The cost of building a new house has gone up sharply over the past year. Not just because of lumber, but because steel, insulation, windows and appliances are all harder to get and more expensive because of high demand and delays. A number of startups have promised to revolutionize construction with new materials and technologies. It’s not easy — the modular construction startup Katerra filed for bankruptcy earlier this month. But there are others looking to disrupt the housing industry. Marketplace’s Amy Scott speaks with Sam Ruben, the co-founder and chief sustainability officer of Mighty Buildings, which uses an enormous 3D printer in a warehouse in Oakland, California, to build houses.