SFPE Discussions

MoE Adoption of Enclosing Rectangles Method

What does the MoE actually intend in its fire safety policy addendum - Adoption of the Enclosing Rectangle Method (July 2017) [PDF, 130 KB]?

The intent behind use of burnout calculations to determine FRR and enclosing rectangles to determine separation distances is reasonably clear. However, the commentary section which is apparently designed to “aid interpretation” is quite ambiguous in a number of areas.

I am interested to know how others are applying this policy amendment now that a year or so has passed since it was released.

i believe the intent is to achieve a less severe result under C/AS4 5.5.7 than the tables in the Acceptable Solution. It should produce a less severe result but I have not needed to apply this in the last year.

In my opinion MoE are just trying to to control excessive costs. Those costs are created by MBIE’s failure to properly administer the Building Code Approved Documents.

If that was the case, updating their policy to mandate the use of ERM as per C/AS4 5.5.7 may have been enough. But this goes further than that.

If a new simple single level classroom building is proposed on an existing site in proximity to an adjacent multi-level building, how far should we go to comply with MoE policy? Undertaking burnout calculations for a new building with all the relevant documentation at hand to provide inputs for determining ventilation factor etc. may be reasonable. But should burnout calculations be done for the existing building also? If so, I suggest that the design costs involved with assessing the existing risk to this extent may exceed the gains achieved, assuming a lower FRR than the previously mandated 60-minutes is the outcome.

You have to make a call on a case by case basis. The guidelines do allow for feedback and confirmation/approval via MoE’s representative for the project. If you think a design process would be unnecessarily costly or would result in excessive design time or approval process you have a duty of care to report that to your client.

Are the calculations potentially absurd for burnout time. Maybe yes depending on the project. MBIE never explained why they removed the S rating table from the Acceptable Solutions.

The Acceptable Solution changes in 2012 were intended to drive more design to C/VM2 and significantly drive up the compliance costs while providing no benefits to any stakeholder. With exception that Fire Engineers could profit from this, and there are BCAs that are using the unnecessary bureaucracy created by this to charge additional fees.

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I recently used the revised June 2018 ‘Ministry requirements’ for a simple classroom block and the ER assessment applies only apply to the imposed risk (new building) - per commentary item 11d . They do not require the existing building exposure to be assessed.
The ‘requirements’ do not mention lower roofs or relationship of buildings of different height. Most schools tend to be single or two level though there are a few taller ones so its probably not a significant issue for the Ministry at this point in time?
There is one significant anomaly with placement of the notional boundary. Commentary item 11e assumes the notional boundary for ER assessment to be placed 1m from the ‘new building’. With the boundary 1m from the new building the walls will need virtually 100% FRR regardless of the distance between the buildings. I assume this should have been 1m from the existing building.

perhaps i am reading this incorrectly?

I take your point about commentary item 11d - I hope that is really what they intend. Assessing emitted radiation from the new building only is obviously the approach we take when meeting the NZBC requirements for protecting ‘other property’ (assuming no sleeping risk or exitways on the same property). But in this case we are meeting MoE property protection requirements. So presumably they are trying to make sure that when we drop a new building on their property that both the existing building and new building are protected to an acceptable level.

The anomaly you refer to on placement of the notional boundary is one of the ambiguities that we have also run into. Given how poorly worded the commentary is, I would concur with the conclusion you have come to. But that does hinge on assessing the new building only. If we were looking at the complete picture (radiation in both directions), it may make more sense to place a notional boundary at a distance from the existing building that aligns with an ERM assessment on the relevant firecells in that building. But I don’t see anything in the commentary that suggests using this approach.

Looking at the commentary under item 11 it makes sense up to 11 (d). Then it seems to depart from clarifying the policy, and has a policy change included in item 11 (i).

Overall it looks like the commentary has evolved over time based on project specific issues.

I have to agree that some of the policy could be quite expensive with respect to design time and costs. The Ministry is probably not anticipating some of the costs or delays so it is best to provide advice and communicate on a project by project basis.

Hi All, In simple terms the MoE guidelines are NOT required for Building Code compliance. The second point is that to deviate from the AS (and not use VM2) is a specific design and subject to FENZ etc…

Also a specific calc may need to be supported by a PS if required…

Alan, only if you are using the calculation to show NZBC compliance. There is nothing stopping a client from having higher requirements. Most schools are a long way from the boundary so no fire rating is required for NZBC, but if MoE want fire separations, calculated by any method they want, then that is up to them, Since it is above the NZBC minimum and not a consent item, it is not an alternative solution and would not need to go to FENZ.
As a taxpayer, I still think the guideline is poorly written and does not achieve it’s stated objective and in some cases increases the requirements from what they were before for no benefit.

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