Insulating an outdoor concrete patio – how much insulation?
MarkyMarko
| Posted in General Questions on
I’ve got a plan, slab on grade, that has a walkout slider opening to a 10’x 24′ outdoor 4″ thick concrete patio. The patio is contained by 5′ frost walls and will be isolated from the adjacent frost walls. The patio is covered by a roof, but very much outdoors and exposed to our Zone 5 winters. I’m planning to insulate under the patio with XPS. What is the practical thickness of XPS that would be recommended for this scenario? 2″, 3″, 4″ ?
Thank you-
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Replies
Because the slab is connected to a stem wall that is below the frost line and the space is outdoors and unconditioned, under-slab insulation would not be needed. That being said, often these spaces are later converted into conditioned space. I would think about adding 2" of insulation under the slab and isolating the interior vertical side of the stem wall that ties to the slab. The link shows the idea of the detail.
https://www.greenbuildingadvisor.com/cad/detail/slab-on-grade-with-frost-wall-w-1-in-rigid-foam
Thanks Randy!
Funny, at first read, my reaction to 'often these spaces are later converted' was yeah, but probably not in this instance; but after less than a minute of consideration, I realized how right you are. Things change.... 2" it is.
Thanks again -