Snow melt question

Wayco Wayne

a sidewalk, 3 x 20 alongside my driveway. What kind of insulation, if any would I need to put down?

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[Deleted User]

We use a minimum

of 1" XPS (*blue or pink board) foam on the botom and the sides. You can chamfer the edge side piece at a 45 degree angle so that none of the foam shows at the top edge of the pour.

ME

The Latin Canadian

side walk

I would use 2" foam insulation or double bubble foil.Either one will make for a faster response.I can useally get good striping in 20 to 30 min.The 2" holds up better after walking on it.

marc

foam under snowmelt

i have had problems with the slab that is insulated frosting up and causing slip hazards. has anyone else experienced this. we usually size 120-200 btu/ft. in the northwest. even with tekmar 661/2 . why melt frost. if you size the load for worst case they work fine. i think you should quit selling efficient snowmelts. the load increases 10-15 times outside. why upsell foam when there is no insulation to contain heat. either they are class 1/2/3 snowmelts. most of what we do are residential driveways. these people complain about fuel bills. with foam under slab they just run alot more. any thoughts. marc

[Deleted User]

Explain please...

I've not had any problems with frost here in Colorado. Sounds like it could be a local problem. When does the frost occur, and does it also occur on other surfaces that aren't heated or insulated?

You've made numerous other comments that cornfuse me.

Systems with insulation run longer? I've found the contrary to be true. If you don't have to heat Mother Earth AND the slab, it takes a lot less btu's. Where do you get your information from?

In my mind, insulation just plain makes sense ANYWHERE theres a heat loss occuring.

And welcome to The Wall!

ME

Boilerpro_3

Another snowmelt question....

I'm installing my first snowmelt and it is for my own home. Our front porch has a roof above (or at least it will by this winter) and is a suspended slab above a unheated basement room. Should the back side be insulated or would it be best to allow some of the geothermal heat of the unheated space below help keep the slab warm. I'm also doing the north facing steps that are under the same roof that are set into the porch along with the walkway out ot the city walk. Any suggestions?

boilerpro

Mike T., Swampeast MO

Interesting Boilerpro...

As long as the temp of the suspended slab stays BELOW that of the basement (45°-55°?) it will receive some radiant heat FROM that space. BUT if the snowmelt raises it ABOVE the basement temp it will be radiating to the basement instead.

I'm presuming this is a new porch floor with embedded tube and something tells me you would leave it uninsulated as you're quite unlikely to raise its temp above that of its surroundings. If you're heating the porch floor from BELOW the slab, you certainly want to insulate as the initial heating method will certainly be warmer than the surroundings.

The steps and walk may react differently than the porch floor, but I'm not certain. The steps/walk have a conductive route to the ground (controlled somewhat with insulation), but (being above grade and having concrete walls I presume) the porch floor has an enhanced convective route (the wind) that you can't alter...

My guesses for trying to balance the two in the same system:

1) Since I believe you've been there for a while, consider whether the porch floor or the steps/walk cover with snow at the same time or one before the other. If one area tends to accumulate a lot more snow that the other most of the time, I'd make a "best guess" adjustment in tube spacing.

2) Since the suspended slab is likely thicker than the sidewalk, don't forget to make adjustment for this difference in mass.

Unknown

Snow melt insulation

Insulation in snow melt systems.

Isn't the highest load always going to be to the atmosphere and melting snow? Hot goes to cold...  So the greatest load will be upward.

Why insulate at all if downward loss is only about 10-15 Btu/hr/sq/ ft.?

I have heard mixed results of the use of the foil/double bubble/poly radiant barrier insulations.

Just wondering if insulation is always needed.

Holly Gates

snowmelt for driveways?

Do people ever put snowmelt in a driveway?

Andy N._3

insulation in snowmelt

I do remember hot rod setting up a system in front of his shop with temperature probes in various places under the slab. he also used different types of insulation and was going to record which slab responded better. perhaps he will be able to answer this question better than I. I have done a driveway for a good friend who was sure that insulation was not necessary.(his builder was sure insulation was not necessary) we sized the boiler for 125 btu's per square foot on a 1500 square foot driveway.(Northern Illinois) I convinced him to let me put some insulation in just to test the theory, and here is what I found:

The builder ran the new system for about three days in a row at about 80 degrees to test the system. this was in january and at the time it de-iced the driveway and basically just wasted a lot of fuel. I shut off the system and a day or two later we got an inch or two of snow. at this time the system was off and the snow melted off of the uninsulated areas. the ground had stored all of the heat and was releasing it through the slab quicker in the uninsulated areas than in the insulated areas. In fact the insulated areas never let enough heat through fast enough to melt anything.

We then got about 6 inches of snow a week later. By this time the system was automated and it immediately kicked on. The insulated areas were melted and dried while the uninsulated areas were striped. it took about twice as long to melt the uninsulated areas as the insulated areas. we used both insultarp and double bubble as insulation. The insultarp reacted quicker than the double bubble and the double bubble reacted quicker than nothing at all.

I am convinced that something is better than nothing. the higher the r value of the insulation the better the reaction time. I now have proof of insulation effects of the tarps and I won't do a job without them. too much wasted fuel. as far as my friend goes, If he ever decides to add insulation to the uninsulated area's, It is possible without tearing everything out.

just my 2 cents worth,
Andy

Mark Hunt

Yes Maam

Mark H

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[Deleted User]

Nice post Andy...

This is the kind of real world, real time information that the internet is all about. Thanks for the confirmations.

I'm sure that there is some validity to the insulation keeping the slab cooler than it might be (by a VERY few degrees) because of the loss of earth contact, but those btu's are more than offset by the insulation keeping the heat where its supposed to be when the system is on.

There's also the effects and issues of night sky re-radiation. Unfortunately, there's not a control on the market yet that has the ability to recognize this issue and address it.

As for me and my money, I'm sticking with the insulation.

ME