Sunnyvale-based Serious Materials, a venture-backed developer of sustainable green building materials, said Tuesday that it has acquired the assets of Kensington Windows,a Pennsylvania-based manufacturer of vinyl replacement windows and doors. Financial terms of the buy were not disclosed. Kensington Windows shut down all of its operations in October, when the firm's parent firm, Jancor Cos., filed for bankruptcy. According to Serious Materials, the firm will reopen the plant within the next 30 days, to make super-insulating windows and commercial glass. Serious Materials is venture backed by Foundation Capital, New Enterprise Associates, and Rustic Canyon Partners.