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Manual \"j\"

Ray M
Ray M Member Posts: 94
in THE MAIN WALL
Who do you belive? I just did a loss/gain using HDS by Siggy and Wrightsofts Man J and have a 54k difference for heat loss????????? I think Siggys the man.


Thanks
Ray M

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Comments

  • Brad White_41
    Brad White_41 Member Posts: 8
    Not bad when spread out over a 25 million BTU heat loss....

    Where do you think the error lies? And what makes you thing one is right and the other wrong? Aside from Siggy being The Man, of course!

    :^)>


    Brad
  • bob_50
    bob_50 Member Posts: 306
    Believe Everyone?

    I think all the heat loss programs estimate about as well as can be expected. I also think it depends on who is useing it and their level of experience. Most heat loss methods were originated by different contractor associations to suit the needs of their members and have evolved over time. Manual J which is often referenced on this site was developed for tin bangers, if my memory is correct. It was developed by NESCA(national enviromental systems contractors assoc.) which morphed to SMACNA(sheet metal and air conditioning contractors national assoc.) and now ACCA(air conditioning contractors of america). I was recently in some million+ Mc mansions and was suprised to see 4" walls with fiberglas insulation and 31/4by12 stacks in the outside walls. I also saw insulated flex scrunched into cathedral ceiling joist spaces. In fact when I drive by this particular house I can see the snow melt pattern on the roof! My point is if these contractors are your constituants, you had better develop conservative heat loss programs. About 40+ yrs ago I was the fitter in what was mainly a tin shop we did 800 to 1000 custom homes per year, mostly forced air. We had special heat loss multipliers for each general contractor. We learned the hard way what worked and what didn't. bob
  • Brad White_41
    Brad White_41 Member Posts: 8
    And that, Bob

    is one of the best explanations for why some of these programs become conservative.

    The notion of loading the program with factors to account for poor installation practices never occurred to me. Makes sense now that you explained it so well.

    Thanks

    Brad
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