Pole barn insulation advice

[Heath568]

I posted this in another online forum and got little advice, so if you have read this twice I apologize.

I live in Kansas City and have been finishing up my pole barn that is 36’X 48’X 12’. Right now I’m putting in the drainage tubes and doing final grade on the site. Once I get my gravel down I will need to start considering insulating at least the roof area to ward off condensation dripping this spring. This will be my primary garage and workshop once I build my house in the next year and a half. For now I’m looking to get the doors on and the gravel base put down use as a staging point for building supplies. When the flatwork is done in the basement I will pour the floor in the garage. There are three bays in the garage that will have floor drains that will run to a drywell and a bathroom in the corner that will have electric heat to ward off cold days. I will probably winterize the bathroom in the winter and have the availability to blow out the lines. I was thinking of putting in radiant tubes in the floor but it would not be cost effective to heat it full time. I’m leaning toward infrared tube heaters for the quick response they provide. The walls have 6X6 posts so I have plenty of space for traditional glass insulation if I go that direction. I would insulate the walls when I purchase the insulation for the house to get a better price.



So I have two questions for everyone out there.



I’m considering putting foam down over the vapor barrier and under the slab in the garage. Do I need it? I was told that it would help the infrared heaters warm the slab more efficiently. But do I need the 1” or 2” foam board? I have included the link to the Foamular 250 site. Will this just add unnecessary cost to the slab with no real gain? Idealy I would like to put in PEX tubing for radiant, but keeping the slab at even 40-50 degrees seems like it would be expensive.

http://www.owenscorning.com/around/insulation/products/foamular.asp


My second question is what do you suggest for roof insulation? I would like to put in closed cell poly spray, but I haven’t won the lottery. Therefore the pink board is looking like the winner. I’m interested in the new radiant barriers, but I have not priced them to see what is out there. I also have two roof vents to let out humid air.

What do you suggest for roof insulation?

Thanks

Heath

 

[Jagmandave]

Another KC guy here, getting ready to do exactly what you already are! One question, doesn't the foamboard go under the vapor barrier? We have heated floors in my plant at work, and that's how they did it........

 

[goaliedad]

far from an insulation expert here, but I was always told the vapor barrier goes on the heated side of the insulation. you don't want the moisture getting into the insulation and condensing. This applies to walls and ceilings- under the slab I would think the vapor barrier would go down first- that's the way they did it when we built the local ice rink! You need to keep the ground moisture out of the insulation.

 

[bebster]

I agree that you want to keep the vapor barrier on the "warm" side of what is being insulated in climates such as yours. Are you planning to heat just the bath in the corner? If so, then it's worth the investment in insulation, which is a lot cheaper than energy over time.

As for the roof, what are the rafters made of and how deep? What is the roof construction?

 

[Heath568]

I was going to put a baseboard heater in the bathroom in the corner to ward off the chills and freezing.

All the talk of radiant has me thinking about it more and more for the whole slab. But I would like to hear from someone who has done it to give an idea of the associated costs of running it.

The walls are 6x6 posts with 2x6 runners between them. The trusses are standard 2X6 with gusset plates and the exterior is standard colored sheet metal.

It makes sense for the foam to be above the insulation. I shouldnt have a water issue with this area. I'm running the trenches for the french drains and eventual gutters this week.

What does everyone think about the 1" foam vs. the 2" foam?

Thanks for the input so far.


Heath

 

[Heath568]

Thought I would try to post a picture

 

[Heath568]

One shot of the outside before I finished the grading.

 

[SnoFalls]

If it were me ... I'd do hot water radiant flow (aka PEX flow) in the slab ... 2" pink on the exterior surfaces.

Your choice how you want the water heated (heat pump with aux gas/electric water heater) ...

2" pink has great moisture resistance ...

This way, you can have the floor "warm" (say 60*) and ALSO cooled (if needed). My shop has a 6" slab, no heat at all, and is a freezer in the winter (colder than ambiant), and an oven in summer (warmer than ambiant). Had it been plumbed with PEX, a cheap heat pump could probably keep it at a constant 60* all year. (Disclaimer, my coldest days are 20* and warmest 99*)

The reason for the "pink" is that vapor inside vs outside the "space" is less of a concern. If you do go to fully finished interior with glass insulation, then you can just leave the pink, add 4" of fiberglass, vapor barrier, and then finish the interior.

 

[bebster]

Heath, I'm just now putting heat in my barn. Here's a post to it, with some photos of radiant in slab. Cape Cod Barn
This may eventually turn into living quarters so I insulated with panels from the get go.

Your structure is about 1/2 the size of mine, and with a lot of insulation in the walls and ceiling, I need about 50,000 BTUs/hr for 0 degree heating to 70 degrees. But I have R=20 in the walls, and R=35 in the ceiling. So real rough, if you insulated to 1/2 of those R values you'd lose twice the heat I do, but with a structure 1/2 the size you'd be in the same ballpark. These calculations are a little complicated and need to be done for your dimensions to be more accurate. Although I'm not an HVAC expert, as an engineer I've had to learn a lot about it since there's not many people in these parts that are knowledgeable.

That will cost what it would cost to heat a house that size. I suspect that's not what you want to do. But you might want to just take the chill off the main space when the outside temps are in the 20 to 50 degree range, but heat the bathroom to a warmer level. That sounds like a good strategy if it were me, and that's what I've done in the bottom level of my barn (which is a space 30x54x10 with two 16' wide garage doors.

If that's the strategy, then you could probably take the chill out of the main space and heat the bathroom for 1/4 of the cost. This partial strategy would dictate how close you'd have to run radiant tubing to get the heat output you need. Happy to give more pointers with some more direction about your goals.

 

[rambler]

This doesn't help you now, but I thought one always rolled the insulation over the rafters & then nailed the tin on. Much harder to do it afterwards now?

For the walls, they make 8' pannels of fiberglass, very easy to install if you go with fiberglass. Need to look a bit, probably from a builder, to find, but it's out there, and cheaper to do than any other type of product.

--->Paul