Cooling outdoor concrete patio in Dallas TX

Discussion in 'Radiant Heating and Cooling' started by cgideon, Feb 4, 2013.

  1. cgideon

    cgideon New Member

    We are about to build a new patio in our back yard outside of Dallas. It will have about 400 square feet of surface. In the summer concrete patios can get very hot. We are going to put in a retractable shade with a mister system to help with the temperature, but we had the idea that we could use radiant cooling in the concrete itself to make it more bearable in the summer. The idea is not to cool any air with it, but just to reduce the temperature of the concrete itself, maybe 10 or 15 degrees.

    This is more of an interesting experiment than a mission critical application. The current thoughts would be using 3/4" PEX embedded in the concrete with an HDPE slinkly closed loop horizontal geothermal system.

    I have tried to contact some geothermal contractors in the area, but I'm not having a lot of luck finding one. At this stage of the game, my very first question is how to determine the size of the cooling system needed. I know for housing there is a very rough estimate of 1 ton per 400 square feet.

    Does anyone have any experience or gut feeling on what might work? I have tried to research as much as I could over the Internet for the last week, but I'm not finding much on this type of usage.

    Thanks,

    Carl
     
  2. zacmobile

    zacmobile Guest

    That's probably because it doesn't exist. Maybe someone else around here has, but at least I have never heard of this sort of application before. It would be the inverse of snow melting which I do have experience with and I know any time you are essentially trying to alter an uncontrolled environment it takes an enormous amount of energy. For example a typical northern snowmelt system needs anywhere between 110-130 BTU/Sq Ft on a design cold day. That's almost 10 times the energy required to heat a floor in a typical modern home!

    If it were to work at all you would need larger tubing as you said and closely spaced as well, it would also help immensely if it was somewhat shaded.
     
  3. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    On paper/calculator the evaporated cooling will work much better. Misting the asphalt. Don't paint in black. Etc. Maybe tie the PEX pipe in to a swamp cooler if dealing with water is a hassle.
     
  4. cgideon

    cgideon New Member

    Thanks for the responses. I know it is a long shot, but I would like to give it a try. We are definitely going with shade and a mister, but with temperatures on concrete hitting over 140degrees in the open sun here, I would just like to see what we could do. As a side benefit, it might make the patio a little warmer on some of the colder days as well. I was finally able to track down a contractor in this area, so hopefully we can get it done.
     
  5. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    My Dear Carl:

    You did not look hard enough.

    What you want to do can be installed. We are only talking about moving heat. All ya All's got too much heat most of the year.

    I heat, (snow melt), drive ways in Ohio, so I am sure it is possible to "cool" patios in TX.

    Geothermal heat exchange is sort of magic, to a point. How may days, out of your 9 month hot season, do you want your guests to think they are comfortable on this patio?

    I am working on radiant cooling. It can be done.

    Carrier made some of his money by having an engineer develop and prove what latent heat is. You wish is just to remove sensible heat if I heard your question correctly.

    Mark
     

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