Help with concrete floor insulation

[C10Dan]

Hi all,

I'm just about finished with my new pole barn workshop and still have to pour the floor. I have an opportunity to buy some reclaimed 2" or 4" thick XPS insulation at a very good price and would like some feedback. I'm leaning toward buying the 4" 40 psi rated XPS, but wanted to know if it's overkill and worth using. Or should I stick with 2" 25 psi rated. It appears now that some codes require the use of 3" in some areas, so is 4" going to be better? Or is there a point where too much doesn't buy you anything?

First of all some history. The building is located near Buffalo, NY. I'm planning for in-floor radiant heat. The building is 46'X48' with 14' high ceiling. The new building is actually an addition where the back of the building (46' width) is attached to a 40'X40' pole barn. The front has three 12'X12' insulated doors.

Walls are insulated with 4' wide R19 fiberglass with poly vapor barrier. The ceiling is blown in fiberglass R49. I ran 4" thick vertical foamular XPS between the post columns down 2' deep. I would have liked to go deeper, but it didn't work out that way. Hopefully 2' down will be deep enough. The vertical insulation is flush with the column posts. I'm planning to pour the concrete floor flush with the posts, and against the vertical insulation, so the edge of the slab is insulated.

I plan to use 10 mil Perminator under slab vapor barrior then my XPS insulation. So what do you feel about going with 4" XPS under the floor? The cost is about $675 more then the 2" XPS for 2,200 square feet. Is it worth the extra money? Thanks for your feedback.

Dan

 

[Radix2]

The option I chose was to do 4" for the first 4 feet around the perimeter, 2" for the rest of the floor. The main heat loss is at the perimeter, so it is an efficient use of your money and materials.

Sounds like that would only be a couple hundred.

 

[C10Dan]

Thanks Radix2. Well here's the deal. The cost of 2" 25 psi rated reclaimed XPS would be $975 for my building. The cost for 4" 40 psi rated reclaimed XPS would be $1650. Now if I were to buy 3" 40 psi (Foamular 400) new, it would cost me over $6000 for my building. New 3" 25 psi (Foamular 250) would cost about half of that, around $3000. Either way I have a huge savings. For the reclaimed 2", I figure I would save about $1000 using the reclaimed insulation.

I don't believe I need the 40 psi rated material. I could get by with 25 psi rated, which seems to be what everyone is using. However, with the big savings using the reclaimed material, I figured I would go with the 4" 40 psi that they have. This material is not wet or saturated and has good corners that are not broken.

I'm mainly wondering if anyone has used 4" under their slab and if there is a benefit to going that thick.

 

[yeldogt]

if it's the proper stuff and a good price .. why not use it? more is always better .. it's a question of cost for whet you get for that extra 2" .. in your case your getting it all at a good price.

 

[like2wheel]

The option I chose was to do 4" for the first 4 feet around the perimeter, 2" for the rest of the floor. The main heat loss is at the perimeter, so it is an efficient use of your money and materials.

Sounds like that would only be a couple hundred.

Does that mean your concrete is 2" thicker in the center, or did you figure out a way to screed in 2" of stone in the center after the perimeter insulation was put down?

 

[toyotadriver]

You live in a cold climate. Go with the 4 inch. The cost difference is marginal. No brainer IMO.

 

[rburke65]

You really do not need the 25 psi either! The 15 psi will do nicely.

 

[revamped]

your new price seems expensive. I did 40x40 2" XPS through HD Contractor Desk for about 1300. Maybe they cut me a deal on that due to all my purchases. 4" sounds like a screaming deal... who cares if it is reclaimed as long as it has not been water logged.

 

[toyotadriver]

You really do not need the 25 psi either! The 15 psi will do nicely.

But the OP can get 25PSI or 40PSI reclaimed cheaper than 15PSI. No reason for him to go with more expensive 15PSI.

 

[rburke65]

Gotcha!

 

[6768rogues]

I am about an hour east of you have I have several heated buildings with no insulation at all in the floors. One is 36x48 and one is 40x60, and both have 14 foot high ceilings. I keep them about 45 degrees minimum and raise them up to about 65 when working in them. I spend about $300 to $400 per year per building for natural gas. My sidewalls and ceilings are insulated, but not as well as yours. I don't think insulating the floors would have reduced that enough to be worth the bother.

 

[like2wheel]

I am about an hour east of you have I have several heated buildings with no insulation at all in the floors. One is 36x48 and one is 40x60, and both have 14 foot high ceilings. I keep them about 45 degrees minimum and raise them up to about 65 when working in them. I spend about $300 to $400 per year per building for natural gas. My sidewalls and ceilings are insulated, but not as well as yours. I don't think insulating the floors would have reduced that enough to be worth the bother.

And you have in floor radiant heat?

 

[6768rogues]

No in floor heat, I missed that in your original post.
I use Reznor hanging furnaces. I like the reasonably low up front cost, low operating cost, ease of maintenance, no floor space used, quick heating from 45 to 65 degrees and the ability to go to Florida if I want to without being concerned about the system going off for a myriad of reasons and freezing. No glycol to think about if I want to leave and be sure it won't freeze. For those reasons, I do not have floor heating in any of my buildings.
Last March we were in FL and our electricity at home went off for about 4 days while the temperature was dropping. I have an electronic device where I get alerts on my cell phone if the temp in the house drops. It got down to 42 degrees and my brother in law was going to supply some supplemental heat if it did not come back on the next day, but it did. My barn did go below freezing and I am so glad I did not have a hydronic heat system.
When we go away overnight or longer in the winter, I turn off our water heater and our domestic water at the main coming into the house. If something happens and the water heater gives out or the house freezes, all that will leak is the water in the pipes. No water spraying until I get home. If I had a water based heating system, I would have to leave the water on for makeup water.

 

[like2wheel]

No in floor heat, I missed that in your original post.
I use Reznor hanging furnaces. I like the reasonably low up front cost, low operating cost, ease of maintenance, no floor space used, quick heating from 45 to 65 degrees and the ability to go to Florida if I want to without being concerned about the system going off for a myriad of reasons and freezing. No glycol to think about if I want to leave and be sure it won't freeze. For those reasons, I do not have floor heating in any of my buildings.
Last March we were in FL and our electricity at home went off for about 4 days while the temperature was dropping. I have an electronic device where I get alerts on my cell phone if the temp in the house drops. It got down to 42 degrees and my brother in law was going to supply some supplemental heat if it did not come back on the next day, but it did. My barn did go below freezing and I am so glad I did not have a hydronic heat system.
When we go away overnight or longer in the winter, I turn off our water heater and our domestic water at the main coming into the house. If something happens and the water heater gives out or the house freezes, all that will leak is the water in the pipes. No water spraying until I get home. If I had a water based heating system, I would have to leave the water on for makeup water.

I don't think the OP was looking for advise on his choice of heating, however, to clear up some possible misinformation, I don't believe in-floor heat in an unattached garage it typically connected to the domestic water supply. It would be a closed system partly filled with glycol to prevent freezing. No problem shutting off the water while vacationing.

I've I've also read that in floor radiant is considered ideal for potential power loss areas because of the thermal mass retention.

 

[Firebrick43]

I say it ain't worth it if you don't have in floor heat. Stick with the two. Also if you do use different thickness of foam keep the slab the same thickness. A slab will crack where you vary the thickness.

 

[4cyclic]

I put an apron on the outside perimeter of my garage, 2 feet of 2in XPS all around except 4 feet x 8ft wide on each side of corners. It helps to keep frost from going under the slab.

 

[C10Dan]

I don't think the OP was looking for advise on his choice of heating, however, to clear up some possible misinformation, I don't believe in-floor heat in an unattached garage it typically connected to the domestic water supply. It would be a closed system partly filled with glycol to prevent freezing. No problem shutting off the water while vacationing.

I've I've also read that in floor radiant is considered ideal for potential power loss areas because of the thermal mass retention.

Actually my building is about 75' from my house. I'm planning to run domestic water to the building for a couple of reasons. First of all, I want water in the building and secondly I do plan to use it to supply my radiant heat system. I know other people who have stand-alone buildings that have in-floor heat like this. My water line from house to workshop will be below the frost line. It will enter well into the interior of the workshop.

 

[C10Dan]

Well I decided to go with the reclaimed 4" - 40 psi rated XPS. I made the trip with my truck and 16' landscape trailer to pick it up. For being reclaimed, this insulation was really nice. It's only going to be buried anyway. I was able to pick through it and take what ever I wanted. If there was a sheet that was cracked, or had rough edges, I put it back. The warehouse worker brought it over to my trailer by fork truck and helped me load it. Since these were 2'X8' sheets, I was able to lay down 3-rows with 2-sheets in each row. By the time I was all said and done, the total height from ground to top was 9', which was about 1' shorter then my camping trailer.

 

[toyotadriver]

Nice shape and under concrete it won't matter what it looks like!! Good stuff! I'd love a deal like that!

What was it reclaimed from?

 

[dynahoe]

question on placement of sheets. if you put poly on top of foam do you need to tape or seal all joints of sheets?

 

[C10Dan]

Nice shape and under concrete it won't matter what it looks like!! Good stuff! I'd love a deal like that!

What was it reclaimed from?

Agreed that once it's under the concrete it won't matter. I'm not sure where they were reclaimed from, but some have a dry dirty side that appear to have been in contact with the ground. They are all dry and none of them have taken on water. There were a couple that I came across that had water in them and were quite heavy. I quickly passed on those and left them behind.

 

[justinjoyal]

question on placement of sheets. if you put poly on top of foam do you need to tape or seal all joints of sheets?

Tape everything, then approved vapor-barrier on top.

OP: 4in ! Definitely nice stuff. The 40 psi rating is great too.

Around here Code calls for min. 30psi under concrete floors and min. R5 or R7.5 (1 or 1.5in thick) depending on applications.

I think you won’t be disappointed.

 

[4cyclic]

you did well.

 

[C10Dan]

Tape everything, then approved vapor-barrier on top.

OP: 4in ! Definitely nice stuff. The 40 psi rating is great too.

Around here Code calls for min. 30psi under concrete floors and min. R5 or R7.5 (1 or 1.5in thick) depending on applications.

I think you won’t be disappointed.

If I understand this correctly, you are saying to put a vapor barrier on top of the insulation, between the insulation and concrete? I've heard of installing vapor barrier on ground, then insulation, and then concrete, but not an extra vapor barrier on top of the insulation. Anyone else done this?

 

[justinjoyal]

If I understand this correctly, you are saying to put a vapor barrier on top of the insulation, between the insulation and concrete? I've heard of installing vapor barrier on ground, then insulation, and then concrete, but not an extra vapor barrier on top of the insulation. Anyone else done this?

This is how it’s done here in Quebec, per Code.

 

[sstec]

I did my vapor barrier, sealed taped and then 6" of foam, taped and sealed. 2 layers of 3" foam. Will be pouring soon. Will let you know how it turns out. sstec

 

[SSpanky]

my building is 50x104 with 16 ft sides. I used vapor barrier, foam, taped seams then radiant tubes.
This will be the second season running, I had no problems last winter with condensation or sweating issues.

 

[like2wheel]

If I understand this correctly, you are saying to put a vapor barrier on top of the insulation, between the insulation and concrete? I've heard of installing vapor barrier on ground, then insulation, and then concrete, but not an extra vapor barrier on top of the insulation. Anyone else done this?

It seems the best way is to put the vapor barrier directly under the concrete & on top of the insulation.
I've been researching this; I'm about a year behind you and in the same area.

http://www.greenbuildingadvisor.com/blogs/dept/musings/polyethylene-under-concrete-slabs
.
.