raunjiga jobeun dedaga hwangido jal an dwaeyo.

-은/는 데다가 means something like on top of that, besides that, or to make matters worse.

So 좁은 데다가 connects one negative point to another:

• 라운지가 좁은 데다가 = The lounge is narrow, and on top of that...
• then the second complaint follows: 환기도 잘 안 돼요

It is often used when listing reasons or problems, especially when the second point adds to the first one.

Because 데다가 attaches to a modifier form of the adjective, not the dictionary form.

For descriptive verbs/adjectives like 좁다, you change them into an attributive form:

• 좁다 → 좁은

So:

• 좁은 데다가 = because it is narrow / and on top of being narrow

This is the normal pattern:

• 작다 → 작은 데다가
• 멀다 → 먼 데다가
• 비싸다 → 비싼 데다가

For action verbs, you usually use -는 데다가 instead.

Using 가 marks 라운지 as the grammatical subject: the lounge is the thing being described as narrow.

• 라운지가 좁은 데다가... = The lounge is narrow, and...

If you said 라운지는, it would sound more like setting up the lounge as the topic, often with contrast:

• 라운지는 좁은 데다가...
  = As for the lounge, it’s narrow, and...

Both are possible in real Korean, but 가 is very natural when simply describing the lounge and its condition.

도 means also, too, or even.

Here it adds another negative point:

• 환기도 잘 안 돼요 = Even the ventilation isn’t good / The ventilation also doesn’t work well

It matches the earlier complaint about the lounge being narrow. So the sentence is basically stacking problems:

1. it’s narrow
2. also, ventilation is poor

Without 도, the sentence would still be grammatical, but 도 makes the additive meaning clearer.

These two are different in meaning.

• 환기를 잘 안 해요 = They don’t ventilate it well / People don’t air it out often
• 환기가 잘 안 돼요 = Ventilation doesn’t work well / It doesn’t get ventilated well

The sentence uses 환기가 잘 안 되다, which focuses on the state/result, not on a person doing the action.

That makes it sound natural for describing a place with poor airflow.

Literally:

• 잘 = well
• 안 = not
• 돼요 = works / becomes / is done

So 잘 안 돼요 is a very common expression meaning:

• it doesn’t work well
• it doesn’t go well
• it isn’t done properly

In this sentence, 환기가 잘 안 돼요 means the ventilation/air circulation is poor.

The correct spelling is 돼요.

That is because it comes from 되어요, which contracts to 돼요:

• 되다 → 되어요 → 돼요

So:

• correct: 안 돼요
• incorrect: 안 되요

This is a very common spelling mistake for learners, so it’s good to memorize 되어 → 돼.

Because 데다가 is written as a separate word after the modifier.

So the correct spacing is:

• 좁은 데다가

not:

• 좁은데다가

Korean spacing can be tricky, but in this expression, the part before it modifies 데다가, so they are written separately.

It is polite informal style, because it ends in -요:

• 안 돼요

This is very common in everyday speech.

Other levels would be:

• 환기도 잘 안 됩니다 → more formal/polite
• 환기도 잘 안 돼 → casual/plain spoken style

So the original sentence sounds natural in normal polite conversation.

Yes, that is grammatical, but the nuance is a little different.

• 좁고 환기도 잘 안 돼요 = It’s narrow, and the ventilation is poor
• 좁은 데다가 환기도 잘 안 돼요 = It’s narrow, and on top of that, the ventilation is poor

So -고 just connects two facts. But -은 데다가 emphasizes that the second point is an additional drawback.

If you want a stronger complaint/listing-problems feeling, -은 데다가 is better.

환기 means ventilation or airing out a space.

Depending on context, it can refer to:

• fresh air coming in
• air circulation
• the act/state of ventilating a room

In 환기가 잘 안 돼요, it usually means the place does not get enough fresh air or the air circulation is poor.

No. It can be used for positive situations too, but it is very often used to add supporting points of the same kind.

Examples:

• negative: 방이 작은 데다가 어두워요
  = The room is small, and on top of that, it’s dark

• positive: 친절한 데다가 일도 잘해요
  = On top of being kind, they’re also good at their job

In your sentence, it naturally sounds negative because both points are complaints.

A very natural spoken-English-style rendering would be something like:

• The lounge is cramped, and on top of that, the ventilation is bad.
• The lounge is small, and to make matters worse, it doesn’t get good airflow.

This helps show the nuance of -은 데다가 better than a plain and sometimes does.