Foundation Cooling

Foundation with Copper

Overclockers are always trying to come up with new, colder, and quieter ways to keep their PCs cool. [gigs] was so dedicated to this, he decided to lay 6 meters of copper pipe to use as a radiator in his new house’s foundation. As of now, the foundation is laid (copper pipes and all), and the forum posts come complete with finished slab pics, though there is no house to speak of yet.

[via Slashdot]

67 thoughts on “Foundation Cooling

  1. I get the feeling this won’t work as well as he thinks. Mainly due to concrete being a relivitly poor conductor of heat and it will hold some of the heat in. Now if he went into the soil that might be differnt. but I could be wrong.

  2. If i were to do it, i would have used PEX tubing instead of copper, it’s a bit more resilient and there’s no corrosion issues, the thermal emissivity is a little less than copper, but there’s a trade off with everything. We’ve got a complete 3 zone in slab heating system in our shop, put in with PEX. And i have a water cooled computer. Time to rig up a heat exchanger and start pre-warming the slab for winter…

  3. You two say it won’t work well….in comparison to what? This will work 1000% better than any local water cooling. Assuming that the ambient temperature is cooler than the pc (and the temperature of concrete underground will be cooler than a PC… guaranteed) the more distance the better. The only thing id be afraid of is springing a leak in the tubes.

    Is it /the/ most efficent way? Nope. Way more efficient than any water cooling rig i’ve ever seen completed? Yep.

  4. The real effect will likely be from the sheer thermal mass of the liquid required to fill the system. It would take quite some time to heat soak that much volume even without any factored dissipation.

    While concrete will make a lousy sink from an efficiency standpoint, there is a hell of a lot of surface area there. It will do something – not likely as quick as he would like or for the reasons he thinks it will, but it will indeed work to some degree.

    Cool idea at any rate.

  5. i’ve seen this in houses built as long ago as the 40’s. one big problem (here in indiana anyway) is from the freezing of the ground in the winter. foundations crack, and leaks formed…then you’re screwed. does work, just hope for no leaks.

  6. ok, being a hvac tech, it will do what he wants, but since cooling the floor will draw moisture to the concrete, he is going to have water pooling on the floor. but it will also draw moisture up from the ground as well. he is going to be plagued with a damp floors, since the floor plan shows that this is a living space, i hope he’s not planning on carpet, or planning to use a lot of dehumidifiers. this application is ideal for heating, but not for cooling.

  7. ok, i’m a noob, no need to post how idiotic the last post was, if it was me, i would have done the whole house for a heating system, not a cooling system for a pc, as far as that is concerned, it brilliant, damn i over
    think everything

  8. @ aztraph

    so you are saying 150 watts of heat dissipated over 2-3sq meters of concrete will cause water pooling LOL

    @ barry99705

    Yep thats partly where the idea came from.

    @ trinidad2099

    I thought about PEX tubing but went with copper because of the better heat xfer thermal characteristics. If the copper is corroded after 5-10 years who cares really. Cut it off and patch the carpet. Who knows what cooling will be available by then.

    @ Manky

    I live in a cool climate and soil / concrete slab temps are 12-16deg year round. We get 10-20 frosts a year but nothing that would cause the slab / pipe to freeze.
    You need over 6kw (6000watts) of power to heat an average slab just a few degrees. I propose to disipate 150watts. “concrete being a relivitly poor conductor” I dont think so.

    @ James Munns

    Thanks for posting this here and I hope your readers are inspired to do similar projects.

  9. gigs – efficiency be damned, the level of motivation is hardcore! And I thought parking my PC case over the AC vent was nifty….

    I just had some recent water issues in my basement, may be worth looking up good products – I am not affiliated with them, just a one-time customer.

  10. Nice planning, I just hope he doesn’t plan to move his PC anywhere else :)

    The loop seems a little short though, I don’t know the heat conductivity and calorific capacity of concrete but they don’t seem very high and the temperature might rise a lot if you pump 150W of heat 24/7.

  11. Uh-Oh

    watch the copper corrode in a few years time…..

    shoulda used PVC

    not sure what environment you live in temperature wise but here, down-under where it reaches 45+ degrees regularly, I’d hate to see what the ground temperatures of the water is

    Sounds a neat idea in practice however, there’s a LOT of factors not accounted for

  12. I didn’t bother reading most of the comments so far, but the current house I rent already had this as it’s original heating method.

    This isn’t a new idea – many houses that didn’t have basements used copper pipes in the slab which there was a second water heater that pumped through it to head the foundation. I’ve never heard if it used for cooling but I guess if you replace the water heater with something then ok.

    It doesn’t work very well at all, which is why nobody does it anymore – but my dad’s old house had a working foundation heating system and he swore by it, so it’s debatable.

  13. @dean outside air temperature doesn’t largely change the temp of a concrete slab. They tend to fluctuate between 16-20 in most urban regions of Australia. Since when does it reach 45+ regularly down under? Do you live in Australia? Because i do, and in urban areas which is where this is it never does.

    The reason this will work, is not because the concrete will conduct heat away from the system (it will but not to a large extent) but due to the size of the system and the amount of water in it that can spread the heat.

    The equilibrium temp will be low because you are spreading 150W heat over what has to be around 4 liter’s of water and 6m of copper pipe, that is a lot to dissipate heat. The transfer from copper to concrete will be largely irrelevant in terms of impact, other than maintaining temps well below air temperature during non winter.

  14. But concrete is such a good insulator I would have thought it would warm up and stay warm after running this for a while.

    Would have been better just to run the pipe through air…

  15. @M4CGYV3R

    I assume he is using a closed system, so he wont be needing a large pump.

    i probably would have chosen for something like pex tubing and put more of it in the ground (like zig zag) but this will work

  16. Hmmm… Just this spring I installed a geothermal heat pump for my house with 1200 linear feet of polyethylene tubing in vertical wells in the back yard. Sure, it works great for having central air for about $40 a month, but just imagine if I employed my system to cool a CPU…

  17. Whats great about hackaday comments? They are educated discussions between enthusiasts

    Whats not so great? Everyone who comments thinks they know better than the person who actually *did* it.

    Still, amazing dedication, i salute you sir

  18. Good god! First off this “nothing new” crap… it’s hacking not a patent website… It’s about taking the “not-new” and doing something clever. I’m pretty sure I can’t order this system from Best Buy so I think it’s a hack!

    Second, I love all the qualified folks talking about floor heating (or cooling!) or the copper corroding in “a few years” Unless your house was built in the last couple years it’s likely got copper tubing just like this.

    This is why I don’t twit? twitter? whatever…

  19. @nick I haven’t stepped in front of a bus but I know it’s a bad idea without doing it!

    @eddie it doesn’t matter that it is a closed system. He may only be pushing water through the pump at the same rate but he is pushing a much larger mass of water round the whole system. You can either look at it as there is more mass, so more energy is required to push it, or that there is more resistance against the pump so a bigger one would be required to push the water round at the same rate.

  20. I’ve lived South of Boston and I had a similar system to heat my house through the floor – radiant heating – it is by far THE BEST way to heat a home. Le me tell you it gets very cold in New England. This type of heat didn’t dry you out (No more nose bleeds or dry skin), walking into the kitchen without shoes/flip flops and feeling the warmth radiate like a summer day. How ever fo cooling the cieling would be the way to go – NOT the floor. Warm air rises – and where does the cool air go??? Think about it – this whole system is backwards. BTW a foot note about floor radiant systems – the wrong floor padding and carpet can make the whole system a waste of energy (too much insilation blocks the heat/cooling from occuing) Just some thoughts – ty for sharing. – Joegeek

  21. @ joegeeks
    “(too much ins[u]lation blocks the heat/cooling from occu[rr]ing)”

    once again this has nothing to do with heating or cooling a house. read the entire post before commenting people. its about a water cooling system for a PC using a concrete slab and copper pipes for a sink. and its a great idea! and bob is right. its gonna need one hell of a pump. im interested in seeing the results. maybe ill do this when i build my house.

  22. @patrick

    Never said it wouldn’t work well, just said I’d rather use pex so i didn’t have to deal with corrosion or the possibility of leaks 15+ years down the road.

  23. speaking from personal experience. cu is the wrong way to go in a slab, soon pin hole leaks will develop from corrosion of the pipe. the only way to combat it is to put a charge on the pipe which given the other systems involved is ineffective and dangerous to them. I just put 1500′ of pex in my new addition in the slab. My advice is to insulate at least 3 inches under the pour with foam sheets and on the exterior side of the walls. This will prevent the slab and foundation from pulling or giving energy to the surrounding mass. whether you are doing a a cpu cooler or radiant floor heat the surface area and thermal mass will go a long way

  24. @bob

    Sure he’s going to need bigger pump than your average pc water cooling pump.
    I merely wanted to point out that you don’t need a ‘hell of a pump’ if you use a closed system there is a big difference.

    In a open system your pump is only pushing the water in a tube that pressure buildup and energy is lost when it comes back in the reservoir.
    With a closed system you don’t have an open reservoir so your pump does not looses so much energy as with an open system.
    Problem with a closed system is that you will need
    an expansion tank.

    For example the water in a ‘big’ floor heating installation (like say 40000 watts and 1000 yards of tubing) can easily pumped by a single 150Watt closed system pump and its pretty quit to.
    Some of the open system pumps are quite noisy (imho).

  25. @nubs-r-us:

    Copper should _not_ be used in a concrete floor. A lot of the houses in Levittown, NY were built with in slab copper radiant heating- nearly all of them failed. Concrete is highly alkaline and does not react well with copper. All modern radiant floors use PEX (polyethylene cross-linked) with no joints to prevent leaks. PEX also flexes if the floor moves or cracks.

    Also- you may not have heard this but even the copper pipes in the walls in a lot of Long Island houses are developing pinhole leaks. It’s one thing when you can just replace the pipe- it’s another when the pipe is buried in a concrete slab.

  26. If you must use copper pipe, why not use the thickest walled copper you can get. Sure the concrete will eat at it but eventually it will neutralize and the reaction will stop. OR you could paint/coat the copper with something.
    All is not lost.

  27. Hey guys thanks for all the comments and lively debate that has been going on in this thread

    I just wanted to set some things straight. All of these items have been dealt with in detail through this thread if you care to take the time to read it but to recap.

    1. Concrete as an insulator

    and will not dissipate heat for the application that I want. Please refer to this:…ity-d_429.html

    Thermal Conductivity – k – (W/mK)
    Concrete, light 0.42
    Water 0.58

    From here you can see that the thermal characteristics of water and concrete are very similar. Real world tests will answer this one very soon.

    2. PEX vs Copper

    Agreed PEX will last a lot longer in concrete than copper. PEX does not have the Thermal characteristics that I want ie it will not work as well as copper to transfer heat into the concrete. This is why I have not used it. I am not interested in this copper lasting decades. I am only after about ~5 years of service.

    3. Corrosion of raw copper in concrete

    Please take the time to read the information here:…_concrete.html

    Absolute worst case scenario. The copper may get corroded after 5-10 years and expose the coolant to the concrete. SO WHAT do you think I will care by then. Who knows what cooling solutions will be available for computers by then. I will just cut the copper off flush with the floor and move on.

    4. Concrete slab cracking due to thermal expansion

    Hot water pumped through copper imbedded in concrete and Heating concrete floors hydraulically isn’t a new technology. In the 1930s, architect Frank Lloyd Wright piped hot water through the concrete floors of many of his buildings. No reports of concrete cracking only the copper pipe eventually failing after many decades. These days wires are laid out in the concrete and shorted to heat a slab. On average it takes 6kw + to heat a house slab just a few degrees. Ask anyone that has slab heating and most of the time they turn it off because it costs so much money to run. I am trying to absorb just 150 watts of heat into 2-3 meters of concrete, do the math guys. The water coming off the cpu block will be at the most 25deg. Concrete is elastic and expands and contracts with heat mitigating wear on the copper.

    Maybe wait for me to get a few tests done before saying how much this is epic fail? If it doesn’t work I’m going to look like an right dick to the 70,000+ people that have visited this thread already. Even if it does or does not work I hope I have inspired some of you to try some crazy things too.

    I have got hold of a pump this afternoon so I can do some experiments this weekend….

    Check out the OCAU thread for results in a couple of days.

  28. *sigh*
    Can everyone get over it?
    When did hackaday comments become so much like Darwin Awards comments?
    I must have missed the memo telling us to be assholes instead of enthusiasts.

    Also, to clarify my position:
    Concerns over the heat dissipation, being laughable in my mind, are because of the size of the system; computer water, as started by many other users, should not produce enough heat to give power to any of these alleged “thermodynamics” concerns. That much copper pipe, even when insulated, will act like a heat sink any way and will dissipate plenty of heat away from the affected system. Warm water works fine for water cooling; the water coming back through the inlet on the computer case will be warm, at hottest, simply by the length and amount of metal the hot water would have to traverse.

    This project, having been done before by other people, has shown that it will work fine as a water cooler system at dissipating heat.

    Retrospectively I think that people concerned over the “thermodynamics” of the situation might just be mixing their units up; Fahrenheit vs Celcius; big differences.

    Anyway… I still find the concerns over “heat dissipation” laughable, especially given the evidence of similar systems working just fine.

  29. If you think concrete isolates very well and you need 40 KW to heat your house with floorheating, something is very wrong, or you have to do your math.
    Proper insulation (‘passive house’) needs 10W/sqm (15KWh/sqm.yr) max cooling OR heating. Our 7W central heating pump has no problems whatsoever to get the water round in the (closed system) tubing across 2 floors.
    Still it seems to be a better idea to have a pvc ground loop (either vertical or horizontal) to obtain water of 10-15°C (50-59°F) year round. Especially in a passiv haus :-)

  30. @everyone stupid

    this is not a project to heat or cool his house. using pipes embedded in the floor to heat or cool has been done forever. what he’s doing is using it as a giant water-cooling system for his pc. it is for cooling his pc. it is for cooling his pc. no more comments about how in-floor heating has been done!

  31. It’s also a short little segment of pipe used to cool his processor, if it fails? blow the system out and cut the stubs off(yes even with a pinhole leak I’m sure you can evacuate the water). Huge loss. If all I had in inventory was copper I’d give it a try, I wouldn’t spend the money on something else when I had something on hand. Of course
    I wouldn’t be modifying my own foundation. I have a coworker who’s got a geothermal system and big computers so I suggested he pipe his water cooling through his heat reservoir to cash in on that.

  32. @eljonco

    Where in my post does it say i use 40 kw to heat my house ?

    Also it wasn’t about the floor heating system itself more about the difference between a closed and an open system.

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