IES-VE User Forum

Hi All,

I have problems with getting the 'local extract units serving a single area SFP' to be shown correctly on the BRUKL 2013 output report. Even though I set the SFP to 0.3 it reports it as 0.8 and flags it as red!
I use IES Version 2014.2.1.0 and VE compliance 7.0.2.0.

Does anyone else have the same problem? How can I fix it and is the auxiliary energy consumption calculated correctly?

Regards,

Eleni

This a known issue and still appears to be in VE 2015 which is disappointing.

This is still current. Fix it now.

It is quite disappointing that this issue has not been addressed even in 2015 version. And is also frustrating trying to explain to your Client that you input the systems/SFPs correctly but still on their BRUKL output report are not reported correctly and are highlighted in red!

Grumpy Tuesdays!

Hi,

Seems there is some strong opinion on this and I'd like to engage it a little. A difficulty I have here is the SFP table on the BRUKL doesn't seem to align to the framework under the NCM, there are no explanations for each term to clarify so we have to base it purely on the sentence for each for example how would you differentiate between "zonal" and "local"? For a fan coil system I have had different people say they'd expect both the local fan SFP and central system SFP be shown in this table under different columns while others (and SBEM incidentally) have said that only the local fan SFP should be in this table - what do you think?

I do agree this needs work and that the values presented here should reflect what has been entered in the software (and simulated!) but if it was well defined we would already have implemented this, instead all we have are some brief summaries of different ventilation strategies that do not link directly to the NCM assumptions and interfaces for defining systems and calculating auxiliary energy so it makes the job far harder and so all we can do here is approach it on a case by case basis.

Interested to hear the thoughts of the experts out there

Phil

Phil,

In my opinion I think using SBEM as a precedent here, as it is written by the the same team that produces the NCM modelling guide would be the correct thing to do? Where the NCM modelling guide is unclear the result from SBEM would indicate their the BRE's intent with regard to populating SFPs in the Local mech vent table on the BRUKL.

I have experimented a little with ISBEM 5.2.d. it's free to download from the official website if anybody else whats to do this.

As you have indicated SBEM treats a fan coil system by placing the SFP for the central AHU at system level (not in the local vent table) and the terminal SFP in column H. There is a reference to this on pg 67 in iSBEM verion 5.2.d user manual "NB: Zonal ventilation is no longer available for fan coil units. Ventilation for this HVAC type is defined at HVAC level"

This seems logical to me . I don't see where the conflict is with regard to the NCM modelling guidance in terms of populating the table.

Of course how the SFP is compared in the notional building is the bigger question which is discussed in an separate thread that is in its third year without a satisfying resolution and is compounded by this new issue. I am with 'complex potential' on that topic but I don't think there is anything useful gained by going over old ground i have read it several times and understand your point of view that the final resolution needs to come from the approval body rather than IES/TAS or anybody else.

That being said could this be the catalyst for change... surely the reason columns D&E exist is to compare the actual buildings SFP to the notional's 0.9 + 0.6W/l/s and 0.9+0.4W/l/s for zonal and local MVHR respectively. 0.4W/l/s being the specific fan power for local exhaust and 0.6 for remote exhaust in the notional building. 0.9W/l/s for supply regardless. Is there another explanation out there? Unfortunately iSBEM doesn't appear to behave in this way undermining the argument. TAS appears to be the exception.

moving on... i believe the table should be populated as follows

column A: For wall/ceiling/window extract fans within the zone
column B: Supply fans (most supply fans will have some form of tempering the air meaning they are normally located remote from the zone anyway in my experience)
Column C: Extract fans located anywhere other than the within the room (remote) i.e. ceiling voids, roofs etc
column D: Heat recovery ventilation located anywhere other than the room e.g. nuaire xbox, ves ecovent in the ceiling void, roof etc.
Column E: Wall mounted Heat recovery unit such as vent axia HR100S?? I don't see a facility with SBEM or IES to select this??
column F: ?
column G: ?
column H: fan coil terminal sfp
column I: k*****n extract

It would be great to get something in the table rather add to the existing confusion/disagreements surrounding sfps.

Kind Regards,

Ben

Here are a couple of tables showing the current state of play for DSM & VE-SBEM with the reporting of SFPs to the local mech vent, exhaust and terminal unit table on the BRUKL Certificate.





As you will see it is not possible to model the systems mentioned under Columns E, F and G using SBEM. This was confirmed with the SBEM Helpline at BRE (developers of the SBEM engine) who said the following.

“The 2013 Non-domestic Building Services Guide was developed separately by parties other than the SBEM development team, who later matched, wherever possible, the descriptions of the systems in it to what could be modelled in SBEM in order to produce the compliance output document in v5.2.d… The systems in the 2013 Non-domestic Building Services Guide which were allocated the codes 67 (Column E), 68(Column F), and 69(Column G) in the BRUKL manual cannot currently be modelled in SBEM and so will not be matched by SBEM to any system definitions by the user."

For DSM in VE 2015, it is possible, using a combination of the UK NCM System type, Air supply mechanism and room level settings identified above, for a user to get the correct SFP reported under Column A, Column E and Column F. It should also be possible, through further development, to get the correct SFP reported under Columns B, C, D, H and I. We don’t think it is possible to get anything reported under Column G.

Hi Terrance,

Thanks for the update.

I've noted to get something into column E at system level you select the ASM=local vent only units and heat recovery with the sfp entered at room level. Switching to the notional building to check what it is receiving it is not reporting any heat recovery?

I presume the difficulty with fan coil units is something to do with system level vent, such as constant volume systems, normally supply both fresh air and all of the space conditioning load wheres in the fan coil system it is there terminal unit conditioning the space and the central ahu providing the fresh air or something along those lines?

If you look at paragraph 46 of the 2010 NCM Modelling Guide you will see that it states that the notional building will only have heat recovery 'where appropriate'; this being when a zone is mechanical ventilated, providing supply & extract. So when the user selects anything other than ‘Centralised balanced A/C or mech vent system’ for the ‘Cooling/ventilation mechanism’ in their actual building systems they won't have heat recovery in the notional building.

For Part L2a 2013 this has not changed (reference is now paragraph 51 in the 2013 NCM Modelling Guide).’

so for column E 'local supply and extract ventilation system serving a single area with heating and heat recovery' the unit must have supply and extract and heat recovery by definition.

The definition on the BRUKL document comes from the non domestic compliance guide which expands the definition slightly to 'Local balanced supply and extract ventilation system such as wall/roof units serving a single area with heat recovery' and sets the minimum standard value for the SFP to 1.6W/l/s.

In direct contradiction to your interpretation of the NCM guide i would argue that it is appropriate for the notional building to receive heat recovery as the the mechanical ventilation system is providing supply and extract as per paragraph 51 of the guide.

The only difference between columns D and E should be the SFP.