In slab pex layout

[bandito]

Hi,

New to hydroponic floor heating. I pretty much get all of it just uncertain about the pex layout in the floor. My floor will be 13' x 21' or 273 square feet. Not a whole lot. I have a few ideas of what I may do as far as a layout. I was wondering if anyone could recommend some resources to help me with my layout?

Thanks

 

[scooterboy]

Bandito
www.loopcad.com

 

[bandito]

I downloaded Loopcad and played around with it to get a few different layouts. I uploaded them to an album under my profile called layouts. I don't have enough posts to be able to add images to this post at the moment.

I was wondering which one is best and also if anyone has suggestions on how to improve the layouts.

I like the one with the loop going around the outside. I figured heat is more required along the edge where the exterior is. That's why I have a 6" spaced loop. Since there probably isn't much heat loss towards the centre I went with 12" spacing for that loop. The little loop is a 3' x 7' washroom. I figure shorter loops where there is more heat loss would be more efficient.

If you have questions please fire away.

 

[kj_mustang]

I would do a total of three loops. Space at 6" close to the edges. Yes routing the first part of the loop on the outside is a good idea. Short loops also will not lower the water temp in the tubing to achieve the design delta T so you will have hotter water coming back in that loop but cold water coming back in other loops.

 

[TurnipTruck]

The rule of thumb is roughly one foot of tube per sq ft of floor.
Half-inch pex loops should be less than 300 ft long.
All loops per zone really should be equal in length.
Don’t put tubes where you are going to punch holes in the concrete, like lifts or walls.
12” loop spacing is fine at the edges and in the middle.

 

[yeldogt]

The loops should mimic the loss and intended use -- also, how you are going to control?

Continuous circulation is more forgiving.

How close to the edge depends on insulation and what's happening there -- Typically you don't want to have the hottest water 2" from the slab edge at a long door -- no insulation. But you may under bank of windows with good insulation ?

The center will need less in a typical garage setting ..... in a very well insulated space where even heat is desired and constant circulation -- it's hard to screw up

 

[Randy in Maine]

Don't overthink this. You are essentially heating up a big rock just as the cavemen did it with a big fire (only yours is concrete with a huge thermal mass and you are using warm water to do it).

I like my 1/2" Pex spaced at 12" with 2" of rigid foam under and around to provide for a good thermal break.

Invest is good insulation with low infiltration rates as it pays for itself every day. I built my shop out of SIPs and I am glad I did.

 

[bandito]

I have 2" of insulation below and on the sides the slab. I was also thinking of running some rigid insulation along the outside of the slab along the garage and man door.

 

[Randy in Maine]

I ran my 2" under the concrete and on the heated building side of the unheated stem walls. Nothing at the doors. On the inside of the stem walls I sort of framed it over with a1"x 10" pine with a 2" pine board on top of that. My walls are 1x8 vertical shiplap pine all nice and polyed up, so it all fits ibn and there is no foam exposed.

I am R-40 or better everywhere and the shop is all nice and snug even when it is really cold out. Still as cheap to heat as I could make it. It stays pretty cool all summer also.

Ants may like foam insulation but they can't get to it at my place.

 

[bandito]

So I finally installed my pex pipe. In an album called "pex tube layout" are some pictures of what I have accomplished.