Canvas Additions

I'm getting into the idea of low mass. Well no kidding, but not for backpacking or alternative living spaces, but for home additions. Living in the SF bay area has led me to disdain all talk of remodel, and picture windows. But, it is the talk of the town and I find it hard not tho think about how my own home could be cool, more useful. The thing is, all the green architecture in the world is still adding more mass and resources than doing nothing, except insulation i suppose. So, while I am interested in smallness, I want more room. Hum, an American. So, how about additions that are made of canvas. Now, I like Yurts and everything, and despise domes, you would have to know me a long time to understand exactly why, and it has little to do with wet patch. But yurts and domes just don't jive with my sense of line. I like straight lines. I'm a mid century modernist by disposition, or at least sensibility. So, on with it, clean straight line structures skinned with canvas or other cloth. The coolest thing about indigenous homes it turns out is not their hippy dippy circle shape (which I do like for its own sense), but really what they are about is low mass. Low mass. I guess I have to address the earth ship issue. I like them, I guess. Do I want to live underground? Maybe. I wont rule out earth ships, but until then, how about a kitchen addition made of canvas?