This past Sunday, July 12, the San Francisco Chronicle printed a very nice article about the “green house” in Tiburon. The remodeling of this house has been a project for me for the past 2 years.
About 3 years ago we purchased this house from Matt Masson, a local realtor. Matt and his family had lived in the home for the previous 28 years. Boy was it clear that he had an eye for real estate. This spot was beautiful and the overall home design with its positioning on the hill side and it beautiful decks were stunning. Matt had even been able some years ago to purchase the open space next to the home so that the views of the bay would never change.
[First lesson – if you ever can purchase property from someone who is a real estate agent and who has lived and loved a property for 10+ years, do it, as this will be a very special place. Thanks, Matt and Roberta]
The article has generated many, many thoughtful criticisms, questions and ideas. This essay will attempt to answer some of these.
First of all, the home is located in a beautiful site in Tiburon and as such it is not an inexpensive home. Homes in this area cost in the $1.5-4M area regardless of their age, upkeep or green features. California real estate, especially in the San Francisco Bay area is among the most expensive in the USA.
This part of the USA is also admittedly one of the very easiest for someone to build a house that achieves net zero energy use. The reason is that temperatures here are never very cold or very hot. In summer, like today, while it is over 100F about 50 miles to the east in Davis, CA and in the 90s 40 miles to the south in San Jose, it is only in the lower 70s in Tiburon. In the winter, because we are virtually on the bay and this part is close to the Pacific Ocean, we rarely see temperatures at night below 45F.
Knowing this, we purchased the home and then researched the area and its characteristics. We also looked over past electricity and gas bills for previous years so that we understood how it performed when it was purchased.
There were many obvious elements that became part of the remodel –
- the original structure had no insulation – so we insulated all of the exterior walls and ceilings including ones that required us to put in faux ceilings to create a space for the insulation
- all of the glass windows and sliding glass doors in the original home were single pane – we changed all of these to double pane, low E, argon filled windows and doors.
- the underside of the home had no insulation and while solid, we felt drafts coming up from the floor in those portions of the house – so we added both insulation and we sealed the home as well.
- the home had mainly incandescent lighting and we made many lighting decisions where we could use LEDs and CF style bulbs. Overall the home made extensive use of LED lights that should not need replacing for the life of the home in many cases and which are VERY efficient.
- the home was heated by gas furnaces and because my calculations showed we could put up sufficient solar photovoltaic panels to cover our needs, we upgraded the furnaces to be electric (but actually dual source – gas and electric) heat pumps. (this choice will be talked about more in a bit)
- the hot water in the home was heated in hot water tanks separately for the main home and the apartment – we decided to put in a single solar hot water system with tankless gas back up and share this hot water between the main house and the apartment.
- Marin County, CA has some of the most urgent water saving programs in the state – we decided to see how much of an impact we could make there by collecting rain water in the winter rains and using it throughout the rainless summers we have to water the gardens of the house. At the moment it is not possible for us to use this water inside the home but this could change.
- Lastly, I like to swim but swimming pools are perhaps the largest and most energy wasteful structures so I researched this and opted for an endless pool with solar heating.
The outcome of these main home elements was that we were able to cut our natural gas usage compared to the previous home by more than 90%. We did not get to 100% because we sill cook with gas (could have gone with an induction stove top but did not know of it at the time) and we still make some hot water during weeks of rain and clouds in the winter. Nevertheless, our decision to move to solar produced hot water and electrical heat pumps has proven successful in reducing our carbon footprint more than many home designs.
Another outcome was that we seem to make much more electricity than we need in the summer but this situation is like the fable of the “Grasshopper and the Ants“. In our case it means that we will need to show an excess of perhaps 3000 KW-hrs for the summer time so that when we turn on the heat pumps we can still break even. We have some advantage as we make much more of the excess power at “peak” times and that power is worth more to PG&E and us so that in the winter when we pull it back at off peak times we can pull more power than we sold.
Last year when we showed the large electrical excess for PG&E on the electrical side the heat pump systems were not well set up and would often default to natural gas instead of electrical energy consumption. we fixed that in mid-January of 2009 and now this coming winter we will have to see how well we do on the overall balance.
Probably our most aggressive experiment was the decision to build 15000 gallon cisterns under the home to conserve rain water and use it in the summer. The tanks were nicely filled by the winter rains and it seems that as our draught tolerant landscape takes hold that we will be able to water this with the rain water we captured. Still the actual monetary savings today will not really justify this as an investment, I believe.
Nevertheless, the aggressive design of this system has helped me think through how systems like this could be designed to be more cost competitive. I see grand plans in many places like Singapore and the middle east to invest in large scale desalinization plants but it is clear to me that careful use of water that we naturally have is a much more cost effective way to engage the water conservation problem. Together with a partner in Indiana, we are working on a novel product in this area.
The home serves as a laboratory for me in “Clean Technology”. Each of the energy, water and other systems in the home are monitored and data is continually collected and stored on a server in the home. This data allows me to make further changes from the initial design to improve its overall performance. Sometimes the installed systems did not perform as was specified and through the monitoring we were able to teach the installers and equipment suppliers how to improve their products or services.
A word about overall costs since that was one of the recurring themes in comments on the web from the SF Chronicle article. Our solar panels were purchased at a time when they cost about $4.50 per watt and then another $2.50 per watt installation. Today the panels cost less than $2.75 per watt! So costs are falling fast. Still at the cost we paid, I believe our payback is more than 10 years unless you include the rebates. Solar hot water for both the showers and heating the pool were 2 very cost effective systems. The pool system should pay for itself in less than 2-3 years. The home hot water in 5-7 years. Overall for a home in this area of California the “green” elements we installed were certainly less than 5% of the overall remodel if you do not include the cistern experiment. If you do then this perhaps doubles to 10%.
Finally, i have realized so much from this home in Tiburon and now am starting a similar but much more challenging project on my home in Indiana. There the mix of power and savings is very different. Indiana has very cold winters and very hot humid summers. The system there will have much more focus on solar heating so that the renewable energy we capture will be more on the heating side but still very substantial on the solar PV side. Again, we will have monitoring systems. But there we also expect to have to innovate in the design of the overall control systems. Look for patents and new system elements to arise from that design! FYI, the Indiana systems are purchased using the lower cost system elements today and that system cost around $60K with the costs split 50/50 between solar thermal and solar PV. In California the system cost was 70% PV and 30% solar thermal.
In conclusion, we are so grateful to have found this house and were able to purchase it from the Massons. Without that starting point and original design, we would not have been able to have been so focused on our “green aims”. The comments in the Chronicle made the home seem shabby and that was certainly not the case! Next, we were able to work with helpful people from many different disciplines and different technology suppliers and that made the project intellectuallly challenging and fun. Lastly, the decision to include some technology that was pretty aggressive – for example the water storage cisterns – are ones that we still do not regret and we will track and see how they perform as the world’s climate continues to change!
Write to me if you have more questions, firstname.lastname@example.org.