A Zero Energy Building (PassiveHouse Plus) in Gökova
by Stephen Berriman
Introduction
I plan to design and build two, Net-Zero single-family houses in Gökova, South-West Turkey. Gökova lays at the bottom of a broad valley about 2 km from surrounded by mountains that reach a height of 1000m. Its climate is classified as ‘Warm’ and enjoys mild winters and long hot summers.
The design is heavily constrained by the need to match the visual architectural form of the traditional Ula-Muğla building style. Both houses are to be identical in design, but with the upper house elevated some 5 m and orientated 12⁰ closer to the North/South axis. There will also be some shading differences as result of interaction between the 2 houses. The land area is a green-field site on a slope formally used as a stepped olive grove. The plot is surrounded in the main by low-level bushes although there are a few trees of significant height and I am working to prevent these being felled during the build of the access roads and other properties. This is not easy in Turkey where it is considered good practice to completely clear a site and its surrounds before commencing build. The properties are to be designed and constructed to meet the Passive House Plus standard.
General Information
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Location: 37.05, 28.37 – plot 116/5
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Passive House Climate Zone classification: Warm
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Land size: 646 m²
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Building footprint size (without insulation): 64.6 m²
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Ground slab size (with insulation): 72.9 m²
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Treated Floor Area (TFA): 138.7 m²
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General Construction: Reinforced Concrete Frame (35%) with Pumice block
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Proposed Roof: I beam timber-frame with clay tile finish
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Proposed Insulation type: XPS, EPS or rockwool for walls, XPS for ground slab and flat roof and blown Cellulose for sloping roof
Passive House
Imagine, a home that’s warm and cosy in the winter, yet offers cool, humid free living in the height of the summer.
A house with air that is clean and allergen free. A passive House offers affordable, low energy living that delivers a year-round healthy and comfortable environment. In addition, a Passive House uses just 10% of the energy of a conventional house yet only costs as little as an additional 10% to build.
Aim
My aim is to build two small, affordable villas in the south of Turkey, typical of the shape and size of similar, popular buildings in this region, but a building that will offer a fabulous all year-round living environment and somewhere that’s use will be carbon neutral. After some research it became clear to me that using the Passive House model would be the gold standard approach to achieving this aim.
Some History
The Turkish take great pride in protecting and preserving their traditional arts. One of these is the style and layout of the buildings constructed the in Gökova/Akyaka region, inspired by the self-styled architect named Nail Çakırhan. Born in Gökova back in 1910, after enjoying a wide-ranging and vary varied career involving are and archaeological excavation and building restoration, ill health forced him to return to Akyaka in 1970. He felt that he needed a home, wherein he could relax and work in peace. He purchased a piece of land about two and a half acres in the Akyaka district and set about designing and building a house, with the help of two experienced craftsmen. His building, albeit very simple in concept, was considered revolutionary by standards in Turkey at the time. Indeed, so taken by his ideas and concepts, he was subsequently awarded the Aga Khan Award for Architecture in the year of 1983. The grand jury’s decision for this award wrote:
“In the design and decoration of this house, there is a neatness and elaborateness, reflecting and maintaining the traditional life style. With its graceful and ancestral and adequate decorations, the design of this house is far beyond the simple repetition of samples in the past. Its extraordinary harmony with nature and superb features of multifunctional usability and indoor effect have been giving great and superb characteristics to this building. This breathable and attractive house is noteworthy especially for reviving the handicrafts and cultural sensitivities”.
Nail Çakırhan
A Nail Çakırhan House
Nail Çakırhan went on the design and build and restore over 100 further buildings in the area maintaining the same general style feel he had crated for his own house whilst incorporating a number of decorative features inspired by the building of the Ottoman era. In 1992 he was awarded honoury membership of the Turkish Chamber of Architects and Engineers. Sadly Nail Çakırhan passed away in 2008.
As a result of his work the Area of Gökova and Akyaka was designated Special Area/Environment Protection status in which the Master Construction Plan of this region states:
In the development of Akyaka ‘The fundaments of Nail Cakırhan’s architectural philosophy, will be followed and applied properly, Akyaka will deserve to be one of the world’s heritages.
thus cementing the unique Nail Çakırhan Ula/Mugla building style, compliance of which has become a cornerstone of any planning consent in the area.
Key Success Criterias
From the outset, I set out 5 key requirements for the project:
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The building must comply with all local building regulations and planning rules – no cheating !!!
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The building must be able to achieve a Passive House Plus (Zero Energy Building) status
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The building must be constructible from materials readily available locally – imported products should be a last resort and only when they offer a clear performance or financial benefit.
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The building construction should be familiar to local builders and offer easily understandable practical benefits over current practices.
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The building should be attractive and affordable to potential owners – ideally cost no more than 10% on a like for like basis.
In addition, the building should have a Net Zero Annual Energy Demand. Heating requirements for the area are low. Indeed, even with little insulation and designs festooned with multiple thermal bridges, the heating demand of a typical house in the area consumes less than 40 kW/m²a. What is an issue, however, will be providing effective cooling in the summer.
Modern and efficient air-conditioning has now been widely adopted in this region, but continual recirculation of air in window-closed buildings concerns users. As a result, occupants are continually trying to balance its use with spells of windows open (which only serves to let the heat back in) – something that has become accepted as the norm and that has to be lived with. This is where I hope the use a of Passive House design will score, offering an, affordable, all-year-round fresh-air environment- a cost effective solution to this conundrum.
Climate Data
Due to the lack of any suitable climate data for the area, Passive House Institute prepared a bespoke climate data set. Although I provided climate data form the local (2 km away) government meteorology station, because the data only extended back some 6 years, Passive house chose to use data from Bodrum, some 100 km distant. Initially, this seemed to be an acceptable approach. Certainly, the temperature profile of the two places are very similar.
However, having studied the data more closely and compared it with daily readings taken at my current location in Gökova, it is clear that the humidity level here is slightly higher than that in Bodrum. During July humidity levels have hovered pretty consistently between 16 to 18 gm/kg (in line with the data supplied by the government meteorology office) compared with less than 14gm/kg for Bodrum.
I believe this is due to the unique location of Gökova at the end of a long gulf surrounded by mountains which, heated by the sun cause a constant westerly, on-shore breeze which bathes the area in moist air from the sea.
Accounting for this micro-climate is important and, as my proposed design matures, although not required for PHI approval, it will be cross checked with an allowance made for these differences, particularly as suitable cooling and dehumidification are the key challenges of the project.
Building Constraints
The design of my Passive house project is quite heavily constrained by local planning and building regulations. In particular the local authorities interpretation of the need to embrace the Nail Çakırhan design philosophy coupled with an arguably over-engineered reinforced concrete structure, has led to a number of features that are in direct conflict with good Passive House design practice.
A snapshot of just some of the more important ones with regard to achieving a passive house design are as follows:
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Building design must be built to comply with the local, Ula-Mugla, small window, red-tiled roof with overhangs, style.
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Roofs must be tiled (red) and slope angle should be 33% (18.5 deg). We have managed to seek a concession to increase this to a maximum of 40% (22 deg)
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External footprint of building(s) restricted to 20% of land area, with very strictly enforced house to land boundary, ‘clear area’ dimensions – 5m to an access road, 3m to the adjoining land parcels and 3.25m to the rear of the property and a minimum of 6 m from any other building.
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The building must be designed to have at least 4 operable chimneys; one accessible from the kitchen, one from the lounge, one from a bathroom and one from a bedroom. These have to be seen to be built and capable of operation, but do not be used and may be capped on following final building inspection.
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Building must have no more than 2 stories, although areas under the ground may also be constructed as long as they are only used as stairs and/or storage.
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Building height must be no greater than 6.5m form the bottom of the reinforced ground slab to the upper surface of the 2nd story ceiling
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A (substantial) professionally designed and verified reinforced concrete frame structure must be used for all masonry constructed buildings.
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The reinforced floor slab must be of a continuous design, in contact with the ground and be a minimum of 45 cm thick
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The minimum size of any reinforced concrete column or beam can be no less than 30 x 50 cm
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Balcony sizes are strictly limited to 1.25m projection and may only extend for a maximum of 30% of the face of a building
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Window size is strictly controlled to ensure they remain in keeping with the style and shape of building in the local area. Large glazed surfaces are strictly prohibited (for aesthetic not thermal reasons). All glazed surfaces need to feature vertical and horizontal cross bar patterns and must not exceed 30% of the ‘face’ of each view of the building.
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The size of glazed external doors must have a rough opening height to width ratio of no greater than 1.3 to 1.
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Roof overhangs are mandatory, but must be less than 1 m from the vertical wall surface.
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Fixed overhang shading of windows, other than those sited below a roof edge, is not allowed.
Developing the solution has been a long, iterative process, balancing the demands of local legislation with an approach needed to meet the Passive House certification. The basic design is now finalised, but there will undoubtedly be some small changes dictated by material availability and builability.
Proposed Design Approach
The design approach is for a conventional (Turkish) reinforced concrete frame building with pumice brick wall infills capped with a blown cellulose insulated, clay-tile finished, box section wooden roof. The exterior is to have a continuous wrap XPS, EPS or Rockwool insulation which would merge seamlessly with the roof elements. In line with the style of other buildings in this area, the construction features first floor overhangs on two faces thus making the upper floor area bigger than the building footprint.
The design also features a roof terrace – this is essentially a flat roof with insulation integrated into the floor that merges seamlessly the adjacent walls. The ground slab is to be insulated on its upper surface using a thin layer of XPS. The plan is for all roof overhangs to be non-structural, false-work in place purely for decorative purposes so as to meet the local planning consent. The only planned penetrations to this thermal envelope will be one small, thin concrete tiled floor, wooden balcony hung on wooden projecting arms and a small number of re-bar inserts used to anchor the parapet wall on the upper terrace.
I considered using a freestanding balcony as an alternative. However, building regulations prohibit overhead shading of such structures which would deny and summer shading and, in this climate, would make them pretty much unusable. Building regulations also prohibit under insulation of the ground slab so this has to be insulated on its upper surface. This generates the building’s only significant thermal bridge, although this is minimised due to the use of the wooden structure. The ground floor, North West corner of the building needs to be underground so as to meet the 2 story height limit, however, it is intended that this adjacent area is used as a garage and store room which will be freestanding and unattached to the building such that the surface in this area is in in fact in contact with ambient air.
The chimneys will be incorporated within the thermal envelope with a thermal break and continuous thermal insulation as it passes out though roof. All but one of the flues will be capped – the one remaining is to be accessible from the lounge which, along with an insulated complimentary air inlet, will facilitate a free-standing, sealed, wood burning stove to be installed.
The houses are situated 50mup a steep sloping ridge with a wide-ranging vista to the east, west and south, and with a continuance of the ridge upwards to the North. So as to maximise this view from any part of the house the house has been designed in and ‘L’ shape. Whilst not the most efficient option from a PHPP standpoint, I believe this offers the best overall compromise solution, whilst remaining within planning permission constraints. Post building approval, it is intended that a terrace and free-standing pergola will fill the space left by the ‘L’. This can then be covered with a tenting material to provide extra shading. Unfortunately, officially such constructions are prohibited at the time of build due to the fear that people would then cover these and then adopt then as an illegal extension to the property.
The building will employ solar water heating (with electric make-up) with a storage tank within the roof-space (outside the thermal envelope), and around 8- 10 PV panels installed on the long, south facing roof element thus enabling the building to enjoy a net zero energy footprint.
Preliminary PHPP (Passive House Planning Package) Analysis
Annual Energy Balance
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Heating Demand: 530 kWh/a
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Heading Load: 1305 W
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Cooling Demand: 2007 kWh/a
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Dehumidification Demand: 305 kWh/a
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Cooling Load: 1369 W
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Dehumidification Load: 608 W
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Solar Water Generation :2264 kWh/a
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PV Electric Generation: 4258 kWh/a (8 panels)
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Domestic Appliance and Electric Lighting: 2747 kWh/a
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Heating and Additional Electric Heating for DHW: 449 kWh/a
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Cooling and Dehumidification: 922 kWh/a
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Nett Excess Electrical Power: 140 kWh/a (4258–2747–449–922) Ie - 140 kWh/a available to sell to local electricity supplier
Note: PHI Passive House Plus standard is met with 6 PV panels, but this does not result in a Net-Zero electrical energy consumption. In this case 925 kWh/a of make power is needed.
Stephen Berriman
BSc DIS MiMechE CEng AMPM CEPHD