[Equest-users] Adding Insulation to existing building

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mikef at facilitymgt.com's picture
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The results may be accurate, I have found that over insulating can cause the
cooling load to increase if there are internal loads.

Same way you can get over heated in the winter if you are scooping snow.
Losing energy thru the wall isn't always bad.

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Agreeing with John per usual...

Any building with internal loads will have some break-point where adding
more insulation to the envelope will be detrimental to annual energy
consumption. It's a bigger deal whenever your internals are relatively
high. The behavior you're describing is fundamentally sound.

A good thermos keeps my coffee hot longer (great in the wintertime), but
it's not the ideal container when my coffee is scalding-hot and I want
the contents to cool down.

I've yet to settle on a favorite analogy myself... this just comes to
mind because I need to make a new pot here at work...

NICK CATON, P.E.

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Mike,

We had similar issues in the models and real life which we rectified after our first LEED project. Insulation keeps heat in or cool in your building. Remember not only would it keep cool air in the summer from moving out of a building through the walls, it also keeps that same heat from moving out through the walls in the summer if generated by some piece of equipment that generates large amounts of heat. So it all depends on what you are simulating in the building. Think of your insulation as trapping whatever is happening in the building. Insulation is not always the key. Sometimes using a form of natural ventilation like a louver can help offset some of those differences in temperature and change some of the issues you are having with your electric bill or gas bill depending on what you are using for heating and cooling.

Thanks,

PETER HILLERMANN

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On this topic, I believe the increase in cooling energy will not happen if
you have an economizer. Theory: The insulation keeps the outside temperature
outside. When the economizer run, it will bring the outside temperature
inside, in effect negating the insulation. (Artificially lowering the R
value) So the cooling load should not increase with an economizer.

Am I missing something in my logic?

I have ran some models and the cooling load still went up even though I had
an economizer.

I use Trace so I don't know if e-quest does a better job on this, but in
theory super-insulating shouldn't be a problem if an economizer is present.

One thing that might be happening is that the economizer runs if the certain
conditions allow, but the program does not look at the tradeoff between fan
energy and compressor energy. If the outside air is 58 degrees the
economizer will run and the fan will have to run a lot, but it might take
less energy to run the compressor and the fan would run less.

This leads into a common discussion in my office. If it is more efficient to
produce colder chilled water and reduce the chilled water pump speed, or vary
chilled water temp and keep the chilled water pump speed steady? It is a
multi-variable complex problem. At the level of determining if it is more
efficient to reduce fans, compressors or pumps I think the modeling software
does not have the resolution. If the piping was installed with too many
bends, it may be better to reduce the pump speed. If the compressor was
manufactured just a little out of tolerance it may be better to reduce the
fluid temperature. I don't want to say it is splitting hairs, but it is
getting close.

What is really needed is a smart system that can every try different things
(lowering water temp vs lowering fan speed) and determine which uses less
energy for that building. (but then I fear the buildings would learn too
much and when I adjust the thermostat; H.A.L would say "I'm sorry Dave, I can
not allow you to do that."

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Nick, my analogy when I talk about coffee thermoses is a metal building
with internal loads and varying insulation levels.

Anyway - back to the original poster, this phenomenon could more often be
true where generally it is cooler outside than inside for much of the
year.

To reply to John E.'s subsequent post -- there likely will still be some
hours where it is cooler outside than inside (and the insulation is now a
detriment) even if there is an economizer. Even while the air system is
providing cooling (whether compressor-based or economizer) the walls may
still be conducting energy -- they don't stop based on the HVAC system
status.

Certainly the availability of an economizer can mitigate this problem, but
might not make it go away completely.

But that's why we have energy models -- insulation that looks great at
both design days will still have some hours in the middle where it might
make energy use higher -- run a model and find out what the net is.
(Unless the building is on Mercury...then always add as much as possible.)

David

David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, BEAP, HBDP

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David,

Remind me never to ask you how a thermos works ^_^.

John,

I wrote most of this yesterday and David beat me to the punch... I'm
echoing much of the same from his response but maybe it'll help as
well??

...

Economizers work just as you describe, and are great energy savers when
the OA temps are conducive to comfort... (moving air generally takes
less energy than moving heat + air)

But sometimes it's 110F+ at your RTU in the dead heat of the summer...
In our local climate and I'm sure many others, the brunt of the cooling
season has OA temps well above what we want to supply to achieve comfort
inside. Economizer function isn't terribly helpful in this situation.
With too much insulation, you still run into the same fundamental
problem of "too much heat inside," with no options but to reject the
heat using your cooling equipment outside, even if you do have an
economizer.

Your assertion holds true, that super-insulation can be a non-issue when
you have an economizer, but only for specific times in the year when the
outside conditions are cooperating. Where having an economizer (or not)
may have a dampening effect on the relative impact/problem of
"super-insulating" on an annual basis, it could only remove the issue
for the brunt of the cooling season in a specific sort of cool,
temperate climate.

Even in such a climate, blasting tons of extra air into the building to
"get around" someone's decision to over-insulate the envelope doesn't
seem ideal... every building should have an envelope construction where
"enough is enough."

There is an easy answer to your office's water query: "it depends."
(haha, I'll be here all night!)

There unfortunately isn't a blanket rule here because the answer does
depends on efficiency of the pumps (or fans), which itself is dependent
on the piping (or duct) static being overcome (variability of that comes
into play for some systems), and the efficiency of the cooling equipment
as well - be it a chiller plant or rooftop DX refrigeration...
everything balances out and playing with different supply temps/flow
rates will return a unique answer for every project if you take the time
to play with it.

...

As David concludes, this is indeed why modelers are ultimately such
popular characters =)!

~Nick

NICK CATON, P.E

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Today I received an e-mail with recommendations from the Construction
Engineering Research Laboratory (CERL) and in the recommendations was an R-50
roof (super insulation).

The recommendations were from the building I ran energy models for and my
results showed that too much insulation increases energy use. I hit 'reply
all' to the e-mail and told everyone that I disagree with their research and
explained what my models showed. I received a call from a person from CERL,
he was a little defensive. We agreed with everything but the super
insulation.

I know this will come up in a future meeting and before I go toe-to-toe with
him and tell the guy he is wrong, I want to make sure I am right.

One of his quotes was "We want the insulation so good that you can heat the
room with a single match." I repeatedly told him that it isn't the heating,
it is the cooling. He responded with, "the building shouldn't depend on the
skin to remove heat". I agreed using the skin for cooling isn't the best
method, but it is what happens.

I would agree with him that super insulation would be great IF the system has
the ability to bring in a lot of outside air. The outside air will be 'free
cooling' minus the fan energy. The large amount of outside air in essence
allows you to artificially make the R value zero (just like opening the
windows) (*snicker to myself - it is fan assisted natural ventilation*)

Will the ability to draw in outside air solve the problem of increased
cooling load for a super insulated building?

Also, to those who are still reading - A part of the energy modeler's job is
to understand what is happening then explaining it to others. (Even
architects)
The analogies below all involve this building with massive internal loads.
The architect insisted that you can reduce energy use by optimizing the
orientation. I ran the model, it only made a 0.05% difference.

-I told him "It is like trying to get better gas mileage by turning down the
radio in your car. The skin load is tiny compared to the servers, lights and
computer loads."
-Later I told somebody "It is like trying to make a bull-doze aerodynamic,
this building is a work horse. If it were an empty house I would agree
rotation matters more."
-And "With this much insulation, the orientation doesn't matter as much. If
you on the beach in a speedo it matters. If you are in a parka covered head
to toe, not so much."

John Eurek PE, LEED AP

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The intent of energy modeling is to understand how to optimize a building's efficiency and this clearly shows this is not efficient. Where's the efficiency in installing enough insulation that it drives up the loads of a system. This would negate true optimization and efficiency. Plus, there's a waste of material and cost by adding something that is not needed. I agree that if you are able to optimize the outside air, that would help, but this sounds like a misunderstanding of true energy efficiency. To play off your scenarios of examples: 2(heating and cooling loads) - 1(heating) = 1(cooling) x 3(increased cooling) = 3(the amount of load caused by super insulating) this just isn't efficient.

I'm on your side that super insulating is not an efficient strategy. Increased load, excess materials and extra cost, it doesn't make sense. I'm interested in their reasoning for this strategy being a beneficial one.
Good luck.

Brian Wolfe, CDT, LEED AP BD+C

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Your analogy regarding optimizing the orientation of a "massive internal
load" in a speedo on the beach sounds like the start of a great pickup
line! Ladies of the mailing list - what say you???

...Having duly noted that important point: Mr. "heat a building with a
match" is on shaky ground. That feat would be awesome in a space
station where it's absolute-zero outside all year (IAQ issues aside),
but as you're noting: we live and pay energy bills in a world where we
have to consider the cooling months as well.

challenge is to redirect the discussion and get him to agree on the
isolated issue-at-hand. It's a lot easier to arrive at a targeted
consensus if you avoid unnecessarily "proving" someone wrong. If you
can keep your cool at the table and respectfully disagree and make your
case while your compadre is flustered/defensive and unable/unwilling to
acknowledge to your well-stated points, then you've already won the
argument for anyone else at the table paying attention.

I would (respectfully) disagree at "the building shouldn't depend on the
skin to remove heat" as this is misleading at best. Nobody is trying to
describe an envelope as a heatpump. It's tempting to point out an
envelope can be an extremely efficient "mover of heat" at times, but
that just complicates the discussion with a disagreeable person, so I
wouldn't go there.

I would offer a modified statement to illustrate the point you need to
convey: "the building envelope should not make the heating OR cooling
systems work too hard." Anyone disagreeing on this fundamental point
hasn't taken the time to play with an energy model and more importantly
isn't using logic.

If necessary, you could make the point explicitly clear to everyone at
the table with a parametric study gradually changing only the envelope
constructions incrementally for your project - one of the graphical
output reports shows end-use consumptions for each run side by side if
I'm not mistaken and would work nicely. You'll see a curve take shape
for the total consumption showing positive, diminishing, then negative
returns as you increase the R-value. From this, you can illustrate the
point that every building has a unique "sweet spot" that no minimum
insulation requirement can readily define. Overly-high minimum values
can definitely force you into "super insulation" (I'm starting to like
that term!), which sounds great until you realize it's costing you.

I would follow the trend your model is reporting to you regarding
economizer OA as a cooling means: Economizers will at best only take
the edge off "super-insulation" problems, and won't address the
fundamental dilemma of providing a means of cooling when the OA is too
hot for the task.

A perspective to share for everyone following along: "CERL" is about as
much as should be said regarding the fellow we're discussing publicly on
the list here (and may already be too much). Anonymity affords us the
ability to criticize, correct and openly discuss issues without harming
anyone's credibility or good name. Just because I find a LEED
reviewer's interpretation disagreeable/wrong doesn't mean I really want
that person to end up losing his/her job, for example. I think it's
appropriate to stick with "Mr. match-furnace" or similar until he should
decide to join the conversation of his own free will =).

~Nick

NICK CATON, P.E.

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I did not mean to sound negative towards CERL, I have their web site
bookmarked. They are a great asset for information.

I'm assuming we both made energy models. We likely just used different
inputs (schedules, plug-loads and 1000 other variable) I'm very open to the
idea my model/assumptions are off.

My goal is to find what is most efficient, not to prove somebody wrong. I
did talk to the guy for awhile, he gave me so much useful information that we
didn't dwell on the insulation topic too much.

One thing I learned from him was about the ASHRAE Datacom series. All our
computer rooms are required to be 72 degrees. I have seen studies showing
that a computer room temperature can be higher without endangering the
equipment, the manufactures even state this. I think having ASHRAE also
saying it may help convince owners to allow the computer room temperatures to
be set a little higher to save a lot of energy.

http://www.ashrae.org/publications/page/1900

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Hey Joe!

I may be missing something fundamental here... can anyone set me
straight?

Understanding that "super-insulation" levels slow the passage of heat
into a building in the hottest hours of the day, I can understand
concluding an envelope that doesn't "breathe" thermally doesn't seem so
bad, but what about when interior spaces are hotter than the exterior
during the cooling seasons (i.e. night/morning)? I speculate this
"night-time heatsink" effect likely isn't very much present in humid/hot
climates, but in dry/4-season climates I think the swing seasons and
portions of the summer can be expected to have this potential...

Perhaps these effects in combination cancel each other out in some
climates/cases, but I've found multiple times in the past that there's a
point where adding insulation beyond a certain point can have a
detrimental effect on the net heating/cooling consumptions over the
year. Is this just a result of my limited experience pool?

John: Sorry, I mis-read the tone of your posting! I do know you to be a
respectful/respectable character, but I thought a caution on anonymity
may be beneficial for the community.

~Nick

NICK CATON, P.E.

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Thanks Joe - this is making sense now!

I'll go back to the drawing board and ensure my economizer functions are
doing what they ought to - if I find anything to the contrary I'll
report back =).

~Nick

NICK CATON, P.E.

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