A methodological shift in both research and practise is now required to plan and manage low-carbon investments in large real estate assets, in order to satisfy the European energy efficiency criteria recently (see EU Directive 2018/844). Even though a rapid increase in large-scale building retrofit rates is expected, new strategic methods should analyse entire building portfolios rather than single-building perspectives in order to determine the amount of energy retrofit that will result in the greatest overall value.  In this paper, discussions on housing decisions is built for the assessment of investment in both monetary and non-monetary benefits of a retrofit expenditure, as well as determining the best efficiency programme across a large building portfolio. In terms of monetary benefit, the savings generated by the investment over its entire life cycle can be achieved. With recent calls for sustainability he environmental benefit in terms of averted CO2 emissions is the first non-monetary item can be achieved. When energy efficiency is also intended as a strategy to maintain the history. Hence, realtors should also examine the value of enhanced indoor comfort and the value of building preservation.  This study also intends to raise knowledge in the sustainable real estates, private residential housing market and green buildings to add to the value of biodiversity and urban ecosystem services, as well as the real estate market.