When you see (sic) it means that something has been copied exactly even though it is a mistake.
He should say 'elements of a good tropical house are' because the word elements is a plural subject. Later in the story we've highlighted in bold when he correctly uses are with elements. For more information on when to use is or are, follow the link.
more information: is or are?
When you see (sic) it means that something has been copied exactly even though it is a mistake.
Breathable means something that you are able to breathe.
Example: The atmosphere of Venus is not breathable.
He should have said breathing.
louvres are slats you can open and close
Here learnt is the past participle of the irregular verb learn. Follow the link below to find out more and to listen to some examples.
more information: learn
Grown is the past participle of the irregular verb grow. Follow the link below to find out more and to listen to some examples.
more information: grow