Executives at Simon Property Group during a recent earnings call said the firm was delaying construction on some of its projects because of the weak sales climate. Instead, it seems to be opting to spend on redevelopment. It recently announced that it will have invested $450 million in upgrading and expanding its 20 New England malls when it completes a five-year renovation plan in 2010. The company said that major renovations are planned for three Boston-area malls, Northshore Mall in Peabody, South Shore Plaza in Braintree, and Burlington Mall.