Going Up!
Just how many balloons would you need to lift a house?
Have you ever looked at a helium balloon and wonder how many of these it would take for
you to drift on the breeze? If you’ve seen Up! then you’d remember the iconic floating house,
held aloft by a fantastic number of helium balloons. The question, is just how many balloons
would this really take?
To start, we have to figure out why a balloon filled with helium floats in the first place, and it
all has to do with density. Just like a boat on water, helium floats because it is less dense
than the air around it. For a balloon filled with hydrogen the entire balloon (including the
weight of the balloon itself) must be less dense than air. The difference in density between
helium and air means a standard helium balloon (weighing roughly 2 grams, and filled with
14 litres of helium) can lift around 12 grams (0.012 kg), once you include the weight of the
balloon itself [1]. So if we take a person of weight 70 kg:
70 𝑘𝑔
= 𝑎𝑝𝑝𝑟𝑜𝑥. 5800 𝑏𝑎𝑙𝑙𝑜𝑜𝑛𝑠
0.012 𝑘𝑔 𝑙𝑖𝑓𝑡 𝑝𝑒𝑟 𝑏𝑎𝑙𝑙𝑜𝑜𝑛
So we’d need around 5800 filled helium balloons just to get your feet off the floor. Of course,
the higher you want to go the more balloons we’d need. If you’re a Mr. Bean fan then you
may be familiar with the image of a pram floating away, held aloft by a bunch of helium
balloons. If we assume the baby weighs around 10 kg, and the pram another 15 kg, then by
repeating the same process above we find we’d need around 2000 balloons to get the pram
and baby off the ground.
If we now consider a house, we’re of course going to need many more. If an old two story
house (like the one used in Up!) weighs around 45,000 kg [2] then we can do the same
calculation as above:
45,000 𝑘𝑔
= 3,750,000 𝑏𝑎𝑙𝑙𝑜𝑜𝑛𝑠
0.012 𝑘𝑔 𝑙𝑖𝑓𝑡 𝑝𝑒𝑟 𝑏𝑎𝑙𝑙𝑜𝑜𝑛
Of course, if we use lighter balloons and larger balloons this number would be lower.
The final thing to consider would be where we might attach the balloons, and here it looks
like the creators of Up! got things right. If we started attaching balloons to the roof of the
house then the only thing we’d manage to lift would be the roof itself. Our best chance at
lifting a house without it falling apart would be lifting from the foundations, much like how
houses are transported on the back of a truck.
So there you have it, if you’re thinking of shifting your house, it might be best to call a house
mover rather than your local party supplies store!