NCM profiles for TM52

[golden eagle]

Hi,

my questions below are regarding TM52 overheating assessment for the priority building school project in relation to occupancy profile

can anyone know if school terms and dates can be used for the occupancy profile in a school project ( example NCM educational profile defined by BRE) ,
I could not see any section in the CIBSE TM52 guide that suggests I cant use NCM profile ,( please let me know if that is not the case) however I have seen a statement from in the guide prepared by IES advising NCM profiles may not be appropriate for TM52 assessment , and no further guidance given how to do or what approach I should use for occupancy profiles . I am aware that the previous guidance (BB101) mentioned summer period for the overheating calculation from May to September ( within the teaching hours which should exclude holidays) so it is only during the teaching hours within the school terms and dates that I assume that overheating assessment should be based on ,
NCM teaching profile which was determined by the consultation received from department of school excludes holidays for the purpose of energy calculation , also BB87 states overheating calculation from may to September excluding august , so Why IES suggests that the NCM profile is not suitable for a school project as a result of prolonged unoccupied hours during the school holidays , they suggest that the user should alter the NCM profile to suit ,which in another terms I guess they refer to include the month of august in the calculation( which is longest unoccupied hours during the summer period ) so although there is no occupancy or reduced occupancy during the period of August or summer school , but that is sometimes all depend on the school premises policy and how long they do this for it may not be a global approach ,

The problem with including August is that it may make the result pass or fail especially for the criterion 1 of the requirements which put limits on the number of hours that the operative temp exceeds threshold temperature by 1K , This limit is 40 hours , so if the numbers are already up to 38 hours say until August, you may end up above 40 hours by the end of August so the classroom will get close to being failed fail where otherwise it would pass

so in my opinion ; unless the occupancy profile given by the school ( including terms and dates ) , I cant see any reason why I should alter or change the profile to include august , you should only consider the occupied hours . NCM should be appropriate otherwise Department of school should not accept these profiles for the energy calculation,

lastly ; can the occupancy profile for a typical teaching day be in line with NCM occupancy profile ( from 7 am to 6 pm – reduced occupancy between 7am 9am and 16pm to 6pm, so very early in the morning , you have teacher or some student occupies the classroom before the teaching starts and similar reduced occupancy after teaching hours as some student stays and teacher for assistance etc.. it would be unrealistic to exclude this occupancy from overheating calculation during out of teaching hours as during which people that occupy the room contribute internal temperature start rising as heat gain in the room , so the temperature and co2 gets sharp rise with start of the occupancy , what are your comments?

[RossThompson87]

Hi,

I think you have read all the guidance that is available. As you can see it's a bit of a grey area.

Overheating tends to be more about design than compliance. I use models of the real (not actual) building for overheating checks. But the NCM templates can be a starting point.

I think the important thing is the client/building control/efa are aware of the temperatures you are subjecting the building to in the simulations.

Be careful with the times you exclude, on some weather files if you model the building as unoccupied at weekends this may exclude many of the warmer days.

I now agree on the weather file and occupancy periods as early as possible with everyone concerned. Otherwise you find yourself going round in circles.

I hope this helps

Ross