I am attempting to establish a few alternatives compared to an ASHRAE 90.1
Wall construction. This much seems pretty straightforward with the only
change between alternatives being a different construction applied to the
exterior above grade walls. All alternatives are modeled as delayed and
with layered materials. The wall from outside to inside is stucco(finish)
R0.08 + Cont. Insulation R-VARIES + Ext sheathing R0.56 +
Framing/Insulation R-VARIES* + Int. Sheating R0.56 (air films do not
change, infiltration does not change, etc.)
*framing 16" Mtl OC taken into account
<<< I should mention the building is very much internal load dominant as an
education building with a lot of laboratory space >>>
The problem described below has been input into eQuest using material
properties for all continuous insulation and a representative R-value for
framing/insulation.
BASELINE - 90.1 - R6* + 7.5 ci na
ALT1 - only ext insulation R0.9 + 12 ci -8% savings (% energy under EUI -
kBtu/sf/yr)
ALT2 - improved ext insulation R6* + 12 ci +1% savings
ALT3 - improved cavity insulation R7.1* + 7.5 ci +1% savings
ALT4 - all insulation improved R7.1* + 12 ci +2% savings
I guess the question really is; does the issue lie within the vav systems
or the envelope or both?
As a novice, I greatly appreciate any help.
I guess your "issue" or question relates to the amount of savings so you're surprised how little savings you get increasing your wall insulation thickness?
Don't be surprised since you mentioned is internal load dominated plus there are other factors like climate, orientation and wall area that play a role so without the building description I don't see any issue with the results you're showing.
Best,n
Nikola Kravik, LEED AP
Sorry that I wasn't more clear, but I am questioning the major decrease in
energy performance between the baseline and the ALT 1 of 8%. The U-value
difference is about 0.003, so I would expect a much smaller decrease around
0-0.5%. THe problem I am having is with the exterior only application of
ALT 1 vs exterior and cavity fill insulation in the baseline.
ie. 90.1 Baseline is R13 fill + R7.5 continuous insulation
ALT 1 is R0 fill + R12 continuous insulation. (very common installation)
Thanks,
nic
Nicholas Fonner
Energy Modeling Group
Henneman Engineering, Inc. | energy. focused.
1605 South State Street, Champaign, IL 61820
V 217.359.1514 | F 217.359.9354 | C
www.henneman.com | nfonner@henneman.com
Again thank you for the insight. I have attached heat transfer graphs from
eQuest that demonstrate (I believe) what you were getting at between the
different constructions' rates. As for the utility rates, I have yet to
explore anything beyond a simple structure so peak demand shaving could
come into play here. THe peak is showing something far better than the EUI
for that run in particular, but the HVAC energy in both kWh and Total Mbtu
are even worse at ~ 18% under the baseline.
Another monkey wrench shows up when I increase the thickness of the
continuous insulation with an improved R-Value of 18 ( > 12.) Again the
results show a decrease in savings of 1% worse than ALT 1.
Nicholas Fonner
Energy Modeling Group
Henneman Engineering, Inc. | energy. focused.
1605 South State Street, Champaign, IL 61820
V 217.359.1514 | F 217.359.9354 | C
www.henneman.com | nfonner@henneman.com
It is under the Building Shell Tab. Before you can access it, I believe
you must run a simulation. You first highlight the particular
"Construction" (does not work with Layers or Materials) on the component
tree panel. Then, you select summary from the tabs over the model window.
This works for HVAC systems, Water-side systems, etc. It very useful to
verify design flows, OA, and in this case construction summaries.
best,
nic
Nicholas Fonner
Energy Modeling Group
Henneman Engineering, Inc. | energy. focused.
1605 South State Street, Champaign, IL 61820
V 217.359.1514 | F 217.359.9354 | C
www.henneman.com | nfonner@henneman.com