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Cool walls for your house

Come March and people start bracing themselves for summer months.

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Come March and people start bracing themselves for summer months. Taking a cue from people's search for heat resistant materials, manufacturers keep experimenting to devise new products that meet market expectations and reap success. Launch of ‘Cool Walls’ is a step in this direction.

For the construction of houses and other buildings, bricks are used in masonry work to raise walls. These walls draw heat during summers, transmit it to the inner space of the house, turning the South and West facing rooms into virtual ovens. Cool walls restrain the heat transmission to the inside of the house and thus, help in keeping the insides cool.

Materials used

Cool walls are raised by using specially manufactured blocks made of temperature-resistant concrete. To raise these walls, a specifically designed mortar is used in joints of the blocks instead of the usual cement-sand mortar. A special property of this mortar is that unlike brick masonry walls that need repeated curing for strengthening of joints, this mortar doesn't demand any curing with water. The walls are ready for use, the moment these are raised.

Blocks for temperature control

Cool wall blocks are solid blocks, made of temperature-resistant concrete. These are produced in different thicknesses to suit the needs of users. The length of the blocks is fixed as 600 mm or say about 2 ft, while a normal brick is 9 inch long. The width (depth) of the blocks is also fixed as 200 mm or 8 inch. Thus, all wall faces present a uniform grid of 600 mm x 200 mm, irrespective of their thickness.

Weight of blocks

A 600 mm x 200 mm x 100mm block weighs about 10 kg. The weight of blocks increases with increase in thickness. Thus, a 6-inch thick block weighes 15 kg, 8-inch one weighs 20 kg and 9- inch thick block weighs around 23 kg. A normal clay brick weighs about 3.5 to 4 kg. Thus, one 4-inch thick cool wall block weighs 2.5 to 3 times more than the conventional brick. Though it can be handled by the labourers at site, it can’t be thrown up at some height as the labourers do in case of bricks when the walls are raised to certain height and platform is erected there for the masons. It is, therefore, advisable to transport these blocks in buckets. 

Weight of concrete

If we compare the weight of temperature-resistant concrete used in manufacturing these blocks with that of normal concrete, then we will find that it weighs almost one third of the weight of normal concrete. The weight of concrete used in blocks is just 850 kg per cubic m. It is almost half the weight of brick masonry. Despite its walls being doubly strong than masonry walls, its lesser weight leads to less weight on beams, columns and foundations, thus, making the design economical.   

Quantity comparison

Depending upon the thickness of blocks chosen for walls, their quantity is quite less in comparison to that of bricks, owing to their large size. If 9-inch blocks are chosen, then only 73 blocks will be required in place of 1,000 bricks, 82 blocks shall replace 1,000 bricks if 8-inch  blocks are used and 145 blocks will be required if 4-inch blocks are used.

Joint thickness

While using the specially designed, no curing mortar for the jointing of blocks, the joint thickness is kept as just 3 mm in comparison to almost 10 mm thick joints in brick masonry. One bag of dry mortar material weighs 40 kg and requires 10 to 12 litres of water to prepare mortar. Like cement-sand mortar, it is also advised to be consumed within half hour of its preparation for better strength. It is further advisable to sprinkle water on the blocks before fixing them in position with mortar. Wherever required, the blocks can also be cut to size by using a cutter machine.

Consumption of mortar

Keeping in view the joint thickness of only 3 mm, only 1 bag of mortar shall be required to raise 100 square feet of a 4 -inch thick wall. Thus, two bags will be required for 100 sq feet of a 8 inch thick wall and about 2.5 bags will be required for 100 sq feet of 9 inch thick wall. 

Cost factor

Cost of cool walls is a shade more than that of masonry walls. These walls cost around Rs 4000 per cubic meter content. Saving of water and labour used in curing of masonry walls, however, balances the cost with that of the traditional masonry walls besides providing  other advantages.


Advantages

Cool walls help in maintaining a temperature differential of at least 5 degree Centigrade in the outside and inside of the building. Another advantage of these walls is that no problem of efflorescence (shora) is faced in their case while appearance of efflorescence is very common in case of brick walls. During winters too, the insulating property of these walls doesn't allow inner heat to flow outside. 


Thickness of blocks

While the length and width of the blocks is fixed as 600 mm and 200 mm respectively, their thickness in walls varies from 4 inch to 9 inches. The available thicknesses are 4 inch, 6 inch, 8 inch and 9 inch. As most of brick masonry walls are 9 inch thick in the house, 8 inch thick or 9 inch thick blocks can well replace these walls and act as load bearing walls. These 8 inch and 9 inch thick walls have almost double the strength of 9 inch thick masonry walls and thus serve their purpose well. The 4 inch thick non load bearing masonry walls in the house can be replaced by 4 inch thick block walls.

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