Escaping the oven effect at home

The very idea that we could be cooking ourselves in our own homes seems absurd. Yet this is exactly what we have been doing, since many of our homes are designed like ovens.

Have you noticed that our roofs in landed homes, which are typically ‘pitched’ (as they are more commonly known), are sealed off with mortar on the top ridges (to prevent water from coming in)? So are the eaves. In effect, we may have prevented water from coming in (which is ideal in a tropical environment) but we have effectively created an enclosed space! An oven!

Studies have shown that our roofs have a huge impact on the amount of heat generated in our homes. Malaysia’s proximity to the equator means that we receive the sun directly overhead most of the day and throughout the year.

So it comes as no surprise that most of the heat in our homes comes from the roof: roughly 75% of all heat gain, in fact. And most of this heat — more than 90% of it — is transferred to the occupants of the house.

At around 3pm, the hottest time of the day, the roof tiles can reach temperatures of around 80° Celsius. And in a typical Malaysian home, which let’s say for argument’s sake, is a double-storey terrace house equipped with a roof made of concrete tiles (the most common kind), the mean radiant temperature (MRT) or internal temperature, is in the region of 32° Celsius. Unbearably hot, in other words!

Not only does this hot air heat up the inside of the house quite considerably, this heat is also retained for most of the night. All of which spells high electricity bills, since much more energy is then needed to diffuse this heat in the form of air-conditioners.

What then, are we Malaysians to do? Well, one solution lies in the breathable roof.

At its most basic, the breathable roof greatly mitigates the oven effect, since, as its name suggests, the heat is allowed to escape. It means the ridge tiles (at the highest point of the pitched roof) are designed to allow heat to naturally convect back into the outdoors and leave the roof.

It means recreating the “Milk Maid effect”. That is, creating holes on the roof eaves to balance the pressure in the roof, allowing heat to leave the structure. Remember always that pressure in a house needs to always be in equilibrium, its effect is exactly like that of the teh tarik man who perforates both sides of a Milkmaid condensed milk can to allow the sweet milk to drip into our teh tariks.

By dissipating heat which builds from above, very little heat radiates into the house. I’m sure you know that if you leave your oven door open, your chicken will not cook. So why not leave the roof ridges open and not let us cook inside the house as well?

In other words, if this system can effectively deal with a huge percentage of the heat in my house I can certainly live with it, especially if my electricity bills are reduced as a result.

These appear simple principles with ready products in the market to make these breathable roofs achievable, yet very little of it is practised in Malaysia, and not at all on a widespread basis. Thankfully, this is changing, and the more we bring these ideas into the public domain, the greater our chances of lightening our carbon footprint.

Again, these present further opportunities for developers to evolve with the times, to become bigger partners in peoples’ lives, although I must stress that these measures do not and should not equate to higher costs, since the technology presented here is not new or revolutionary. All it needs is (some, not total) cognisance, and effective implementation.

Where at one time developers put a roof over our heads, we now must think to add value, since the times we live in calls for it.


Sam Tan is executive director of Ken Holdings, the developer of  an award-winning green certified project Ken Bangsar.

This article appeared on the Property page, The Edge Financial Daily, March 25, 2011.