[Equest-users] Thermal Blocks

[Paul Diglio]

Jeff:

I've seen some of the other e-mails from the forum and I do not agree with the 
terminology other people are using, i.e. space v. zone v. thermal block.  Some 
of these replies are exceedingly long and contradictory.

Let's leave 'thermal block' out of the discussion.   Take one floor of an office 
building.  The baseline would usually require one HVAC unit for this floor per 
90.1.  I would create zones in the wizard for each large office space, the 
restroom, the utility rooms, the corridor and elevator lobby.  I would use the 
same procedure that you used below to add these zones to the HVAC system.  
Having the separate zones allows you to adjust the airflow and temperatures to 
the individual zones and also to find out where unmet hours might be occurring.

As an example of my understanding of a thermal block, say the office building 
has 8 floors and each elevator lobby is supplied by the same common HVAC 
system.  I would zone each lobby as described above and add them to the elevator 
lobby HVAC system.  This is a thermal block because it is a collection of spaces 
that share the same system and space characteristics.

Paul Diglio






________________________________
From: Jeff Ross-Bain <jeff at rbgb.com>
To: Paul Diglio <paul.diglio at sbcglobal.net>
Sent: Wed, May 4, 2011 9:39:19 AM
Subject: RE: [Equest-users] Thermal Blocks

 
Hi Paul,
So you establish individual zones in the building footprint window (2) and 
discriminate between corridors, classrooms… but what about all the little 
closets, odd offices here and there, rest rooms, mechanical rooms, meeting 
rooms, etc.? It seems that the zoning patterns would then become a nightmare. In 
your Zone Group Definitions window (14) you would then assign the same system to 
each of those zones? Here is a screen shot of a zoning pattern. I have used this 
approach for years:
 
 
 
 
Jeffrey G Ross-Bain, PE, LEED AP, BEMP
404-228-2893 office 
404-408-2577 mobile
www.rbgb.com

________________________________
 
From:Paul Diglio [mailto:paul.diglio at sbcglobal.net] 
Sent: Wednesday, May 04, 2011 9:21 AM
To: Jeff Ross-Bain; equest-users
Subject: Re: [Equest-users] Thermal Blocks
 
Jeff:

ASHRAE 90.1 allow spaces of similar thermal characteristics to be combined in 
thermal blocks.  I do not include what you call support spaces because the load 
and occupancy is much different than, say a classroom.  I would define the 
corridor as a separate zone within the thermal block but served by the same HVAC 
system.  This allows you to have a different set-point, airflow, occupancy and 
schedules for the corridor.

You do not have to define a separate shell for each block, you can define the 
block by custom zones in the wizard.

I divide up a thermal block into as many reasonable zones as possible.  This 
allows me to find out which area of the thermal block is causing any unmet 
heating or cooling hours.  It also allows me to change the HVAC system control 
zone to that zone which is the hardest to satisfy in the summer and winter.  
These zones can be served by a single HVAC system.

For a proposed model that needs to conform to an actual design, defining 
multiple zones per thermal block allows you to balance the airflow to zones that 
have unmet hours without increasing the overall airflow of the HVAC system.  I 
define the zonal airflow in the Zone tab.  I reduce the airflow to the zones 
without any unmet hours and increase the airflow to those zones that have unmet 
hours.  I do not define the total fan CFM in the Airside Systems tab.

What were the comments from the LEED reviewer?

Paul Diglio
 
 

________________________________
 
From:Jeff Ross-Bain <jeff at rbgb.com>
To: equest-users <equest-users at lists.onebuilding.org>
Sent: Wed, May 4, 2011 9:05:15 AM
Subject: [Equest-users] Thermal Blocks
Hi All,
 
Are there any additional discussions out there regarding thermal blocks besides 
what is in ASHRAE Standard 90.1 and the User’s Guide? I have received comments 
back from a LEED reviewer that seems to reflect an interpretation of that 
concept which I have not seen before.
 
In a nutshell, does each thermal block require a separate shell with individual 
HVAC system? I understand the concept of having individual thermal blocks or 
combining these if they are similar space use categories. I am assuming then 
that the similar space use categories (say a college classroom building) can 
also include support spaces such as corridors, storage spaces, faculty offices, 
etc. 

 
So if several thermal blocks are combined into one, can they not be served by a 
single, similar type of HVAC system?
 
I hope that I have made myself clear and many thanks for your thoughts and 
comments.
 
Regards,
 
Jeffrey G Ross-Bain, PE, LEED AP, BEMP
404-228-2893 office 
404-408-2577 mobile
www.rbgb.com
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