Using roof insulation is one way to keep the attic space cool, and therefore the rest of the house cool without using electricity. If you have any cracks or leaks in your roof, then the insulation will not work properly. It is important to get those problems fixed with the help of Allstate Roofing before adding insulation.
If you have chosen to insulate your roof, there are different types of materials you can use. Before going into the different types of material, let’s look at how your house gets heated.
There are 3 main ways, through radiation, conduction and convection. Radiation, heat comes from anything that emits heat, for example, the heat you feel when you stand in the sun or in front of a hot oven. It can travel through any air space and even through a complete a vacuum. This is how the sun’s heat energy reaches the earth.
Conduction and convection requires a medium for the heat transfer. Conduction is what happens when heat flows through a material from the hotter part to a cooler part. Heat one end of a metal rod and slowly the other end gets hot as well.
Convection happens when there is a medium that can move, in this case air is usually the medium.
Heat gets into the house in all the 3 ways. The heat from the sun heats up your roof tiles through radiant heat, it travels through the roof tiles (conduction), the hot roof tiles heats up the air in the attic space (through radiation and convection), which in turns heats up the ceiling boards and plaster ceiling. Finally the room below gets hot through radiation, conduction and convection from the ceiling.
The objective of roof insulation therefore, is to make it harder for heat energy to get into the living space below. Besides the roof, your house can get hot from walls especially when the sun heats up the wall directly.
Now that you have a better understanding, let’s consider the options available to insulate a roof. At the end of this article, there is a list of material that I don’t suggest you use if you want to DIY. Let’s look at the common material first.
Aluminium foil is the most common type of roof insulation material. It is usually a laminate made of several different materials including paper, aluminium, polyethylene and woven fabric. Some types include a layer of bubble foil as well. Whatever the material, those that are thin sheets do not really help against heat conduction. They have a shiny reflective surface acts to reflect radiant heat. However a percentage still get’s through.
Although the thin sheets do not by themselves provide much insulation against conduction heat, if they are fitted on the roof trusses, they trap a layer of air. Since air is a bad conductor of heat, it forms a barrier against heating through convection. When air is not trapped in a layer, once heated, they flow about in the attic thus transferring heat to the ceiling boards.
Aluminium foil that has bubble foil will help reduce heat through radiation and conduction.
The advantage of aluminium foil is that they are light and therefore easy to install. It doesn’t become messy. Properly installed under the roof truss, they provide additional protection against rain if your roof leaks. The disadvantage of aluminium foil is that low quality ones tear easily. Materials like paper and polyethylene can disintegrate over time under the hot roof.
Stone wool is made by blowing air though molten rock much like cotton candy creating fibers. The fibers actually conduct heat so the reason stone wool works as a heat insulation is by the trapping air between the fibers. Due to the structure of the fibers, they act as a good noise barrier.
Stone wool roof insulation is done by laying them down between the beams that support your ceiling. They are quite bulky. Most manufacturers of roof insulation in Malaysia wrap stone wool with aluminium foil to prevent this and also reduce dust.
However, because of the size and wrapping, there may be gaps that is not covered thus reducing the effectiveness in certain installations.
Cost approximately RM 3.50 per sq. ft.
Cellulose insulation is a type of material similar to paper, cardboard. Sometimes made from recycled paper, cellulose insulation material are treated with chemicals to make them fire retardant and to control pest. The insulation properties of cellulose is very good and again, what it does is it traps a layer of air to reduce heat convection.
Cellulose is blown with a special blower that spreads the material between the roof beams and other crevices.
Advantages of cellulose roof insulation is it fits between beam and part of wooden trusses so that it forms a complete barrier. The disadvantage is that it may be a bit difficult to locate wires and pipes in the attic for repair since they cover everything up.
Cellulose insulation will be the most pricey at slightly below RM 4 per sq. ft.
Less common roof insulation material
Zinc sheets or plywood – some house owners install either one of these material under the roof as additional security measures. Since they trap a layer of air between the roof tile and the plywood itself, it will have some effect. To ensure easier repair to the roof, it is better to use screws rather than nail when installing them.
Roof insulation material – stuff to avoid
Styrofoam – never use this material as insulation in the roof. In a fire, it gives off acrid poisonous smoke and fuels the fire.
Untreated cardboard, egg carton, newspaper etc. are material to avoid. Do not use them because they can cause a fire to spread very quickly. You may not be aware when a fire could be smoldering for example, lightning strikes. They can start a fire at your home from the roof. Such fires may not be immediately apparent as wood and other flammable material slowly smolder until the fire grows.
Electrical shorts can also cause sparks that eventually lead to a fire. With paper material up in the attic, your home can quickly turn into an inferno, or smoke can knock you unconscious. Either situation, it won’t allow your family time to escape.
Untreated cellulose like paper are termites’ favorite food so best is don’t use them.
Reuse Office Ceiling Tiles – May Help
One material that I considered is re-using office ceiling tiles. They are fire retardant, made from mineral fiber and absorbs noise as well. They would definitely help reduce heat but by how much, I wouldn’t know. I’ve seen them when companies renovate their office or when the move. However I don’t have any idea how much these cost used.
All you need to do it to place these tiles on the attic floor or nail them to the rafters. It could be a bit of work to get them up the attic because of their size (usually 2×4 ft) but if you can get them for free or the cost of transportation, it could be a good way to re-used them. Try at you own risk!
Aluminium foil being the cheapest are commonly installed together with either stone wool or cellulose insulation. Used together, they provide the best way to cool your house.
Installation of roof insulation
One important thing to note. Correct installation of the different types of roof insulation plays a important part. Wrong installation means you won’t get the result you expected. A cooler house at less monthly cost.
Read our series on passive cooling here for others ways to have a cooler home.