Introducing our new EnerPHit office

What are we doing?


WARM wanted a new office which was comfortable, had good air quality and was cheap to run: after several years of designing wonderful buildings for others we decided it was time for us to build a Passivhaus for ourselves.


We ended up finding an existing building, not ideal especially considering our limited budget, but on the plus side it is a fantastic opportunity to learn. We are hoping to achieve the EnerPHit standard – the Passivhaus standard for refurbishments which takes into account the difficulties inherent in refurbishing to a challenging energy standard.


The project is particularly important to us as we want to be able to truly walk our talk.  This means all of us getting our hands dirty and having a go at the details that Karl and Pete have put together.


Situated in Stonehouse, WARM are pleased to be part of the regeneration of this area of Plymouth. The property is of cavity wall construction dating from the 1960s, and was a first floor flat with a shop below. Our office will replace the flat whilst the shop will continue to run beneath, although we are treating the whole building.

before work

Like many of our clients we have a tight budget which means we’ve had to make some difficult decisions. For example, we’ve kept the existing roof structure which is incredibly wonky creating more difficult airtightness details.


Our retrofit comprises of:

  • 250mm EPS external wall insulation & 50mm cavity fill,
  • 300mm roof insulation between I-beams on top of the existing roof structure,
  • Rationel triple glazed windows throughout,
  • amazingly stringent airtightness (no drafts),
  • heat recovery ventilation for good indoor air quality, and details to ensure minimal thermal bridges.

All of the modelling and drawings have been created by WARM so there is no one to blame!


For more information about the EnerPHit standard click here.


Work started in late March 2013 and is due to finish by July 2013.

Follow the weekly progress of the build here.


Learning opportunities


This project is special because it is one of the first refurbishment projects aiming to achieve the EnerPHit standard. Passivhaus has only recently begun to concentrate on refurbishing existing buildings, as previously the focus was on new build. Elements of the existing construction of the property are common throughout the UK and we will gain a good understanding of the problems encountered and how to solve them. As significant proportions of the UK building stock will need such refurbishment, this project provides a really valuable learning opportunity for us.


The training aspect will continue long after the build is complete as we will undergo long term monitoring of energy consumption. We’ll look to publish this highly useful performance data and use it to inform future work.