De or het wandverwarming?

The correct Dutch article is:

de wandverwarming

Rule Words ending in -ing: almost always de. See the rule

How to use wandverwarming

the wandverwarmingde wandverwarming
this wandverwarmingdeze wandverwarming
that wandverwarmingdie wandverwarming
our wandverwarmingonze wandverwarming
your wandverwarmingjouw wandverwarming
every wandverwarmingelke wandverwarming
which wandverwarming?welke wandverwarming?
a big wandverwarming / the big wandverwarmingeen grote wandverwarming, de grote wandverwarming