Landlords already have an incentive to make their units more energy efficient--they can capture the revenue stream that currently goes to the gas, electric, and

Landlords already have an incentive to make their units more energy efficient--they can capture the revenue stream that currently goes to the gas, electric, and oil companies. I'm not sure why more landlords don't do this though. Probably because methods that don't disturb tenants (e.g. exterior rock wool or foam insulation) run afoul of zoning/setback/property tax assessment rules, and those that do comply (e.g double stud wall retrofits) disturb the tenants and/or reduce marketable space.