Monday, August 22, 2011

Retrospective on System Remodel

This post is a retrospective on what I think I've learned by the system remodel we did on our house over the last year. First a brief review. Our goals were to reduce the carbon footprint of the house as much as possible, hopefully to net zero energy, primarily by somehow reducing gas usage for space heating and hot water. We started out with a solar thermal hot water system that completely removed gas usage for heating in summer but required gas for an old tank-based gas heater in winter. We succeeded in completely eliminating gas usage for hot water though an on-demand electric hot water heater as backup, offset by solar PV. We did not succeed for space heating, however. Our original plan was to install a geothermal heat pump and also offset as much as possible of the geothermal heat pump with solar PV. As it turned out, we abandoned the geothermal heat pump for reasons discussed below. We did not have enough solar resource on our roof to offset the electricity usage anyway, or, at least, we could either offset an electric car or the geothermal heat pump but not both. We are able to offset the on-demand electric hot water heater, but, in the end I estimate that we will still draw around 1000 kwh from the grid with an electric car and use around 250 therms of gas for space heating and cooking (cooking only amounts to around 1 therm a month).

Of course, whether we really succeeded in reducing our carbon footprint so much remains to be seen, I'll be measuring our energy usage over the next year (including some new measurements on exactly how much solar electricity we are generating thanks to the new Tigo MPP balancing system and monitoring tool). But I think we did learn some important lessons about the process of green remodeling and the technology available today. Below, I've listed some lessons I think we learned from our system remodel.

Geothermal heating and cooling systems are a ripoff in Northern California
We paid $9K to get a design for our geothermal system before pulling the plug. Cost was one reason we decided not to do it. The entire system was originally spec'ed at $60K and it surely would have grown by at least 20%. Recently I spoke with a couple who moved into our neighborhood from upstate New York. A good friend of theirs runs a geothermal contractor there and they said that $9K was how much one would pay on average for an installed system, and the geothermal contractor didn't need any expensive design. Why is geothermal so expensive in northern California? Hear are some speculations:
  • There are only three geothermal design firms in northern California, one in Santa Rosa, one in Sacramento, and another one I know not where. With that little competition, they can charge as much as they want.
  • Given the more complex geology of California, the state needs to regulate it more and drilling is more complicated than in New York. But 10X more complicated?
  • Geothermal HVAC systems are priced as a premium product, for $5M houses in Woodside and not for your average - but still quite pricey by standards of the rest of the country - house.
It seems like there is a real market opportunity for operators in the rest of the country to expand into northern California and start taking some business.With a 10x price differential, a contractor could move in and undercut the competition. Even better, a nationwide contractor (if such a thing could ever exist) could get economies of scale and achieve even lower prices (but see below for caution).

Geothermal technology today is designed for cold climates and is not well integrated with newer HVAC technologies like HRV
The system they were proposing to put into our house had a huge 80 gallon buffer tank connected directly up to the ground loop. The system was designed so that the heat pump would run flat out, cooling or heating the buffer tank until the temperature was uniform, then shut down. Though they never really told me why the buffer tank was needed (despite my asking), I suspect it was because the pump could not withstand intermittent operation. If there were no buffer tank, in our mild climate, the pump would end up going off and on frequently. Since it would have had to start pulling 3 x 300 ft. columns of fluid every time it started, the pump would probably have worn out sooner.

On top of that, we would have needed a whole second air handling system and ducting, parallel to the HRV ducting we were installing, for the air conditioning (we have hydronic radiant for heating). I asked why the second ducting system was necessary and they just shrugged. Our house is designed in such a way that it would have been impossible to fit in a second ducting system. Fitting the HRV ducting was a challenge in and of itself. The original forced air heating had ducting under the house, but that was removed when we had radiant installed. It simply isn't possible to find an integrated HRV/geothermal air handler.

But recently I ran across an article on ductless air conditioning systems. The article was written with air source heat pumps in mind, but it could equally well apply to ground source heat pumps. The basic idea is to run the refrigerant lines from the heat pump to small air handlers (basically fans) in each room. Since the refrigerant lines are much smaller, this would have worked well in our case. We could have run two lines to the two HRV systems on opposite  sides of the house, and installed heat exchangers there. Except the HRV systems aren't designed with outside assistance for heat exchange...Oh well.

Embedded Global Warming Potential (GWP, Climate Change Potential, CWP?) does count
When I started the project,  I wasn't convinced the embedded GWP was such a big issue. By this I mean the carbon equivalent embedded in the products or processes used to do the work. My focus was reducing the carbon footprint of the building over the long term, since I figured that the building would  be around much longer than I will, and reducing the carbon footprint over that long a time period would result in big gains. What I missed was that some treatments with excellent carbon footprint reduction potential have such large GWP themselves that they can equal or exceed the carbon footprint of the carbon-based energy use they eliminate. Closed cell foam is an example. While I probably would put closed cell foam in anyway if I were doing the job again, I think I might have put in less (just the ceiling for example) and done the rest in open cell foam which has far lower GWP potential (but see below).

Architects, even those claiming expertise in green building, are by and large mostly interested in aesthetics and not particularly concerned with the detailed engineering and fact-checking necessary to achieve really energy-efficient buildings
We originally selected our architect because one employee of the firm was involved with me in a local city-wide sustainability initiative, and also because I had seen a house designed and built by the architect's firm that had a very high Green Point rating. This employee left the company around a month after we started the design process, and the owner of the firm, who we continued working with, exhibited less than diligent attention to our remodel. He tried to convince us of dubious enhancements such as a solar hot air heater. When we need heat here in northern California, it is usually raining and cloudy. Such technology is more appropriate for climates like in Boulder, Colorado, where they have very cold but sunny days in winter. He also routed our HRV ducting through uninsulated attic space, which very likely will substantially reduce the amount of heat recovery we will get. From a practical standpoint, this was probably the only way to get the ducts routed, but he could at least have then recommended we insulate the ducts with additional insulation afterward. As it was, I didn't realize the error until the end of the job, by which time, we were so fed up that I decided wait and install it myself later if heat loss from the ducting becomes an issue. I had to spend a substantial amount of time researching energy efficiency technologies myself on the Internet, because the architect simply disappeared after drawing the initial plans. After that, the project manager (aka general contractor) and his assistant took over, and they were even less knowledgeable and interested than the architect. On the other hand, I think if we had been building a 3000 sq. ft./$5M house from scratch in Los Altos Hills, the architect would have been all over it, with passive solar, etc., and we would have been extremely satisfied with the result.

So I have the impression there is a kind of market hole here of professionals who are both knowledgeable about how to do plans for extensive remodeling construction and interested and engaged enough in the technology of energy efficiency and  renewable energy that they are willing to do the detailed fact checking necessary to ensure that a project accomplishes its energy reduction goals. I would have appreciated some discussion of choices, with some detailed analysis of what they could accomplish for my home. I got none of that, except as I calculated it myself. There is now software for doing these kinds of calculations but so far as I can determine, the architect we worked with didn't have access to it, or, if he did, had little interest in using it on our job.

Construction "professionals" are not interested in green technology and energy efficiency, even when told that energy efficiency is the top priority, since they have been so ingrained to simply look at cost.
We constantly ran up against this problem with our project manager. He was always looking for the lowest bid came from a subcontractor that knew little or nothing about green building. For example, I specifically told him that I wanted a 7 kw system with MPP balancing. His assistant came back to us with a collection of bids from small contractors for systems sized at around 5 kw, and none of them had MPP balancing. The best I could get was one guy who proposed a 6 kw system using microinverters (I've discussed the problems I see with microinverters here).  At least, this guy was a professional. One of the bids was from a nonprofit who sends "volunteers" up on the roof. Considering that we had a roofing professional fall from our roof and injure himself, I wanted nothing to do with that one. The reason they came back with these systems was because they were trying to hit a cost objective rather than the energy generation specifications I set out for the project. I finally had to tell the assistant to call Tigo and ask them for recommendations about solar contractors. That's how I got connected with REC and they did a fantastic job.

Neither the project manager nor his assistant kept a close eye on the subcontractors. They never visited the job except to let the subcontractors in and lock up at night. Of course, I know that contractors are usually managing 3 or 4 jobs at once but there were a couple times when we had a specific green technology installation, like with the HRV or the thermal bridging treatment, where serious problems could have been avoided if the project manager had shown more interest and diligence in actually checking up on what the subcontractors were doing during the job rather than leaving it up the the manager of the company doing the subcontracting.

Most construction technicians know nothing about green building techniques and care even less.
After all, they are getting paid by the hour, and, unlike professionals, they don't take much pride in their work. It is just a job (note that this was not always the case, people in building trades used to take much more pride in their work 50 years ago). A friend in construction told me that a survey showed something like 60% of most people working in construction today have had a substance abuse problem,  and that the overwhelming majority did the work because they didn't think they could do or couldn't do any other. And, to a large extent, I believe it is not the fault of the people in construction, I'm sure they would in the end rather feel good about the work they do. Construction technicians have no incentive to upgrade their training, so many are operating on knowledge obtained years ago, which doesn't reflect the latest results of building science. There is nobody paying them to take classes in the latest technology, and, because they really  don't have much interest in their jobs except to earn money,  they're not about to spend any time or money trying to upgrade their skills on their own. I believe this is because, in the last 40 years, the increasing right-wing tilt to the American political and social scene has devalued the contribution and importance of skilled labor at the expensive of massively overcompensated executives. Even though many construction technicians earn good salaries, they don't take much pride in their work because society doesn't really value it.

In my opinion, this point is the most serious problem for politicians who propose government programs to increase energy efficiency in the existing housing stock (commercial buildings are different, there a clear bottom line case for efficiency and people being paid to oversee the process with the interests of the building owner at heart causes better results). Even if the money were there, the knowledge simply isn't. I checked the curriculum at our local community college and there are only three programs for people in the trades to upgrade their skills, with only three or four courses per program. There are no programs in solar PV or solar thermal installation, proper building insulation, or HRV installation. If you want to learn about solar PV installation, you need to drive to Hopland and take courses at the Solar Living Institute. The Solar Living Institute has some excellent programs, but I don't understand why the knowledge for green building isn't being taught more widely. If we really want to achieve an 80% reduction in carbon footprint of our society by 2050, we have to work with the housing stock we have.

So there you have it.

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