Jo no vull planxar avui, perquè fa calor a casa.

That is true. In Catalan, subject pronouns are often omitted because the verb form already shows who the subject is.

Here, vull already means I want, so:

• Jo no vull planxar avui
• No vull planxar avui

are both correct.

Adding jo can give a little extra emphasis, contrast, or clarity. It can feel a bit like I don’t want to iron today... with slight stress on I.

In Catalan, the normal negative pattern is to put no directly before the conjugated verb.

So:

• no vull = I do not want

This is the standard way to negate the sentence. A learner coming from English may expect something like I want not to..., but Catalan normally does not do that here. Jo no vull planxar is the natural structure.

Vull is the first person singular present tense of the verb voler, which means to want.

So:

• voler = to want
• vull = I want

This verb is irregular, so vull does not look exactly like the infinitive voler.

After voler, Catalan normally uses another verb in the infinitive, just like English uses to + verb.

So:

• vull planxar = I want to iron

Other similar examples:

• vull menjar = I want to eat
• vull dormir = I want to sleep

So planxar stays in the infinitive because it depends on vull.

Yes. Catalan word order is fairly flexible, although some positions sound more neutral than others.

In your sentence:

• Jo no vull planxar avui

is completely natural.

You could also hear:

• Avui no vull planxar
• Jo avui no vull planxar

These versions shift the emphasis slightly. Putting avui earlier often highlights today more strongly.

Here perquè means because.

So:

• ..., perquè fa calor a casa. = ..., because it’s hot at home.

The accent matters. Catalan distinguishes several similar forms:

• perquè = because
• per què = why / for what

So in this sentence, the single-word form with the accent is the correct one for giving a reason.

This is a very common Catalan pattern. Catalan often uses the verb fer in weather and temperature expressions.

So:

• fa calor = it is hot
• fa fred = it is cold

Literally, fa calor looks something like it makes heat, but you should learn it as a set expression meaning it’s hot.

This is one of those places where Catalan and English structure the idea differently.

Because fa calor is a fixed idiomatic expression. In this kind of temperature expression, Catalan normally uses the noun without an article.

So the natural form is:

• fa calor
• fa fred

not normally:

• fa la calor
• fa el fred

for this meaning.

A casa means at home or at someone’s home. It is a very common expression and works a lot like English at home.

So:

• fa calor a casa = it’s hot at home

If you say a la casa, you are talking more literally about the house/building, not just the idea of home.

So:

• a casa = at home
• a la casa = at the house / to the house

Yes, but that changes the focus.

You could say:

• Perquè fa calor a casa, jo no vull planxar avui.

This puts the reason first, so it sounds more like:

• Because it’s hot at home, I don’t want to iron today.

The original order is more neutral in everyday speech:

• Jo no vull planxar avui, perquè fa calor a casa.

A rough guide for an English speaker is:

• vull: roughly like bool, but in many accents the final ll has a palatal sound that English does not really have
• planxar: the x here sounds like sh, so roughly plan-SHAR

A few useful pronunciation notes:

• x in planxar is pronounced like English sh
• the stress in planxar is on the last syllable
• què in perquè is stressed because of the accent

Exact pronunciation varies by dialect, but those approximations will help you recognize and say the sentence.