[Bldg-sim] zoning for a small single family dwelling

Nick Caton ncaton at smithboucher.com
Thu Apr 15 16:48:00 PDT 2010


I would echo Liam's suggestions with some additional thoughts...

 

eQuest is powerful and flexible, but one thing it doesn't particularly
excel at is modeling airflow between zones.  You can certainly build an
accurate model for a small residential project with 1 zone, and
over-zoning will only make it a more difficult task.  

 

However, unless you have a pretty fancy HVAC system in mind, you're
probably talking mechanically about a single-zone system anyway
(1-thermostat)...  

 

That said, even with 1 zone you can still define individual spaces
grouped under a zone if you wish to.  You can "connect" two or more such
spaces thermally (as with say an open kitchen/dining/living space) by
redefining their partition walls as "air" instead of frame walls (and
maintaining the space relationships) in the detailed mode, post-wizards.
I may be misunderstanding, but I don't think going crazy with spaces
will cause you any serious headaches if you're mindful to tie open
spaces together (remembering many residential doorways stay open 90% of
the time).

 

Understanding the solar decathalon is a college-level competition, I'll
stick my neck out and make the brash assumption that you might be fairly
new to energy modeling in general (please forgive me if this is out of
line)!  Some potentially useful advice to that end may include a few of
these "wish I knew this when I started" items:

*         The best/most accurate/time efficient energy models result
from good communication between all designers/disciplines involved.
That's between the energy modeler and each other.  It's your job to stay
abreast of everyone's progress.  

*         Ask questions!

*         Energy modeling to assist with optimizing design elements can
happen at various stages of building design - but take care to stay
mindful of the order of design.  At a "preconceptual" level, you might
hammer out various building envelope massing/orientation/glazing/shading
layouts for rough comparative results (eQuest may not be the most
time-efficient tool for this... suggesting Sketchup + IES-VE plugin for
a free option) - doing so, you and all parties need to intimately
understand there will be a good deal of inaccuracy in such models, and
that's okay for their purpose.

*         It's more productive to shift optimizing design elements such
as HVAC control elements, load balancing through thermal massing
options, and daylight harvesting nuances to a later stage of design.
Before such systems are laid out, you have little capacity to obtain
results accurate enough to be meaningful to the final design.

*         The phrase "comparative results" is a much more
practical/manageable goal than "accurate results" during early design
phases.  Seek to make apples-to-apples comparisons to guide the design
decisions in the right direction, not to provide the final answers.  

*         Sleep, 3 meals a day and regular exercise go a long way.

*         Subscribe to bldg-sim and equest-users and bookmark the
corresponding archive search pages - these are fantastic resources for
learning and exploring.

*         Saving your progress more often than is necessary is much
better than the alternative.  Save excessively and in separate
directories.  Really.

*         Otherwise simple energy modeling tasks can become VERY hard
when the design team is not on the same page regarding the end-goals.
"Saving Energy" is something everyone can agree to... but is your metric
in dollars, EUI, % improvement, tons of CO2 and/or carbon footprint?
Leaving such end-goal priorities unanswered can create major friction,
so address this early!

*         If you pursue energy modeling seriously, you will inevitably
and necessarily learn a heck of a lot and fast.  Never however assume
you're the smartest head in the room - you can always learn and grow
from others' perspectives if you keep your eyes and ears open.

 

Hope some of this helps, best of luck!

 

~Nick

 

 

NICK CATON, E.I.T.

PROJECT ENGINEER

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

Check out our new web-site @ www.smithboucher.com 

 

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Liam
O'Brien
Sent: Thursday, April 15, 2010 3:03 PM
To: jacobfaiola at yahoo.com; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] zoning for a small single family dwelling

 

Jacob,

I have found performance of passive solar houses to be particularly
sensitive to zoning choices.  If you "over-zone" your house, you'll find
that the direct gain areas overheat even if the other zones are cool,
unless you properly distribute the energy using mechanical or natural
circulation.  For 1000 SF, I would consider going with two zones.  One
for the direct gain zone, and one for non-direct gain zone, depending on
the interior layout.  For houses of that size with minimal glazing one
zone would probably be enough.  My belief is that unless you truly know
how the air flows between zones, you're not gaining anything by using an
excessive number of zones.  Also, you might consider using a simulation
tool that accurately models thermal mass using the finite difference
method.  

Liam O'Brien

________________________________

Date: Thu, 15 Apr 2010 12:44:51 -0700
From: jacobfaiola at yahoo.com
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] zoning for a small single family dwelling

I am modeling a 1000 sf single family dwelling for the Solar Decathlon,
a net zero home design competition.

I would like to maximize the accuracy of the model. Does it make sense
to zone each room individually so I can precisely assign activity areas?

Or should I just zone the whole house as single family residential and
let eQUEST figure that out?

 

thanks,

Jacob Faiola

 

________________________________

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