Greetings,

I have downloaded a trial version of LoopCAD and am working my way through a residential design.  I have already ran the heating and cooling load calculations with another piece of software (Elite RHVAC).  I have used this almost daily for the last 10 years and am very comfortable with it.  But anyway, under the panel loads I select to input heating data manually.  It then gives the choice of including the back loss from my calculation or not. 

At this point I should admit I am not experienced with radiant heating design and not completely sure what is included in the back loss, common sense would indicate back loss is heat flowing backward through the insulation into the ground and not contributing to any space heating.  That being the case the choice of floor covering and insulation under the slab among other variables would determine this.  I am sure this is operator error with the software but when i select "calculate automatically" it doesn't seem to do anything and default back to whatever percent I have selected.  Possibly when I choose to enter my own heating loads manually the software can't do an automatic calculation. 

I am going to further speculate that foundation perimeter losses are not considered back loss and i would need to calculate them using another method and sum that with my other building envelope loads.

I am sure as this design progresses I will have more questions, but any help on these would be greatly appreciated.

Regards,
Axis

The capability of the LoopCAD depends on the version you have. The LoopCAD Editions with ACCA Manual J, ASHRAE and CSA F280-12 do everything and there’s no need for any additional external calculations. In these LoopCAD Editions, the downward losses are calculated automatically, unless otherwise specified by the user.

There are a variety of different types of downward losses, and when dealing with radiant heated panels, or snow melting, these are often referred to as "back losses". The Standard Edition of LoopCAD does not provide the automated calculations of the downward losses, but it does allow the user to specify it as a percentage of the room losses. There is a detailed explanation of all these different types of downward losses and how they are calculated in the help information section of LoopCAD. Brad McCrea of Avenir Software Inc. also provides great customer support and he will surely quickly answer any questions you have about this software.

Thanks for the quick reply sailawayrb. The version I downloaded was MJ8 which includes the Professional along with the Manual J calculations. I may just enter the home using the built in Manual J as it probably wouldn't take long using reports from my software. I do need to research these losses a bit to at least get a basic understanding on what is happening. Using any piece of software that does automatic calculations I run the risk of garbage in - garbage out. My background is in forced air systems and can tell you from experience it takes many years of doing to get a good 'feel' for how things work.

You are most welcome. Yes, I fully agree and you are precisely right. We have been doing HR for over 10 years and we have used LoopCAD for about 5 years. It's a very good product, but like any software, you do need to learn the subtleties, limitations and work-a-rounds. I highly recommend LoopCAD and we have no affiliation with Avenir Software Inc.