I'm looking for a general discussion on load calculation software. Since this is the residential forum I'm looking for software geared more towards homes. I use Trane Trace 700 at work which is great but it is very sophisticated and I cannot use it at home without paying for a license of course. I'm also aware that a Manual J is the norm, but I'm curious if there is any software out there that homeowners could use, particularly free. I understand that a Manual J is very thorough and is probably the best bet for the an accurate load calculation, but I'd like to learn about other decent computer software out there. Thanks people!

HVAC - I believe Sailor has one on his web site. Borst Engineering.

There are some links under "Computer Models for Home Energy Calculations" at:

http://www.residentialenergylaboratory.com/links.html.

Excellent information gentlemen! Keep it coming.

All residential software is base on ACCA Manual 'J' information. You get what you pay for, if you have time to learn Manual "J' and the software you choose. Free software is like free advice.

If you don't own a seat in AutoCAD you could step down to Wrightsoft, our favorite for design/build radiant floors, snow melting, HVAC duct work and high velocity. Far from free but more than the particular homeowner could hope for.

"All residential software is base on ACCA Manual 'J' information. "
That is not at all true. Heat loss calculations are based on fundamental heat transfer equations, which existed long before Manual J.

"Free software is like free advice."
So the implication is that the free advice that you are offering is not worth much?!

Manual J is very thorough and is probably the best bet for the an accurate load calculation

There is a lot of evidence that in the hands of an average (ie, nobody on this forum) installer, it is often quite inaccurate and that for an existing building, past usage is more accurate.

Also consider the BEopt software.

Posted By Lee Dodge on 10 Jul 2013 11:18 PM
"All residential software is base on ACCA Manual 'J' information. "
That is not at all true. Heat loss calculations are based on fundamental heat transfer equations, which existed long before Manual J.

"Free software is like free advice."
So the implication is that the free advice that you are offering is not worth much?!

Perhaps you could elaborate? Which current residential heat load software programs use other than Manual 'J' data?

I've used Elitesoft RHVAC for several years, and it has not failed me yet. We routinely downsize central AC systems, so it is important that load calc software be reasonably accurate.

Posted By FBBP on 10 Jul 2013 12:45 PM
HVAC - I believe Sailor has one on his web site. Borst Engineering.

Yes, we have both HVAC cooling load analysis (based on CLTD/CLF) and heat loss analysis software (based on UA Δt) that is available for free DIY use on our website. Both are based on current ASHRAE methods and there are also detailed instructions for using both these software tools on our website.

Borst Cooling Load Analysis Software

Borst Heat Loss Analysis Software

We also have psychrometrics software that is available for free DIY use on our website. This is useful for determination of the heat and water vapor properties of air. If you know the building elevation and dry bulb temp, and also know either the wet bulb temp, the relative humidity, or the dew point temp, the software will then determine ALL of the commonly used psychrometric parameters: barometric pressure, wet bulb temp, relative humidity, dew point temp, partial vapor pressure, saturated partial vapor pressure, humidity ratio, specific volume, density, and enthalpy.

Borst Psychrometrics Software

Being an engineering design/build company associated with more complicated and integrated HVAC building issues, we prefer the ASHRAE methods. However, there is nothing wrong with the ACCA (Air Conditioning Contractors of America) Manual J method. The Manual J method is essentially a simplified version of an older ASHRAE (American Society of Heating, Refrigeration, & Air-Conditioning Engineers) method to better enable HVAC technicians to perform these types heat transfer analyses. A well done Manual J analysis is often more than adequate for most residential building HVAC designs. Well done in this case meaning that the person doing the analysis is actually capable of determining/obtaining the correct inputs required by the software, properly using the software within its design limits, and fully understanding the HVAC design implications of the software outputs.

For residential heat loads Elite is based on ACCA Manual 'J'.

http://www.elitesoft.com/web/hvacr/elite_rhvacw_info.html

Good choice. With the right operator, it is hard to go wrong.

For residential heat loads Elite is based on ACCA Manual 'J'.

http://www.elitesoft.com/web/hvacr/elite_rhvacw_info.html

Good choice. With the right operator, it is hard to go wrong.

For residential heat loads Elite is based on ACCA Manual 'J'.

http://www.elitesoft.com/web/hvacr/elite_rhvacw_info.html

Good choice. With the right operator, it is hard to go wrong.

Posted By Lee Dodge on 10 Jul 2013 11:18 PM
"All residential software is base on ACCA Manual 'J' information. "
That is not at all true. Heat loss calculations are based on fundamental heat transfer equations, which existed long before Manual J.

"Free software is like free advice."
So the implication is that the free advice that you are offering is not worth much?!

Correct and I believe the ACCA Manual J method is still built on a 1950's data foundation!

Several residential load calculation methods have been published in North America over the last 30 years. All use the UA Δt heating formulation and some variation of the CLTD/CLF approach for cooling.

ACCA. Manual J, 8th edition (ACCA 2011) is widely used in the United States. Cooling loads are calculated using semiempirical heat gain factors derived from experimental data taken at the University of Illinois in the 1950s. These factors, associated overview, and references are found in the 1985 and earlier editions of the ASHRAE Handbook—Fundamentals. The 8th edition retains the underlying factors but provides increased flexibility in their application, in addition to other extensions.

ASHRAE. The 1989 to 2001 editions of the ASHRAE Handbook—Fundamentals contain an updated method based on ASHRAE research project RP-342 (McQuiston 1984). In this work, cooling factors were re-derived using a transfer-function building model that included temperature-swing effects.

F280. This Canadian adaptation of the CLTD/CLF procedure (CAN/CSA Standard F280) also uses cooling methods based on ASHRAE RP-342. Heating procedures include detailed ground heat loss estimates.

A key common element to the better cooling methods is attention to temperature swing, via empirical data or suitable models. Throughout the literature, it is repeatedly emphasized that direct application of nonresidential methods (based on a fixed set point) results in unrealistically high cooling loads for residential applications.

HVAC software accuracy is only as good as the engineering data and the heat transfer math model basis that is used. I suspect many users of HVAC software consider ease of use more important than actual accuracy. Of course, proving which software method/product is truly more accurate is not easily accomplished and often not believed even when accomplished...sort of like proving which religion is right, if any. Unfortunately, lack of proof always makes for a great business model for extracting $$$ from ignorant people.

Most interesting.

My point was; th residential "software" is based on Manual 'J' standards. As we rarely refer to other countries on this blog, one might assume my reference was meant for N. America. Other forms and formulas are not as current and consequently relevant as ACCA's Manual 'J'. Certainly Sailor's "free" software could expected to be current and relevant given his consummate grasp of the subject. Now if he would perform a proper heat load for the folks he invites to use the software, well....:-).

Heat loads, regardless of the method one uses to attain them, are not particularly easy, more especially in renovation work, where many assumptions must be made as to the quality of construction, insulation value and infiltration to name a few.

When a cooling load or heat loss analysis is required for a new building design, I would agree that uncontrolled outside air infiltration is by far the most challenging software input parameter to quantify and it also often has the most significant effect on the cooling load and heat loss analysis results. Fortunately, we can now design and construct new buildings with practically zero uncontrolled outside air infiltration and we now have affordable residential HRV and ERV systems that allow us to efficiency bring in the required and precisely controlled/known flow rate of outside air.

For existing building renovation work it would be more accurate and far less time consuming (with the corresponding lower cost passed on to the HVAC consumer) to use the actual existing heating/cooling system usage and associated/measured indoor/outdoor temps to solve this problem rather than performing a more expensive and unnecessary cooling load or heat loss analysis. Yes, one can perform a blower door test to try to quantify uncontrolled outside air infiltration for an existing building, but this can also be expensive and may not provide accurate results either. Actual uncontrolled outside air infiltration is a very complicated function of the actual leakage area of the building, the geometry and height of the building, the actual building orientation relative to actual prevailing wind direction (which can often vary significantly), and the actual wind magnitude (which can also often vary significantly). A blower door test in conjunction with a smoke test (and perhaps infrared temp test) likely has more value for identifying and fixing leaky problem areas in an existing building rather than improving the accuracy of an unnecessary cooling load or heat loss analysis.

Yes, I specifically associated my previous response to North America on the expectation that most folks who frequent this site are from North America. We do a significant about of international business and I can assure you that the USA is not even close to being the center of expertise/excellence for HVAC design and construction.

HVAC-Calc is one to consider as well...

Here's one homeowner's review of HVAC-Calc:

HVAC-Calc Review

It is somewhat dated so it would be interesting to see a more current review from an independent and unbiased source.

I continue to use that software as it is very user friendly. One caution is that like anything GIGO is always a great possibility. Pros who have done hundreds or thousands of calculations have a general expectation of what the result should be and would quickly spot an unusual load.

Pro's may also be aware of things homeowners aren't. For instance in MI in a typical home the BTU difference between a heated or unheated basement likely won't change appliance size or have a significant impact on heating bill.

One thing to bear in mind is that a gas warm air furnace 1 size larger (most manufacturers have increments of 20 or 25kbtu) may be cheaper to operate with very little additional up front cost. By the same token manual J has some fat built in (insurance BTU's) so one doesn't want to go over the top and have a grossly oversized system as that could cost more to run.
With geo systems our most common size graduations are 12,000 btu's with a very large up front cost consequence if we over size.

So good calc software will give you a number, but you still have to recognize if it is a good number and know what to do with it.

Good Luck,
j

"All residential software is base on ACCA Manual 'J' information.Free software like eds https://www.eds.tech