pool heating baseline system

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Can anyone tell me what the baseline pool heating system should be if the
design calls for heat pumps? Per App. G Table G3.1.11 the requirement is
that the energy source be the same, in this case electricity. Can we model
the baseline as electric water heaters or should the system type (heat
pumps) also remain the same in the baseline since electric resistance pool
heating is unconventional? Theres a huge energy savings difference between
the two baselines and was wondering how others have modeled this in terms of
Your opinion and insight is much appreciated.
Thanks in advance for any response.


Mirza Sajjal's picture
Joined: 2011-09-30
Reputation: 0

Isn't the pool heating system considered as a process load for 90.1 since it
has no effect on the overall building design? It would be exactly the same
in the baseline as it is for the proposed case.

...just a thought, although I haven't run into this scenario with any of my
sim projects.


Pasha Korber-Gonzalez's picture
Joined: 2011-09-30
Reputation: 600

Whether or not it's a process load may come down to semantics (I think
you can make a case either way if you reference the 90.1 glossary terms
- see 'process load' and 'process energy'), but I think it's moot in a
broad sense...

If there weren't significant savings to be credited, then I'd probably
try to call it a process load and make each model identical. That would
be the simplest and most time efficient approach.

However, if there are major savings using heatpumps relative to
"conventional" heating means, then even if it is a "process load" I
would pursue modeling them differently as an exceptional calculation.

Oh, and 90.1 does define a baseline efficiency (COP) for heat pump pool
heating equipment: Take a closer look the table in chapter 7. You
might also review the prescriptive pool requirements for other means to
differentiate the proposed design other than in heating efficiency.

Best of luck!



Nick-Caton's picture
Joined: 2011-09-30
Reputation: 805


Thanks for the response.

I would assume pool space conditioning and pool water heating are not
process energy (?) as 90.1 defines process energy as:

"Energy consumed in support of a manufacturing, industrial, or
commercial process other than conditioning spaces and maintaining
comfort and amenities for the occupants of a building."

I did notice the baseline efficiency for heat pump pool heaters in table
7, but was trying to figure out if the system types had to be the same
in baseline and proposed since App. G mentions only energy source:
"Where the energy source is electricity, the heating method shall be
electric resistance."

Considering the savings are significant when using electric resistance
pool heating in the baseline, I want to prevent any issues I may
encounter during the LEED review process since the reviewer may have a
different interpretation/opinion.


Mirza Sajjal2's picture
Joined: 2011-09-30
Reputation: 0

Mirza -

I agree with your logic about the intent of the standard and its definition of non-regulated process. This may be a prejudice that harkens back to LEED v2.1, but if I see a regulation in 90.1 for efficiency, I assume that ASHRAE intended to "regulate" the energy use of that category, and thus it falls on the non-process side of things. While there may be circumstances where "pool heating" might seem more like a process load (eg freeze protection for an outdoor decorative fountain in a cold climate?), it seems like the intent of 90.1 was to regulate pool heating energy usage for a large proportion of typical pool installations.

I think your question re: how to interpret the wording of G3.1.11 is important.
On the face of App G, the standard appears to reward heat pump pool heaters, by allowing them to compare to straight resistance heat in the baseline.
In my admittedly limited experience, I haven't seen an electric resistance pool heater, so I share your reservations about making a false comparison. (then again ... http://www.little-giant.com/water-heating-products/pool-spa-heaters/electric-pool-spa-heaters.html)

If we can't find help for you on this list, an "unofficial interpretation" by the 90.1 Standards Committee might be the way to go.
(Maybe Nick could even slip the question in when he's out at the winter meetings this week ;) ?)

Aaron Dahlstrom , PE, LEED(r) AP

Dahlstrom, Aaron2's picture
Joined: 2011-09-30
Reputation: 4

Well I've given a little extra effort =)... I've flip-flopped a few
times, and now feel confident of the following:

1. This query boils down to this paraphrase: Does Table G3.1.11
(Service Hot-Water Systems) or G3.1.12 (Receptacle and other loads)
apply to pool water heating?

2. Definitions Section 3: service water heating - heating water
for domestic or commercial purposes other than space heating and process

3. We can strike out space heating, so we can conclude pool water
heating is either a process energy OR service water heating... it cannot
be both.


a. Per the definition Mirza transcribed below, pool heating is
pretty clearly "...maintaining comfort and amenities for the occupants
of a building."

b. So (clearly) pool heating energy simply [IS/IS NOT] a process
energy, and therefore [IS/IS NOT] a process load. Read that whole
definition from both angles, and you can see this definition was not
crafted by an English teacher! This doesn't make anyone's life easier,
but I maintain this definition can be read either way.

5. Where the glossary fails us, we have to look elsewhere.
Fortunately, this seems much more clear: Pool water heating must be a
form of service water heating, otherwise it wouldn't be explicitly
addressed multiples times under Section 7 "SERVICE WATER HEATING."
Clever eh =)?

In conclusion, within the context of "do I model pool energy under the
requirements of Table G3.1.11 or G3.1.12?" The answer is clearly
G3.1.11 because it is a variety of service hot-water system. To extend
the argument, pool water heating is NOT a process energy and so should
NOT be modeled as such (equally in both models), even if it would save
time (bummer!). I might suggest documenting the pool heating
consumptions/demands separately from domestic water heating consumption
in the LEED template.

Table G3.1.11 is agreeably crystal-clear in requiring you to use
straight electric resistance heating for the baseline pool heating

If LEED was an episode of "America's Next Top Model," and the 90.1-2007
steering committee were the judges, heat-pump pool heating strategies
would be rated "Platinum-Sexy."

I might also watch more TV... kinda sad... ^_^



Nick-Caton's picture
Joined: 2011-09-30
Reputation: 805

It's unfortunate that I've caught onto this discussion late, as it is right in the middle of a current tax rebate modeling project I'm working on.

My query (more of a confirmation really) is how are you all handling the latent load from the pool? I've input it as a process load, 100% latent.

How do you account for the thermal mass of the pool water? Latent heat is handled above. What about sensible effects? I've entered the pool water in the "Contents" tab covering 80% of the floor area with 500 lb/ft2.

Also, what is the group's read on the space conditions to be maintained in the proposed vs. budget cases? I've modeled them identical in both: 85 deg F, 55% RH per ASHRAE recommendations. It doesn't show up on any building meters, so wouldn't be double counted as service water as discussed below and misc equip.

Finally, what system is appropriate for the budget case model? I've just let the compliance tool select the system, and it chose PIU - the same as the none pool zones in the building.

Edward M. Allen, PE, CEM

Edward Allen's picture
Joined: 2011-09-30
Reputation: 0

Classification: UNCLASSIFIED
Caveats: NONE

'Pool heating' conditions the pool space for the comfort of the occupants.
(Ever jumped into an unheated pool?) So I would say it is not a process

"Energy consumed in support of a manufacturing, industrial, or commercial
process other than conditioning spaces and maintaining comfort and amenities
for the occupants of a building."

It would fall under that same arena as water heating for showers.

Classification: UNCLASSIFIED
Caveats: NONE

Jeurek's picture
Joined: 2010-10-07
Reputation: 0

John and Edward - thanks very much for your input!

Up to this point I've been trying to address the problem with the
assumption the pool is not part of an enclosed/conditioned space. I'm
pretty sure my position below stands strong in that case.

I'd reiterate: I do feel you can make a case either way regarding
whether energy spent heating pool water is or is not a process. Either
you treat this heating energy as a service water heating system, or as a
process load. In the case of an enclosed/conditioned space, you could
use either approach, but either way I agree one should define and assign
the pool's thermal mass and the heating system's incident internal
heating load (with the correct latent/sensible fractions) to the
corresponding space.

If the actual design for an enclosed space containing a heated pool
should have air conditioning (cooling , heating and/or dehumidification)
in addition to pool water heating system, it seems to me intuitive to
model the actual HVAC system(s) in the proposed and the appropriate
Appendix G system in the baseline model (likely using the same baseline
system used elsewhere in the building). The pool's thermal
loads/massing incident on the space would then be present for such
system(s) to react to as required.

Edward: Conditions maintained (cooling setpoints/heating
setpoints/humidity control parameters as they apply) must be maintained
identical in both baseline and proposed models when you're discussing a
conditioned space - you're right on, and you can find support within
Table G3.1 to back you up if needed. The notion to sub-meter the pool
heating loads in a separate run for LEED reporting is only a suggestion
on my part - disregard if you don't feel it's necessary.

Again, I haven't actually completed a pool model under LEED review, but
I think everyone ought to have some flexibility to model pool heating
either as a process load or as a service water heating system. The
"most right" decision would depend on the specific circumstances of the
pool's design, but I think if I were in a reviewer's shoes I'd accept
either approach/interpretation if well-explained & documented.



Nick-Caton's picture
Joined: 2011-09-30
Reputation: 805

similar to the camera reset function not working, or editing the .pd2
file to change viewing angle & etc, i am now having a problem viewing
the 3d representations.

see attached screen caps.

i think this might be driver related as all projects i have tried
opening (3.61, 3.63, and 3.64) are displaying similar results but am
still trying to hunt down exactly what is going on.

has anyone seen this type of 3d representation (in equest) before when
previous 3d views were displaying "properly?"

Patrick J. O'Leary, Jr.'s picture
Joined: 2011-09-30
Reputation: 200

turning of 3d acceleration did the trick. not sure why it was working
before but ... turning off my 3d acceleration fixed the problem.

Patrick J. O'Leary, Jr.'s picture
Joined: 2011-09-30
Reputation: 200

An extra nuance/correction to the discussion:

I just noticed this - in the case of an enclosed & air-conditioned space
containing a pool of any sort, one should note that natatoriums are
specifically mentioned in G.3.1.1 exception b. This may require you to
use Baseline System 3 or 4 for the air-conditioning side.

Best not to assume it should match the baseline system used elsewhere in
the building.


Nick-Caton's picture
Joined: 2011-09-30
Reputation: 805