EnerPHit – the low energy design spec for London retrofits

Passivhaus isn’t the only option for creating a low energy eco home in London. EnerPHit is a similar standard incorporating airtight, high-quality insulation with a mechanical ventilation system, but the certification is a little more lenient than PassivHaus. 

That makes the EnerPHit standard the perfect choice for home-owners in the UK looking at low energy solutions for their renovation, refurbishment, retrofit or extension projects.


EnerPHit might have been created because it’s  so cost-prohibitive to try and retrofit a traditional UK home to Passivhaus standards. The average UK home is just too draughty, and often PassivHaus requires incredibly thick insulation – something most UK homes don’t have space for.

Internal Wall Insulation 

Because it’s so difficult to retroactively apply to a typical bricks-and-mortar British home, the Passivhaus building design specification is usually reserved for new builds in the UK. Internal Wall Insulation (IWI) can be up to 300mm thick for a Passivhaus retrofit, losing too much interior space for a thin-bodied Victorian London townhouse.

External Wall Insulation

What’s more, External Wall Insulation (EWI) is often prohibited by conservation officers in London, as it affects the external aesthetics of the building – something conservation officers hate.

EnerPHit is a low energy design specification that allows for slight draughts, for lower-quality insulation and windows, and doesn’t need the same rigorous building physics modelling proof. It still uses the Passivhaus approach to low energy construction, but it isn’t as severe in meeting Passivhaus’ strict guidelines on heat loads, insulation and over-heating.

Following the EnerPHit approach will still result in a very comfortable home with huge energy savings, just not to the same extent as a PassivHaus. But just as it’s not as stringent, EnerPHit also isn’t as expensive – and that’s great news for home-owners in the UK that want to create an eco-friendly, low-cost home.

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