ARCHITECTURAL DESIGN COMPETITION

FOR PASSIVE HOUSE IN BULGARIA

DID Proekt Ivan Ivanov Dipl. Arch.

(639 - user rating)

Building-Metric-Sheet-7.xls
Envisaged measures for reduction of energy consumption:

  • Southern orientation of volume of the building and the windows, measures against overshadowing the house in winter and overheating in summer.
  • Passive use of solar energy.
  • Compact shape (minimum ratio of surface area and volume) S/V=0, 65.
  • Insulation required for achievement of the standard for "passive building”.
    - U value of the fencing exterior walls U=0.0884 W/(m²K)
    - U value of floor facing the terrain U=0.0736 W/(m²K)
    - U value of the roof U=0.0849 W/(m²K)
    - Triple glazed windows with gas (krypton) between the glass panes U=0.71 W/(m²K) and G>50%
  • Air-proofness of the building– we use steam permeable and air-proof foils.
  • Wall Trombe-Michel behind the southern facade.
  • Prevention of thermal bridges.
  • Passive cooling and heating with recovery of the energy from spent air combined with forced ventilation and heat exchange with recuperator.
  • Solar collector (11 pcs.) for domestic hot water – installed area of 18 sq.m.
  • Collection in a filter-bed of rainwater from the house roof and their utilization for domestic needs.
  • Energy saving electrical appliances and lighting.

1. Determination of the orientation of the plot.
Following the executed surveys of the real estate we arrived at the decision described in the design. We analyzed the sunlight, shading and the wind rose during all seasons (the data have been taken from a meteorological station near the village of Lozen). The prevailing winter winds are mainly south-western and western. The existing building and tree vegetation with the orientation we have chosen are situated to the west and form a natural protection against the winter wind, moreover they do not overshadow the building. As an additional barrier against the winds we have offered a fencing of the real estate of perennial bushes, with a height of about 2 m, coniferous trees and a barbeque with pergola in the western part of the land plot.
We selected this variant as the thick fences generate whirlwinds while the porous barriers (such as a combination of trees and bushes) increase the tranquil zones.
By use of the deciduous vegetation in the southern part of the yard which is planned as to not overshadow the building, we channelize the summer north-western winds. With a wind catcher on the roof these winds are used for passive cooling.
2. Design.
The natural heat in the exterior areas depends on the location of the sun and the properties of the ground surface to give out. Therefore, the heat curve is lags behind against the curve of the height of the sun with about one month, i.e. the hottest day is not June 21 but somewhere around the last days of July, and the coldest day is not December 21st but some of the last days of January. The degree of falling of sun rays in summer (June 21, 12:00 h.) for this geographical latitude is 70º7´, and in the end of July it is about 60º. This way we determined the inclination of the southern facade.
The sunscreen devices along the southern facade are with changing inclination, not admitting sun rays in summer, and to the opposite admitting them in winter.

At the base of the southern facade, at the foundation of the wooden farms there is an inclination which we use to direct the reflected sun irradiation towards the building (in winter months).
Traditional houses in cold climate areas are with roofs inclined towards the unfavorable direction and windows mainly along the southern facade. We thus solved the inclination of the roof to the north.
The volume of the building is compact, with proportion (ratio of surface area and volume) S/V=0, 65, which is less than the volume of a cube with length of the wall of 9 m.
The windows are mainly along the southern facade, a small openable window is envisaged at the eastern and western side. They are installed upon the external insulation layer of the wall.
The premises in the building are separated into temperature areas – heated and not heated. The border between both areas is of double partitioning wall, and the cooling, heating, ventilation systems and the vertical pipes for water supply and sewerage pass between the walls. The kitchen, bathrooms and the toilet are planned so as the piping (hot, cold water and sewerage) to be placed in one vertical branch and as short as possible. Thus, we minimize the loss of energy.
The kitchen has a connection with the warehouse where a place has been envisaged for separate waste collection.
To the south the village of Lozen is bordered by the Lozen Mountain. The prevailing vegetation is beech, oak and pine. Taking into consideration the requirement for economy of the design, we selected wooden structure for the building (we use local materials) made of pine. Compared to beech and oak, pine is the most inexpensive construction material. The exterior and interior partitioning walls are made of OSB panels with heat insulation between the profiles; these are produced of waste material from the wood processing industry.
For the facing of the building we also used waste material of the wood processing industry, and the exterior wooden panelling is made of boards (covers), which are cut out during the processing of the wooden trunks.

We decided to use a Trombe-Michel wall (solar wall) behind the southern facade. The cooling and the ventilation of the premises is achieved through the „chimney (stack) effect“. The wall is solid, built of masonry, collector-accumulating heat. It heats up during the day, accumulates heat and radiates it during the night.
By use of a wind catcher (barjiils) on the roof the building is passively cooled during the warm months. The prevailing north-eastern and northern summer winds are caught and the cool air falls down and cools the premises. After it has passed through the building, the warm air is lifted and escapes through the cooling tower. We have borrowed this method of passive cooling from the traditional architecture in the places with warm climate.
We also use controlled forced ventilation by cooling/heating of the fresh air via ground air heat exchanger in the soil at a depth of 4 m where the temperature in winter months is between 5ºС - 10ºС, and in summer - between 10ºС -15ºС. The air heated in the house using a recuperator delivers heat to the incoming fresh air, so therefore recovery of the energy from the spent air is in place.
To achieve the high energy efficiency of recycling of spent heat, we use heat exchanger with the so-called counter-current or opposite scheme of movement of both flows - the supplied fresh external air and the spent internal air. Their efficiency reaches 95%, and minimum is considered to be 80% „back recovery” of the energy.
The activation of the forcing systems occurs only in the cases when the passive means are not able to ensure the required level of ventilation.
The wall is hermetically sealed by use of steam permeable and air-proof foil along the entire surface of the external cover.

We selected solar collectors (11 pcs.) for domestic hot water along the southern slope of the roof. The installed area is 18 sq.m.
Due to the high price of the photovoltaic panels, they are not provided for in the design. It is possible to place them at the northern slope of the roof which is with area of 107 sq.m.. Taking into account that 8 sq.m. of panels are necessary for 1 kW of power, then the power of the roof panels will be about 13 kW, absolutely sufficient to meet the demands of a single household.
We also suggest the rainwater from the roof of the building to be collected in a filter-bed located below the slab at elevation ±0,00. The filter-bed is divided into two sectors. The first sector contains the water collected from the roof which may be used in the kitchen and the bathrooms. After it has been used once, the water goes to the second sector where again after filtration it is used for cleansing the toilet cisterns. Finally, the water goes into a septic filter-bed where it is treated anaerobically (without oxygen) and filtered by the roots of plants (wastewater treatment system „Wetland“) and is used for watering the garden.