A heat pump for a greenhouse?

Q: What about installing the heat pump in a greenhouse? Maybe removable for the summer.

A: I have not done this in a greenhouse  but I think it is a good idea. Effectively I have done this by bringing plants indoors in the fall and keeping them in our sunroom. The sunroom receives a very small amount of heat from our house heat pumps (it is at the end of the ductwork) but, using LED grow lights (powered by my solar panels) I was able to get red ripe peppers at Christmas. They tasted great!

I have no insulation in my walls

Q: So your walls are insulated with 4″ fiberglass batting?  Earlier I had the impression that your house has no wall insulation.  What about homes much older that ’74 with NO wall insulation? 

A: Yes our house has 2” by 4” stud cavity walls filled with fiberglass. The only answer, John, is to get wall insulation. You can do this without having to remove and replace all your siding by blowing in spray foam or dense packed cellulose from the outside. This requires drilling holes in the siding but these can be patched afterwards or a small section of the siding can be replaced. If you have no insulation today in your walls you are losing money through the  walls the way that water runs through a sieve. 

Should I insulate a crawl space?

Q: What about sealing/insulating crawlspace walls and plastic on soil to insulate crawlspace? 

A: Insulating walls in crawlspaces is a very good idea. It is a lot easier to insulate the underside of the floor than to try to insulate the soil because you can just push fiberglass in between the joists. 

Response: Hi David, Thank you for replying. I had noticed condensation problems in the crawl space due to uninsulated HVAC ducts sweating in the summer. Venting the space in the summer allows humid air into the space where colder pipes sweat badly. Researched this and found a revised opinion on what to do with crawl spaces. The advice I read (sorry, no references) was to seal the wall vents, insulate the inner walls and cover the soil base with heavier plastic. Wetness due to water inflow may require drains and a sump pump. I am moving in that direction (DIY) having previously insulated the joists under the floor and ducting but still experiencing the moisture issue. Thank you again for sharing.

Reply: It sounds like you have two sources of moisture in the crawl space. The vents and the soil. I think you will need to deal with both to stop the water condensation on the HVAC ducts when the AC is running. Sealing the vents will help but without dealing with that wet soil it will probably not be enough. I think the plastic sheeting on the soil will help, but it is a band aid, not a cure. The real question is why is there so much moisture in the floor in the first place? Is the ground water high near you? If not, are your gutters in good shape? Overflowing gutters can put a lot of water in the soil right by the house and this will wet the soil under the crawl space. I have seen this and repairing the gutters (I put a perforated metal plate on the  top of the gutter to keep the leaves out) and replacing split downspouts (and adding extenders to the bottom of the downspouts to keep the water away from the foundation), worked. I also sealed cracks in the basement concrete with a can of spray foam – cheap and effective as a water barrier as well as an air barrier. Once you have solved this problem, I think replacing your hot water tank with a heat-pump hot water tank will help. It will not only cut your bills and carbon footprint but it will dehumidify the basement air too. Once you have done all this, I would insulate the HVAC ducts, but if you don’t deal with the moisture first, you will risk getting dampness and mold on the insulation.

Yours sustainably,
David Green
Make money by cutting your home’s carbon footprint to zero. We have done it. 

What insulation should I use in a stone basement?

Q: What about solid stone walls/floors and insulation? Ensuring breathability.

A: Probably the best solution here is to use a product like rockwool boards for insulation. They are breathable so you reduce the risk of mold behind the boards. They are also fire proof, unlike most foam insulation. It is probably a good idea to also install a heat-pump hot water tank. Unless you have very high electricity prices these are cheaper to run than heating water with a boiler, even one powered by natural gas. If you use solar panels to generate your electricity it will be much cheaper than heating your hot water with natural gas. They also dehumidify your basement which will reduce the risk of mold. 

If you sell your SREC are you double counting the carbon footprint reduction?

This concern was raised by a person who attended one of my Zero Carbon, Zero Bills webinars. Here is the question and my answer:

Queation: Hi David, I really enjoyed your talk last week on your zero carbon adventure. I did have a question, which didn’t get answered. I have a friend that works at National Grid and she told me if you sell your solar RECs, which I believe you did, you can not claim to be carbon free as those rights go with the REC? After your talk, I went back to her and she felt that this was definitely the case and that you would need to buy RECs to offset the ones’ you sold, to make the carbon free claim and you should also tell people you sold your RECs and brought other ones. 
Just wondering your thoughts on this 
Thanks and thanks again for a wonderful talk. I plan to share this with some folks 

Hi Rob, I have occasionally heard this perspective before and I think that reasonable people can disagree on this one.

I have two concerns with your friend’s perspective. 
The first is that I have not counted either RECs or SRECS in my calculation of my carbon footprint. I have actually cut my carbon footprint to zero by using the fab four, it is Eversource that is claiming it has cut its carbon footprint when it has not done so. So, I think it is more accurate that I say I have cut my carbon footprint and it is Eversource that has been allowed by the state regulators to claim it has cut its carbon footprint (by buying my SRECs) when it has not done so. But I have genuinely cut my carbon footprint and it is zero. The SRECS have not been counted in any part of my carbon footprint reduction. My carbon footprint is zero because I no longer burn heating oil and I generate all my own electricity, including that to heat my house, using heat pumps, powered with zero-carbon solar panels. 

My second point is that, where I do count the SRECs is in the financial subsidies. I genuinely receive this cash so I do not think it is right to remove it from the financial forecasts. There are many subsidies involved in going zero, from net metering and zero-interest loans (which are essentially funded through all of us in MA paying the highest price price for electricity in the US, other than Hawaii) to federal and state tax credits. SRECs are calculated per kWh I generate, the federal tax credit is calculated based on the price you pay for the solar system you install. Why should one subsidy not count just because it is based on kWh generated rather than on the price of the solar system? SRECs were replaced with SMART in 2018 and so it is only owners of legacy systems that receive them. I do not see why a subsidy should be dismissed for those who installed systems prior to 2018 but should be allowed for those who installed systems after 2018.

In my opinion, SRECs are just a form of subsidy, paid from a regulated utility to an owner of solar panels, which means they are ultimately paid by all electricity customers. This is essentially a regressive form of taxation because it takes money from everyone who uses electricity (including poor people) and funnels it to those who can afford to install solar panels which tend to be wealthy people or investors. I think this is rather unfair, but I do not make the laws Rob, I just abide by them.
Please share these thoughts with your friends, I am interested to hear what she says. 

To preview the book Zero Carbon Home click hereTo preview the book Zero Carbon Pool click hereTo see a 3 minute interview of David Green by NBC Boston anchor Joy Nakrin click hereTo see the T-shirt with a lifetime carbon footprint of zero click hereTo see the next live webinar by David Green click here
Services by Zero Carbon® LLC – Combatting Global Warming, One House at a Time™

On Jun 19, 2020, at 2:31 PM, greenrob@aol.com wrote:

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 www.eventbrite.com 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 dgreen@greenzerocarbonhome.com

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