The Paris Agreement entered into force on 4th November 2016 and it is the most ambitious effort to reduce Greenhouse gases (GHG) emissions after it was adopted by the Parties to the United Nations Framework Convention on Climate Change (UNFCCC) in 2015. The Parties have through the Nationally Determined Contributions (NDCs) committed themselves to a significant reduction in the GHG emissions. This can be done through an effort in its own country or by using the market mechanism in Article 6 of the Agreement. After the 24th session of the Conference of the Parties (COP) in Katowice, Poland in December 2018, the finalization of Article 6 Rulebook was postponed to being finalized at the COP 25 in Chile. Globally, the building sector is single handily responsible for 30% of final energy consumption and more than 55% of global electricity demand (IEA) and nearly 40% of total direct and indirect CO2 emissions. Therefore, targeting the building sector, creates a huge potential for contributing to a low carbon development. Globally, energy efficiency measures have enormous potential for supporting a low carbon development. To set the need in a context, this knowledge product is based on a UNDP contract covering Mongolia. It is, therefore, based on Mongolian realities and therefore the experience can best be transferred to countries with similar cold climate and stage of development. Having this in mind we focus on addressing cases when data is scarce (e.g. the non-availability of heat meters, non-availability of area corresponding to electricity consumption, etc.) and ways to overcome such issues.