Net Zero Energy Homes

How-to: Net Zero Energy Home

By David Fairley, homeowner

Fairley’s Family Folly: My Quest for a Net Zero Energy Home in San Francisco

By 1990, the writing was on the wall. Global warming was happening and humans were the cause: pumping billions of tons of CO2 into the atmosphere. It was going to wreck the planet unless we did something to stop it.

Being gung-ho environmentalists, my wife and I decided to try to do our part. In 1991, we sold our car. Our house is in the middle of San Francisco, so it was possible to live, even raising a son, without one. 

We also put serious effort into reducing our electricity consumption. We converted all of our lightbulbs to compact fluorescents, paying a lot for the clunky U-shaped, flickering bulbs available then. We got rid of a number of phantom loads – appliances that suck energy all the time, like our Dustbuster - and we unplugged others. We even disconnected our doorbell and replaced it with a hand bell.

Our big purchase was a Sun Frost refrigerator; it cost $1,900, which was a lot back then, but it was more energy-efficient than any refrigerator produced by the big companies like Frigidaire or Whirlpool. And it still is. It was a great purchase and it has more than paid for itself.

In 1997, we were the first San Franciscans to take advantage of the newly passed Net Metering legislation that enabled installation of solar panels tied into the electric grid. Occidental Power of San Francisco installed a small (less than 1 kw) solar system on our roof. In 2006, we complemented these photovoltaic panels with solar thermal panels to heat water.

Zero Net Energy

All these changes had reduced our energy consumption, so we started thinking about taking this to the next step.  We felt good about what we had achieved, but could we do more? Could we actually reduce our impact on the planet to zero even if it is a 100-year old house in downtown San Francisco? We didn’t know if it was possible, especially for a building that survived the Great Quake of ’06. Sure, a new house might be able to be super-efficient and generate its own power, but this old building was a different animal.  Initially, I only had a vague idea what I wanted and even less clarity around how to go about it. I first looked into companies that make energy retrofits of homes. But generally, these involved more energy-efficient appliances, weather-stripping and better windows, all of which we’d already done. We were looking for a company that was cutting edge, innovative while being creative and very comfortable navigating very new waters.

I held off for a while.  Then a (dim? fluorescent?) bulb went on – “zero net energy.” That sounded good. As I had no idea how to go about it, I Googled it and, lo, there was someone living in nearby Pacifica who was a recognized expert.

I called and was delighted that she was interested to help. First off, she asked me what I meant by zero net energy. Apparently, there are several ways to define it – do you literally generate as much energy as you consume, or do you think of it on a dollar basis, where you pay zero at the end of the year? Are you talking about all household energy, or just the electricity, and ignoring the natural gas? I realized I wanted a house that would be appropriate in 2040 – one that produced all the energy it needed and used no fossil fuels. In other words, we wanted an all-electric house that produced as much electricity as it consumed over the course of a year.

She put me in contact with several experts on different aspects of the problem. What she and they made clear was the importance of making the house snug and, in particular, sealing the attic so that the warm air in the house doesn’t wick up through the roof, sucking cold air in from the outside. I always thought that insulation was more important, but it turns out that even with a well-insulated house, you can still lose significant energy through this ‘stack-effect’.

All this was great in theory, but I didn’t feel competent to coordinate the whole thing myself, and neither the Pacifica expert, nor the specialists, knew anyone locally who could do the job. It took more floundering around before I chanced on someone through a referral who turned out to be an ideal contractor for the job, Eric Sweet and his company, emeraldECO. He shared my desire to do right environmentally, had the curiosity to look for new approaches and products, and he could actually do the work.

Our house may have been especially challenging. Built in 1905, it still had plastered walls, some of these with holes and cracks. The house had an old leaky furnace that wasted a great deal of heat. The gas backup water heater was old and inefficient. The changes made to the house over the last century left us with many significant holes in the floor and the ceiling. The electrical system still had fuses instead of breakers. We had replaced some of our windows with double-glazed, but some were still the single glazed, leaky ones from the original house. This was going to be a project!

Eric visited our home in June of 2016. There were certainly lots of areas that needed attention, but he brought his PMP Project Management experience with him. Before anyone lifted a hammer, we needed to know how the house performed and we needed a detailed plan for how to reach our goal. The initial step was a blower door test. This is a 3 hour procedure that uses a specially calibrated fan to pressurize the house and precisely measures how much air escapes through the many leaks. This test established a baseline level of leakage. We planned to perform another blower door test at the end of the project, and it would give us accurate info on how well we were able to seal up our leaky house. This test also enabled us to get a rebate from Energy Upgrade California. 

In addition to measuring the air flow, emeraldECO brought their Infrared Camera and took pictures of certain areas around the home. This type of camera can ’see through’ walls, floors and ceilings – allowing us to easily determine where air was flowing into and out of the house, as well as what spaces had –and didn’t have – insulation. An eye opening experience indeed! In conjunction with the test, Eric and his team performed a detailed analysis of our power consumption. They logged into our PG&E account and were able to download our Gas & Electrical usage for the last ten years. By analyzing this stack of data and combining it with years of experience, Eric & his team were able to determine key areas where we were using more power than we should be. This process took time, but it was invaluable. For any project, it really helps immensely to gather all the critical information, analyze it, and then put a plan in place to achieve the target. 

The plan in short:

· Remove the old solar system

· Remove the roof (that needed to be replaced anyway)

· Remove old insulation

· Fill attic with spray foam

· Seal up under the house with spray foam

· Replace the entire electric panel

· Remove gas furnace

· Remove gas water heater

· Fix and upgrade the Solar Hot Water System

· Install a new bi-directional heat pump to heat and cool the house

· Seal up many gaps and cracks in the house envelope

· Upgrade many CFL bulbs to LED

The original solar PV system was still functioning after 20+ years but it was old technology and we were ready for a modern upgrade. Occidental Power came out and removed the old system – it may well be in a museum now! Eric’s team contracted with a roofing company and they removed the old roof. emeraldECO then was able to remove all of the old insulation and debris that was in the attic space. This allowed us to install new efficient bath fans and his team wired up ceiling lights – something that was not typically part of 100 year old houses. In order to maximize the insulation in the tight attic space and also prevent air movement, we needed to remove all of the old knob and tube electrical wiring in the attic. Again, emeraldECO was able to make all the electrical changes that we needed. Following that, the entire attic was filled with spray foam and the leaky basement and crawl space area were also sealed with spray foam. For years, cheaper fiberglass has been installed in these types of spaces, but nothing beats spray foam for its ability to stop air movement and provide superior insulation at the same time. 

Once the new roof was installed, Occidental put on the new solar system, and the old Solar Hot Water panel was re-installed on the roof. For over a year, the solar water heater had not been operating properly so it was going to need some attention. Ironically, just as the project got underway, Eric’s team noticed a trickle of water leaking out of our old gas-powered backup water heater. Since most water heaters are made out of regular steel (and not stainless steel), they will eventually rust and leak. The moment it starts to drip, it is time to replace it. Some water heaters might drip for months, while others will suddenly and catastrophically fail. This can cause very expensive water damage, but since nobody wants to go for weeks without hot water, you typically get whatever water heater is ‘on the truck’. 

emeraldECO jumped into action. This was not the ideal order of the project as it was planned, but we were living in the house throughout this process and hot water is one thing we can’t live without. Eric quickly removed the leaking gas water heater, drained and tested our solar storage water tank and moved this unit into its new position. He reconfigured all of the plumbing (not a trivial task, mind you), replaced several sections of aging pipe, installed a hot water recirculation system to provide instant hot water and save on wasted water, and he wired up an electric backup system for hot water when the sun didn’t provide enough hot water. Eric installed a new Solar Thermal pump and controller to get the sun-powered hot water flowing. 

It’s important to be able to measure and quantify energy usage, so emeraldECO  also set us up with several smart home controls that we use to program and manually turn on and off the hot water recirc system that they designed as well as the electric backup water heater from our smart phones. This helps us to keep our energy bills lower by not running these loads when California Time of Use electrical rates are highest. 

New Electrical System

For years, we had all used Natural Gas to heat our homes, heat our water, power the clothes dryer and cook our food. Gas was cheap and it seemed to work well. Occasional attempts in the 1900’s to use electricity often resulted in high energy bills. But times have changed. Gas now comes from fracking operations, which are damaging water aquifers across the country. Gas leaks and unintended explosions are becoming more frequent.  In fact, during the initial blower door testing, it was discovered that our house had multiple leaks in the old gas lines. Gas is primarily Methane – a potent, climate changing greenhouse gas that is 25 times more damaging than Carbon Dioxide – and let’s not forget San Bruno natural gas is highly explosive and extremely dangerous. We still live in a high risk earthquake zone. When the earth moves, gas lines break, and fire is usually the result. The price of gas is climbing too – more than doubling in the past 10 years and will more than double again in the next few. It was becoming increasingly clear that it was time to shut off the gas line and go all electric. 

The house had a rather old electrical system that was never designed for modern electrical appliances, so we would need a new panel. emeraldECO brought in a local electrical contractor to do the work. Eric spec’ed all the requirements of the new electrical system – larger panel to handle the new solar system on the roof, a new line to the induction stove, electrical wiring to the laundry room for the new clothes dryer and wiring for the new heat pump out back. 

We bought a Kenmore induction stove/convection oven and a Whirlpool heat pump dryer. 

Heat Pump

Eric researched heat pumps and vendors. We intended to have the new heating system in place before the winter, but as often happens, there were many surprises throughout the process that caused small delays and in the current economy it can be tough to get everyone working on our schedule. We finally decided on a Carrier heat pump (yes, Trump’s Carrier). The cost was on the high end because, naturally, we wanted it to be highly efficient, but also because we wanted it to be quiet – lest we alienate our neighbors. Schmitt Heating installed the system. It was up and running early February 2017. We had a few months without any central heat, so we borrowed a few space heaters and wore sweaters. Our electrical consumption increased during that period. After the heat pump was installed, emeraldECO did a site visit to determine that everything was running smoothly and discovered our back-up system - the electric resistance backup heating element - was actually working for multiple hours each day, when it shouldn’t be. He cleverly re-programmed the controller and it has remained off ever since. The heat pump has operated very well and is very efficient. Around this same time emeraldECO brought in a local company that could install matching double-pane wood windows that were comfortable, efficient and would keep the look and feel of the house. Eric also was able to seal up several older windows that we didn’t want to replace. 

How has it worked?

Overall we’ve been extremely happy with the results and feel good about our choices. The heat pump works great, is quiet and uses little electricity as advertised, and has the additional benefit that it also cools the house when we sin and use it on some SF’s few hot days. Most of the time the house is comfortable without heating or cooling thanks to the thorough sealing+insulation that emearaldECO completed.

The induction stove has also been a pleasant surprise. It has several advantages over a natural gas stove. My wife likes it because it’s safer. The stove works by jiggling the molecules in the pot – it doesn’t have burners, so the stove only gets hot only where the pot has heated the stove surface. I like that it’s super fast. It can boil 2 cups of water in under a minute – much faster than an electric kettle designed just to heat water. And that it’s energy-efficient, more than a regular electric stove and even a natural gas stove, because both of these waste energy heating the air. It’s not perfect. Only certain pots will do – we were able to use some of our old ones but needed to buy some new ones too. You can tell with a magnet: If it sticks the pot it’ll work. I’m the cook of the house. I expected to taste a difference in the food the stove cooks, but I didn’t. You just have to be careful because water starts to boil fast and furious before you know it.

The heat pump dryer? Well, it’s very efficient. It uses less than half the energy that a typical electric dryer would. But it’s also loud and it takes fore-e-ver to dry stuff. Clothes do come out really soft, though.

The bottom lines

The figure shows the amount of net daily energy our house has used over the last 30 years. Natural gas consumption was converted to kilowatt-hours (kwh) to facilitate comparison with electricity.

We spent 25 years mostly focused on reducing our electricity consumption. From 1989 to the early 2000s we’d sweated to reduce electricity consumption by 2/3. Just turning down the thermostat cut our total energy use more.  The improvements that emeraldECO implemented got our net consumption down close to zero. It was 5 kwh/day in 2017 and 1.5 kwh/day in 2018. Almost zero! As Maxwell Smart said in Get Smart, “Missed it by that much.” But, based on my calculations, if climate change heats the Bay Area by 2oF, we’ve got it!

Our panels put out about 20 kwh/day on average, so the reduction in consumption from the house sealing and insulation, the heat pump, and other efficiency measures cut our energy use to about 20 kwh/day from the approximately 40 kwh/day we were using in 2013-2015.


If we had it to do over…we’d still do it. It’s a real investment in the future and it’s made our lives pleasanter.

It’s also been an education. California’s Title 24 will require all new homes built to be “zero net energy” starting in 2020. But this applies only to electricity. Natural gas can still be a large energy consumer (and Greenhouse Gas/GHG producer). In any case, the amount of new housing is small compared with existing homes, which are overwhelmingly not energy-efficient. This represents a substantial fraction of our total GHG emissions [nice to have a good reference here]. 

What I’ve learned is that retrofitting a house to be ZNE is hard, in part inevitably so, but also in large part because there are many boulders in the path to ZNE that could, and should, be cleared away. The first is just making information available about the value and possibilities of making your house much more energy-efficient and climate-friendly.  Second, and probably most importantly, we need more people like Eric Sweet and emeraldECO who combine technical know-how, a willingness to innovate, and the practicality to look at what’s possible and appropriate for a given house. ZNE retrofits aren’t one-size-fits-all; existing houses are unique and require individual solutions and informed, dedicated and competent people to figure things out.

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