The £800,000 extension and refurbishment project integrates a new highly insulated timber frame within a brick shell to meet EnerPHit standards
OEB Architects has extended and refurbished a Victorian townhouse in Kentish Town, North London, to meet the low-energy EnerPHit standard, the Passivhaus standard for retrofits.
Situated within a Conservation Area, the extensions at roof level and rear are clad in zinc and are rectilinear in form to complement the surroundings.
Inside, rooms are lined in white with storage walls that reveal an adaptable plywood structure with coloured exposed surfaces behind.
To meet Passivhaus standards, a new highly-insulated and independent timber frame had to be built inside the existing brick shell, replacing the original internal structure and leaving a three-storey void within the brick shell, essentially creating a building within a building.
This also meant that the internal layout could be reconfigured, with rooms divided by a series of 900mm-deep storage walls placed orthogonally across the plan.
The storage walls give a sense of solidity to the new construction, containing all built-in functions of the house: kitchen, WCs, desk, and plant.
Solid oak flooring is used throughout and continues onto the new staircase, where a lightly reflective white ribbon balustrade runs continuously up through the full height of the house.
A new second-floor study has been placed within the zinc rooftop extension. Here the plywood structure remains exposed, with joints between components exposed to represent the room as being made of different parts. Adjustable open shelving spans between plywood posts, where objects can be displayed.
Airtightness was achieved using Smartply Propassiv OSB and triple-glazed replacement sashes for the windows.
The client has integrated a smart-home system into the project which is visible throughout the house in brightly coloured powder-coated conduit.
The result is impressive. The clean white surfaces, paired with warming wood, are an obvious match for our aesthetic, but the house is deeper than that. The use of a single system of modular plywood components throughout the house will allow us to adapt it as our needs change, key to the long-term sustainability of the building.
The insulation and airtightness measures have led to a house that is not only efficient, but comfortable everywhere – it’s strangely pleasant to live without draughts. As an engineer, though, my favourite aspect is how it’s possible to see through the white skin of the building, into its wooden structure and colour-coded services, simply by opening a cupboard door or entering the study. We’re looking forward to seeing how the building works with us in the coming years.
Building automation follows the overall minimalist brief. Unobtrusive sensors in each room continually monitor indoor air quality, feeding back to the ventilation system. Interior lighting automatically tracks the daylight outside, from a cool midday to cosy dusk. A custom digital simulation of the house predicts interior temperature, closing reflective blinds and opening windows to prevent overheating, while determining whether solar power is best used to charge batteries or heat water.
Despite the advanced technology, wall mounted controls are traditional and familiar rather than glowing screens. Significant effort was spent ensuring the technology can grow with the evolving needs of current and future owners, like the plywood cabinetry, modular, standard and interchangeable components allow pieces of the system to iteratively adapt to the future.
Andrew, client and homeowner
Start on site November 2017
Completion date August 2019
Gross internal floor area 240m²
Gross (internal + external) floor area 367m²
Form of contract or procurement route JCT Intermediate
Construction cost £800,000
Construction cost per m² £3,333
Architect OEB Architects
Structural engineer Bob Johnson Structural Engineers
M&E consultant Green Building Store
Passivhaus designer CANDO
Landscape consultant Boma Garden Company
CDM consultant OEB Architects
Approved building inspector BCA
Main contractor Bow Tie Construction
CAD software used Vectorworks