I'm building a wooden garden room and have used tongue and groove cladding for the walls. I'm planning to add 50mm Kingspan insulation foam boards inside. Should I install a non-breathable plastic barrier on the inside of the walls before adding the insulation, or is a breathable membrane better?
2 Answers
You really want to keep moisture moving out instead of getting trapped. It's best to use just one moisture barrier to avoid a 'mold sandwich' situation. If you put plastic sheeting on the inside and then add insulation, moisture could get stuck between them. Just think about how moisture will flow.
It really depends on where you live. If you're in a wetter area, you might want to make sure the interior can let moisture escape. A breathable membrane could be a safer choice to avoid trapping moisture inside.