I expect especially resource-limited colonies could eventually use a double hull, with vacuum pumps to actively re-capture leakage. A standard mechanical vacuu

I expect especially resource-limited colonies could eventually use a double hull, with vacuum pumps to actively re-capture leakage. A standard mechanical vacuum pump can reach 1/1000th of an atmosphere, so in theory this scheme should be able to reduce leak rates to only 1/1000th that of an equivalent single-hull design.