Process to calculate heating loads after creating ModelIT building?

[rossd01]

Hi all,

Relative newbie here, however I've been making excellent progress in creating a residential block of flats from which I have to calculate the heating energy consumption. I've had a look at the forums (and extensive pdf tutorials) but i'm still a bit confused so please accept my apologies if this has been repeated.

So, I have created my exciting model of a block of residential flats, based in the UK, containing 8 floors, all thermal constructions assigned (I haven't added any components). My question is - what now?

I need to calculate the heat loads to try and meet this heating energy consumption for the building. The main questions I have (and in an indicative process order) are:

1. Windows/Air Flow: do i need to assign opening parameters for the windows? Every window opens but being residential, i don't know when that would be...I'm unsure how to go about this.

2. Use Patterns: I know patterns of use for each room is important, so would that would that be next? Something within Building Template Manager?

3. Solar Simulation: At the first 'modelling' stage, would i run suncast to gather solar gains data for the next step?

4. Final Heat Loads: So, with all this and the model running, how do I get an output file with heat loads? Is that available in Vista?

Sorry if this is very vague! I don't mean to act dumb, the creation of the model was time consuming but straightforward being as it existed in the one part of IES VE (Model IT) so i'm confused about the process now i need to venture out of that part. Based on my goal, if someone could lay out that process, that would be great.

Thanks folks!

[Complex Potential]

First things first.

What are you actually wanting from the model and why? If all you want to do is size radiators and central plant then you just need a simple steady state heat loss model (this basically just needs you to input heating setpoints, infiltration and possibly fresh air rates although I recommend dealing with those by hand). On the other hand, if you want to know annual heating energy consumption then you will need a dynamic model which is far more complicated.

If you are after annual heating energy, again I'd ask why because the requirement for such a thing is quite rare outside of "how much is it going to cost to run" types of questions which are a legal minefield by the way.

CP

[rossd01]

CP, thanks for the quick reply! My apologies again if it seems as if i'm swimming up a stream backwards, but in recent weeks I feel i'm really getting there with this. IES has been my first foray into computer modelling so its certainly been a learning curve!

So, my model. The ultimate objective is to design a ground loop system to meet the heating energy demands of the building.

The program I am using is called Ground Loop Design [GLD] (my license expired so i need to call them in the USA to see about getting it extended) and that takes the heating loads output from IES VE quite easily, allowing you to physically design the ground loop/plant size based on the data from IES VE. I'm interested in how the ground responds (say, over 25 years/lifespan of the plant), which GLD allows me to visualise (temperate mainly). One of the big selling points of the ground loop software is that it can take yearly loads, so (in my haste) I may have jumped on that in believing that that is what i need.

Now, i know this is a forum for IES VE so I want to keep it on point, but as a background to the Ground Loop Design software, it takes Design Day (DD) loads as a minimum which consist of the following per block or zone:

- one peak hourly heating load and/or one peak hourly cooling load
- Annual Equivalent Full Load Hours (AEFLH) for heating and/or cooling

Their blurb says that typically, a designer generates Design Day loads from a building energy simulation tool (say, IES VE) that can calculate loads for both peak and non-peak times over the course of a full year and the sum of the peak and non-peak values over the course of the year add to the annual load or AEFLH. Now, they do say I can use a simple calculation but that i'd need to estimate the AEFLH which could result in errors in sizing (up to 40%...!).

As you have explained it, the steady state heat loss scenario would be much more straightforward (thanks for clarifying!) where i guess i would design the plant/ground loop for peak demand? Would this work for this situation? It sounds like the data GLD needs may be the opposite in that it needs the full yearly loads. If so, what would be the process for that?

My main worry would be that this simple calculation could possibly result in sizing issues for the ground loop, as i wouldn't have data from throughout the year based on the changing seasons etc., unless of course the steady state model can account for that. Again though, i may be overcooking the turkey in doing things I don't need to do but GLD may need that extra data.

Honestly, anything to keep this as simple as possible is ideal - I'd be happy with a 'close enough' approach as a first pass to illustrate whether the ground can meet the demand of the building, which is the objective. Then it would just be what process I need to follow based on using the packages within IES VE.

Thanks you so much again for your input, really really appreciated!

[Complex Potential]

HI Ross

Ground loop systems would be one of those rare occasions where you need a dynamic model.

I'd not worry too much about window openings for heating loads because windows are likely to be closed in the heating season. Just make an allowance for minimum fresh air as per the design.

As for usage patterns, again if it is for heating loads only you may not actually need to worry about internal gains at all, just the heating setpoints and schedules.

Running and applying suncast for dynamic simulations is always a good idea.

The final hourly heat loads can be pulled out of vista/vista pro easily enough.