perimeter tubing and PEX UV issues

Hammer

I'm in the process of installing radiant floor heat in a free standing garage (my first radiant project). I'm a mech engineer, so it's a dream come true! The garage is a pole building, so there is no foundation (except at the posts), so the floor slab will basically be "on grade" b/c the wolmanized base between the poles/posts sits on grade. I've got a couple inches of polyiso board around the perimeter and under the floor, but since there will not be any earth to "help" prevent heat transfer, I'm wondering how far I should keep my perimeter tubing run away from the wall. I know the earth won't help much if the slab is slightly below grade, but any amount would help. Normally I would figure ~12" away from the outside wall, but with the nature of the pole building, I'm thinking 2' to 3'. Additionally, I'll have base cabinets/casework and shelving around a large part of the perimeter, so it seems wasteful to have the tubing too close to the wall and under the casework & shelves. Any thoughts?

My second question concerns UV breakdown of barrier PEX. I will have a wall-mounted manifold where the tubing will come up thru the floor. The last couple feet of tube in each supply/return run will be exposed. Everything I read says that PEX should not be exposed to UV for more than 30 days to 90 days (depending on who's literature you read). Since the garage has windows and a large door, there will be times when natural sunlight will be in the building. Is there something special I should do w/ the exposed parts of the tubing? Can I just cover them w/ Armaflex or some type of rubber or cellular insulation? I really don't want to "box in" the manifold.....I want everyone to see it! Thanks for any suggestions.

hr

Some thoughts

do a heat load calc to determine the load. Be sure you "heat" enough of the slab to handle that load. I'd be nervous about holding back 2- 3 feet without knowing the heat flux. Selves don't typically block the output, buy skirted cabinets to the floor would.

Vanguard, for one, makes a split plastic protector for pex tubing. It holds up much better than foam insulation and looks more professional. Let it go right down into the slab to protect the penetration.

I've also used one size larger pex to "home make those sleeves. PAP works best as you cand bend a 90 at the bottom to exisit the slab into the layout.

Black pex lso available to migate the UV. I've heard UV can also come from flourscent lights?

Good for you "going radiant" you'll enjoy,and spend a lot of comfortable time in that shop.

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