Roof ventilation is something worthwhile to consider when you renovate you house. Everyone who lived in a terrace house in Malaysia will know how how the upper floor is during the day. Installing roof ventilation not only keeps the house cooler, it also reduces electricity consumption.
Over the long run, having roof ventilation will save you money. Ventilating your roof will not require major renovation in most cases unless you plan to rebuild your home.
Most new houses have a layer of thin aluminium sheet just under the roof tiles. This is called a radiant heat barrier and its job is to reflect infra red radiation away from your ceiling.
However as the air between the roof tiles and aluminium sheet is slowly heated up during the day, heat comes through the thin aluminium sheet. The aluminium sheet is not really effective against heat through conduction. Imagine if you heat up a piece of metal on one end, over time, the other end will also get hot. This is how conduction works. As the air is heated more, you will feel the heat coming through the ceiling and you will feel it on the upper levels of your house.
Some people term it roof ventilation, however, the correct term is to ventilate your attic. The attic is the space between the roof and the ceiling. There are several ways to cool the attic.
Turbine Ventilator Fan
When there is no wind and the turbine is not spinning, it is designed in such a way to let hot air escape from the attic.
Hot air naturally rises and escapes through the turbine. When the wind blow and the turbine spins, there is a small added suction effect to remove hot air from the attic.
The key reason why the turbine spins is not to suck the hot air out but to prevent rain from entering the turbine. As the wind blows, the turbine spins at a speed where raindrops do not enter through the curved blades.
There are reports that such turbine ventilation fan do not really help and causes dust in the upper rooms because a small hole is cut into the ceiling. Over time, the dust from the attic will fall into the room. Besides dust, turbine ventilators that are not well manufactured may have bearings that fail after some use.
When the bearing fails, the turbine no longer turns as fast and may allow rain to enter your roof. Others have reported the contrary, that the turbine fans DO work. It could be a combination of proper installation and turbine fan design that helps to reduce attic temperature.
Installing the turbine fan properly is key to its long life and proper function. Since it is up on the roof, most house owners would not be able to determine if the installers have done a good job.
Some turbine ventilator are installed at a slight angle. This prevents the turbine to spin freely since it is usually not perfectly balanced. Other sloppy installation allows water to seep due to lack of sealing where the roof tile have been removed.
Roof or ceiling insulation
Adding additional insulation to the roof or ceiling is becoming popular in Malaysia. This method involves installing insulation material wrapped in aluminium sheets to reflect infrared heat as well as create a heat barrier towards convection heat. Rock wool, fibers or other insulating material are the usual material that is sandwiched between the aluminium sheets.
Newer insulation material include bubble wrap sandwiched between aluminium sheet. The effectiveness of these types of barrier depends on trapped air between the fibers or bubble wrap, as well as the reflectivity of the aluminium sheet. Air is actually a very good heat insulator provided it does not circulate, therefore the need to trap it in a fixed place.
The reflectivity of aluminium over time will reduce as dust falls on the sheet however provided the material is thick enough, insulation will work for many years. Installation is quite easy since the manufacturers sized the roof insulation to fit between the rafters.
Roof cross ventilation
The vents can be rectangular or round but the most important is they have slits or grill to prevent birds or other pest from entering your attic. Some vents are made using asbestos sheets with slits cut into them.
Ridge ventilation is also not popular in Malaysia. The reason could be one of added cost and potential leakage with our monsoon rain and strong winds. This is nothing more than having a slightly raised section of roof at the ridge to allow hot air to escape from the attic. There are some roof tiles made especially for the ridge but again it is quite hard to find such roof tiles if at all. Some developers have been creative enough to design a roof with a raised ridge to allow better ventilation. With ridge ventilation, you’ll avoid the problems that may happen with turbine roof ventilators. Since the have no moving parts, ridge ventilation is more reliable.
Since this requires modification to an existing roof truss, it may be expensive to opt for this unless you are doing major renovation to your home. A better option for an existing will be to install the roof insulation and roof cross ventilation. This would be the best bet for a cool home without burning a hole in your pocket. If you planning for a complete house renovation and have the budget for it, then go for it.
Here is another type of ventilation that is not that common today. Perhaps it doesn’t look that nice. It allows natural ventilation to cool the attic space. It may be a little harder to put this type of ventilation grill in once the wall is built. Besides a circular shape, such grill can be rectangular as well.
Here are more ideas to keep you home cool. Most of them without using electricity.