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5A Castle Hill - Passivhaus


This project involved extending and upgrading the existing house to the low energy in use Passivhaus EnerPHit standard.

  • Retrofit Passivhaus building.

  • Energy requirement for heating extremely low, better than new build Passivhaus standard

  • Energy consumption better than predicted.

  • Extremely air tight, almost to new build Passivhaus standard

  • Fresh, filtered air 24/7, with heat recovery.

  • Acoustically superior with triple glazing.

  • Cool in summer

  • The project comprised the extension to, and comprehensive refurbishment of, an existing detached house built in 1959.

  • The accommodation includes:

  • 4 bedrooms, each with ensuite

  • Living Room

  • Kitchen / diner

  • Utility

  • TV Room / snug

  • Home office

Features include mechanical ventilation with heat recovery providing constant pre heated filtered fresh air; tripled glazed windows; high levels of air tight construction; very high levels of insulation keeping the house warm in winter and cool in summer.

During the first winter, the house was heated by just four towel rails. In occupation monitoring shows that the house is using less energy than predicted by the thermal model prepared at design stage.

Recipient of a Berkhamsted Parish Council design award.

Project Information


Berkhamsted, Hertfordshire


£600K Approx. 250m2


Completed August 2018


Concept designer.
Passivhaus designer/modeller.
Planning Application.
Tender Information.
Contract Administration.

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