One Sunday a while back, I dropped by an open house that had just been remodeled and put on the market. It was a speculative renovation, otherwise known as a “flip.” In keeping with the usual modus operandi of such projects, the builder had refitted the modest mid-1960s rancher with shiny granite countertops, gridded plastic windows, glossy prefinished flooring, and so on.

This familiar slate of so-called upgrades, as painfully predictable as it was, wasn’t the real problem, though. The builder had also made some heavy-handed changes to the home’s original floor plan, evidently hell-bent on pumping it up to the overblown market standards of recent years. And here he made a classic amateur mistake: So busy was he swaddling the place in glitzy finishes that he completely overlooked a number of eye-popping flaws in his “improved” design.

The worst of these was the layout of the entry and living room — probably the very last place you want to screw up a house. The builder, convinced that a really huge living room would impress potential buyers, had combined the former living room and master bedroom areas into one gigantic rectangular room with — drum roll please — no windows at all.

Oh, the front door (which led directly into the room, another no-no) did have some glass in it, but this captured only the feeble light from a shadowy, roofed-over porch. Rather than the effect of extravagant space the builder was after, his living area felt more like the rumpus room in a church basement.

Compounding the error, he provided an elaborately appointed kitchen completely open to both the living and dining rooms — but also lacking any windows. In fact, the only direct light in the whole vast space came from a single sliding glass door in the dining ell.

For the builder to presume that his open floor plan would miraculously allow him to make do with the light from a few far-off windows was a blunder of epic proportions. For one, building codes have minimum requirements for window size in habitable rooms, and I doubt that he satisfied even those rock-bottom requirements.

More importantly, though, windows have a purpose beyond just providing adequate light — otherwise we could fit every home with artificial lighting and call it a day. When humans occupy an enclosed space, they have a very clear psychological need to see natural light as well as a view of the world outside. Hence, a purported living area that lacks windows inevitably feels oppressive and claustrophobic.

The lesson is simple: If you’re remodeling, don’t miss the forest for the trees. Lavish materials and fastidious detailing are fine, but by no stretch of the imagination can they compensate for a fundamentally defective floor plan.

Therefore, approach any architectural problem from the broad-brush aspects that really matter — the things that will make the place livable, like solar orientation, circulation and convenience — and satisfy these fundamentals before worrying over details of color and finish. Otherwise you may end up as this builder did — with a very fancy mess, but a mess nonetheless.

Read Arrol Gellner’s blog at arrolgellner.blogspot.com, or follow him on Twitter: @ArrolGellner.