[Equest-users] Thermal Blocks

[Paul Diglio]

Bill:

You say that it is incorrect use of terminology to talk about multiple zones per 
thermal block then go on to say similar zones can be combined into thermal 
blocks and yet later you say you don't have multiple zones in a thermal block.

What is the difference between 'multiple' and 'similar'?

You also write that space and zone both have specific meanings in eQuest then 
later you sayyou would model each thermally-unique area as its own space/zone.  
I don't understand your comments.

Paul Diglio





________________________________
From: "Bishop, Bill" <wbishop at pathfinder-ea.com>
To: Paul Diglio <paul.diglio at sbcglobal.net>; Jeff Ross-Bain <jeff at rbgb.com>; 
equest-users <equest-users at lists.onebuilding.org>
Sent: Wed, May 4, 2011 11:18:19 AM
Subject: RE: [Equest-users] Thermal Blocks


I’m also curious to hear Jeff’s LEED reviewer interpretation of thermal blocks. 
I’ll add some general comments.
 
I believe it is incorrect use of terminology to talk about “multiple zones per 
thermal block” in eQUEST.
 
The words space and zone both have specific meanings in eQUEST. For each space, 
there is a single corresponding zone.
Multiple zones can be applied to a single system. (Unfortunately, multiple 
systems cannot be applied to a single zone, but that is another thread.)
The term thermal block does not have a precise meaning in eQUEST, but I would 
not describe the group of zones assigned to a single system as a thermal block.
 
If you wanted to try to model the exact intent of a proposed design, you would 
model each thermally-unique area as its own space/zone. A generalization is that 
a zone is an area served by a single thermostat.
To simplify a model, similar zones can be combined into thermal blocks per the 
guidelines in ASHRAE Standard 90.1.
Modelers have to make judgments calls on if/how to combine zones into thermal 
blocks.
 
In eQUEST, the decision to combine zones into thermal blocks really should be 
done at the wizard input level, when the zones are defined. You combine multiple 
zones per the design intent into a single zone definition for simulation 
purposes.
You don’t have multiple zones in a thermal block. Each thermal block is 
defined/modeled as a single eQUEST zone.
You could still assign multiple thermal blocks/zones to a single system, but I 
would be wary of over-simplifying a proposed design.
 
Regards,
Bill
 
 
From:equest-users-bounces at lists.onebuilding.org 
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Paul Diglio
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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