How To: Properly Plan And Pick Parts For An Air-Cooled PC, Part 1

What better way to wrap up a scorching summer than with a last word on cooling? We explain the most important rules for creating ideal airflow, address the potential effectiveness of side fans, and discuss the finer points of graphics card cooling.

At least in Europe, the summer wasn't really all that warm (Ed.: Yeah, try living in Bakersfield, CA). But for a PC owner or do-it-yourself builder, the issues of waste heat, cooling, and ambient temperature are always worth thinking about. That's why we're going to start at the very beginning in this, our introduction to cooling. Every year we have new readers, and every year we see some of the same questions posed in our forums. The very last thing we want is for an expensive project to fail as a result of a mistake made in the most basic tenets of keeping hardware running at acceptable temperatures.

Because the topic is extensive, and because we want to offer a comprehensive tutorial, we'll present the whole story in two parts (the second of which will appear next week).

So, first we'll talk about the best sort of chassis, including the mounting location of the power supply. Then, we'll take a look at the potential drawbacks of other solutions. Optimized airflow is the most important consideration in an air-cooled system, so we plan to go into a lot of detail on that. Then, we'll take a look at classic case fans, and show why even a beginner doesn't need to be afraid of applying thermal paste. If you also bear in mind the importance of having space between your multi-GPU configuration and understand why the often-maligned side-panel fan can be useful, your PC will be better-equipped to survive next summer's heat.

This thread is closed for comments
    Your comment
  • compton
    After reading the charts of PSU placement and the GPU cooling diagrams, I'm even more convinced that my Lian Li PCA05-NB is a great solution. The motherboard is upside down, so that GPUs (In my case an axial fan gpu) faces towards the top. The CPU is now at the bottom back of the case and with the rear fan acting as an intake and not exhaust, you get great CPU cooling. The PSU mounts in the bottome front as well. The great part of this design is all the heat ends up in the top. As an option, you can vent the top to release the heat rising from the GPUs, but I like the case because it has very little venting. Through unusual case design and careful component selection I have an almost silent system - but with overclocked CPU and GPUs. The front fan is the exhaust, but has a bezel over it. With a few bucks worth of acoustic dampening material I can even hear myself think sometimes. I regard low temps and low noise output to be two sides of the same coin, but I know that many seem to not mind loud systems and mainly just care about temps. It's never been easier to build a near-silent system, even with high performance gear.

    If you plan ahead of time, you can make a super quiet and cool running system. It's easier to build a cool and quiet system from the start than retroactively go back and try to make a noisy (and/or hot) system quiet with great temps.

    I'll be waiting for article 2.
  • Mark Heath
    Good timing as the Australian summer approaches. You guys in the US think you have it hot :S
  • buzznut
    Guten hunger YAH!
    I want my next PC to be able to play Crysis AND make me hot dogs and Iced Frappuccinos.

    All kidding aside...curious though, the test setup is on AMD CPUs. What about Intel CPUs? I would assume many of the concepts are similar.
  • 100100
    Finally! A definitive article on how to air cool effectively! :D
  • frostmachine
    Great guide. I live in a perpetually hot n dusty place. This will come in handy.

    Would be better if there's some tips on dust management.
  • beetlejuicegr
    heh i am just showing you a pic from my pc that the airflow is totally different because there is a watercooling system on the cpu, i hope that the picture is self explanatory for all.
  • amirp
    Hey I have a question... for the PSU you say to not put it in upside down (ie. with it's opening facing up into the chassis..) but this is how I have mine in my ANTEC300 case since there is little room between bottom of case and the PSU if mounted right-side up. So what should I do?!!
  • BulkZerker
    amirpHey I have a question... for the PSU you say to not put it in upside down (ie. with it's opening facing up into the chassis..) but this is how I have mine in my ANTEC300 case since there is little room between bottom of case and the PSU if mounted right-side up. So what should I do?!!

    PSU's don't pull that much air, normally. So unless your Unit kicks it's fan speed way up there then don't royy abotu it and do as suggested. If it doesn't work then you can always just flip it back to where it was.
  • darkrydr3
    BeetlejuiceGr, your cpu core temps are pushing 70 or 90 degrees C... thats hot!
    Mark HeathGood timing as the Australian summer approaches. You guys in the US think you have it hot :S

    LOL, you both in the US and Australia think that it is hot at your home.
    Come taste the hot weather + high humidity in the Gulf countries.
  • marraco
    Great article. It would be good to have also words on noise and dust (filters)
  • amk-aka-Phantom
    MAGPCLOL, you both in the US and Australia think that it is hot at your home.Come taste the hot weather + high humidity in the Gulf countries.

    Seconded :D
  • ickarumba1
    This is a decent article.

    However, the compilation of articles on Silent PC Review provide much more thorough details on air-cooling effectively. SPCR also comments on noise characteristics, with detailed comments on specific component selection. It makes this article kind of redundant.
  • v73
    So how is cooling in system with bottom PSU, downdraft cooler, top and rear exhaust and NO side fans (without any holes for silent system)?
  • Based on this the tower format is a heat failure as the best orientation would be for the motherboard to be laid on the floor of the case. One other aspect that wasn't mentioned and I don't know how much of an affect it would have, is Bernoulli principle that dictates moving air to have reduced pressure and temperature over surrounding static air. Tunnel structures for airflow to assist air speed inside the case?
  • jemm
    Great work! As someone pointed out, dust intake is a problem when you have lots of fans pulling the air inside the case. While not all places are dusty, my place sits behind a school and there are dust everywhere. So my solution come from Organza, a thin, plain weave, sheer fabric traditionally made from silk. I fixed the fabric outside the case, and it works to filter the air.
  • ojas
    great article, was going to revamp my cooling system in december anyway, this article helped a lot, and confirmed a lot of my suspicions (like the side fan).
    only prob with the side fan is that most manufacturers don't include dust filters on the side went, even if the front and psu intakes have it. you can always make/buy one though...

    MAGPCLOL, you both in the US and Australia think that it is hot at your home.Come taste the hot weather + high humidity in the Gulf countries.

    i was going to make a similar comment regarding Indian summers :D. I only see my hard drive below 30*C during winter!
  • You did not address or test air pressure. I spent many days testing multiple formats such as the tests above at my previous position and when I included air pressure, the whole story changed.

    Positive air pressure in a case, that has optimal channels for air movement, will cool components better than neutral, or negative pressure.

    All else equal, the positive air pressure creates more small eddies that pull more heat from the surface of components, which would otherwise be missed.

    You can test this, grab a good tower case, with a bottom mounted PSU, well groomed cabling, and make sure the case has no perforated walls (which defeats the purpose of air pressure testing). If you have 6 fans, 3 point in and 3 point out, in any configuration, it will cool less effectively than arranging the same 6 fans in a 4 in 2 out configuration.

    Try it and see if you get the same results...also any thermodynamic engineers care to join in? I am no engineer, just interested.
  • ramicio
    A 60 watt light bulb emits approximately 90% of its energy through heat, so about 54 watts of heat. A computer drawing 60 watts at idle isn't going to be a particularly warm one. The power supply alone is 80%+ efficient. You just can't compare a light bulb's heat output to a computer's. Plus, a computer's heat is spread out over a higher area.

    As for the case you're working with in this article...I would not recommend it to anyone. These cases with the hard drives mounted sideways may be slightly handy, but there is basically no airflow over them. I don't see why a person with a simple tower would need quick removal. If you want server-type features, man up and buy real server hardware. Hard drives don't need much airflow to stay cool. There is no need to add anything to a hard drive to cool them, they should be properly cooled in the first place.
  • Ichy
    The guid was great and so are a lot of the comments. However, I would like to see how the Raven and Fortress cases stack up in comparison. More so the Fortress as it mounts the PSU a bit differently than the Raven.
  • chesteracorgi
    Nice article, but ....

    One principle that you wander arouind, but do not directly address is rational airflow. Cooling is best had when you have a directed airflow from one side of the case to the other with good venting. The best solution for a single GPU rig is intake from the front bottom and exhaust to the top rear. This scheme works with natural convection to maximize cooling. Adding a side fan to a single GPU rig disturbs the airflow with side cross currents and blows hot air around the case.

    I differ from you on the issue of GPU cooling. Exhausting the heat from a shrouded reference GPU card is like pissing through a pin hole. There is a lot of splash back of hot air directly on the GPU. Open-air bench tests of GPUs show the non-reference multifan configurations to be superior to the reference design. The problem with the enhanced cooling designs is, as you state, a lot of hot air splash into the case. However, this is where good case design and ventilation take over. The case is a much more efficient means to exhaust the heat from the GPU than the fan and small aperture of the reference design GPU.

    One caveat is the muiltiple GPU rig does not follow in line with this design. In the case of a multiple GPU rig the blockage of airflow causes some problems. In the case of muiltiple GPUs, you are correct in emphasizing spacing between the cards to assist airflow. Multiple GPU rigs should either use a reference card (or enhanced reference design) that exhausts the top card out of the rear of the case. The bottom mounted card can use either exhaust (referece or case exhaust) method depending on case ventilation. This is also an exception to the side door fan. In cases populated with multiple GPUs, a fan blowing air towards the GPU cards will enhance cooling and longevity of the GPUs. The eddying of the (irrational) airflow may not be avoidable in a multi GPU rig.

    One observation about CPU cooling: you do not take up closed loop liquid cooling. While tests show that closed loop cooling is little (if any) more efficient than good tower cooling they ignore the fact that closed loop coolers have the advantage of exhausting the heat directly from the case. With the radiator mounted at the rear or top of the case, virtually all of the heat exhausted from a closed loop does not create any hot air splash on other components. While the CPU itself may not experience an advantage over tower cooling, the other electronic parts (north bridge, south bridge, GPU(s), HDDs & SSDs, etc.) all benefit.

    I look forward to your next article.
  • serendipiti
    at least in [Europe] the USA the weather is not that warm.... sorry but I live in Spain, and as far as I know, Europe... And here the summer is hot. California is hot too, because they have MEDITERRANEAN CLIMATE... So Italy, Spain, Greece and France all have Mediterranean climate and the weather in summer is hot.
  • lilcinw
    This is perfect. I was just searching the forums for info on airflow yesterday.