Snow Melt & Bubble Wrap

Rankin

Basically, the homeowner was given some bogus advice in regards to insulation and put down bubble wrap. His 1/2 loops are on 6" centers, some on 5, he did max 250' loop lengths, and has about 1500 sq ft of concrete. Up here we're about 160 BTU's per ft2, does anyone have a definitive r-value for bubble wrap? I know they claim 3, but I've been doing my homework on this and it's not looking good.



Should I even attempt this system? Money isn't exactly an issue on this system, this gentleman would really like to have a snow melt system, but is it even worth my trouble to go through with this? Does anyone think it'll work? Think it'll work fine? Should I advise him to grow potatoes to sell in his nearby yard to help offset the cost of running this system?



Any input is greatly appreciated!



Thanks



Rankin

Ironman

It Should Work...

The R value of the slab is less than the bubble wrap. Therefore, the heat will go up faster than down. It will just take longer and use more fuel.



It would actually work with no insulation because the ground temp is higher than the air temp when snow is accumulating and heat moves toward cold. Not a good idea, though. The slab would probably require idling also. A very expensive system to operate.

Mark Eatherton

Gee.....

No one's ever asked that question around here. Like most people that have large snowmelt systems, and yours is NOT large, commonly say, "I can afford to burn dollar bills on my driveway to melt snow, but the neighbors complain about the smell and the fly ash...



That, coupled with the Smart Husband syndrome, where he says "Honey, I'm going to go take care of the driveway. CLICK........



I have had people tell me that their slabs that don't have insulation actually don't have to fire in early to late Spring snow storms, but due to night sky re-radiation, on an insulated slab, they generate ice.



I did a test on insulation. BFB (bubble foil bubble) did the worst of all I'd tested. When we tested it in the schools lab, it had the equivalent of 1/2" of sheet rock.



So, depending upon how the system is located and operated, insulation can be either good for you, or cost you money and create potentially slick and dangerous situations.



Interestingly, while I was pulling the sensors and data loggers out of the system I tested, as I was walking up the driveway, shooting the slab, it was 2 degrees cooler than the low temperature had gotten the night before, and the ground next to it was above freezing, like 40 degrees F. And yes, this was a well insulated (2" XPS foam) driveway.



We have another saying in the snowmelt biz. If you need to know how much it will cost to run it, you probably can't afford it.



Kinda like asking how many GPM a Testeroza gets...



In most cases, it gets used for a couple of months, then it gets shut off, and becomes a "feature" for when they get to sell the home.



In my estimation, if the slab were to be hooked up to a water source heat pump, sized to handle the solar energy falling on the slab, and store and use that energy for anything you need hot water for, the system could possibly recover more energy than it uses...





HMMMmmm. Green snowmelt :-)



ME

Ironman

Very Interesting

Mark, are you then saying that given the overall picture, it would be better to not insulate at all?

ScottMP

insulate

I think a tee shirt is better than nothing.

I did a side walk way at my house and used bubble wrap.

It works .,..... not well ..... but it works ..... I was in a rush, thought of the snowmelt at the last minute and it would have taken longer to dig deeper and the wife wanted her walkway back. You know how it is ,,,,,, " what are doing now ? "

It works and melts the snow.

I would never do it again with out 2" foam board. Especially if a owner expected quick results. And they ALL do.

Scott

EricAune

Devils advocate

Here in Minnesota, and other places I'm sure, the ground temperature for the first four feet in the dead of winter (when I want the snow melt the most) can be much colder than the air temperature for a better part of the day...that being a warm day, say like 30 degrees or some other tropical temperature.

Mark Eatherton

Sorry, I got distracted....

I'm up in the mountains installing my new Lochinvar Knight WBN boiler and lost track of time.



The only correct answer is, it depends. What are the customers expectations, wishes wants and needs. I know Siggy and I and others have said if you are going to pour heat to the slab that insulation is absolutely necessary, but based on my findings, it COULD cost more to operate, and may operate more often due to the lack of Earth contact



My gut says to insulate it, but my brain sees this as a possible issue from slip fall hazards and wasted energy.



If the slab is idled, absolutely insulate.



But if the slab is operated "On Demand", then insulation may not be that beneficial. It has to do with location, operating conditions, soil structure and water table location.



I see a need to do a LOT more testing than just the R value of a given insulation...



ME