<p>Is there a definitive scalable 3D printer? </p>

<p>I've seen examples of Chinese companies printing entire houses, and I'm curious as to printers / filaments that are intended (or at least able) be scaled up for (very) large print jobs. </p>

<p>Since most hobby printers can take hundreds of hours for something that can still be held in our hands, so I'm curious if there are any designs for printers that are meant to extrude material efficiently with a easily scalable printing area. </p>

<p>Open sourced / free is preferable; though I'm interested in <strong>any</strong> designs that exist, commercial included.</p>

If I understand your question correctly, it sounds like you're looking somewhere within the
RepRap
realm. The RepRap community is mostly responsible for the boom in consumer 3D printing in the past 10 years, and that's most likely because it's
open source
. RepRap designs are mostly dynamic (and most parts can be 3D printed), so you could theoretically build a larger frame for your machine and use a slicing engine that allows you to set the build volume. I believe
Slic3r
allows you to customize the build space, I'm not sure though.