Why don't we use awnings anymore (2022)

In hot areas, even the shade of rooftop solar panels can make a substantial difference inside a building. And there's the ultra low tech method of just planting more shade trees.

Unfortunately with most US build tract housing, there's not enough room between most houses to provide dedicated shade by most any method. I wonder if shade between the roof gaps between houses would be useful.

Shade trees covering the roof doesn't sound very compatible with those solar panels though

Problem with shade trees is that trees have the unfortunately tendency to loose branches or fall during severe weather and having them next to your house isn't ideal when that happens. Also, depending on where you are located, those trees may end up being a great way of letting a wildfire spread to your home.

The bigger problem with trees is the damage its roots can do to foundations.

Which is a great pity because I’d welcome planting more trees around suburbs.

Even if the trees aren't shading the house directly, they will have a cumulative cooling effect; they capture the sun before it hits and warms up the ground, they have constant evaporative cooling, etc.

I once heard a story from a sustainable design architect. The customer wanted to cut down all their shade trees to install solar panels. The architect explained that, after doing a bunch of energy modeling, the shade trees were actually saving fifteen times more energy than the PV panels would produce.

So what happened? Naturally, the customer fired the architect. They only wanted to look green, but they didn't care if it was actually green. :-/

Shade trees can be pretty nice to have, especially when they are deciduous and automatically provide dense shade in the warm months and less shade in the cool months.

They can also destroy pavement, and foundations, and underground utilities.

They can be messy. Leaves fall and generally need dealt with somehow, and many kinds fruiting trees produce fruit that is big enough for a person to twist an ankle on just by walking through their own yard.

They can be expensive to maintain properly, and even when maintained properly they can drop heavy things that damage expensive things.

It isn't necessarily a straight forward comparison.

While I'm sure that well-placed trees can be a great benefit to the overall cost of owning and living in a dwelling, I'm also sure that they can be a great detriment.

If I had a choice, I think I'd rather have big solar panel arrays than big shade trees.

Did the architect look at the whole picture, or just compare energy?

Trees cost a non-zero amount of time and money by just existing and doing their normal tree stuff when they're near a dwelling.

If you want "the whole picture," trees also have many non-zero benefits apart from just energy — habitat, outdoor cooling/comfort, habitat, cleaner air, habitat, lower stress hormone levels, and oh did I mention habitat? :-D

Since the only upside of PV is energy, it seems like you should at least show it's energy positive (vs wasting 1,400% as much energy on net). That huge energy waste is a big hole to dig out of using only secondary incidental benefits.

If a tree is unhealthy or too close or too big, then of course you do something about that. But to do it because of solar (thinking it'll be more "green") is often misguided.

My dad lived in a house that was well-shaded by trees. They kept the house cool but there ARE downsides...

The biggest one is dealing with all the leaves in the fall. If your yard is big enough, you can easily lose a whole weekend to cleaning up the dropped leaves so that they don't kill your grass over the winter and spring. You also have to clean them out of the gutters multiple times a year, around the foundation, etc.

That house also had an absurd amount of spiders in it, which I attribute to both being close to the woods and shaded by trees. Not to mention vermin such as mice, chipmunks, squirrels can extremely destructive to the house, vehicles, and machinery when their own homes and food sources are right nearby.

The whole picture includes everything that is good as well as everything that is bad about all of the choices under consideration.

It is impossible to make an informed (instead of faith-based) decision without looking at all of the things in an unbiased way.

Trees near dwellings are seldom hands-off, and solar can have benefits beyond supplemental energy production. It isn't a straight-forward comparison.

Thanks, that's exactly my point. You need to look at the whole picture, not just "trees cost a non-zero amount of time and money." Glad we're on the same page!

> solar can have benefits beyond supplemental energy production.

I'd be curious what you mean by that.

> The biggest one is dealing with all the leaves in the fall. If your yard is big enough, you can easily lose a whole weekend to cleaning up the dropped leaves so that they don't kill your grass over the winter and spring. You also have to clean them out of the gutters multiple times a year, around the foundation, etc.

These kinds of comments are hilarious to me. Having a mulching mower makes leaf maintenance a breeze. Owning a house comes with responsibilities. If you're not going to keep up with things, then hire it out. If you're not even going to bother with that, then boy, I don't know. Some people just come across as the juice isn't worth the squeeze.

I thought you were at least going to come out with limbs falling on the house, but you just went with sheer lack of wanting to do yard work. I appreciate the laugh

Your previous paragraph of sheer, blind adoration of trees does not suggest that we are even reading from the same book, much less from the same page. (And to be clear: It's fine to adore trees. But it's not fine to say that this seemingly-blind sort of adoration represents an unbiased view.)

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Meanwhile, some nonexhaustive notes on solar:

Solar panels are obviously often used to support existing electrical services, since grid-tied solar is easy(ish).

Similar to the shade from a tree, rooftop solar does help prevent sunlight from heating a dwelling. The panels themselves obviously cast a shadow, and they're mounted with an air gap between the panels and the roof (providing both airflow and thermal isolation). Furthermore, because nothing can ever operate over-unity, 100% of the electrical energy they produce is energy that is removed from the situation of the sun directly heating the roof. (Are they better at this than a shadetree? IDK, but they're better than zero for sure.)

With energy storage, solar can be used off-grid day after day when that is a necessary or useful thing to have -- allowing one to maintain many aspects of modern Western life even in the absence of a grid connection. After a bad summer storm, a person can use solar to help stay cool and to avoid tossing the contents of their fridge, and can do so without needing to maintain a generator or manage a fuel supply. (It's expensive to get there, but there's also lots of things relating to the qualities of modern life that are expensive.)

Solar panels can improve the longevity of the roof they're mounted on, by reducing exposure to heat, UV, wind, and precipitation.

Solar panels won't crash through my roof and into my living room, but good shade trees do that sometimes.

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I can go on, but must I?

Again, "sheer blind adoration of trees" isn't really my position. I recognize there are costs, downsides, and contraindications. By contrast, you seem to think PV is all upside and trees are all downside.

Again, even accounting for PV roof shading, the energy audit showed a 15x improvement in keeping trees vs. cutting down trees and adding PV. That roof shading was already 'baked in.' Accounting for PV roof shading is basic stuff in sustainable architecture.

If we're being fair, we should acknowledge that solar panels can also reduce the longevity of the roof they're on, due to poor installation, the addition of new roof penetrations, and wind funneling. It's easy to say "well don't get a poor installer then," but of course the problem is you don't always know that going in! The presence of PV also greatly increases the cost of replacing/repairing a roof, since the PV has to be essentially uninstalled and reinstalled to access the roof beneath.

Well-positioned trees will shade a structure in the hottest parts of the day (normally south and west), which is precisely the "evening peak" when the grid is most stressed. PV instead produces most of its energy in the "afternoon lull," when electricity demand dips. So trees are effectively producing 'negawatts,' (credit to Amory Lovins) reducing demand on the end-of-line distribution grid at exactly the right time of day.`

At the risk of stating the obvious, if trees are crashing through your living room they're not "good" shade trees! Any competent arborist will be able to give you advice on setbacks, trimming, and (yes) removal if necessary. Remember that the trees are most likely giving you a much greater "energy payback" than PV[1], so you should use an appropriately levelized playing field when comparing the expense of paying an arborist every ~decade vs. the expense of paying PV installers every ~2-3 decades.

If I seem one-sided in my presentation, it's only because I'm needing to counter-balance your initial extremely one-sided presentation. My point is precisely that you need to look at both the cumulative upsides and the cumulative downsides of both technologies, and not simply look for evidence supporting a preconceived bias, in either direction. I think we're in agreement on that!

Anyway the exchange has been fun, and hopefully enlightening to at least one other reader, so I'm voting up all. cheers

[1] To quantify this, I would encourage hiring a sustainable design professional to do an in-person energy modeling of the home or business in question.