Guardian: How can a mortgage have a carbon footprint? Surely it just boils down to a few bits of paper or electronic transactions? Look more closely. The bank or building society runs offices, buys computers, uses data centres and sends lots of paper mail. Its people travel – often by air. And it hires third-party services ranging from cleaners and caterers to ad agencies. When you take out a mortgage or loan, or pay for an overdraft, your interest payments feed all this activity, sending a …