How to

16 January 2017

Indoor Ventilation Tips to Maximise Heat

It sounds counterintuitive; but good ventilation is one of our best allies in keeping homes, offices and other indoor spaces warm. As a term, ventilation simply refers to the process of moving air in a controlled manner. There are several core principles behind the notion that it can be used to heat our homes; but, in short, it’s all about harnessing convection to maximise efficiency by moving the right kind of air to the best possible places in order to optimise the performance of the overall system. Bringing hot air to where it’s needed; moving cold air closer to heating elements; and circulating oxygen to maximise the efficiency of the latter, are all key features of good ventilation.

Remember: Heat Rises

Many people put horizontal-facing fans next to their radiators or heaters in the hope that the warm air they create will be blown to where it’s needed. There are various reasons this doesn’t work very well: thanks principally to convection.

Because they have more energy, the molecules which comprise hot fluids (gases or liquids) vibrate more; and are therefore more spaced-out. This means they’re less dense; and they’re inclined to move upwards and away from the heat source, rather than remaining stationary or moving down to the floor. The air you’ve heated with the radiator on the wall is all going to the ceiling first. In other words, rooms heat from top to bottom.

You, meanwhile, are not on the ceiling; you’re roughly mid-way up the room. That means you won’t feel the warm air generated by the radiator until there’s enough of it in the room. To counteract this, you don’t need a fan next to your radiator: that will just blow the cold, low-down air around. Instead, you need a fan positioned high up or on the ceiling itself, to act upon the warm air rather than the cold; pushing the former from high to low and hopefully onto you.

Circulating Air

Ceiling fans, however, can’t fix things of their own accord. Again, this is partly due to convection: as soon as the fan has blown the hot air downwards, it will try to go back upwards again, meaning only the area directly beneath the fan will see much benefit. However, convection is a double-edged sword. Indeed, it can actually be harnessed in order to maximise the efficiency of our heating systems.

Let’s imagine a scenario: you’re trying to heat Room A with a heat source in Room B. If there is only one channel (say, an open door) between the rooms, the process of warm air moving into the cold area will be quite slow, because hot and cold air would be moving in opposite directions, pushing against each other: like a road with two-way traffic all using one lane. Indeed, such a scenario would be so inefficient that it’s doubtful Room A could ever reach its maximum potential temperature.

However, if there were another channel for air to move through – a ventilation shaft, for instance – there would be room for air to move efficiently from warm Room B to cold Room A: like adding an extra lane to a road. That way, hot air moves in its own space and cold air is circulated back to the heating element through its own channel, to itself be heated up.

Adding ventilation is therefore of twofold benefit: it gets hot air to the desired place faster, and it moves the coldest air right to the heat source. Since the latter contains a lot of oxygen, this could even make fuel-burning heaters work more efficiently.

Of course, if you have an electric ventilation system which pumps air through vents from heating elements, you’ll be fine. But the costs of such systems can be quite high, and relying on convection can be a cheap, energy-efficient alternative.   

James Stannard

James has a Bachelor’s degree in History and wrote his dissertation on beef and protest. His heroes list ranges from Adele to Noam Chomsky: inspirations he’ll be invoking next year when he begins a Master’s degree in London.