The "Technology Connections" youtube channel recently discussed awnings too. (And it had more or less the same message as this blog.)
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Because those are the actual reasons.
We still sometimes use things like awnings, just in the form of 'porches' or modern-looking 'slat awnings'
Changes in architectural fashion has made some forms of awning look dated.
Fabric awnings need upkeep to keep them looking smart. When the awnings are above ground level, it's semi-expensive upkeep. Building owners are tempted to keep those tired, sun-bleached awnings in place rather than renewing them - contributing to the dated reputation of awnings.
Awnings also face competition from interior curtains and blinds, which are much simpler to maintain.
And there's shifting building use. A few decades ago an office worker would prize a desk by a big window with lots of natural light to read paperwork by, but in the age of PCs nobody wants direct sunlight on their screen. Internal blinds let workers control the light levels to match their needs.
But not significant competition. If the blinds are very reflective a small amount of sunlight might end up going out again but in general, once the solar radiation converts to heat you can't get it back out through the window. That is particularly true for modern multi-pane windows.
This is especially true if you have an overhang, trees, etc providing even modest shade.
An awning is a net benefit over a curtain alone, but there’s overlap in functionality so having a curtain reduces the net saving from adding an awning.
While I understand this “once the heat is inside” thing I still can’t help but feel closing the curtains (and blackout curtains) makes a non-trivial impact on the overall daytime temperature of a sun facing room.
I get the goal is to reflect the energy back out and of your curtains are pure black that absorbs all the energy it would, in theory, heat the room as much as just leaving the curtain open but it still intuitively feels like you should close that curtain anyway.
I mean insulation is inside the wall of the house and it keeps the heat out. How is that any different than a set of blackout curtains besides the R value? (Hint: it’s probably the lack of insulating properties in a curtain… though there would be dead air between the curtain and window and dead air is a moderately good insulator itself.
TC should do a video on that. I’d love to see some numbers on the effect curtains have on indoor temperature.
The alternative to awnings are shutters or, like you said, plants, but not curtains.
Shutters can effectively block sunlight, but they also emit IR radiation 24 hours a day based on their temperature. If it’s hot outside, thick reflective curtains really can save more energy across a given day than shutters though they also work better together at some point you might as wall just seal up the window.
The radiation of the sun has to go somewhere. More of it will be reflected back by shutters, and whatever is absorbed can more readily be dissipated outside than inside.