Learn Dutch: Jullie moeten dit oude huis echt verduurzamen. - You really must make this old house sustainable.

The prefix ver- is frequently used to turn an adjective into a verb that means "to make [adjective]" or "to become [adjective]". Here, it combines with the adjective duurzaam (sustainable) to create verduurzamen, meaning "to make sustainable".

Since huis is a het-word, why does the adjective oude have an -e ending?

Adjectives in front of het-words only drop the -e ending when the noun is indefinite (like when using een or no article, as in een oud huis). Because we are using the demonstrative pronoun dit (this), the noun phrase is definite, so the adjective follows the standard rule and keeps the -e ending.

Is verduurzamen used specifically for houses, or is it a general term?

It is a general term meaning "to make sustainable," but in the Netherlands and Belgium, it is a massive buzzword specifically tied to housing. When Dutch speakers talk about een huis verduurzamen, they mean upgrading it with things like better insulation, heat pumps, or solar panels to reduce its energy consumption.

Why is the main verb verduurzamen placed at the very end of the sentence?