How UV sensitive is regular foam plastic?

[sanben]

Hello!
We are going to add insulation to the part of our basement that is above ground. Everywhere the insulation will be visible, we'll use pre-fabricated insulation elements that have a fiber cement board as a surface layer. However, where we're building a deck, I'm tempted to use regular S100 foam insulation since it won't be visible anyway. There is a bit of a price difference... The facade to be insulated faces north and, as mentioned, there's a deck over it, so excessive light shouldn't come in. What's the worst that could happen? I've read in other threads that it becomes "yellow and hard." I assume the insulation capacity might be slightly reduced then? Could it be a good idea to cover it with ground cloth?

 

[Håbbe01]

Hi!
We are going to add insulation to the part of our basement that is above ground. Everywhere the insulation will be visible, we will use prefabricated insulation elements with a fiber cement board as the surface layer. However, where we are going to build a terrace, I am tempted to instead use regular cell plastic s100 since it won't be visible anyway. There is a price difference, after all. The facade that would be insulated faces north, and as mentioned, a terrace is above it, so there shouldn't be an excessive amount of light. What's the worst that can happen? I have read in other threads that it becomes "yellow and hard." I assume the insulating ability might deteriorate a bit then? Could it be a good idea to cover it with ground fabric?

Always some rodent that is eager to test the durability

 

[useless]

You can glue fiber cement boards with stone adhesive, making it the same as prefabricated foundation elements.