The EnerPHit standard provides requirements for retrofit projects designed to maximise the thermal efficiency of the building and drastically reduce its energy consumption and heating requirements. 

This article assumes that you are already familiar with the Passive House standard. If not, refer to our guide to Passive House Requirements for an overview. 

EnerPHit focuses on the same core criteria for the project as Passive House while accepting that meeting Passive requirements is generally not possible for a retrofit project. This is because important elements, like orientation and structural form, are already decided in an existing house.

For example: if a building was originally constructed in a way that creates numerous areas of thermal bridging through its basic fabric, it will be challenging to eliminate them entirely.

The stringent Passive airtightness requirement of 0.6 ACH will be equally difficult to achieve if the building was not originally built paying close attention to airtightness. 

Other aspects of existing buildings that cannot be determined by the renovator include its form, orientation, conservation and planning restrictions, existing architecture and its position relative to neighbouring houses. 

EnerPHit is designed to offer all the advantages of passive certification while remaining realistic for refurbishment projects. 

More energy is required to achieve ‘Passive’ comfort levels in an EnerPHit home - but it is still a considerable step up in energy efficiency from most existing homes; even from new builds.

Retrofit is a renovation of a building undertaken to significantly improve its thermal performance.

Typically, this involves improving – or replacing - the building fabric, rather than simply introducing renewable energy systems.

We know that starting out on a renovation or retrofit journey can be overwhelming.

Here is a non-exhaustive list of pointers for the build to get you started: 

• Internal and external insulation with optional weather-proofing over-cladding concept 

• Replace existing windows with triple-glazed timber-aluminium composite models. The EnerPHit U-value threshold is 0.85 W/m²K but, according to the Passive House Institute, there is no reason why Passive-standard windows of 0.80 W/m²K - or less - should not be used. View our Passive house product range here.

• Minimise thermal bridges e.g. by overlapping areas of external and internal insulation and adding a breathable airtight membrane to floor insulation. 

• Improve airtightness e.g. by ensuring the windows contain robust seals and are installed using best practice methods to reduce the possibility for air leaks. 

• Efficient mechanical ventilation with heat recovery (MVHR).  

• Install or upgrade renewable energy sources. 

• A Passive House approach incorporating thermal performance, air-tightness & ventilation 

As is the case with Passive builds, the Passive House Institute provides an EnerPHit Retrofit Plan and a Passive House Planning Package (PHPP).

The Passipedia resource also contains a wealth of knowledge for first time and experienced renovators alike. 

The majority of the United Kingdom falls into the Cool-Temperate zone, meaning your windows and doors must have U-values of 0.85 W/(m2K) or lower to meet EnerPHit standards. 

However, the Passivhaus Institute has recently released new data in the PHPP V9, which takes into account climate data. As a result, the UK now contains three zones: 

• Cool-Temperate, which covers the majority of the UK. Window U-value required: 0.85 W/m²K

• Cold, which covers parts of the Newcastle area and Scotland. Window U-value required: 0.65 W/m²K

• Warm-Temperate, which covers London and the South West. Window U-Value required: 1.05 W/m²K