Cool Roof 2: Cool Roof, Cool City

 Los Angeles is in the middle of a record-setting (again!) heat wave. NWS reposts that LAX airport, along the coast, recorded a high of 102 F (old record of 99 F in 2020) while Downtown LA hit 112 F. 

Several people asked about our Cool Roof and Heat Pump. I wrote about replacing our asphalt shingle roof with a composite shingle "Cool Roof" back in 2012. Our roof went from reflecting 30% of solar heat (absorbing 70% of the heat) to reflecting over 70% and absorbing less than 30%. If you look closely at the shingles, they incorporate bits of recycled glass, tumbled to a frosted gray, green or blue. From a distance, it looks like a light-medium gray. You wouldn't even know it was a cool roof unless I brag about it. 

When you install a cool roof, you mitigate the Urban Heat Island (UHI) impact of urbanization. "Georgescu et al. (2012, 2013) reported that summertime statewide warming due to projected urban expansion for Arizona could be reduced by about 50% with the complete integration of highly reflective cool roofs." SoCal would likely be similar. 

So, which should you pick, a cool roof, a green roof, or a photovoltaic (PV) solar roof? The answer turns out to be dependent on local climate and geography. Materials change the radiative impact of buildings. They can reduce the amount of heating during the day, but they can also disrupt the amount of cooling at night. They can heat the air above the city, strengthening the urban heat dome. There are so many variables, it takes a radiative full-physics model and a supercomputer to track them all. 

Take the case of Phoenix and Tucson, studied by Salamanca et al: Citywide Impacts of Cool Roof and Rooftop Solar Photovoltaic Deployment on Near-Surface Air Temperature and Cooling Energy Demand. "In Arizona, cool roofs reduced daily citywide cooling energy demand by 13–14%, while rooftop solar photovoltaic panels reduced them by 8–11% (without considering the additional savings derived from their electricity production)."

But, if you were in London, Brousse et all found that cool roofs would be most effective in reducing extreme heat. Nonintuitively, green roofs wouldn't make much difference overall (but help during the day). Vegetation makes a minimal difference on a city-wide scale. Rooftop solar might have an overall heating effect, as would running AC. But, if the rooftop solar energy was used to run AC, and people could take shelter from the heat indoors, they could be a net benefit. 

In Sydney, Khan et al found that PV solar could disrupt the cooling diurnal land-sea breeze and heat the Sydney area overall. 

Governments can encourage behaviors good for society and suppress behaviors that are detrimental with subsidies/fines. If you were running the government, you would like to find out the cost-effectiveness of different interventions (eg subsidies) and fund what gives you the most bang for the buck. If you had even more money, then fund the slightly less effective but still helpful stuff. 

COOL ROOFS reduce heat experienced inside the buildings and in the urban environment. Require them in new construction. Replace dark roofing materials with cool roofs first. If you have money left over install rooftop solar. 

In 2012, I got a 10% tax credit on the cool shingles we used, but that is only a small amount compared to total cost of installation.  The shingles cost the same as the darker colors in the same product line that absorbed more heat and didn't qualify for the tax credit. I didn't need a nudge of a few hundred bucks to do what I knew would make my house cooler. 

Adding rooftop solar was not on my radar back in 2012 because I figured that the prices were still high and technology was still changing. A few people in our neighborhood installed them, but they were much bigger energy consumers than we are. We hadn't installed a heat pump yet. 

BTW, Lawrence Berkeley Laboratory puts out an annual pricing survey called Tracking the Sun, with useful data on actual installed prices of solar systems. 

DIGRESSION:

When we got our heat pump back in 2020 (or maybe 2019?), people asked why we didn't get solar panels as well. I dragged my feet because the rooftop solar salesmen (and they are always bros) were so sleazy, and I also didn't want to buy anything made with forced labor. I was waiting for the solar supply chain to clean up. I am also waiting until I replace my roof again. The timing just wasn't right. 

Besides, I know that California has an excess of solar power during the day. It used to be worse, but utility-scale batteries have been soaking up the excess solar power so that we need to shut down feed in (curtail) solar farms less than in prior years. For the last month, we have been curtailing solar farms during all the hours rooftop solar would have produced at my location. 

Even during the heat wave this week, we had to curtail cheap solar farm power. 

Yes, even during the hottest day ever (so far) in LA. 

There just wasn't much value-add for society if I add solar panels to our cool roof. 

Vacation at Home

 First Costco wrote about how some of their customers shop by cargo bike. 

Then AAA (the American Automobile Association!!!) wrote about 8 car and taxi-free days in Paris. 

And I'm even quoted in the LA Times about getting glasses at Costco by eBike. Well, they didn't mention that I biked there. But I biked home from the Torrance Costco during peak evening traffic and I kept catching up with the same SUVs at each red light for the first 5 miles. 

The media is finally catching on that getting around by cars can be a PITA and bicycling for transportation can be fun, efficient, and healthy. It can be normal, if only we reallocate space for it. We shouldn't have to fly to Paris to experience a city with great food by bike. I mean, Paris is great, if you like French food, but the food in Torrance is way more exciting (I am saying this unironically). 

South Bay weather is nicer than Paris'. 

We have the beach, we have mountains (or the hills of Palos Verdes Peninsula). 

We could be paradise. And we don't have to go on vacation to experience it. We can stay right here at home, and live our best lives just by going about our normal business. It would also be cheaper, for both our personal pocketbooks and for society's. 

True Cost to Own 2

I just heard a cringe podcast where they were discussing lack of street parking near our city's high school. One speaker said that, our region is hilly, and eBikes help with that. But not everyone's family can afford an eBike so many kids have no choice but to drive. 

This is a classic case of car brain where people no longer notice the high cost of car culture and car ownership. 

When our teen daughter was added to our car insurance policy, our premiums when up ~$2,000/yr even without adding another car. If your teen can delay becoming a driver by just one year, you can buy a decent eBike, lock, lights, and panniers. You will also save hundreds of hours chauffeuring your teen. 

Another year, another AAA "Your Driving Costs" report has dropped. It's time to update True Cost to Own. The cost of owning and operating a new vehicle in the US has increased to $12,182 in 2023.  New cars cost 4.7% higher than in 2022, but used cars went down in price. 

Remember, this is an average over the entire US, and Los Angeles tends to have higher insurance and fuel costs (both gasoline and electricity). This is also for the average new car sold which, at $34,876, is significantly cheaper than the typical new car I see in our school district (Tesla Y, ~$45,000-$52,500). 

The typical behavior in our area is for the parent to buy a new car and give their old car to the teen. Then they park the old car out on the street, making street parking even scarcer. It's not more people making street parking scarcer. It's more cars. 

I'm doing the calculation a bit differently this year, inspired by a LA Times article about a Culver City High School teacher that had their students run the numbers on car ownership over a lifetime. I don't get into the messiness of predicting inflation rates or marginal tax rates. 

Suppose you don't buy that new car and save that money instead in a balanced mutual fund. Using the Vanguard Benchmark Returns on Target Retirement Funds, you can expect to get ~8.25% long-term returns 

Using an online Savings Calculator, assuming 

Annual Savings: $12,182

Annual Increase in Savings: 3% (car costs have been going up faster than that)

Returns: 8.25% from balanced funds above

Taxes: 0% (if in tax-advantaged retirement account)

Then you have $1,0983,667.47 in year 24. 

Start when you turn 16, and save a million dollars by 40. 

In 50 years, age 66, the car-free saver will have $11,199,484.63. 

But, wait, you can save $18,264 pre-tax (33.3% combined CA+Fed tax rate) while $12,182 car costs are post-tax. But then you pay taxes on withdrawal from retirement accounts. So the amount will vary, but the message is the same. Living car-free or car-light (my family) is a huge money saver. 

Now I want to talk about the really pernicious part about car ownership, the externalized costs borne by others. 

This is painfully obvious to me every time I go to city council to beg for a bike lane and am turned down because "poor people need a free place to park their vehicles" on the public streets. 

I am charged the same price for my groceries whether I use the supermarket's huge and hugely expensive parking lot. I walk or bike to post of my groceries. I even bike to Costco for some of my trips. Yet, I pay for that parking lot. 

Even though road wear is proportional to axle weight to the 4th power, I am paying property taxes to maintain my city streets even though I get around on a 50# eBike instead of a 4,500# electric SUV. 

A 2020 Harvard Kennedy School study found that Driving is more expensive than you think. "Massachusetts' car economy is roughly $64.1 Billion, with more than half of that coming from public funds."

"Using publicly available data, the authors put the annual public tab at $35.7 billion, which amounts to about $14,000 for every household in the state. Those that do own vehicles pony up an additional $12,000 on average in direct costs."

You might nitpick that Massachusetts is snowy and snow plows are expensive. But, a 2021 Ulupono Initiative study in Hawaii found that "Public costs amount to roughly $15,000 per taxpayer ($24,400 per household), annually, even if they don’t own a car."

Furthermore, "Personal vehicles cost an additional $16,200 per household per year. With the public costs above, each household’s costs total $40,600 per year (or 51 percent of pre-tax income)."

Then there is the opportunity costs of the land. "Land value of public lands dedicated to road, highways, and parking is $3.9 billion, covering about 14 percent of the available urban land in our state."

Next time you see me bicycling for groceries, thank me for subsidizing your roads and parking. And drive carefully and slowly around cyclists. Dangerous road conditions are what's holding back the 60% of the public that is "interested but concerned" about riding bicycles. The more of us that are bicycling; the fewer cars in front of you, competing with you for parking, polluting your air, costing your city big bucks in road repair and climate change adaptation...

California AB 1909 states: 

“Existing law requires the driver of a motor vehicle that is passing or overtaking a bicycle to do so in a safe manner, as specified, and in no case at a distance of less than 3 feet.

This bill would additionally require a vehicle that is passing or overtaking a vehicle to move over to an adjacent lane of traffic, as specified, if one is available, before passing or overtaking the bicycle.”

Drivers are required to pass cyclists with at least 3 feet of clearance (and that is from the furthest point of my bike, including handlebars and cargo).  If there is more than one lane, drivers are required to change lanes before passing cyclists, just as they would do when passing another vehicle. This is why it makes sense for cyclists to ride 2-3 abreast in a pack instead of strung out in a single file line. Drivers can pass them in a shorter distance, making it safer and more convenient for everyone. 

This is now in California Vehicle Code 21760.