ARCHITECTURAL DESIGN COMPETITION

FOR PASSIVE HOUSE IN BULGARIA

Peter Tchordov Dipl.Eng. Arch. Sofia Kodjamanova - Tchordova Dipl.Eng. Arch.

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Building-Metric-Sheet-18.xlsx

CONCEPT DESIGN NARRATIVE

Sustainable building configuration and placement
The building simplicity in form and material is meant to disconnect from the neighboring housing. Its cubic shape and spruce facades that serve as flat canvases for the ruby-red composition of the openings contrast the surrounding locality. The design of the building with two cubic volumes set on top of each other extended to the north side of the plot with garage and entrance makes the different functionality recognizable from the outside. The site offers a chance of unobstructed sunlight not shaded by trees or buildings, which provides possibility to maximize the passive solar gains in winter by large-area glazing on the southward-facing surfaces. The house is set in the northern part of the plot at the setback lines. The development footprint has been designed to minimize impact on site – driveway and access path have been located close to the municipal roadway allowing less hardscape throughout the site thus increasing the permeability and reducing surface runoff. Vegetated roofs have been used as strategy to reduce heat island effect and stormwater runoff in a sustainable way.

Functional layout
The building is oriented with its long side north-south. The entry and garage are organized as adjacent cubic components placed outside of the compact thermal envelope of the house. The entryway is through an air-lock to prevent outdoor air from interacting directly with conditioned air within the building. A clear zoning has been aspired in the interior floor distribution – north-facing “buffer areas” servicing access and utility functions and south-facing living area with dining room and spacious open kitchen. On the ground floor there are also mechanical room, study/guest room with adjacent bathroom and a storage/housekeeping room close to the kitchen. The definition into functional zones of the spacious open day time area is supported by the different ceiling height opening the spatial composition toward south. From the living room the occupants can get to the outside on a terrace on the same level offering a natural extension of the interior living space to the outside. The terrace decking of natural spruce wooden planks creates a flowing transition from the inside to the exterior. Upstairs there are two bedrooms oriented to the south with terrace access and a bathroom located on the northwest side.

Building construction and envelope

In order to meet the local seismic requirements and to provide beneficial thermal mass in the interior of the house, the structural system consists of solid construction of load-bearing walls of masonry and reinforced concrete ground, floor and roof slabs. The wall masonry will be executed with environmentally friendly pumice blocks which contain no toxic or harmful substances and have excellent thermal and acoustic insulation. The façade is clad with thermally treated wooden spruce planking with open joints. Color accents are set in environmentally-friendly laminate boards in ruby red free of formaldehyde and phenols. The timber façade cladding is installed on wooden I-beams set in front of the bearing exterior wall. The intermediate portions of the wooden structure are filled with cellulose insulation.
Perimeter insulation shall be placed on the slab-on-grade underside and wood fiber insulation boards on the topside. The roof slab is insulated with wood fiber insulation boards. The flat roof surfaces of the building have been developed as vegetated roofs improving the annual energy performance of the building, increasing the roofing membrane durability, reducing noise and electromagnetic radiation, reducing the amount of stormwater runoff and improving the overall ecological performance of the house.
The generous fenestration on the south façade provides not only for a bright, friendly atmosphere in the living rooms and for high solar energy gains, but also allows a generous view of the garden. Exterior blinds on the south-facing glazing surfaces ensure a controlled sun and privacy protection. The external shading effectively controls solar heat gain and light levels and has a decisive positive impact on the interior climate in the summer months. Compared to the south façade, the other three elevations are characterized by punctuated timber facades with modest square openings. The implemented Passive house certified window and transom-mullion systems feature frames in wood-aluminum having a long life and constructed to withstand the impacts of time – in physical terms and also esthetically. By reason of the weather resistant properties of the outer shell, maintenance is reduced to practically zero. At the same time natural spruce wooden frame in the interior reveals its soft side for a warm ambience. With Ug value of the triple glazing of 0,60 W/(m²K) and frame values of Uf = 0,78 W/(m²K), Uw - values of 0,78 W/(m²K) have been reached meeting the requirements of the Passive House Standard.

Implemented materials
The design focuses on the systematic implementation of environmentally friendly and renewable building materials. The objective is the use of materials that are nontoxic, recyclable or made from recycled content, renewable and obtained from local sources.
The renewable building material wood found ample application in the façade construction and the interior design. Local spruce timber is used for façade cladding, interior flooring and terrace decking. Thermal treatment of the wood is used as chemical-free timber preservation method. Environmentally-friendly laminate boards set color accents in the façade. Their core is made of 100% biological secondary components obtained from renewable resources and is fully recyclable. The exterior walls are insulated with cellulose insulation manufactured from recycled paper and being the least polluting insulation. In addition to excellent thermal insulation properties, cellulose insulation also offers a very high summertime heat-shielding due to its high storage capacity which is beneficial for the hot summer months. The floor and roof slabs are insulated by means of wood fiber insulating panels that are biodegradable and recyclable.

Interior design
The interior design aims to create a modest and natural ambience for the occupants. White plastered wall surfaces and natural wood flooring dominate the interior. The harmonious transition from wooden flooring of living room and bedrooms into terrace decking on ground and first floor creates an interlinkage of interior areas and open space.
Objective is also to ensure the low toxicity of implemented materials. Adhesives, sealants and primers will be selected to meet prescribed VOC limits.

Technical installations
Energy for heating and domestic hot water is provided by means of a passive house compact unit with integrated heat pump as an economical and comfortable technological solution. The device integrates all mechanical systems required in the house: a heat pump is added to the ventilation unit with heat recovery, using the latent heat of the exhaust air as a heat source for producing both supply air heating and domestic hot water in an integrated storage tank. The integrated ventilation system with heat recovery is supported by a ground heat exchanger of 40 m length installed 1,5 m below the surface which is particularly beneficial with its cooling effect in the summer months. The clear layout of the building enables short and straight routing of the ventilation ducts. Through the use of a solar thermal system of approx. 6 m2 supporting the domestic water heating up to 70% of the annual demand can be provided by the sun as a renewable and free energy source.
In order to create a comfortable indoor environment, especially with respect to the hot summer climate, passive cooling strategies have been considered. Since the roof is a major source of heat infiltration, green roofs have been chosen as a design strategy enabling vegetation to significantly reduce temperatures through evapo-transpiration and the absorption of heat. The building was designed to also take advantage of natural ventilation. The potential for night ventilation can be considered for cooling the high thermal mass in the interior of the building. A thermal chimney effect can be integrated into the house with the open stairwell. An operable window in the corridor on the upper floor enables an updraft of the rising hot air escaping upwards from the ground floor.