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  1. #14
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    I'll be a taker. Manual J can work on an old home, I have one. But you have to know your home, the wall construction, and air leakage, jsut like any home. Just like on new homes, construction quality varier widely. I have a 87 year old home that dispells all myths about old homes being leaky and poorly insulated. It's performance rivals many highly insulated new construction homes with all sorts of fancy modern materials.

    A good contractor knows the homes and what construction is common in the area. A homeowner also has some responsibility to know soemthing abotu how his home is constructed, or he'll end up wiht a poorly designed system. If in doubt, existing utility bills can provide some useful information. IF you only have a $150 natural gas bill in Jan, you won;t need more than an 80k furnace. Then by evaluating the amount of shade and windows you have, and what climate your in, you can determine what AC size will match that furnace size to a certain extent.

    It is a science not some magic. It's seems like an art form because some vairales are not always easy to determine. Thermal mass (usually a lot higher in older homes) is not taken account in Manual J.

  2. #15
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,765
    Quote Originally Posted by taxgirl View Post
    Manual J is just
    Phil. The AOP forums are for equipment owners to ask questions about their systems, or a system they are thinking of getting. Not the general topic threads you are making. Stop posting them in the AOP forums.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  3. #16
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,788
    And take that wig & makeup off! LOL.
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

  4. #17
    Join Date
    Feb 2012
    Location
    Toronto Canada
    Posts
    1,088
    Your scaring the children!!!

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