FPSF Garage Slab Insulation

[Tracs]

I built my 24x30 garage in 2014 with a frost protected shallow foundation. The slab has radiant heating.

It has 2" of ridged insulation under the slab and vertical around the outside perimeter.

6kw boiler provides the heat for the system. It seems capable enough in the coldest of winter days. Runs at full power 50% of the day.

Manitoba, Canada gets to -30C in the winter.

I never installed horizontal ridged insulation frost wings/shield around the bottom of the slab.

The slab is only partially back filled still and I could easily add them, but for the $250 it will cost for insulation, I'm not sure if I will see the cost savings in the heating. I doubt I will instantly start saving $50/month. Electricity costs are about $0.08 kWh

Would you put the frost shield/wings in now after the fact? Do you think they make that big of a difference?

As I said, the boiler heats the garage currently on the coldest of days.

 

[Highbeam]

6kw? That's a little one. You must have built this shop very well. Good job!

 

[Tracs]

6kw? That's a little one. You must have built this shop very well. Good job!

R20 in the walls
R50 in the ceiling
T16 Overhead Doors
Double pane pvc windows
Insulated entry door

 

[jack stand]

I believe the "wings" are not to benefit your heating costs but to prevent the frost from heaving the soil under your FPSF* and the possible damage. Unless your FPSF is high, dry and on great draining soils, I'd think of it as very cheap insurance that may also (slowly) pay you back.


* it's part of the design of any FPSF that make's the whole "shallow" part work.

 

[Tracs]

I believe the "wings" are not to benefit your heating costs but to prevent the frost from heaving the soil under your FPSF* and the possible damage. Unless your FPSF is high, dry and on great draining soils, I'd think of it as very cheap insurance that may also (slowly) pay you back.


* it's part of the design of any FPSF that make's the whole "shallow" part work.

That is interesting information and it makes sense. Can we get confirmation on that?

My garage FPSF is high, dry, and on great draining soils. But if that is the purpose of the "wings" I will certainly install them.

 

[Radix2]

That is interesting information and it makes sense. Can we get confirmation on that?

My garage FPSF is high, dry, and on great draining soils. But if that is the purpose of the "wings" I will certainly install them.

This is the guide for FPSF https://www.homeinnovation.com/~/me...de-to-Frost-Protected-Shallow-Foundations.pdf

The question would probably be do you want frost protection in case you stopped heating your building.

Look at the guide and see how it compares to your construction and heating plan, but as above, the wings are basically to push the frost away from your foundation by using the earths heat.

 

[jack stand]

That is interesting information and it makes sense. Can we get confirmation on that?

My garage FPSF is high, dry, and on great draining soils. But if that is the purpose of the "wings" I will certainly install them.

I'm new to the FPSF and for that matter, 4' frost depths. I just did a small addition to the house and from what I read about them (FPSF), that's what I understand the purpose is of the horizontal insulation extending outward beyond the slab and below the finished grade. I thought that they have been used for quite a while "up" your way. Double check me for sure, wouldn't be the first time I was wrong.
The pic is what I did, also with radiant in the slab. The wood was just form work to support the foam that was essentially the form. I extended the foam (under the gravel in the pic) about 24"- 30" out.

 

[climb.on]

I believe the "wings" are not to benefit your heating costs but to prevent the frost from heaving the soil under your FPSF* and the possible damage. Unless your FPSF is high, dry and on great draining soils, I'd think of it as very cheap insurance that may also (slowly) pay you back.


* it's part of the design of any FPSF that make's the whole "shallow" part work.

Jack Stand is absolutely correct here. The wing is to keep frost from driving under and heaving the slab. DON'T skip it!

 

[Tracs]

Well.....1 year later and I have finally started on the frost wings.

I sure wish I would have know about them at the time of construction. I did 1 side today, the 30' side. I am so sore. WOW.

I also got some white aluminum flashing to cover the slab's side styrofoam.

 

[Tracs]

For anyone following along I finally finished it off today. I had to redo the south side. I didn't level the ground under the foam very well and when I back filled and walked on it, it started to crack. So I took it out, leveled it and even put another layer of 1.5" foam on that side.


I would have liked to gone deeper in the ground with the horizontal wings, but the slab itself was built very high. It is only in the ground about 6".


Hopefully it is something I never have to do again, lol.