket to save a small fraction of $100 a year in heating costs makes no sense. We didn’t like the idea of having a large piece of rolled up bubble-wrap in the garden either.
  • We did not use a pool chemical blanket either. Pool chemical blankets are liquids, usually alcohols, you pour into the pool that create a thin layer on the surface that reduces evaporation (and heat loss) from the pool. Over four weeks in the summer of 2017 I did experiments with and without a pool chemical blanket. I found that they do reduce the loss in temperature of the pool overnight by about 1°F (the pool naturally loses about 2-3°F overnight) but they cost about $50 a week. I can replace that lost heat with my heat pump and solar panels at about a third of that cost and with none of that inconvenience.
  • I opted not to install the standard unglazed, mat-style solar hot-water panels because solar electric (photovoltaic or P.V.) panels powering a heat-pump water heater are more cost effective. Plus, the net-metering agreement with our utility allows us to accumulate a credit for excess electricity generated on sunny days so we can use that electricity on cloudy days. With solar hot-water panels you are out of luck getting warm water on cloudy days and there’s less opportunity to store the excess from sunny days. You can learn more about the combination of photovoltaic panel and heat pump water heaters in this blog post.

Instead of installing solar panels only to power your swimming pool, you are better off installing solar panels for your house and installing a few extra to power your pool. Instead of installing solar hot-water panels, I covered the roof of my house with a 15kW array of 46 Sunpower 345W panels and covered the roof of my garage with a 13kW array of 40 Sunpower 327W panels. That sounds like a lot of solar panels, but I make money on every solar panel. Solar panels are cheaper than they have ever been and are heavily subsidized. My total investment in solar panels, after the tax breaks and subsidies, was about $42,000. My savings are over $5,500 per year on electricity bills. My investment in solar PV panels produces power at about 7 cents per kilowatt-hour (after tax breaks and subsidies). That’s about one-third of what I would have paid my electric utility company here in Massachusetts, which is now 23 cents per kilowatt-hour. The solar panels will pay for themselves in about 7 years. But the most important economic measurement is the internal rate of return (IRR): 13% per year after taxes.

My overall investment (after tax breaks and subsidies on the solar panels) for the entire zero-energy retrofit of my pool was about $10,000 and I am saving about $3,000 a year on propane and electricity bills. The investments pay for themselves in just over 3 years and the IRR is about 44% after tax. That handsomely beats the growth of the Standard & Poor’s 500 stock index of 11.7% over the last 43 years. It also beats the return on investment we achieved by going zero on our house, which was about 15% per year. Additionally, the S&P return is before tax and before fees whereas my return is after tax and with no fees. Finally, financial markets are risky especially when seeking the highest returns. The risk associated with energy efficiency improvements and solar are usually nil and are will increase with inflation.

Much as I found with going zero on our house, the conventional wisdom on going zero on a pool was often wrong and did not make financial sense. I found that using the standard financial evaluation process used by companies and investors together with some simple experiments cut through the myths. So I think I’ve found a way to both go zero and make money. This represents an inflection point for the zero energy movement. Going zero is no longer like buying an expensive lifestyle statement for your house or pool. It’s cold, hard cash in your pocket, proving you can save money and save the planet!

You can read more about my experience and a summary of my books, Zero Carbon Home and Zero Carbon Pool, detailing how I did it all

David Green lives and works in Dover, Massachusetts.