Heatherland Poolhouse in southwestern England

Heatherlands is a substantial addition to an existing house, built in an area of outstanding natural beauty on the Dorset Devon border. It responds carefully to the folding of the landscape and roof pitches of the existing house. The folds create splits which highlight views, both concealing and opening to them. A new living room forms a transition point between the old and the new, collecting reflected views and light. Situated to the West of the existing house, the structure takes the stance of a traditional outbuilding, acting as a paddock boundary whilst protecting the gardens. The addition defines a new approach to the building, entrance court and outdoor terrace to the South. Adopting a number of sustainable strategies the building includes passive ventilation, sustainable materials and highly insulated construction. The existing building is wrapped in shingle, which will weather together with the new larch rainscreens, covering the addition.

The brief focused on the ability for the clients to obtain essential health facilities for avid swimmer.s They wanted a major upgrade that included a gym, sauna and pool as well as a new master bedroom suite, living room, garages and storage. The pool facilities, including changing, washing and exercise spaces, are housed in a sunken level. Meanwhile household program is woven in, tying the new functions tightly into everyday life. The new living room is positioned to the West end of the existing house, suspended above the pool, collecting reflected light and views as the sun tracks the from South-East split openings to the low Western picture window. This also provides a visual connection to a restored Airstream trailer that functions as an additional guest room.

To reach the pool, the route turns from the living room and descends into progressively heavier and more enclosing areas including vertical, top lit spaces within the core, before being released into the space of the pool room. This approach provides a series of buffer zones between the main house and the humidity of the pool. Above, the master suite pushes out Westwards, opening to spectacular views and providing it with a sense of privacy from the main house.

Sustainability
Back to the wind
The building’s orientation puts it’s back to the wind sealing the interior space against climatic extremes. The West face is very simple, composed of two solid, timber-clad overlapping planes with minimal window openings, except where views allow openings at the junction of the two planes. The solid facade also provides controllable ventilation openings, utilizing the prevailing wind as an active support to help drive the passive ventilation system. To the far side of the building, a core rises up forming a eight metre space adjacent to the warm service core drawing air through.

Passive ventilation 
From the outset the design principles were for a passivley ventilated building. The aim was to future proof the building against summertime overheating risk resulting from climate change. Delivering a cool internal environment was a major priority. The natural ventilation flow rates were determined to achieve five air changes per hour at one degree temperature difference. This purge ventilation was coupled with thermal mass to provide suitable operative temperatures via manually controlled grilles.

Core and skin
A monolithic service core and base provide the thermal mass for the building. The core houses a sauna and wood burning fire, which maintains a higher temperature in the core. Above the sauna a buffering space helps promote stack ventilation during the summer months and re-circulates warm air in the winter, further stabilizing the overall temperature of the structure. These structures are then wrapped by a continuous, highly insulated timber frame stressed skin to maintain stable core temperature.

FSC timber
The entire skin of the building is wrapped in FSC Larch with varying widths and chamfered profiles, breaking up the large expanses of cladding. The larch will weather naturally without the need for finishing, is low in embodied energy and is UK sourced.

Passive solar gain
The large windows to the end of the pool are South facing for passive solar gain in this high volume space. At the height of summer the trees will come into leaf protecting the façade from intense sunlight and avoiding overheating. The two large windows to the East and West have solar low-emissivity coatings to avoid excessive heat gain throughout the year.

Site
The intention was to respond carefully to the folding of the landscape and pitches of the existing house, blending the new building into its surroundings. The impact of the mass of the building was reduced by pushing it into the slope of the land and following the existing contours of the site so that the addition is read as part of the landscape.

The existing Arts and Crafts house built in 1912 sits on a large sloping site over looking an Area of Outstanding Natural Beauty. There are strong features from the style such as the large chimneys, fireplaces and dark internal Elm finishes but the most distinctive trait is its extensive, sweeping pitched roof. To the West it runs down for eight and a half metres, and its pitch is repeated for the porch, the bays and the gables. The upper storey is clad with cedar shingles, with pantile roofing, while the lower storey is rendered. Behind this the lower storey is a metal frame while the upper storey and roof is timber frame, an advanced system for the period.

Large mature gardens of approximately one hectare sit high above the Holcombe Valley, with a glimpse of the sea at the Dorset town of Lyme Regis. This privileged position also held inherent difficulties. The site is restricted and steeply sloping, in an area renowned for extremely unstable soils. Mature trees concealing the house and gardens, leave only select views of the countryside, while a third of the site is agricultural land.