Heat gains from DHW delivery inefficiency
Heat gains from DHW delivery inefficiency
Changing the DHW delivery efficiency does not affect the space heating load. It seems that IES does not make any use of the heat losses of the DHW system. If the storage and pipes are inside the heated space, in Winter this lost heat would contribute to heat the house. Am I right? It seems a really bad flaw, almost hard to believe...
Re: Heat gains from DHW delivery inefficiency
Hi,
What you're saying is technically correct, even infinite amounts of DHW heat losses will not affect the space heating load. However, it's not exactly a flaw. For instance, to which space would you add the DHW heat losses? This heat loss really can go anywhere, in fact some (very poorly designed) buildings have that piping on the outside.
If you want to account for DHW losses going to a space, you need to add them separately using an internal gain, and use a different fuel so that the total fuel consumption doesn't change (if you're worried about it).
I agree though that there should be a better way of doing it. The software is dangerous in that it projects a façade of certainty, accuracy, ease of use, pretty pictures -- with little possibility to inspect the results at a detailed level -- meanwhile the reality is that thermal modeling is a bit more complicated and you can easily have completely incorrect results. But thems the imperfect tools we have, so the more you know their limits the better off you are.
What you're saying is technically correct, even infinite amounts of DHW heat losses will not affect the space heating load. However, it's not exactly a flaw. For instance, to which space would you add the DHW heat losses? This heat loss really can go anywhere, in fact some (very poorly designed) buildings have that piping on the outside.
If you want to account for DHW losses going to a space, you need to add them separately using an internal gain, and use a different fuel so that the total fuel consumption doesn't change (if you're worried about it).
I agree though that there should be a better way of doing it. The software is dangerous in that it projects a façade of certainty, accuracy, ease of use, pretty pictures -- with little possibility to inspect the results at a detailed level -- meanwhile the reality is that thermal modeling is a bit more complicated and you can easily have completely incorrect results. But thems the imperfect tools we have, so the more you know their limits the better off you are.
Re: Heat gains from DHW delivery inefficiency
Thanks Joseph. I think my expectation comes from using SAP prior to IES but your comment does make sense. There seems to be a lack of reviews on IES, or did I look in the wrong place? I am currently writing a case report about the energy modelling I did and trying to acess the appropriateness of IES for small companies and to model individual dwellings. From what I have seen, seems that IES is designed for larger scale projects and for people with some knowledge on modelling, which smaller companies might not have. One argument that might support this conclusions is: is it expectable that one knows the delivery efficiency of the DHW system of a house? I feel tired just of the idea of looking for such information.
Across my research, I seem to find a need for a better tool than SAP, which roots date back from the 80`s, while having the same narrow purpose, simplicity of use and user friendly interface.
I would thank any comments on my conclusions.
Across my research, I seem to find a need for a better tool than SAP, which roots date back from the 80`s, while having the same narrow purpose, simplicity of use and user friendly interface.
I would thank any comments on my conclusions.
Re: Heat gains from DHW delivery inefficiency
RR,
Regarding reviews, I think you need to look at journals, there are several comparisons and reviews being made there and examinations of their capabilities. The US DoE website has a compendium (though not critical reviews) of different thermal simulation packages. There are no formal online reviews for a few specific reasons:
1. It's a small market compared to other software that might have tens or hundreds of thousands of users.
2. To review it requires specialist knowledge and significant experience. But if you have this, you don't necessarily know other software to a similar extent. And if you do have this knowledge, chances are you don't have time to waste on online reviews.
Most of the time when people recommend a software, they are in fact recommending the software that they just happen to be using. So when you read an online review raving about IES for example (or any other building simulation software), remember, they more than likely have no idea about the pros and cons of IES versus other software packages, they just like how it "looks and feels". I have found it is quite hard to make an educated choice if I were to have one to make. If you want to get people's opinion about this, get it from the proverbial horse's mouth, go to a symposium and get people's opinion about it. Some people will swear IES, Ecotect, BLAST, EnergyPlus, TAS, ESP-r, TRNSYS, IDA, are each the best thing since sliced bread, and clearly they can't all be right.
Regarding what I think of IES, I disagree regarding what it seems designed for. My experience is that it works better on mid-size to small models. After a certain number of zones the whole thing comes to a crashing halt and takes forever to solve, especially with MacroFlo. You results file can crash (at the end of the simulation!) if you have too many zones and too many desired results. Also, IES is definitely not designed with the Engineer in mind; my sneaking suspicion is that it is designed with the Architect / novice engineer in mind. It looks nice, has lots of nice-looking results graphics, but results inspection is difficult, getting information on what the software does under the hood is next to impossible (in other words, transparency), which, for an engineer, is absolutely essential. So you get a result at the end but you have no means of validating this result. Plus it has numerous unexplained / obsolete / inactive features, and bugs / unexplained eccentricities that unless you tinker around with it you can (and will) generate inaccurate results and not know it. The only way of figuring that out unless you look at the results and ask yourself "does this make sense?", and there could be 1GB of data to go through! Basically, if you don't ask a lot of questions or don't know better IES is a great software to use.
At the same time, it offers a lot of features that are hard to find under one roof, not a single software is perfect (far from it), so we keep using it. But definitely I wish it were better.
Regarding reviews, I think you need to look at journals, there are several comparisons and reviews being made there and examinations of their capabilities. The US DoE website has a compendium (though not critical reviews) of different thermal simulation packages. There are no formal online reviews for a few specific reasons:
1. It's a small market compared to other software that might have tens or hundreds of thousands of users.
2. To review it requires specialist knowledge and significant experience. But if you have this, you don't necessarily know other software to a similar extent. And if you do have this knowledge, chances are you don't have time to waste on online reviews.
Most of the time when people recommend a software, they are in fact recommending the software that they just happen to be using. So when you read an online review raving about IES for example (or any other building simulation software), remember, they more than likely have no idea about the pros and cons of IES versus other software packages, they just like how it "looks and feels". I have found it is quite hard to make an educated choice if I were to have one to make. If you want to get people's opinion about this, get it from the proverbial horse's mouth, go to a symposium and get people's opinion about it. Some people will swear IES, Ecotect, BLAST, EnergyPlus, TAS, ESP-r, TRNSYS, IDA, are each the best thing since sliced bread, and clearly they can't all be right.
Regarding what I think of IES, I disagree regarding what it seems designed for. My experience is that it works better on mid-size to small models. After a certain number of zones the whole thing comes to a crashing halt and takes forever to solve, especially with MacroFlo. You results file can crash (at the end of the simulation!) if you have too many zones and too many desired results. Also, IES is definitely not designed with the Engineer in mind; my sneaking suspicion is that it is designed with the Architect / novice engineer in mind. It looks nice, has lots of nice-looking results graphics, but results inspection is difficult, getting information on what the software does under the hood is next to impossible (in other words, transparency), which, for an engineer, is absolutely essential. So you get a result at the end but you have no means of validating this result. Plus it has numerous unexplained / obsolete / inactive features, and bugs / unexplained eccentricities that unless you tinker around with it you can (and will) generate inaccurate results and not know it. The only way of figuring that out unless you look at the results and ask yourself "does this make sense?", and there could be 1GB of data to go through! Basically, if you don't ask a lot of questions or don't know better IES is a great software to use.
At the same time, it offers a lot of features that are hard to find under one roof, not a single software is perfect (far from it), so we keep using it. But definitely I wish it were better.