[Greenbuilding] Anyone know about the Legalett Slab System

[Lynelle Hamilton]

Wow, thank you for the detail!

I will have to raise the house up 24-30" in order to be on grade with 
the septic at the south side. The other 3 sides will have some variant 
of a retaining wall or slope.  I have concerns about the Legalitt from 
that perspective as well. That and the level of insulation--I've 
traditionally done R34 under the slab. They do have a water system 
option, but I've not yet found the pipe diameter specs on the website 
for it.

I've always thought concrete to be a better transfer medium for radiant 
heat. Do you notice a difference with your floor system?

Lynelle


On 2017-07-16 10:58 PM, John Salmen wrote:
>
> Interesting. If a slab is to be used I am a fan of frost protected 
> foundations or integrated footing in a cold climate. A lot less ground 
> invasive and a lot less concrete. Not so effective here on the west 
> coast as we don’t need much depth.
>
> Now ‘if a slab is to be used’ in a consistently cold place heating the 
> slab makes sense if there is sufficient insulation below. The use of 
> air has  a very ancient history – as does water. Air though only 
> contains a tiny fraction of the energy storage potential of water. 
> They will both transfer heat but what it means practically is that air 
> will transfer heat quickly and water will transfer it more slowly. 
> From here on it it gets more complicated looking at pumps and fans to 
> figure out who is working more efficiently but strong suspicion would 
> be that water flow would be drawing less energy (heated to a lower 
> temperature, slow pumping velocity)
>
> What is generally more important to me environmentally is both 
> minimizing materials and being a bit qualitative about what the 
> material is for the job it needs to do. We currently waste a lot of 
> materials on buildings. What seems like a good idea is often bad design.
>
> Look at the pictures on the lego slab site. A structural slab can be 
> as thin as 3” and work well if reinforced properly. The buildup they 
> have with what looks like 2-3” pvc pipe (or in another picture 
> galvanized duct would probably require 6-8” of concrete. That is a lot 
> of energy intensive material to no structural effect (simply contains 
> pipe). Someone could try to make an argument about ‘mass’ but 
> typically a well insulated drywalled house with a few tile floors has 
> more than enough ‘mass’.
>
> Also a radiant water slab is typically ½” polyethylene pipe classed as 
> either a type 1 or 2 plastic – a bit better on the scale than PVC 
> which is a type 3 and has long been recognized as not the greatest – 
> in comparison.
>
> The most important element is insulation and they are using plastifab 
> brand type 1 expanded polystyrene. About 98.8 percent air and 1.1 
> percent of some vinyl monomer (PVC) – expanded with pentane. I don’t 
> have issues with that so much as it is effective for the job it is 
> doing and can go having some life as it is a solid isolatable and 
> recyclable material (for some uses). Its wholesale cost is generally 
> abound 16 cents a board foot and retails for about 3 times that. There 
> are better foams and monomers out there but guess what PVC is cheap – 
> so industry uses it. What can we do but be efficient with what 
> industry gives us thankful people.
>
> I italicized ‘if you use a slab’ as I’ve eliminated concrete slabs in 
> projects as only a footing is required for load bearing elements and 
> have used the foam as the floor system with ply sheathing laminated 
> over the foam supporting interior walls and finished floors. Radiant 
> heating tubes are imbedded in the foam. An FPS footing can be done 
> without an integrated slab. Check with your engineer.
>
> Thanks for the opportunity to comment on that.
>
> Best
> John
>
> *From:*Greenbuilding 
> [mailto:greenbuilding-bounces at lists.bioenergylists.org] *On Behalf Of 
> *Lynelle Hamilton
> *Sent:* Sunday, July 16, 2017 6:23 PM
> *To:* Green Building
> *Subject:* [Greenbuilding] Anyone know about the Legalett Slab System
>
> Has anyone had any experience with this?
>
> Many thanks!
>
> Lynelle
>
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