CZDG-Moderate Climates

Climatic Design, Zoning, and Guidelines for
Moderate Climates (Gilan and Mazandaran Provences)

Morteza Kasmaei
Building and Housing Research Center
Affiliated to the Ministry of Housing and Urban development
BHRC Publication No. R-521, Tehran,  2010



Creating healthy and comfortable spaces is one of the main objects in Sustainable Design. In present research, the climatic data of meteorological stations of Gilan and Mazandaran provinces and their adjacent areas has been used to study the effects of climatic condition of main populated areas of these provinces on architectural design of residential buildings. Based on the results of this study, guidelines for architectural design of residential buildings and built environments in the populated cities of the two provinces have been proposed. These guidelines, which can be used in all moderate climates of Iran, provide recommendations on the site selection, orientation, and layout of buildings, the size, and position of openings, and shading devices, and building materials for walls and roofs.


Climate: The Given Conditions
Moderate temperature, high humidity, and heavy rainfall are the main climatic features of almost all of the meteorological stations of these two provinces.

Traditional architecture
Traditional architecture in Gilan and Mazandaran is the outcome of centuries of optimization of material use, construction techniques, and climate consideration. The main features of this architecture are summarized in the following paragraphs.

– Buildings are built on a platform that is 50 to 100 cm above ground. Unconditioned space below the building is naturally ventilated by providing opening in different walls of the platform.
– Windows are large, completely open able and are built from wood and glass.
– Sun shades are the most common and important element of the building and effectively provide desired shade. In some cases, they shade the whole windows and exterior walls and protect them from rain.
– Roofs are steeply sloped and usually projected from one two or all sides of floor plan to protect exterior walls from rain.
– Balconies, which are the semi outdoor spaces, are a significant part of buildings.
– The main orientation of the residential buildings is north south and the main yard is located in south side of the buildings.
– Plan of small buildings is liner or “L” shape, but larger buildings have combination of those plans and “U” shape plans too.


Design Guidelines
For design of outdoor spaces, three main goals have been outlined:
1- Reduce chilling effects of winter winds
2- Provide shade and air flow in hot periods
3- Provide sunny exterior spaces in cold periods
Based on Mohaney Tables, for all parts of this climate, building layout should be elongated in east-west axis. However, regarding other aspects of design, two different groups have been recognized

Group 1, (almost all cities of Gilan and Mazandaran)
1- Orientation north and south, long axis east-west
2- Open space for breeze penetration, but protection from cold winds
3- Single banked rooms for permanent air movement
4- Medium openings, 25 – 40 % of related elevation
5- Windows in north and south walls at body height on windward side
6- Light walls with low thermal capacity
8- Light roofs, reflecting surface, and cavity

Group 2, areas far from the Caspian Sea with high altitude
1- Orientation north and south, long axis east-west
2- Compact courtyard planning
3- No air movement required
4- Small openings, 15 – 25 % of related elevation
5- Windows in north and south walls at body height on in windward side
6- Heavy external walls, over 8 Hours time lag
8- Heavy roofs, over 8 Hours time lag
The following design goals are formulated based on climate analyses of the Gilan and Mazandaran provinces.

1- Reduction of building heat loss during cold period
2- Permanent  provision  for  ventilation
3- reduction of indoor air humedity
4- Use of  solar  radiation for heating
5- Protection of indoor spaces from sun penetration in hot period
6- Reduction of wind affect in building heat loss
7- Provision of indoor exposure to the outdoor climate
8- Protection of building from rain
Based on the above design goals, reduction of building heat loss and wind affect in building heat loss during cold period are the first and second priorities in building design for all parts of these two provinces. However, in relation to the other design priorities the main cities of this reign can be divided in two groups.
The following design guidelines are formulated based on climate analyses and the study of traditional architecture of the Gilan and Mazandaran provinces.

Site selection
The best location for buildings in sloped sites is the mid portion of southerly slopes. In windy sites, it is recommended that top portion of hills not be selected for building location. In addition, it is preferred the westerly and easterly slopes are not be selected for building development.
On Greenfield sites, disturbance including earthwork and clearing of vegetation should be limited to 12 meters beyond the building perimeter, 3 meters beyond surface walkways, patios, and surface parking and 4.5 meters beyond primary roadway curbs.

Site Design
Disruption of natural hydrology should be reduced by reduction of imprevious cover and use of pervious materials in site surfacing, including sidewalks, parking loats and roads that are not used by heavy vehicles. Storage and use of rain water for irigation should be consided. In site design the following goals should be considerd.
– Location of buildings and site elements should be determind in relation to the prevaling wind dirction.
– In coold parts of the region, ever green trees shoub be located in windward side of the biuldings to form wind breaks.
– Site elements shoud be located in a way that allow use of prevalling breezes in natural ventilation.
– In locating site elements, ther shoud be nothing left in southern part of building and within 30 degrees of  south elevation.

Site Pattern and Dencity
In this region and all huimed climates of the country, since provision of continuous and efficient ventilation is necessary, open planning and wide, free spaces between buildings that help to achive good ventilation is beneficial. In ditermening the necessary distances between buildings, wind shadows have to be considerd.
The most beneficial site layout is when the windward row of buildings cosists of low detached houses, the midel row consists of mixed height apartments and the leeward rows consists of  long and tall buildings.

Building Orientation
In selecting suitable building orientation it is important to respect to the sun and wind. The object is to maximize solar heating in under heated periods, mimimize solar penetration to the interiors in over heated periods, and to conside the effects ofwind orientation. In relation to the effects of cold winds in building heat loss, best orientation is the one that makes smaller incident angle with the direction of cold winds (less than 22.5 degrees). In respect to the winds, and for natural ventilation, the best orientation is the one that is in effective zone of prevailing winds (grater than 60 degrees). In relation to the use of sun’s energy to heat the building, the best orientation in all parts of this region is south east and the worst orientation is west.


Orientation of street network
To provide adequate airflow in streets, the prevailing wind should be oblique to the streets, the angle between the wind direction and the street could range about 30 to 60 degrees. To provide adequate airflow in streets and natural ventilation for the adjacent buildings, the angle could range about 30 to 45 degrees. In respect to the cold winds, for reduction of building heat loss in under heated periods, the direction of cold winds to the streets should be greater than 60 degrees. In respect to the sun’s energy, and to direct sunrays to the streets in cold periods, the best direction for streets in this region is 15 degrees west. North south and 30-degree west directions are the second and third best directions. However, to increase the amount of sunshades in hot periods, the best direction for streets is north-south axis. 15 degrees east and 15 degrees west are second and third priority.

Building Form
In his region, open elongated plans with wide porch and steep roofs are preferred. In humid regions, the planning should be directed towards optimum ventilation conditions. In this respect, detached hoses are the best building type. Two story town houses with open stairwell are the next best building type for the humid regions.

Main Building Spaces and Plan Organization
From climatic design standpoint, three main spaces are necessary in residential buildings: interior, semi outdoor and outdoor spaces. Balconies are very useful in this climate for both shading the windows and walls and providing a suitable semi outdoor space. In cases that for cooling of the building mechanical systems are going to be used, the best plan organization for the building is the dense and compact form. Nevertheless, in cases that for cooling of the building in some periods cross ventilation will be used, the plan of the building should be open and elongated to the east-west axis. In this case, interior of the building should be open and windows should be large and operable.

Relation of building to the ground
In all parts of this region unless elevated areas and areas for from Caspian Sea, building should be raised from the ground. Raising the building on the stilts also is advantageous in humid climates. Firstly, this enables better ventilation by locating the windows above the zone of maximum wind damping by the surrounding vegetation, and secondly, it enables cooling of the floor from below. In addition, the building is better protected from floods.

Size and location of windows
Based on Mohaney’s tables, size of openings, doors, and windows should be about 20 to 40 percent of the area of related elevation, but large openings are advantage in this climate provided that they are effectively protected from penetration of sun during the hot periods, driven rain and intrusion of insects.
The most effective height of the windows from the human comfort aspect, which is important in this climate, is about 0.5 to 1.5 meters above the floor (the occupied zone). In bedrooms, it is particularly important to bring the windowsill as close as possible to the height of the beds, thus ensuring adequate airflow around the occupants’ sleeping area. When upper windows have to be used, it is preferable to use horizontally pivoted windows with upper hinges, which, when open, would direct the airflow downwards. It is important to select a type of window that is 100% open able. In many instances, solar protection may be combined with rain protection, not only with respect to the windows but also for the whole area of the walls, by extending the roof beyond the floor area.

Building Materials
Because of the permanent ventilation requirements and the small outdoor diurnal temperature range, the heat capacity of the building should be as low as possible. When heavyweight materials must be used, it is possible to minimize the effect of the heat capacity by covering them with an insulating layer. Refer to section 19 of Iran National Building Code to select type and thickness of insulation layers for building shell in desired areas of the region. Based on the recommendations that are given in the mentioned code, type and thickness of insulation layers for suggested and common envelope materials in the region are as follows. It is Also recommended that insulation layer be applied to the inside surface of the outer portion of wall.
– Solid Concrete Block wall with cement mortar facing: 7 cm expanded Polystyrene
– Composite wall with a layer of brick and a layer of concrete block: 6 cm expanded Polystyrene
– Composite cavity wall with a layer of brick, air space, and a layer of concrete block: 5 cm expanded Polystyrene
– Sloped roof with asbestos cement: 8.5 cm expanded and extorted Polystyrene or 14 cm Polystyrene
– Floor on unconditioned space: 4 cm polymer insulation layer

Climatic Zoning of Gilan and Mazandaran Provinces
In relation to the main climatic design goals, all cities of Gilan and Mazandaran provinces are grouped in two zones and two sub zones. The geographical boundaries of these two zones are shown in Climatic Zoning map of Gilan and Mazandaran provinces, which could be used in determining the design recommendations for different parts of the region.

Climatic Zoning map of Gilan and Mazandaran provinces

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