This document is an example of Recommendations for EU states that gives guidance on how to proceed with zero-energy buildings.  It is likely the recommendations apply elsewhere.  The document answers questions like "How do renewable energy sources contribute?".  Other information includes

• Buildings are central to the EU's energy efficiency policy, as they account for nearly 40 % of final energy consumption. 
• The importance of the building sector for energy efficiency improvements was highlighted in the European Commission's Communication on energy efficiency and its contribution to energy security and the 2030 framework for climate and energy policy and in its Communication on a framework strategy for a resilient energy union with a forward-looking climate change policy. 
• Full implementation and enforcement of existing energy legislation is recognised as the first priority in establishing the Energy Union.
• The Directive on the energy performance of buildings is the main legal instrument addressing energy efficiency in buildings in the context of the 2020 energy efficiency targets.
• Article 9 of the Directive sets a specific target that by the end of 2020 all new buildings must have nearly zero or very low energy needs. The nearly zero or very low amount of energy required should be covered to a very significant extent by energy from renewable sources.
• National legislation transposing the requirements of Article 9(1) is required to ensure that by 31 December 2020 all new buildings are nearly zero-energy buildings. The same nearly zero-energy target but with a shorter deadline of 31 December 2018 applies for new buildings occupied and owned by public authorities. This should create a transparent national legal framework for economic operators regarding requirements for the energy performance of new buildings as of the end of 2020. 
• In parallel to requirements for new buildings, the Directive requires Member States to put in place support policies to stimulate the refurbishment of existing building stocks towards nearly zero-energy levels.
• The Commission has issued a Report to the European Parliament and the Council on progress by Member States towards nearly zero-energy buildings. Further information has been gathered from Member States as part of their reporting obligations on the subject matter.
• Progress by Member States has slowly improved but should be accelerated. Although measures to support the growth in nearly zero-energy buildings at national level have increased, Member States should step up their efforts to ensure that all new buildings are nearly zero-energy by the target dates in the Directive. 
• The Directive on the energy performance of buildings is currently under review. Principles for nearly zero-energy buildings are one of the pillars of the current Directive and are set to become the norm for new buildings as of 2020. The review will assess whether additional measures will be needed for 2030. The development of new policies and approaches should be based on solid foundations. It is crucial that the nearly zero-energy buildings requirements for 2020 are fully implemented.
• This is further supported by Article 9 of the Directive, which provides that the Commission may issue a recommendation on nearly zero-energy buildings to Member States.