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  1. #1

    Is buying Manual J worth it for me?

    I recently bought a house and got some great advice from this group on sizing a new heat pump for it. My current house is a transitional home until I can complete the design and construction of my "dream" home. I want to be smart in designing my dream home to be energy efficient. Learning about heat/cool loads and Manual J calculations has made me realize they can be useful in making design decisions for my dream house.

    I am considering technologies such as SIPS which almost eliminate thermal bridges.
    So the overall wall performance of a SIP with R24 insulation is close to R24. This contrasts with say a 2x6 wall with R19 batts that because of bridging may only yield R13. I assume manual J takes into consideration this overall performance when it provides information walls like a 2x6 wall with R-19 batts.

    I also am deciding whether or not to have a flat ceiling over my living room (with an uninsulated air space between the roof and the ceiling) or a cathedral ceiling (made with traditional framing or maybe an R40 SIP).

    I am wondering if I should spend the approximate $150 to buy Manual J so I can determine how these and other options effect heat/cool loads.

    1. Does Manual J provide information on new construction techniques like SIPS and ICFs?

    2. As a layman of hopefully at least average intelligence but with NO background in HVAC, will I be able to understand the information in Manual J so I can apply it?

  2. #2
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    Dec 2006
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    Middle Tennessee
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    *

    Quote Originally Posted by azalea4va View Post
    As a layman of hopefully at least average intelligence but with NO background in HVAC, will I be able to understand the information in Manual J so I can apply it?
    understanding the whole maanual J concept is one thing

    proper application requires many years of experience



    .

  3. #3
    Join Date
    Jun 2009
    Location
    Central Texas
    Posts
    47
    Manual J will definitely get you thinking about building construction methods/techniques as they relate to energy conservation. If you are willing to invest the time it should more than pay for itself.

  4. #4
    Join Date
    Jun 2010
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    Philadelphia PA
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    The ACCA manuals J, D, .... are ANSI standards that are referenced in the I Codes.
    They are NOT how to design etc. I think you'll be disappointed since the real meat of the standard Room level info) is so complicated that software is the only way to go.
    The AE version is simplier but if your goal is to review and understand the alternatives, then the manufacturers R values or window manufacturer real data will be more useful
    I'd suggest you save your money.

  5. #5
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    Aug 2003
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    Fort Worth, TX
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    Quote Originally Posted by azalea4va View Post
    I recently bought a house and got some great advice from this group on sizing a new heat pump for it. My current house is a transitional home until I can complete the design and construction of my "dream" home. I want to be smart in designing my dream home to be energy efficient. Learning about heat/cool loads and Manual J calculations has made me realize they can be useful in making design decisions for my dream house.

    I am considering technologies such as SIPS which almost eliminate thermal bridges.
    So the overall wall performance of a SIP with R24 insulation is close to R24. This contrasts with say a 2x6 wall with R19 batts that because of bridging may only yield R13. I assume manual J takes into consideration this overall performance when it provides information walls like a 2x6 wall with R-19 batts.

    I also am deciding whether or not to have a flat ceiling over my living room (with an uninsulated air space between the roof and the ceiling) or a cathedral ceiling (made with traditional framing or maybe an R40 SIP).

    I am wondering if I should spend the approximate $150 to buy Manual J so I can determine how these and other options effect heat/cool loads.

    1. Does Manual J provide information on new construction techniques like SIPS and ICFs?

    2. As a layman of hopefully at least average intelligence but with NO background in HVAC, will I be able to understand the information in Manual J so I can apply it?
    You may want to consider the cost of SIP wall construction vs. 2 x 6 with exterior applied insulating foam board, such as discussed in this link:

    http://www.buildingscience.com/docum...perfect%20wall

    Here in my town, one of the members of this forum, Paul42, built a stick frame house in hot, humid Texas that is over 4,000 square feet (including basement, a rarity in Texas). He cools it with a two ton heat pump. He put all of the ductwork in the conditioned space, applied 2" polyiso foam boards on the exterior side of the sheathing and studs, and sealed the drywall to the studs on the interior. Not sure if he used standard batts between the studs.

    I've had success taking my 51 year old mid-century modern ranch house in the same town from a leaky, hard to heat and cool relic to a comfortable home that is affordable to heat and cool, year round. Now I have money to spend on things like decks and exterior paint. My fifteen year old three ton condenser maintains my summertime setpoint of 75 degrees on the hottest days of the year, and consistently keeps indoor humidity in the low 40's. If I can do that to 51 year old construction, then building a house from the ground up, conventionally, but with present day sound building science knowledge applied, could net even more impressive results.

    To directly answer your OP question; if you're a super hands on person and will be for the entire design and construction of your house, then by all means get a copy of Manual J. 8th Edition will likely have more info re: SIPS and ICFs vs. Manual J 7th Edition.

    Also, if you're engineer-inclined, crunch some imaginary mock-ups of SIP vs. stick built with "outsulation" regarding rate of heat transfer and then compare results to cost of construction. I'd be curious myself as to what you come up with. I by no means am down on SIP construction. I just like to consider if there's more than one way to achieve a desired result, and which is more feasible and practical.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  6. #6
    Join Date
    May 2010
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    New Jersey
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    Where can you get MJ8 for $150?

  7. #7
    They are NOT how to design etc. I think you'll be disappointed since the real meat of the standard Room level info) is so complicated that software is the only way to go.
    I have software, an "abridged" Manual J calculator I got at http://www.acca.org/speedsheet/. Data put into the spreadsheet comes from Tables in Manual J.
    You may want to consider the cost of SIP wall construction vs. 2 x 6 with exterior applied insulating foam board, such as discussed in this link:
    Yes, that is a great site. From that same site (http://www.buildingscience.com/docum...l-construction, because of thermal bridging, a 2x6 wall is 6" batts has a "whole wall R-value of R-13.7". Adding 2"
    of poly iso to the exterior yields an 8" wide wall with a whole-wall R-value around R-27. That non-standard width creates additonal costs. An XPS SIP panel half as wide (4") has a value of R-24, is stronger, and creates an extremely tightly sealed envelope. You are correct, there will need to be a cost analysis when I get to the point of seeing how much a builder will charge for building with the various choices.
    if you're engineer-inclined
    Guilty, I have a PhD in Computer Science.
    Where can you get MJ8 for $150?
    See http://www.acca.org/store/product.php?pid=172. Actually I should have read that page, it explicitly mentions its has info on things like SIPS.

  8. #8
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    May 2010
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    New Jersey
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    That is the manual, not the software needed to use it. Once you do the sizing you will get a handle on the relative impact of roof, wall, and window insulation. I found it surprising.

  9. #9
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    Aug 2003
    Location
    Fort Worth, TX
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    Quote Originally Posted by DavidNJ View Post
    That is the manual, not the software needed to use it. Once you do the sizing you will get a handle on the relative impact of roof, wall, and window insulation. I found it surprising.
    On the ranch type homes I've run calcs on around here, it was an eye opener to find, for heat gain, which components were the worst offenders for heat gain. At first blush I thought it would be ceilings under attics and exterior walls. Turns out it is single pane windows, followed by marginally insulated ceilings below ventilated attics. I ran one scenario in my own home with R50 in the attic over our 2nd bedroom and the shaded single pane window facing south. Attic temps at 130 and outdoor temps at 100. The single pane window dumped more heat into the room than the entire ceiling area did. An eye opener indeed.

    Not all rooms are like that, I know. A friend of mine's dealing with the dreaded bonus room over a non conditioned garage scenario right now. You could dump all kinds of cool air in there, and sitting in the room you'd likely still feel a bit warm simply due to high radiant heat transfer. It's the envelope, dude.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  10. #10
    Join Date
    Aug 2009
    Posts
    1,127
    Quote Originally Posted by azalea4va View Post
    I have software, an "abridged" Manual J calculator I got at http://www.acca.org/speedsheet/. Data put into the spreadsheet comes from Tables in Manual J.

    You are correct, there will need to be a cost analysis when I get to the point of seeing how much a builder will charge for building with the various choices.

    Guilty, I have a PhD in Computer Science.
    http://www.wrightsoft.com/products/r...iew_video.aspx

    Then you will love this software!

  11. #11
    http://www.wrightsoft.com/products/r...iew_video.aspx

    Then you will love this software!
    After a quick try with the demo, it does some neat things and it is amazing. But IMHO, the user interface is HORRIBLE (Example: in one place you delete something by hitting the DELETE key but in another place you delete something by hitting the space bar). I got really frustrated trying to use it. That tends to be a problem with all technology. Us techies create some device (or software) that does amazing things but short-change the necessary efforts to make it "usable" and to make documentation that is "readable".

    "That's the thing about people who think they hate computers. What they really hate is lousy programmers." (Larry Niven and Jerry Pournelle, Oath of Fealty).

  12. #12
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    May 2010
    Location
    New Jersey
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    Then try the Elite RHVAC: http://www.elitesoft.com/web/hvacr/e...vacw_info.html

    I've got both demos but haven't pulled the trigger. I'm leaning toward Elite because of the duct stuff included.

  13. #13
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    Aug 2009
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    1,127
    Quote Originally Posted by azalea4va View Post
    After a quick try with the demo, it does some neat things and it is amazing. But IMHO, the user interface is HORRIBLE (Example: in one place you delete something by hitting the DELETE key but in another place you delete something by hitting the space bar). I got really frustrated trying to use it. That tends to be a problem with all technology. Us techies create some device (or software) that does amazing things but short-change the necessary efforts to make it "usable" and to make documentation that is "readable".

    "That's the thing about people who think they hate computers. What they really hate is lousy programmers." (Larry Niven and Jerry Pournelle, Oath of Fealty).
    Good quote. Programmers tend to be lousy at human interface. I'd like to blame the Windows culture but that would be unfair. I work in hospitals and a lot of the major software in use has been ported from 1980s era DOS with a partial GUI pasted on top. Actions that might intuitively require a tab or return are randomized, and occasionally can only be done with a mouse click. Right click or scroll is sometimes activated in a frame, and sometimes not. New programs tying into established OS APIs and resources do much better.

    I remember in college in the computer lab I had to print out 30 pages of instructions - well, keystroke commands - to navigate a word processing program. Then I had a roommate with a Mac and with 60 seconds of instruction, I was good to go. Very impressive. I still find that I can get around on most Mac programs far better than Windows. For the kind of programs I use, I consider it poorly designed if I have to access help to do something.

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