Auxilliary heating definitely increased the error bars, especially wood-burners, which can operate across a significant range of combustion efficiency (and installed system efficiency), and BTU content of the fuel will vary quite a bit by species & moisture. The error is potentially so large even if the wood volume used was known, I'd be reluctant to hang much on the fuel-use stake in the ground in most of those situations.

If you use blower door data with the an adequate Manual 'J' you can't go wrong.

The quality of construction is part of the input. One can easily model different scenarios to come to a reasonable conclusion.

Another instance where Manual 'J' is best.

"If you use blower door data with the an adequate Manual 'J' you can't go wrong."

Of course you are correct, but not everyone wishes to pay for such services and energy usage is a free counter check. Most times a home is what it appears to be which is the quality of construction part you refer to, but not always.

We explain to potential clients about home performance and expectations based on build dates. Our contracts deny responsibility for homes where construction quality was not code minimum when built. This is different than hanging them out of course as we refer them to energy auditors that they may employ before or after their purchase with us.

If Manual J was best, it would be used on commercial projects where accuracy is critical. It isn’t. Manual J is only appropriate for simple new residential construction projects and it was intentionally designed by ASHRAE to be used by simple minded people who typically work on these simple residential projects.

As for Manual 'J' and the simple minded.

Those interested in the truth may find the first paragraph of this document of interest.

http://www.buildingscience.com/documents/guides-and-manuals/gm-system-sizing-pro

And the D.O.E. found it useful, ref. page 5.

http://www.nrel.gov/docs/fy14osti/62122.pdf

It is common knowledge in the HVAC industry that Manual 'N' is the commercial standard as referenced in this document.

http://www.cwgdn.com/files/forms/bldg/HVAC_Permit_Submittal_Checklist.pdf

We use both for new construction and especially old where upgrades and additions make HVAC system modification particularly challenging and software based on Manual 'J' or 'N' principals is indispensable.

The best Manual 'J' , 'N' and 'D' software is of course Wrightsoft , which I have been using for nearly a decade to design radiant floor heating, snow melting and more than ever, high and low velocity ducted HVAC systems.

Frankly, most of our commercial low-rise work is much easier than residential due to the complexity and diversity of construction, more especially in renovation.

Blower doors can only tell you how big the holes are, not where they are. A house with the same blower door numbers can have infiltration rates an order of magnitude apart.

And at any infilrtation rate it's impossible to say just how much heat-exchanger effect is at play.

The ideal is to have sufficiently low blower door numbers that it really doesn't matter where the leaks are or how much heat exchanger effect occuring. But it is at best a very crude way to estimate the heat loads of air infiltration (though better than a WAG.)

I is the combination that makes it more accurate than anything currently available.

Most who do a blower door follow up with envelope improvements before we replace equipment.

Blower door testing doesn’t come close to what happens when actual wind blows across a building causing actual infiltration. Blower door testing is certainly better than nothing…and so is Manual J.  However, neither provide the accuracy of a properly done energy usage analysis when you have an existing building with a heat source.

Let's face it in residential, we have a pretty good idea of what we are going to use, but we do the numbers anyway because sometimes we are suprised.
By far the best sizing tool in my arsenal is experience. Monitoring my systems and how they perform has added more to my design strategy in the last 2 years then man J did in the last 20.
Not all R19s are equal, infiltration is a big load contributor and knowing how different insulations perform matters alot when using cookie cutter load calculators.

Amen

Sounds like Man J hawking to me when it clearly is not needed by the OP given his situation. Lots of discussion about this questionable practice here:

http://www.greenbuildingtalk.com/Forums/tabid/53/aff/12/aft/83077/afv/topic/afpg/3/Default.aspx

Sounds like Man J hawking to me when it clearly is not needed by the OP given his situation.

Not sure what you mean by "hawking", but (reminder I have the Michigan revised IRC but the references are usually close) Chapter 14 under system sizing 1401.3 ......heating and cooling equipment shall be sized ...... based on building loads calculated in accordance with the provisions of ACCA Manual J........or other approved (the use of the word approved here gives the inspector the authority to accept other calculations or deny them) methodologies.

As an inspector I can tell you that this is not always enforced but it is always code (meaning the contractor is still responsible to do it) it is also demanded for some of the utility company rebates in our AO. I can tell you many of the resi contractors and inspectors I meet have never done/seen a calc based on actual use.

So if hawking means following the code in those areas governed by the IRC or something similar, then you are correct. If the OP is in an area governed by the IRC then clearly the manual J is needed in his situation (or other approved load calc).

FYI icfbound not sure what you intended to illustrate with your link, but I don't think it illustrates that doing a Manual J load or put another way, following code is a "questionable practice".

Well, you can’t really fault someone just for marketing what they do for a living provided that they don’t overly distort the facts when doing so. Good knowledge and good experience is certainly very important here. Without that, even using the most expensive software isn’t going to get the job done right. In fact, the job can be accomplished quite adequately with just a pencil and a hand calculator if one knows what they are doing. In fact, Manual J was expressly developed back in the 1960’s such that it could easily be accomplished with a pencil and slide rule by the average HVAC person at the time. These days it is just wrapped with impressive looking software such that anyone can use it…even if they lack good knowledge and good experience. I am always reminded and still very impressed by the fact that we went to moon with just pencils and slide rules…way back in the day when men were men and didn’t waste their time debating subjects such as these with women, LOL!

"way back in the day when men were men"
what are we now?

http://www.computerweekly.com/feature/Apollo-11-The-computers-that-put-man-on-the-moon

"Well, you can’t really fault someone just for marketing what they do for a living provided that they don’t overly distort the facts when doing so......"

But didn't you when you made this comment?-

versus endlessly just hawking that Manual J analysis is the cure for world hunger and that they do it.....

I actually addressed that comment on that thread since icfbound took it to heart and continued to perpetuate the misconception that Man. J is extraneous and a "questionable practice".

What code do you follow in your area of operation?

Joe, being an engineering company, we are not limited by the limitations of Manual J. We can accomplish a heat loss analysis using more modern and more accurate ASHRAE methods (or any other method we choose) and PE stamp it such that it could be approved in every State. In fact, we are not limited by IRC prescriptive code in general and we can totally depart from the code as required using engineering principals.

Joe, being an engineering company, we are not limited by the limitations of Manual J. We can accomplish a heat loss analysis using more modern and more accurate ASHRAE methods (or any other method we choose) and PE stamp it such that it could be approved in every State. In fact, we are not limited by IRC prescriptive code in general and we can totally depart from the code as required using engineering principals.

But those who follow the code are wrong? You are dodging the point and you know it (I hope). You suggested man. J was not necessary in this case and you are full of beans.

You may not have thought of code because you do more commercial and use ashrae or whatever, there maybe other ways to calc load that the inspector may or may not approve. Inspectors most of the time may be willing to sign off because you stamped it (but make no mistake about it, they don't have to nor may anyone totally depart from the code), but the fact remains with most codes some sort of load calc is required and you were dead wrong to suggest manual J was unecessary in this case.

If you don't see that then I think your followers may wanna consider what else you don't think about when offering advice.Ignorance of code just because you think you may "totally depart from it" is not very attractive in a contracting firm.

Joe, Manual J is indeed not needed here and is not even appropriate here given this is an existing building with an existing heat source that could be used to accomplish a far more accurate actual energy usage analysis. The only reason a Manual J or better predictive method would be needed here is if a totally different heating system was also being accomplished (e.g., going from a furnace to hydronic radiant floor heating, etc.) in which case a room-by-room analysis would be required.