Og help me, I borrowed a book on thermodynamics this weekend...

…as part of my increasing desire to understand heat flow and storage in concrete walls. Mostly, I got the book to relate British Imperial and US Customary System units of measure to my understanding of SI units, as I am realising more and more that I will need to know all three systems if I am to work in this crazy mish-mash of units the architecture and construction industries in Canada call home.

I’ve also been looking through my high-school calculus book. While static heat flows and storage are relatively easy to calculate, in reality, everything goes in curves and cycles as the earth spins in space and moves around the sun. I can see all the curves in my mind’s eye, but putting numbers on them is going to be… interesting.

Math is fun. :slight_smile:

Why am I going to all this effort? Career advancement. :slight_smile: I plan to get certified as a “residential designer” under the Ontario building code rules, and then design solar-powered houses. Where necessary, I will refer things to architects, engineers, or electricians for approval, of course, but for the simple houses I am looking at, a lot of it is rule-of-thumb.

My first week-long course starts on September 25th. Loyalist College, here I come! :smiley:

If you’re trying to underrstand the heat flow in your concrete, you probably don’t really want a book on thermodynamics. You want a book on Heat and Thermal Diffusion, which is whole different animal. Just as much fun, though.

There are lots of computer software packages that will model heat flow in structures. The biggest problem is knowing the diffusion constants for the materials you’[re working with.

Well, thanks, CalMeacham! Half the problem with looking for this kind of stuff is knowing what to call it. Looks like I’ll be going back to the library again this week.

I’ve found references to various software, but I haven’t found anything in the “free” price-range yet. I have a horrible suspicion that it’s all addons to AutoCad and other software in the thousands-of-dollars range. Can you recommend anything, especially freeware or open-source?

I don’t have any specific to recommend, but you may want to ask at Eng-Tips (which is, BTW, a good place to ask technical questions). Try starting here.

I can’t recommend any free software, but in the spirit of sharing mundane pointless stuff, I wanted to mention an interesting monster of a program that might actually be used by people in your field. One of my housemates recently installed a trial version of COMSOL Multiphysics to help with his investigation of the Taylor-Couette problem. His trial period expires at the end of 11 days, so if he doesn’t have results by then, he’ll revert to using plain vanilla MATLAB for his research.

Good luck! I remember replying to your earlier thread asking for cheap/free design packages but it didn’t seem to get much of a response. I’ll just repeat what I said there: few, if any, cheap software packages are available that can match your needs. If you want a powerful architectural, structural, mechanical and electrical design package, you’re going to have to pay megabucks for it.

Also, I assume you’re familiar with the requirements of Bill 124 for building designers? You’ll need to pass Ontario government exams both in “General Legal” and “Houses/Small Buildings”. Focus on the legal and Part 9 of the OBC. Also, be aware that the new Code is coming out in 2007 so if you’re not in a rush, it might be worth it to wait awhile and study the new Code and write those exams.

The only law of thermodynamics I know is Murphy’s Law of Thermodynamics:
Things get worse under pressure

Of course, there’s also Sir Edward Boyle’s Law: “The greater the external pressure, the greater the volume of hot air”.


I just love it when guys talk nerdy. :cool:

I can recommend software. Check out FlexPDE at pdesolutions.com. This is code-based software that solves any kind of PDE for field variables - you just have to be able to write the equations. They have lots of examples you can start from including heat conduction problems. There’s a low price for the student version (it might even be free, I can’t remember). You can try the demo for free off the web (it runs all their example problems and lets you substitute other values in the code).

If you are just doing diffusion problems, by the way, it isn’t hard to write your own program to do it. Use the finite volume method rather than the finite element method. I’ve done that - though I was using SAS as the programming environment (it’s an interpretive language used mostly in Statistics and the interpreter costs more than FlexPDE so my program isn’t an option for you).

I think there are free programs out there. Google “free fem” or things like that and see what you get. I haven’t tried any of them.

I am a big fan of Incropera & DeWitt’s text on Heat & Mass Transfer; I cut my teeth on the less-hideously-colored third edition, and they’re up to five editions now. You can learn the basic rules of thumb there (convection, conduction, radiation) but you’ll probably need specialty textbooks for dealing with construction materials. The problem sets are designed to be five-to-ten-minute exercises each, whereas the design of a house is going to be a complex set of interacting systems for which you may need a computer simulation. Best of luck!

Thanks, Hodge. I was afraid of this.

I’ve been going through basic calculations with Building Science for a Cold Climate (ironic in the face of all the heat we had a couple of weeks ago), with the goal of putting together a spreadsheet to calculate insolation for various window areas and such, given latitude, longitude, type and area of glass, clearness factor, and tilt of window. A lot of this is derivable from the geometry of the situation, plus things like Snell’s Law, but it gets kind of hairy. That’ll give me my energy input.

I can do simple heat-flow calculations, and also heat-storage calculations, which will givwe me my storage capacity. The plans for the house give me my external wall area, and distributing the heat flow over that gives me the desired outward heat flow per unit area. Then I can back-calculate and find how much insulation there needs to be. :slight_smile:

But there are a lot of unexplained areas, especially at corners.

Yes, my first course in September is for General Legal. Vacation days are booked and everything. Exams are separate, of course. I’ll be taking the House or Small Building course later (depending on which is available when). I believe that Small Building is a superset of House.

AFAIK, the 2006 Building Code is already out and posted on the Ontario government website; it’s the redaction into a book that is taking some time. Which is leading to some question about what version of the Code do I need for this course. But the lady at Loyalist says that at a minimum, the 1997 edition with all updates is needed.

Thanks! That looks like a good book to go on my list. (And it’s turning out to be an expensive list. I just discovered that I can’t find the copy of Allyn J Washington’s Basic Technical Mathematics with Calculus that served me well for lo these meny years, and new ones are in the $140 range too… thank the gods for the Toronto Public Library.)

Well, you know the vernacular versions of the Laws of Thermodynamics?

  1. You have to play the game.
  2. You can’t win.
  3. You can’t break even.
  4. You can’t quit.


And I just reserved a copy of Heat and Mass Transfer through the library. :slight_smile:

Yes, I’d dearly love to be proven wrong, but there’s just too much money to be made in these areas and the people with the required specialized knowledge are generally unwilling to put forth the effort for no compensation.

Yes, if you write Small Buildings, you’ll also be qualified for Houses. You’d also be able to work on small commercial or industrial buildings if the opportunity ever presented itself.

I should have been clearer. Yes, you can download the new Code from the website but it does not come into effect until Jan 2007, at which point the actual publication should be available for purchase. As for studying, don’t forget to get the illustrated guide to the Code. It can clarify the sometimes byzantine wording of the OBC, itself.

I was looking for publically-funded tools that had been relased at no charge, by open-source people at universities, or organizations such as the National Research Council, or even US sources like NASA for the physics. Don’t they put out a lot of info?

I thought some provisions of the new code had already come into force, but maybe not…

I just came in here to mention Octave in case you weren’t familiar with it. It’s a free, open-source matrix-manipulation package largely compatible with MATLAB. (It doesn’t have internal graphing capabilities (though it can interface with gnuplot) and it’s not as fast, but hey, it’s free.) If you have a finite-element model you can probably use Octave to run the corresponding heat-equation PDE simulations. You may also be able to find free Matlab packages out there that do more of what you want; these can often be converted pretty painlessly to Octave.


I think you’d also get a lot of mileage from a Google Scholar search on “thermal mass”.

Is Daniel Chiras’ The Solar House still considered the authoritative book in this area?