The Conduit is In

On Wednesday, I came home at noon to the happy sight of a PG&E crew hard at work...having lunch. But they earned it:

The trench shows where the conduit will be laid. When I got back home at night, the trench had been filled in, up to the new breaker box. But PG&E had taken two of the four boards we have laid over the muddy area where we had to take out the sidewalk. :-(

They came with some pretty impressive equipment:

Fortunately, despite the day-glo markings in the street, they didn't put their John Deere to work on it,  so no trenching in the street. I wonder if the will come and remove that legal graffiti or if we'll have to live with it until it wears off?

Update 3/3/2011: It snowed in the mountains last week, so PG&E couldn't come and pull the cable last week, but they did show up on Wed. this week and we now have 200 amp service. The breakers for the new circuits aren't in yet, though, but that should happen next week. 

The Sun

Periodically over the last few months, I've been checking the temperature on the solar hot water tank. It hasn't been  over 80 degrees since the beginning of December. When I checked last weekend, it was 84. Here's why:

This picture was taken around noon last Wed. looking south from the west side of the house. The sun is over the redwood trees now, which means the solar thermal collector on the northeast side of the roof is getting more than 4 hours of sun a day.

Spring is on its way.

Little Flags

I went out front this morning and saw that PG&E had put in a bunch of little fluorescent flags and sprayed around some fluorescent paint:

It looks kind of festive, but the point is to show the guys digging the trench where the gas, electrical, and cable TV conduits are underground.  There are some markings in the street too. I wonder what those are for, theoretically, they shouldn't have to dig the street up. Hmm.

Now, if the guys digging the trench had an augmented reality app for their iPhones that let them point the iPhone at the conduit box and it would provide a picture of what was underground, they wouldn't have to send out a crew to stick in the little flags and spray up the street and ground with officially sanctioned graffiti.  Sounds like a business!

Anyway, these are signs of progress. With the drywall guys whaling away at the inside and PG&E spraying fluorescent paint and sticking flags in everywhere, I'm starting to get a little confidence that we just might have everything wrapped up by the end of March, which is what the current schedule says.

How to Account for Residence Time?

If you recall from my last post, I estimated a carbon payback time for our closed cell foam insulation at around 214 years, based on an estimate of 120.38 kg (0.12038 metric tons) HFC emitted and an estimated savings of 0.562 metric tons (mt) of carbon per year (30% reduction in annual natural gas use). The calculation assumes that HFC245fa has an instantaneous global warming impact (GWI) of 1000x carbon dioxide.

There is one problem with this way of measuring the impact HFC245fa relative to CO2. It does not take into account that the residence time of HFC245fa in the atmosphere is around 7-10 years while that of carbon dioxide is around 450-500 years, and when the HFC breaks down, there are no long lasting products remaining. So this means a kilogram of HFC245fa put into the atmosphere now will cause 1000x the global warming of a kilogram of carbon dioxide for 10 years, but then it will be gone. A kilogram of carbon dioxide, on the other hand, will continue to warm the planet for another 490 years before it disappears. Simply comparing the two gases based on their instantaneous GWI therefore doesn't seem quite right.

This is a problem system engineers face all the time: how to calculate a number that lets you compare the impact of two different technologies/treatments/etc. on a system. The number is called a figure of merit. In effect, it lets you compare apples and oranges along some common metric, like for example the percent energy in the pure red color light (at 700–635 nm wavelength) reflected by their skins, of value in judging their relative contribution to solving some problem. In our case, we want a formula to calculate the weight of carbon dioxide equivalent (CO2e) for the HFC that takes into account both the instantaneous GWI relative to CO2 and the residence time relative to CO2.

My previous post calculated the CO2e for the HFC like this:

       wt. CO2e   = wt. HFC * instantaneous  GWI

But, as mentioned, this doesn't account for the residence time.

So we need to adjust the right hand side so that the reduced residence time for HFC over the equivalent amount of CO2 is accounted for. This means that we need to multiply the instantaneous GWI by a number that will decrease when the residence time of the gas for which the GWI is desired decreases relative to CO2 (or correspondingly increases if the gas has a longer residence time). One way to do that is to divide the residence time of the gas by the residence time of CO2 and multiply the instantaenous GWI by that to obtain a time adjusted GWI:

       time adjusted GWI = instantaneous GWI * (residence time of HFC / residence time of CO2)

If the residence time of the HFC increases relative to CO2, the factor on the right side will increase, causing the time adjusted GWI to increase, and vice versa, which is what we want.

Now we can use the time adjusted GWI for the CO2e calculation:

      wt. CO2e = wt. HFC * time adjusted GWI

In the case of HRC235fa, we have:

     instantaneous GWI      = 1000
     residence time of HFC = 10
     residence time of CO2 = 500
     time adjusted GWI       = 1000 * (10 / 500) = 1000 * 0.02 = 20

Plugging the time adjusted GWI into the equation for CO2e for our case gives:

      CO2e = 0.12038 mt * 20 = 2.4076 mt

At 0.562 mt of carbon eliminated per year, this gives a payback time of:

    payback time = 2.4076 mt CO2e / 0.562 mt CO2 per year = 4.284 years (!)

This is considerably better than the previous figure of 214 years. The carbon offsets for 2.4076 mt CO2 come to only $24 rather than $1203.80 as calculated in the previous post.

People who are not used to making engineering tradeoffs look at this kind of calculation and scratch their heads. Which number is right? Are we just playing with numbers or is there some kernel of truth  in all this arithmetic? I suppose you will have to answer that question for yourself. But if we are ever to come up with sustainable technical solutions to the systems in our society upon which we depend, we are going to have to come up with ways that fairly and accurately compare different kinds of solutions that have differing impact. Having a single number that summarizes this impact, like the time adjusted GWI, makes such comparisons a lot easier.

Update on GHG Impact of Closed Cell Foam

If you recall from this post, I estimated how much CO2 equivalent green house gas (GHG) would be released during the closed cell foam insulation of our house. I made a math error. At 11.7 lbs/therm and 106 therm/yr eliminated by the insulation (figuring at 30% of the heating carbon), that's 1240 lbs per year of CO2, not 2907 lbs as I said in the post. So the estimated carbon footprint payback time would be more like 145 years and not 80. Gulp!

Well, I now have exact figures, this time in metric, where it is easier to spot errors. Ponzini used 0.76 cubic meters of the B component, of which maximum 12% is HFC-245fa, or 0.0912 cubic meters. The density of HFC-245fa is 1320 kg/m**3, so the weight of HFC-245fa emitted is 120.38 kg. Since HFC-245fa is about 1000x as potent a GHG as CO2, that would be 120,380 kg CO2 equivalent, or 120.38 metric tons. Assuming again a 30% reduction in heating gas use due to the insulation, 1240 lbs of CO2 eliminated is around 0.562 metric tons, so it would take 214 years for carbon footprint payback. Double gulp!

Note that the 30% reduction in heating gas is just an estimate. It is based on a spreadsheet model of our house that I made a few years ago, which didn't take the floor into account, and probably has other errors. So it's possible that we might get better performance, or even maybe worse if I overestimated somewhere. We will see in the coming years.

A carbon  footprint payback time of 214 years sounds like a long time, but fortunately, there's carbon offsets. You can buy tax deductible carbon offsets at Carbonfund.org at $10 per metric ton. They have a variety of programs in the categories of renewable energy, efficiency, and sequestration. I like the forestry projects because, in theory, they can be long-lasting, 80-100 years. Here's a link to one, the Nez Perce Reforestration Project in Idaho. Though HFCs stay in the atmosphere a much shorter time than CO2, as discussed in the previous post, the foam will outgas for a while until it stabilizes, and I would like my credits to last as long as the house or even longer. So I am on the hook for a donation to Carbonfund.org of $120.38 $1203.80.


Now, you might ask, since carbon offsets are so cheap and the insulation was so expensive, why not simply buy carbon offsets. Actually we do that already for the gas we use for heating, and there were other reasons for using closed cell foam in this house, as discussed in the last post. But there is no guarantee that the next owner of the house will be so diligent. With the foam in place, the house should be good for another 30-100 years, long after I'm gone. And it will continue to save carbon.

Clarification on the Electrical Service Upgrade

The Lovely Wife brought up an issue with my last post. She asked why if our intent to save energy we were getting a much bigger breaker box. Also, I thought I would clarify a bit how our underground electrical service works. Most houses in the US have their service from wires strung in the air from the power pole to the house.

The reason we have a bigger breaker box is because we are getting at least 4 new circuits in the breaker box which will serve the house. These are three 220V/20 amp circuits for the on demand  electric  hot water heater, and one  220V/40 amp circuit for the electric car charger. There  may be a couple of additional 110V/15 amp circuits for the HRVs and the garage. All our existing electrical circuits will remain unchanged on the existing inside house circuit  breaker panel, which has no space for the new circuits. The old panel on the outside of the house, which you saw in the photo on my last post, is much smaller because it contains only one breaker in it,  a 100 amp  breaker for the whole house. The new one will contain the 200 amp breaker for the whole house, plus the breakers for the new inside circuits.

As for saving energy, our system remodel is designed to save on heating gas through much more effective insulation. When it comes to electricity, though, we are substituting  electricity for other sources of energy that are harder to make renewable. The on demand  hot water heater will  substitute electricity for gas for backup hot water heating (the  main hot water heating is solar),  and the electric car charger will substitute electricity for petroleum-based gasoline. Then an expansion of  our  solar PV system will offset all but 2000 kwh/yr of our electricity use with clean, 100% non-fossil carbon based solar electricity. The 2000 kwh/yr (estimated) that we do not offset will be drawn from the grid. Since the State of California has a renewable mandate of 20% by 2020 (with 33% being a stretch goal), the likelihood is that the grid will become much cleaner before transportation fuels or heating gas do (btw: don't let the media story of "clean" natural gas fool you,  natural gas produces fossil carbon and thus contributes to global warming too, it just produces much less of it, about half that of coal or oil).

Because our service is underground, the upgrade process has been very complicated.  Most people in the US (and many other parts of the world too) have service from an aerial line that runs  from the poles on the street where the utility has their lines to the house. Upgrading such an aerial  line is much simpler, the lineman comes, removes the old line, installs a thicker new line, and you are done. Of course, you still need to get a new breaker box with a larger breaker for the 200 amp service.

In our case, the utility lines are buried in conduits beneath the streets, along with the phone lines and the cable lines. This makes our neighborhood look much neater, without a lot of poles along the streets with wires draped over them. But it does make upgrading the service much more difficult. Here is a picture of the cement box where the electrical lines enter my and my neighbor's property:

Somewhere beneath that box, two conduits lead out at angles to our  houses. My neighbor had his service upgraded to 200 amps  in 1985 when he had central  air conditioning installed.

When PG&E comes, hopefully on Feb. 23, they will dig a trench from the box to the place where the pipe from the new breaker box is, under the area where our sidewalk used to be (and  will be once again when the job is through). Here you can see a clear space to the concrete access box, which is right next to the green sword shaped  leaves in the center of the picture (it's a naked lady, native California plant that blooms in August):

There are still a couple of clearing items that need to be done, the small  rock  wall, and I think we will probably have to repair the irrigation  in our neighbor's yard if the trenching damages it. But I think PG&E shouldn't otherwise have a problem with digging the trench.

Progress on Drywall and Electrical Box

We now have a firm date from PG&E when they will come and start installing our 200 amp service. Trenching should occur on Feb. 23, when they will install the conduit and backfill. On Feb. 25, they will pull the new cable, connect it to the grid, and transfer the meter. In preparation, we now have a new breaker box on the side of the garage:

This box is considerably  larger than  our existing breaker box:

I think we are  going to need to paint the new one or something so that it isn't as visible.

Today we had the gardener come an clear out all the vegetation between the concrete box on the border between our property and our neighbor's, where the underground electrical service for both our houses comes in. We were warned by PG&E that we had to have all the vegetation out in a straight line between the breaker box and the concrete box or they would not dig the trench.

The drywall guys started this week in earnest. Paul convinced them to install the Thermablok on the south hallway wall studs, but, as you can see from the following picture, they didn't quite get the concept:

On this wall, there are a couple structural  members that consist of two 2x4 studs right next to each other, like the one in the middle of the picture. Rather than gluing two pieces of Thermablok on the studs, they glued one on going up the center. I guess they thought it was a standoff for the drywall or something. Anyway, we had them rip out the drywall that they had installed and redo it. Unfortunately, I didn't have time to check afterward whether they did it right the second time or not, so I don't know if they got it in. Paul called the owner and I put a message in Spanglish on the wall as to what they should do. The drywall is now up:

There are a couple places in the house where the studs have bent or warped a bit with age. Here you can  see that on the top right next to the steel strap:

These areas are going to require some planing to make them more even so that the drywall doesn't protrude. We have decided on a smooth texture to our drywall, so there is no room for hiding imperfections in the surface.

There are also some problems around the windows. We had the windows replaced in 2004 from the outside. Here you can see how they used nails to shim the window:

In other places, the caulking bead goes from an eighth inch on the top to a quarter inch on the bottom. Previously, we had a nice contemporary finish where the drywall wrapped into the windows and there was no molding. Now, we will need  some kind of wood trim to  hide the imperfections. We're planning on using a stained wood, which matches the wood in the downstairs windows.

New Concrete or Urbanite?

PG&E has finally begun to respond, and we now have a date of Feb. 28 for the start of the 200 amp upgrade. We began the process in late October, and in November were given a start date of December 24. December 24 came and went, and in early January they began asking the same questions that they were asking us in early November when we started the process, suggesting that someone had forgotten about our application. The Lovely Wife sent a irritated note to the woman in charge and someone else,  who forwarded it to the manager. Now, things seem to be moving along, if still somewhat slowly. We would like to get an earlier start date, since Aerovironment is supposed to come on Feb. 28 to do a site assessment for the electric car charger. The 240V/40 amp circuit needs to be in place and hot by the time Aerovironment shows up. In any case, sometime in the next month  we expect PG&E to have the service at least started.

This week, we began the process by having the concrete removed on the area around the gas and electric meter, where our underground service enters the house, as you can see below:

Because we have underground service, it is not simply a matter of stringing a new wire. We need to have a trench dug, the conduit removed and replaced with a larger one containing a larger cable. However, there are complications. Since our house was built,  the code has changed and now they will not put a breaker panel  directly next to a gas meter where the current one is, probably due to the possibility that a spark from the breaker could ignite a leaking meter, especially during an earthquake. So they need to  move the new breaker panel around 4 feet down the side of the garage,  on the other side of the gate to the back yard. The electrician is coming this week to put in the new breaker panel. He will wire in all the new circuits,  including the three 220V/20 amp circuits for the electric on-demand hot water heater, the circuit for the car charger, and probably a couple of 110V/15 amp circuits, like the new one in the garage where the plug-in converted Prius will be plugged in. That leaves only connecting up the new breaker panel to the main and into the old main panel, which will become a subpanel, for the service upgrade to be complete.

We also want to reroute the rain gutters on the west side of the house so that we do not have two downspouts emptying onto the sidewalk on the west side. They leave a mess there every winter: leaves from our neighbor's Polycarpus trees, gravel from the roof, a wet spot that doesn't go away because the area doesn't get any sun at all, and, to top it all off, green moss that makes the sidewalk slippery. The new design will drain around 2/3 of the roof on that side forward and down a spout on the front next to where the concrete is currently out rather than through two spouts onto the sidewalk. The water will drain out into a narrow strip garden between the driveway and the neighbor's property. The garden will need to be replaced, because it is exactly there that PG&E will be digging the trench.

The removal of the concrete left open the question: what to do about the hole? Our original plan was to simply lift one section of the sidewalk off or have PG&E tunnel under it rather than remove it, but the need to move the breaker panel impacted more of the sidewalk than we had originally anticipated so it had to be removed. To handle the new roof drainage, we had planned to slip a pipe under the sidewalk for the downspout drain. Now, we have to replace a larger section of the sidewalk. We could of course have fresh concrete poured, but cement production has one of the highest green house gas production rates of any product, so avoiding new concrete seemed like a good idea.

Besides, the old concrete is still in good condition. These days, they don't take a jackhammer to concrete when they want to break it up, but use a saw to cut it very precisely. Unlike the concrete in our backyard that we had removed a few years ago to enlarge the garden, this sidewalk didn't have any rebar embedded in it so it was fairly easy to remove and came out in regular pieces as you can see in the following photo:

The pieces look like the concrete pavers we saw at Lyngso Garden Supply last week, just bit thicker and denser. In fact, they look as if they should work quite fine as urbanite, the sort of fancy name people in the green garden trade give to concrete that has been removed, broken up, in some cases dyed, and reset as pavers. One of our neighbors had her backyard redone last year and had her concrete sidewalk broken up into urbanite:

The advantage of urbanite is that the cracks between the slabs allow water to seep in rather than run off as a sheet. This recharges the water in the garden and reduces the load on the city storm drain system. Plus, it looks much nicer than a single slab of concrete.

So our plan now is to reset the concrete slabs as urbanite in gray decomposed granite, and not dye them, since the current color matches the driveway and the rest of the sidewalk. For the water drain, our garden designer, Chris (from Garden Escapes by Chris Todd) recommends a small gravel-filled channel level with the urbanite surface rather than a pipe. This will drain down into a pebble filled faux streambed in the small strip garden where the water can filter in. Chris will be in charge of resetting the paving and redoing the side garden once PG&E is through.