Sand for Thermal mass under radiant floor

Ted_9

That's funny.

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Chad_5

Thermal mass

Would like to hear from some radiant installers about using sand as a thermal mass under a radiant floor. What are the Pros (if any) and Cons (if any). Also suggestions for alternatives beside concrete for more thermal mass storage. Thanks in advance.

radmix

sand

Sand is a very poor conductor of heat. what is your application

Mad Dog!!!!!!!!

The heat can also crystallaize the sand which ...

I believe staunches heat transfer. Not good...as I was taught. Mad Dog

Mike Reavis_2

\"sand which\"

pun intended?

Andrew Hagen_2

Mass

Why do you need more mass? In general, more mass is a bad thing for a heated floor because of the lag in response time. Have you considered outdoor reset with a low mass radiant floor? The performance is much better.

Paul Fredricks_3

Yeah, I caught that too.

Not sure about radiant, but think of how fast the sand at the beach cools down when the sun goes down.

Tom Hopkins

While we're on the subject....

A recent job added a small sidewalk snowmelt with 1 1/2" slab pavers. I tried to get them to pour a concrete base but lost out. The landscape contractor set the final grade and we wound up with about 4" of compacted sand above the tube. Under is compacted gravel and 1 1/2" foam board. A little scary when i saw the depth of sand.

Any underperforming sand bed snow melts out there? I imagine I could run some pretty high temps. Maybe a remote swith to bring it up to idle in anticipation of snow? I'm controlling with a Tekmar 650.

Unknown

I asked the owner

I asked the owner of one building that used sand under the concrete with copper coils,( he didn't believe ploy that time) and then asked his brother with the building that had ploy tubes in concrete... The one with sand, took way longer time to response. The ploy in concrete was much quicker but the owner stills regred for not putting any insulation under concrete and sides due to his furance friend told him it wasn't needed..

Dave Larsen_4

sand

I have two comments that i usually tell contractors about this subject:
1. while thinking of expansion and contraction of the pipe: I put the question to siggy about ten years ago and his first reply was " what is glass made from?"
2. I've told a few contractors to please put a plexiglass floor over the sand as future money can be made by displaying the worlds largest ant farm!

Just my opinion

Chad_5

Thermal Mass

The project is an addition to a grocery store and they want to go on off peak with their electric rate. I spoke with the energy rep. for the electric co. and the off-peak program they are talking about is on for 8 hrs. and off for 16 hrs. every day. I'm located in a northern climate where the temp. can be well below zero for several days. They only want to design to 60 deg. temp. The power company says the sand is just fine and will work but will be slow to respond. I'm still not sure I like the idea of sand. What would be the best way to size the boiler for this application.

Thanks,

Guru Understudy

Ericjeeper

Best explanation of sand

Think about the your feet standing on sunscorched sand in the afternoon sun.. Now just wiggle your feet down about two inches.... Ah instant relief.. it is cool down there.
Crushed limestone is a much better heat storage media.

Tim Doran_4

Minnesota

Sounds like the program that the utility companies offer in Minnesota. They have promoted this application for years. They forget to mention the huge amount of "peak" demand power that will be used to keep the building at set point and the associated cost. Check out the specific heat of sand as compared to maybe concrete.

It has ben my experience that most grocery stores have a fairly low btu/sqft requirement due to high internal gains. I would suggest a hydronic system in a fairly thick slab using electric boilers, you can add water storage to increase the mass if need be.

Tim D.

[Deleted User]

It's OK...

Provided that you mix it 1/3 portland cement to 2/3's sand, include 21 ounces of super plasticizers and 6 gallons of water. But at that point, its no longer sand, it's thermally conductive GROUT!

Let's think about this for just a moment. What seperates the grains of sand...Air? and the thermal capcity of air is...LOW!

I wouldn't go with just plain sand. You have one chance to do it right, inexpensively...

ME