Haus Ltd - Holly Hill Passivhaus

Project Details

Project - Holly Hill Passivhaus
Client - Mr & Mrs Lovesy
Architect - Frances Forward, Haus Ltd
Structural Engineer - Paul Tanner Associates
Environmental Consultant - Mark Standen
Offsite-fabricated Composite Timber Frame Specialist - Gruber Naturholzhaus GmbH
Offsite-fabricated Precast Insulated Concrete Specialist - Glatthaar-Fertigkeller Ltd
Mechanical Subcontractor - Tritec GmbH
Electrical Subcontractor - Prestige Electrical (Southern) Ltd

Project Overview

Holly Hill Passivhaus is a four bedroom, two storey family home set in rural Kent, designed by Haus Ltd and certified by the Passivhaus Institute. Architect Director Frances Forward worked collaboratively with a team of specialist partnering firms in order to produce an extremely low energy and highly efficient dwelling within this sensitive context. The house consists of an insulated pre-cast concrete basement and super-insulated laminated timber frame superstructure, which were pre-fabricated offsite in Germany, then transported and erected on site by the German partner firms.

The structure is clad with larch (echoing the woodland environment) and will weather naturally over time to a silver-grey. The diagonally pitched roof is covered with pre-weathered dark grey zinc to match the aluminium faced timber triple-glazed windows and doors. An array of photovoltaic panels on the south-west pitch of the roof is capable of generating more electricity than is required for a single dwelling and two solar thermal panels directly heat domestic hot water. Rainwater is harvested, filtered, then recycled and used in WCs. As there is no mains sewer near the site, foul drainage is treated using a package treatment plant; water of near potable quality is then discharged into the pond which becomes a landscape feature within the garden and home to local wildlife.

The house is serviced by a "compact unit", housing the mechanical ventilation and heat recovery (MVHR) system, a mini airsource heat pump and a hot water cylinder linked to the solar panels. The unit supplies fresh warm air to each room in the house and extracts stale air via bathrooms and the kitchen. This innovative piece of equipment recovers 89% of thermal energy from the extract air. The site is steeply sloping with a fall of approximately 6m from west to east, providing opportunity for the house to be half buried into the hillside with each of the two levels touching the ground. The south and east facades open out to the landscape and garden, and are highly glazed with large triple-glazed windows allowing natural light to penetrate the main living spaces and providing useful solar gain in winter, as well as maximising views out to the fields below.

The large roof overhang and electrically controlled external blinds protect the internal spaces from overheating in the height of summer and the sitting area on the balcony to the south. Technical and services spaces are located to the north and west of the building at the lower level, dug into the hillside and with lightwells to allow natural light into the rooms during the day. The end result is a high quality, low maintenance 'treehouse' set into the hillside overlooking the fields below.