snowmelt dilemma

Gary Jansen_4

Designed a snowmelt system for a new home going up. Tubing, manifolds, boiler all ready for contractor to put in this upcoming week. Yesterday I was informed the missus of the house hates the look of concrete, no matter the finish or look. She likes the look of asphalt, and has demanded it in place of the concrete. The last thing I want to do is tube an asphalt driveway. Architect and project manager have suggested tubing being imbedded in crushed and compacted stone, then asphalt over the top.. Tubing in stone just does not sit well with me.  Another suggestion was tubing in compacted sand and then asphalt again over the top. I don't like the idea of sand as a heat transfer medium. I believe my response time with either of the suggested methods will be slow and unacceptable to the owners after installation.

Has anyone ever run into this situation? What are your suggestions?

What about insulation, then 2"of concrete with tubing in it, then asphalt overlay?

I'm sure the concrete will crack over time, but it's under the asphalt anyway.

Thanks, Gary

Steamhead

Pour it in concrete

and put a layer of asphalt on top.

Gordy

Second that

It will be most effective than the other options given. The only thing that comes to mind is asphalt does NOT keep water from passing through itself. It is porous. Eventually winter salts deicing chemicals brought in from areas other than at the home, will penetrate the asphalt and eat the concrete. One way to prevent that is a waterproof membrane on the concrete before asphalt is laid. Another thing make sure there is a crown poured into the concrete sub layer. Any water that cannot drain off the concrete layer once passing through the asphalt will eventually deteriorate the asphalt, even after a waterproofing membrane is applied.

j a_2

Gordy

Don’t know your location, but how popular is residential snow melting in your area….Up here in Boston I have only had a few chances to install it….I think its great, but thats just me...

Gordy

It's not

That popular in northern Illinois. I can see it where snowfall is consistent each winter, but around here it's hit, and miss year to year.



My advice may be extreme, but you want to protect that snowmelt detail (tubing bed). Asphalt is okay if 4" thick but the usual 2" mat residential drives get does not last. Especially with heavy vehicles. 2" okay on a concrete sub layer 5" thick. Sub base is everything with either.

j a_2

advise

Sounds like same weather as here….in Boston….Your advise sounds very logical to me…Thanks

Gordy

Asphalt

I'm a concrete guy. No one thinks about the maintenance of asphalt . Diligent sealing is key to longevity.

Seems like a lot of extra dollars to have the asphalt look ( to do it right). If black is the desired color there is colored concrete alternative.



MadDog (Matt Sweeny) did his own driveway with concrete then asphalt detail snowmelt. Actually using it as a heat exchanger in the summer for DHW in the summer months.



Steve whitbeck, and RobG did the sand layer with pex, and then asphalt. Maybe they will chime in.



Putting tubing in an ever moving sub grade seems like trouble for the tubing life to me friction excessive settling all puts friction wear, and tension stress on tubing. In an abrasive material sub grade.

RobG

Asphat snowmelt

As Gordy said (you have one hell of a memory Gordy), I did my old house (I moved last year) in asphalt in 2002. For me it was kind of a last minute thing. I was replacing my driveway due to a pesky maple tree destroying the old one and as I looked around my garage I found that I had almost all the materials needed, how could I resist.



I remember they said it was okay at a Wirsbo training course in MN (before it was Uponor). Insulation, tubing, sand, asphalt. Be sure and run cold water through the tubing as the asphalt is being laid. Water was going in one manifold at about 50 degrees and coming out the other at about 120. It worked well for me for 13 years and I assume it is still going strong.



Rob

Gordy

I always remember

Great minds, and interesting wisdom, and material things they produce ;-) .How thick was the sand layer Rob, and what time of year? 120 back seems low for 350* asphalt with insulation under sand. Not saying your mistaken there is a reason. Me thinks a thick sand layer, and shows the insulating properties of sand.For me its one thing to experiment for yourself, another to do it for a client.

RobG

Sand

Sand was about 3" if I recall correctly. I did it in June or July (it was hot). I would never have done this for a client without having tried it for myself. I would do it now though. I just ran it as an on /  off system as I am in Virginia with not allot of snowfall. Response time was good, if I turned it on as the snow started falling it would start melting within a couple of hours typically. I had one snowstorm that I was on vacation when it hit and arrived to two feet on the driveway and three on the apron from the plowing. I parked on the street and turned it on and within twenty four hours had a clean, dry driveway. I still had to shovel the apron though     I can't remember what the water temp was but it wasn't high, 100 maybe? The biggest thing I worried about was the sand shifting from the tube expansion but I never had a problem.



Rob 

Gary Jansen_4

Thanks, Guys

I am going tp propose a 4-5" concrete slab with 2" of insulation under the slab, followed by a 2" overlay of asphalt. The crowning of the concrete as well as a waterproof membrane will be discussed in great detail at our general meeting.

Anybody have a guess as to where to find or what to spec for the membrane?

Will it be able to handle to asphalt overlay temperature upon installation?

Thanks, Gary

Gordy

Membrane

Can be linseed oil on the concrete, or a hot tar emulsion. Primer does not count before asphalt. All your trying to protect the concrete from ithe salt proper drainage will take care of the water



Here is the way I look at it. Sand bed has success, but what happens when the asphalt needs replaced, and you go in with skid loaders to tear out the asphalt.? Tubing and sand on styrofoam = a mess.



Going the concrete bed protects the tubing in the future. You end up with the asphalt as a sacrificial media . That can be removed , and relayed with out damage to the system.



But then all this is futile with either detail with out a properly constructed sub base.



The big question I guess is what kind of life expectancy the owner expects to get from the driveway. And how diligent they are with the maintenance of the asphalt in either case.



How big is it?

Mark Eatherton

I agree...

Concrete with asphalt on top. And for a few dollars more, if the system is conducive, set it up so it can heat hot water for WHATEVER use when its not melting snow, this way it can pay forward energy consumed in the process of melting snow.



Now, about sensor placement. I'd use the typical Tekmar snow/slab sensor, but instead of placing it in the middle of the slab, have a small side extension of the slab (concrete and asphalt with active loop of tubing below) where you can hand lay the asphalt perfectly to the top of the sensor cup. I'd also place a bare sensor well in the top of the concrete for the reverse solar collection system "collector" sensor. 5/8" PEX connected to a short piece of 1/2" L copper with cap silver soldered on works great and can be replaced WHEN it fails.



Turbox Max reverse indirect tank, FPHXers (if needed) and a few other details and you're cooking with the sun. Keeping the asphalt cool during warmer months HAS to extend the life expectancy of the asphalt materials as well. I know it will with concrete. Expansion and contraction damages concrete more than anything we can throw at it, other than chemicals, which also won't be necessary. Done right, we can now economically justify the installation of snow/ice melt systems. To say nothing of minimizing the wear and tear of internal finishes due to tracking salts and other snow melting chemicals in from outside.



ME

icesailor

PEX & Asphalt:

I have no experience or opinion on this. As far as I am concerned, there would be a layer of insulation, sand with the tubing in it, Concrete and an asphalt overlay. If there's a problem with the asphalt, it can be peeled up like a ceramic tile floor on a concrete slab in Vegas or Florida.

You know how rumors become Urban Legends. Like toe old timer I knew who folded his very old family business because he loved Copper and hated PVC. To the point that he swore that if it ever came to PVC only, he would retire. He did.

I was told by some of that type that people had left  Water PEX coils and straights on asphalt for long periods of storage on some job sites, and the PEX picked up the taste and aroma of asphalt over time. I've never seen it with the thousands of feet of PE well pipe and water services I installed. Why take chances.

A black asphalt overlay will sure soak up some sun. It goes both ways. I never thought about using a driveway as a Solar Collector. On a Square Foot basis, I'll bet it is a cheap collector.

hot_rod

$$$ driveway

4" slab, 2" asphalt + snowmelt



You might show them samples of colored concrete. I have seen very nice stamped, brown and black drive way slabs.



Has anyone modeled the performance of tube in or at the bottom of a 4" slab and asphalt above?

Gordy

I agree

HotRod stamped concrete is a beautiful thing. Would probably be cheaper than concrete asphalt detail.



That's why I asked how big a driveway.



Wondering if lack of communication between husband, and wife. One wants snowmelt the other wants asphalt because it melts off quicker than concrete still gotta do snow removal though. Some don't care for the rough broom finish. Stamped is elegant, but can be slicker than snot once sealed



Response time may be a little slower, have to anticipate snow fall in advance.



I like harvesting those btus for other things though especially if that drive gets full sun.

hot_rod

I like the look and "grip" of pervious concrete drives. I have never tried a snowmelt in pervious, it does have a lot of air space voids, so you you'd lose some conduction. But it may still perform better that a thick slab/ asphalt build up, especially if the tube is at the bottom of 6" or more of build up.

If it is a large drive I'd consider zoning just a few loops for solar. If you need to run a large 200W or bigger pump, and a HX pump, there will be times that you spend more in KW pump operating costs than you recover from the slab for DHW I doubt you will see above 110° from an exposed slab.

Like an un-glazed pool collector they perform well when ambient and supply temperatures are close, but performance drops like a rock when air temperature drops.

One 4X10 glazed or tube collector might supply more, hotter, and year around DHW than a slab?