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Cool Home Design

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The seventy year old single storeyed, flat concrete roofed Kayavil house located at Mayyanad (Kollam district in Kerala) offered the perfect setting for Architect Dr. A.S Dili, Professor at Department of Architecture of TKM College of Engineering, Kollam to experiment constructing a well-designed passive solar home.

Situated on the banks of the Paravur Lake, Mayyanad’s costal line along the Arabian Sea is famous for its fishing as well as warm and humid climate. Dr Dili wanted to construct an independent family unit on the first floor of his existing house in this area and to do so, decided to use his extensive research in vernacular architecture and passive thermal design. “The project was to include a two bedroom unit with attached baths, kitchen and living/dining area and additional spaces like storage facility, work area and utility space. Also, the home needed to be a low cost building construction with cool indoor temperature all the year round without compromising on luxury and comfort.” briefs Dr Dili. Thus, drawing on the conventional architectural wisdom he created the systems embedded in the indigenous Kerala architectural design.

The house completed in the end of year 2012 with semi open veranda around is very reminiscent of traditional Kerala houses “Kovilakoms”. The steel framework stair case from outside leads to front lower terrace attached to the semi open verandah that appears like the conventional sit out “Poomukham”. The main entrance to the house is from this “Poomukham” through an entry foyer at a rise of eight inches. Adding distinct elements to this area is the pebble courtyard with plants provided at a lower level (seventeen inches) from the foyer, terra cotta colored rustic finish floor tiles, pebble boarders, low sitting area and calcium silicate false ceiling. Dr Dili explains the design concept, “The terrace had different levels due to additions and modifications over a period of time creating a multi-level floor. Instead of leveling the floor, this feature was utilized and enhanced while planning the family unit. The entry foyer, living room and one bedroom with attached toilet is located at one level whereas, entry to the dining room, kitchen plus work area and second bed with bath is situated seventeen inches below the living room, given access with granite steps fixed in steel fabricated framework. Utility space has been provided at a three steps depth from the work area. Pre laminated wood is used for flooring the bedroom and living area and premium quality vitrified tiles are used for flooring the other rooms to add a touch of luxury. Factory made doors with processed wood are used for external and bedroom doors while PVC doors are used for toilets. The building has incorporated environment sensitive and low cost structural system based design. It utilizes locally available low cost material like coconut wood, used raw wood, locally available cement hollow blocks and minimizes concreting by usage of Ferro cement for toilet roofing and staircase and steel box sections to fix kitchen slabs.”

Passive Design Technology

The house is equipped with an effective passive environment control system by fitting the attic space of the building with glass wool insulation which is kept well ventilated with slits of appropriate sizes. Furthermore, instead of concrete slabs, high finished gypsum board false ceiling has been provided above the walls. The heat flow through the roof and false ceiling towards the interior is controlled by two inch thick glass wool which is evenly laid on the top of gypsum board. Thus, the attic space between the roof and false ceiling acts as a radiant heat barrier to provide comfort to the interior space and keeps the house cool in all seasons of the warm-humid Kerala climate. Additionally, the grill work of 10mm diameter steel bars is installed around the attic space above the external walls to provide security and ventilation of the area. “This passive thermal design is derived from the similar attic spaces in traditional houses of Kerala where heat transmitted to the attic space from the roof is directed to the outside air through the grills and fiber net covering around the attic space protects the area from external surroundings. While, the domestic “active” cooling system in concrete buildings consumes precious energy and raises the cost of living. The design of this independent two bedroom dwelling unit on the terrace of my existing house successfully demonstrates how by assimilating modern day construction technology with conventional methods, passive thermal comfort is achievable within low cost and construction time frame.” says Dr Dili.

Construction Methodology

The low cost technology is adopted in the project by selecting appropriate structural system and materials and through effective management of construction. This approach enabled the completion of total built up area of 1350sqft within seven and a half months. Dr Dili elaborates, “Construction was started with the erection of Trafford shaped, powder coated steel sheet roof supported by GI pipe pillars and GI rectangular tubes main truss frame. Building the roof at the beginning of the project ensured proper curing of the masonry at the time of construction of the walls since the sun light does not fall on the walls directly and also protected workmen from severe weather conditions. As stiffness of the wall is related to its thickness, certain folding have been provided in appropriate locations to stiffen the four inch thick locally available concrete hollow block masonry walls with M-sand cement mortar. Also, six inch thick concrete belt has been inscribed into the wall to add a tie effect to the walls. This belt when reinforced with eight inch diameter steel bars, acts as a lintel beam above the doors and windows. Total height of the walls is nine feet and the use of river sand has been limited for plastering which reduced overall cost and improved the finishing of walls when emulsion paint was applied.”

Materials used

• Roof – Galvanized Iron tubular sections, Mild steel tubular sections and other sections, Powder coated Trafford shaped steel roofing sheet of 0.35mm thickness,

• Main frame work of the roof truss – 1.5X3 inch steel box sections, Purloins – 1.25 inch angle sections with 1/8 inch thickness, Support – 2 inch dia GI pipe

• Roofing sheet – 0.35mm thick Trafford shaped powder coated steel sheets.

• Walls – 4inch thick cement hollow block with M – Sand Cement mortar

• Wall plastering – with river sand cement mortar

• Belt concrete (6 inch thick) above lintel level – with 8mm steel rods (4nos) using 6mm stirrups

• False ceilinginside rooms – Gypsum board (12mm thick) with glass wool insulation on top

• Semi open verandah (Poomukham) – Calcium silicate board (6mm) thick

• Windows – two inch steel box section (outer frame), 10mm steel rods (window bars) are welded horizontally at a spacing of 11cm directly over the frame for protection with one inch steel box section for shutter frame

• Window Glass – 4mm glass pasted directly on window shutter frame using silicone sealant

• Wall finish – emulsion paint on smooth putty work

• Flooring – Pre laminated wooden floor (Living room and a bedroom), 2’-0”x 2’-0” vitrified floor (Dining, second bedroom and Kitchen), 15” x 15” rustic finish ceramic tile (semi open verandah and entry foyer) and 1’-0” x 1’-0” 1 ordinary ceramic tile (work area)

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