Slab insulation
jameshaug
| Posted in Energy Efficiency and Durability on
I need to insulate a slab and usually use rigid foam. However this project is a woody area and there are lots of termites nearby and I know they love foam. Is Roxul drainboard or rock wool a good option in this case?
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Replies
James,
Here are links to two relevant articles that you probably want to read:
Sub-Slab Mineral Wool
If Ants Like Rigid Foam, Should We Stop Using It?
As a good alternative, you can always insulate above the slab and inside the walls with rigid foam.
Just and fyi, Roxul doesn't warranty their product as being termite proof. They just mention anecdotally that rodents don't like it due to a lack of feedback from customers that mention rodent problems.
On the other hand, because of the density of MW I have no clue as to whether termites could nest in dense mineral wool and its effect on R-value.
Also living in termite country myself I've only found comments that imply a maximum depth of subterranean termites is 18" (see link: http://www.termites.com/damage/structural-damage/termites-under-house-slab/).
Perhaps knowing this depth you could design your slab edge accordingly.
BSC has some alternative approaches to the termite dilemma (Fig 3, 4)
http://buildingscience.com/documents/insights/bsi-059-slab-happy
my 2 cents.
Thanks for all the responses. I'm sure more will come. I actually called Roxul and asked them. They claim that it can be used under a slab but not under footings as structural support. It is less attractive to bugs as is rigid so is the better option. What I'm wondering is why doesn't Roxul or someone else develop a product for use in this manner that is bug resistant? I get all kinds of comments from people who deal with bugs and they won't warranty their work if there is foam involved. Or say things like we warranty it for 10 years. Not helpful. This is a big issue that needs to be honestly addressed. Especially if more of this product will be used in the future i.e. passive house.
James,
There are manufacturers that treat their foam against insects. I don't know how effective they are though:
http://www.performguard.com
James,
NOTHING is bug resistant, that's the reality of living among nature. Rats, mice, termites, ants, etc. can and do live in Roxul, EPS, wood walls, attics, etc. That's just the reality of it. What one can do is try and PREVENT infestations but nothing out there is 100% fool-proof, besides a solid monolithic concrete slab or wall but once you introduce INSULATION, that's when it introduces pests.
Ask yourself, what is insulation? It's typically soft, warm, weatherproof material. Now is it any surprise that pests would like a soft, warm, weatherproof material to reside in?
Life is short, worrying about this stuff is beyond our control. Just take the normal precautions, spraying termicide below the foundation, using Borate, keeping water away from foundation, monitor the foundation once built, use termite breaks and monitor stations, etc. Remember, even in the end when your body is in the ground, pests and microorganisms will get to it and decompose it. Don't quicken the process of getting there by stressing or worrying about things you can't prevent or control fully.