Because even though it's already built, someone else could use it who doesn't know better.
Someone who doesn't know better? You mean someone who doesn't care about keeping utility usage low, who has no intention of renting out 40% of the living space to help pay for the mortgage, and who perhaps has an absurdly long commute? How exactly does THAT help the world, the environment etc.?
If you, as a Mustachian, use it, you're purposefully wasting.
Nope. Gonna have to disagree there. There are Mustachian ways to use large spaces.
You say it's already built.. fine. But your use of it requires another one to be built.
Say there's a family that wants 5,000 sqft place. You choose to live there, in one that's "already built" - they gotta build a new one for that family. If you chose to live in a smaller place, that place that's already built could be used, instead of building a new one.
That's a little absurd, no? There is no shortage of 5000 sqft homes in this country for whoever wants them; sometimes it's just one person or a couple, BTW, not "that family." And by NOT buying a small place you're leaving that small place available for someone who wants it. And your car analogy doesn't work...
It'd be like saying buying a new car every year doesn't waste resources because the car is already built. That's true, but irrelevant.
...I wouldn't agree that that's true, since for the most part cars are--at least compared to houses--pretty disposable (depending on the manufacturer they may not even be built to last 10 years, much less 100), and buying a *NEW* car every year or three supports that incredibly wasteful "build 'em crappy but good looking and move 'em off the lot" mentality.
But even if it were true, note my emphasis on NEW. The new car does not exist now; it's
going to be built sometime in the next 12 months to feed that idiotic consumerist urge to "get something NEW." But the OP is not talking about buying a new home at all, much less a new home every year.
Fundamentally MMM (himself) is about not wasting resources to save the planet (e.g. giant trucks to haul you one mile to your grocery store). 5k sqft for two people is the opposite of that.
It would be the opposite of that IF you kept the whole place heated and cooled as if someone were living in every room, and did so with the usual American thoughtlessness (setting the AC at 66 or 68 and the heat at 73 instead of dressing appropriately), and filled the place with TV's, and so forth. That's wasteful because it is actually USING UP resources and spending money unnecessarily. Moving into an existing house is not "using up" anything.
If OP wants to buy a giant house.. okay. I don't care. But it's very likely a poor investment, and it's not a Mustachian thing to do, in general.
Here's why I disagree: when we moved from Small Single-Family House to Large Multi-Unit, our out-of-pocket mortgage expense went from just under $2000/month to $0 in fully rented months and $1200-ish when there are vacancies. And get this: the portion of the multi-unit that we occupy is well over twice the square footage of our entire Small Single-Family House and definitely what most folks on this forum would consider excessive. But who cares?
It's saving us $2000 a month, most months! And it's a much more "us-friendly" neighborhood, in other words, we're happier here... which as I seem to recall is another Mustachian goal.
I just think we could use a bit more tolerance on this thread and a bit less in the way of absolutist judgments, a la "if your home exceeds X square feet per person, I'm going to judge you as inferior to me." I mean, come on, people.