"These changes to our mortgage products have been brought in to keep pace with the needs and demands of borrowers."
The green mortgage is applicable on properties which have an EPC rating of A or B and rewards the purchasing of lower-carbon and energy efficient homes with a lower interest rate.
It has also increased loan to value amounts for buy-to-let and holiday let mortgages, launched new products for limited company buy-to-let and holiday let mortgages, and is allowing portfolio landlord applications for the first time in its history.
The Society is also raising the maximum LTV on its buy-to-let and holiday let mortgage range for personal customers from 70% to 75%.
Alun Williams, chief executive at Swansea Building Society, said: “These changes to our mortgage products have been brought in to keep pace with the needs and demands of borrowers. We have made the decision to increase the loan to value maximum on a number of products to make them more desirable, and we have, after 99 years, decided to allow applications from portfolio landlords.
“Introducing our green mortgage is something we feel is very important to the future of the Society. It incentivises the purchase of energy efficient homes, and this is something that we believe will become an increasingly important factor when people consider a home for themselves and their families.”