Dear Bldg-Sim community,
I'm trying to plan a LEED energy model which has a swimming pool and am
stuck thinking about how to model the baseline condition.
A pool has such specialized needs that I have doubts whether one of the
specified baseline systems in ASHRAE 90.1 can do an acceptable job of
controlling temperature and humidity.
At present, I am reasonably confident that I can schedule the pool occupancy
properly, add moisture in amounts that parallel the pool evaporation and
specify the pool heater energy.
My facility requires a "System 6" parallel fan powered VAV box HVAC system
(95,000 sq.ft., single story, multi-purpose facility). This is not a system
type that makes sense for a pool, so I hesitate to use it at all. If I have
to, for purposes of following 90.1, I think it might meet temperature loads,
but it certainly won't meet humidity loads, at least not at the specified
20F airside delta T. That, of course means that overall energy use will not
even be close to what will actually be needed and the baseline will compare
poorly with the actual (very efficient) HVAC system.
I'll appreciate any guidance from those among you who have done LEED
projects with pools!
Thanks in advance.
BPT BizCard_RGB_0507
James,
I suggest looking at the exceptions to the baseline system type table in section G3.1.1. A latent load differential criteria would be a nice but it is not there so here's hoping one of the criteria there gives you a reasonable and manageable comparison.
Paul Riemer
James,
I was involved in modeling an Aquatic Center recently. This was not a LEED
project but a utility DSM project but I think our approach would be
applicable. We assumed that the pool space was a process space. For this
case, the proposed design system and controls should be of the same type in
both the baseline and the proposed design. In our project, we took credit
for a controls innovation that modulated outside air based on indoor
humidity level instead of outside air (as is allowed through an exceptional
calculation method by LEED).
I developed a spreadsheet to complete a mass and energy balance on the
space and figured out the outside air for each hour of the day throughout
the year based on the proposed control strategy. Then I developed an 8760
schedule for outside air and used it with the proposed model.
To figure out the latent losses from the pool to the space, we followed the
Shah Method (do a google search and you'll find a spreadsheet of the
method). The results seemed to be more modest than those following the
ASHRAE method. However, both were high when compared to values used for
solar thermal system sizing (by the solar contractor). As I matter of fact,
I couldn't "turn down" the Shah model far enough to get close to those
values, which were about 1/2. In contrast, the mechanical engineers design
values were about double the Shah Method results. It was very frustrating to
go through such a detailed analysis only to be unsure of actual latent lose
values. In the end, I modified the Shah method results so they would be
consistent with the solar contractor's annual load estimate. The contractor
had done several local installations that delivered as expected.
Part of the analysis considered the impact of having the pool covered vs
having a solar thermal system that met 60% of the annual load. This is part
of the ASHRAE 90.1-2004, which the project needed to adhere to. This adds a
little extra through regarding scheduling the latent losses in doing the
modeling.
Good luck. This is one area of modeling that could surely use some help. But
based on my mixed results, I don't know if you want to follow the path I
did.
Ellen
Hi Jim;
Several Timeshare vacation condos with athletic facilities & pool have
Tranter ?? brand heat pumps that are specially
designed to reduce humidity in the pool space and reclaim that heat for
the rest of the building.........
Massanutten resort near Harrisonburg VA has a large Tranter..........
see http://tranter.com/dt
also see..... http://www.massresort.com/v.php?pg=3
John R Ross III PE