De spouwmuur heeft isolatie.

Because Dutch usually writes compound nouns as a single word.

So spouwmuur is made from:

• spouw = cavity / hollow space
• muur = wall

Together they form one noun: spouwmuur.

This is very common in Dutch. English often uses separate words where Dutch uses one compound word.

Also, in Dutch compounds, the last part is the main noun. So spouwmuur is a kind of muur.

Because spouwmuur is a de-word.

In Dutch, every singular noun is either a de-word or a het-word, and you usually have to learn that with the noun.

Since the head of the compound is muur, and muur takes de, the full compound also takes de:

• de muur
• de spouwmuur

A useful extra point: in the plural, nouns always take de:

• de spouwmuur
• de spouwmuren

Heeft is the third-person singular present tense of hebben (to have).

The subject is de spouwmuur, which is singular, so Dutch uses heeft:

• ik heb
• jij hebt
• hij/zij/het heeft
• wij hebben

Even though spouwmuur is an object and not a person, Dutch still uses hebben normally, just like English does in sentences such as The house has a garage.

Because isolatie is being used here as an uncountable/material noun, like water, sand, or furniture in English.

So Dutch can say:

• De spouwmuur heeft isolatie.

This is like English The cavity wall has insulation, where insulation is not being counted as one item.

If you want to talk about a specific insulation layer or the insulation as a particular thing, Dutch can use an article:

• De isolatie is nat. = The insulation is wet.

So the lack of an article here is normal.

No, this is a very basic Dutch main clause with normal word order:

subject + verb + object

• De spouwmuur = subject
• heeft = verb
• isolatie = object

So it matches English fairly closely.

One important general Dutch rule is that the finite verb usually comes in second position in a main clause. In this sentence, the subject comes first, so the verb follows it immediately.

Yes. This sentence is understandable and natural, but Dutch also has other common ways to express the same idea.

For example:

• De spouwmuur is geïsoleerd.
  This means the wall is insulated.

• Er zit isolatie in de spouwmuur.
  This means there is insulation in the cavity wall.

The difference is mostly in focus:

• heeft isolatie focuses on having insulation
• is geïsoleerd focuses on the wall’s state
• er zit isolatie in focuses on the presence of insulation inside it

A rough English-friendly guide is:

spouwmuur ≈ spow-myur

A few details:

• spouw sounds roughly like spow, with ow like in cow
• muur contains the Dutch uu, which does not exist in normal English pronunciation
  It is similar to the u sound in French tu or German über
• The r at the end may be light, depending on accent

So an approximate learner pronunciation is fine at first, but the hardest part is usually uu in muur.

A rough approximation is:

heeft ≈ hayft, but with a smoother vowel

More exactly:

• ee in Dutch is a long vowel, not a strong English diphthong
• ft is pronounced clearly at the end

So if you say something close to hayft, you will be understood, but native Dutch pronunciation is a bit tighter and less glide-heavy than English hay.

The plural is spouwmuren.

So:

• de spouwmuur = singular
• de spouwmuren = plural

This is a regular plural with -en.

Because it is a compound noun, only the final part changes for the plural:

• muur → muren
• spouwmuur → spouwmuren

Usually you would refer back to it with hij in standard grammar, because de-words that are singular often take hij as a pronoun.

For example:

• De spouwmuur heeft isolatie. Hij is in goede staat.

In everyday Dutch, especially when talking about objects, people may sometimes avoid repeating a pronoun in ways that feel too formal or unnatural, but grammatically hij is the expected match for a singular de-word like spouwmuur.