Joseph Thurrott Architects

The Maryville Passive House is a continuation of research into the development of appropriate contemporary architectural form that responds to regional vernacular building typologies whilst affording flexibility to the occupants' changing lifestyles.  

 

Passivhaus energy performance criteria

1. heating demand (space heating)

≤ 15 kWh/(m2a)

 

2. primary energy demand

≤ 120 kWh/(m2a)

 

3. air tightness (air changes / hour when house is pressurised to 50Pa

≤ 0.6 h-1

 

Architecture:

The Maryville Passivhaus is a reinterpretation of Scottish rural vernacular buildings. By splitting the house in two distinct volumes a larger footprint is achieved whilst maintaining the proportion of familiar 6m wide gable-ended buildings found throughout the Scottish countryside. The volumes are wrapped on three sides by a white rendered envelope whilst the timber clad south elevation is extensively glazed providing maximum passive solar gain. The living, dining and cooking spaces are arranged around a south facing landscaped court, reinforcing the connection with the rear garden. A double-height living volume serves as the focus of the house permitting an abundance of direct sunlight into the heart of the home.

 

Key design elements:

The overriding emphasis of the design is to keep the spatial organisation simple. Two rectangles form the basis of a straightforward plan. By shifting the rectangles in plan, two positively defined external spaces are created: an entrance court to the north and a garden court to the south. Circulation to the first floor is situated along the axis of the shift. The pitch of the roof is articulated throughout the first floor, providing a relief from the traditional flat ceiling. Whereas the internal pitch of the scissor-trussed roof is set at 30 degrees to suit the scale of the bedrooms, the external pitch of the roof is set at 45 degrees to harmonise with the external landscape and to optimise solar collection in the PV and hot water panels. The fenestration is designed to take maximum advantage of passive solar gain. Should there be a need for additional accommodation, the double height living volume is designed to accommodate the insertion of a floor plate without disturbing the external envelope.

 

External envelope:

Factory insulated, timber-framed superstructure with timber scissor trusses supported on in-situ concrete strip foundations with a concrete ground bearing slab. The superstructure is wrapped in a continuous thermal skin comprising a proprietary rigid insulation render system and timber cladding for the walls. The roof trusses are filled with insulation and clad in standing seam zinc. All windows and doors are triple-glazed with argon/krypton gas cavity fill. The envelope is extensively detailed to eliminate thermal bridging. A continuous air-tight membrane lines the inner surface to ensure the envelope meets the Passive House air loss performance rate of 0.6 air changes per hour when pressurised at 50 Pa.

 

Air, Heat, Water, Electricity:

The air quality of the internal environment is controlled by a Mechanical Ventilation Heat Recovery system. In addition, the MVHR system serves as the primary heat distributer. A water-borne heater coil integrated into the MVHR system provides supplemental heat if and when required. DHW is generated by roof mounted solar collectors and stored in a proprietary cylinder housed next to the MVHR in the utility room. During the winter months, DHW is generated by an air-source heat pump. Electricity is provided by solar PV panels and supplemented by green-tariff mains during the winter months. Secondary or back-up space heating is provided by a high efficiency wood burning stove located in the centre of the house to maximise the distribution of radiant heat energy.  The specific primary energy demand is designed to meet the Passive House performance rate of less than 120kWh/(m²a).