LEED-NC v2.1 Energy &
Atmosphere Credit 1 Final Submittal
by Donald W. Cott, PhD,
PE, LEED AP
Thermal Systems
Engineering, North Pole, Alaska
don.cott@ak.net, / http://home.gci.net/~tse
October 2007
PURPOSE
This document constitutes the Final Summary Submittal
for an application for Leadership in Energy and Environmental Design (LEED)
certification under the ground rules of the United States Green Building
Council (USGBC, www.usgbc.org) in
accordance with the LEED New Construction Version 2.1 Reference Guide (LEED-NC 2.1). It summarizes the supporting documentation in
pursuit of credit for Energy & Atmospheric Credit 1 (EAc1).
This submission is in behalf of the Cold Climate
Housing Research Center (CCHRC), of Fairbanks, Alaska, for the new building
called the Research & Test Facility (RTF) under construction at 1000
Fairbanks Ave, Fairbanks, Alaska 99708; on the campus of the University of
Alaska Fairbanks (UAF).
HISTORY
This document and the supporting documentation was
first submitted in Nov 2006 in an initial submittal version. Since this is the first LEED application this
author has performed, an assortment of critiques were noted by the LEED Review
Team, and communicated to CCHRC on 20 Aug 2007, with a 30-day deadline for
response. The critique was communicated
to me on 28 Aug 2007, and this document represents a part-time effort through
the intervening two months. My thanks for
the additional month of grace after I fell on my face trying to make the first
deadline. All the critiques are
addressed, although the result is not optimized. This Summary and all the supporting
documentation will be posted on the web at http://home.gci.net/~tse
within the next few hours. Many of the
links are local, and so will only work with the on-line version.
ENERGY MODEL
The supporting documentation constitutes an Energy
Model of the RTF, using the Department of Energy (DOE) supported computer code
DOE-2.2, version 2.2-44e4; fronted by eQUEST version 3.61 build 5360. This useful software was developed by James
J. Hirsch & Associates of Camarillo, CA (http://www.energydesignresources.com/). If the reader desires to execute and
experiment with the RTF energy model, the eQUEST/DOE-2 software and
documentation is available as a free download from http://www.doe2.com/eQUEST/. In that event the input files for the LEED
Comparison are: 118-DEC.inp.txt, 118-DEC.pd2.txt, 118-DEC.SIM.txt,
120-ECB.SIM.txt, 120-ECB.pd2.txt,
120-ECB.inp.txt.
The .txt is appended to facilitate handling over the Internet, they
should be removed for the files to be recognized by eQUEST and DOE-2. The weather file used for these simulations
is FAIRBAAK.bin, the TMY2 file for Fairbanks, Alaska, downloaded from the
eQUEST web site in September of 2007. All the required input files for the RTF
energy model are bundled herein, or if they have been separated, may be
downloaded for free from Thermal Systems Engineering at http://home.gci.net/~tse/.
The electricity rates used for all computations
are those charged by the Golden Valley Electric Association, Fairbanks, Alaska,
for General Service 2(1). They are
broken down into block, demand, tax, fuel, & minimum charges for each month
in “REPORT- ES-E Summary of Utility-Rate”, near the end of each of the .SIM
files (118-DEC.SIM.txt & 120-ECB.SIM.txt).
The fuel oil charges were highly volatile during the construction
period, and suppliers wouldn’t even venture a guess beyond “today.” It was rather arbitrarily assumed that the
delivered price would be $2.50/gal the first year, with a heating value of
138,000 Btu/gal, independent of any demand charges, basic service charges,
taxes, ratchets, etc.
“REAL” VS. “LEED” ENERGY MODEL
The USGBC LEED development team had the formidable
task of developing a methodology that would allow comparison of actual designs
(Design Energy Cost DEC case) and minimum standard compliant designs (Energy
Cost Budget ECB case) for a remarkably wide range of climactic conditions, but
most especially for subtropical construction emphasizing cooling for occupant
comfort. People in subtropical zones are
very lightly dressed, and wish to be comfortable in light clothing while they
work inside the subject buildings. Hence
the rather narrow comfort criterion of Table 3 LEED NC 2.1 pg 140 is
required. People in Fairbanks, Alaska,
just don’t dress that way, and would be complaining about the heat in the above
referenced comfort range (65F-75F). In
Fairbanks winter conditions everyone wears heavily insulated clothing, and long
johns would be insufferable for occupants in the required comfort range. So for the LEED comparison autosizing of HVAC
systems is used in eQUEST, and the controls are set to maintain the required
“Comfort Criteria” (CC). Requirements
are as follows “To conduct the simulation, an analog mechanical system must be
created. The simulation must be a
thermodynamically similar model that can be used to simulate passive
conditioning schemes.” (LEED NC 2.1 pg
141) Further, “Both the ECB Method and
the LEED EMP [slightly modified DEC] assume that even if a heating or cooling
system is not installed at the time of construction, future occupants might
elect to use energy-consuming temporary measures for conditioning needs. Special cases of absent heating or cooling
systems require the modeling of a default system to establish the ECB.” (ibid,
pp 141-142)
The actual RTF design has
no cooling system other than opening windows during office hours. But the LEED DEC and ECB cases both use
identical (but differently sized) DX cooling systems for comparison
purposes. The actual RTF design allows a
wider variation in temperature. The
actual RTF simulation file is included as Real-RTF.SIM.txt,
and the corresponding input files are Real-RTF.pd2.txt
and Real-RTF.inp.txt. This simulation uses a Sherman-Grimsrud
algorithm to relate outside wind direction and magnitude to ventilation with
open windows (“Energy Simulation Training for Design & Construction
Professionals”, Sept 2004, James J. Hirsch & Associates, pg 16). In this simulation the office basement zone
gets quite warm due to the always operating 6 KW Information Technology (IT)
room. There is actually an auxiliary
ventilation system for that room, but that additional system isn’t yet modeled
in the actual RTF simulation. The
actual-RTF simulation is included only for academic interest, since it isn’t
required for the LEED comparison. It is
interesting that the projected annual operating energy cost of the actual-RTF
is $23,600 (Report ES-D of Real-RTF.SIM.txt); compared to $25,953 for
the DEC’’ case and $35,041 for the ECB’’ case in Table 1 below. So natural ventilation saves about $2,353
annually. Note that the actual-RTF and
DEC cases are identical in terms of envelope components. This latest set of runs actually are
different in the treatment of the NFS fill below the building, but that should
be negligible with 4” of insulation under the slab. The main difference is natural
ventilation. The much higher cost of
utilities in the ECB’’ case is because of the much reduced “standard”
insulation in the envelope components.
So above standard insulation saves about $9,088 annually. No estimate has been made of the increased
capital cost of the actual RTF vs. the “standard” RTF, most of the really high
resistance components were donated by various venders.
DEC/ECB COMPARISON
The LEED EAc1 requirement is that the proposed
building be modeled, and the actual design, the Design Energy Cost (DEC) model,
be compared to the minimum-cost standard prescriptive design as prescribed by
the American Society of Heating, Refrigerating and Air-Conditioning Engineers
(ASHRAE, http://www.ashrae.org/) Energy
Standard for Buildings Except Low-Rise Residential Buildings Standard 90.1-1999
(ASHRAE 90.1-1999). ASHRAE refers to the
minimum-standard prescribed design as the Energy Cost Budget (ECB) design. For Fairbanks, Alaska, the appropriate
prescribed building envelope requirements are in Table B-24 of ASHRAE 90.1-1999
pg 114; as specified in Table D-1, pg 126 of the same reference.
Table 1a summarizes the energy distribution in the
building for the DEC case, as follows:
Table 1a. DEC/BEPU
excerpt from 118-DEC.SIM.txt.
118 - LEED EAc1 Final Submittal Fan Tuning HRVs DEC Sim DOE-2.2-44e4 9/24/2007
2:02:57 BDL RUN 1
Modeler: Don Cott; don.cott@ak.net; http://home.gci.net/~tse/
REPORT- BEPU Building Utility
Performance
WEATHER FILE- Fairbanks AK TMY2
---------------------------------------------------------------------------------------------------------------------------------
TASK MISC
SPACE SPACE HEAT
PUMPS VENT REFRIG
HT PUMP DOMEST EXT
LIGHTS LIGHTS
EQUIP HEATING COOLING
REJECT & AUX FANS
DISPLAY SUPPLEM HOT WTR
USAGE TOTAL
------- -------
------- ------- -------
------- ------- -------
------- ------- -------
------- --------
EM1
ELECTRICITY
KWH 21113. 1446.
82059. 0. 20252.
0. 6811. 12349.
0. 0. 1374.
0. 145404.
FM1
FUEL-OIL
GAL 0. 0.
0. 0. 0.
0. 0. 0.
0. 0. 0.
0. 0.
BFOM FUEL-OIL
GAL 0. 0.
0. 219. 0.
0. 0. 0.
0. 0. 0.
0. 219.
GFOM FUEL-OIL
GAL 0. 0.
0. 1092. 0.
0. 0. 0.
0. 0. 0.
0. 1092.
TFOM FUEL-OIL
GAL 0. 0.
0. 746. 0.
0. 0. 0.
0. 0. 0.
0. 746.
TOTAL ELECTRICITY 145404. KWH 10.673 KWH /SQFT-YR GROSS-AREA 10.673 KWH /SQFT-YR NET-AREA
TOTAL FUEL-OIL 2057.
GAL 0.151 GAL
/SQFT-YR GROSS-AREA 0.151 GAL
/SQFT-YR NET-AREA
PERCENT OF HOURS ANY SYSTEM ZONE
OUTSIDE OF THROTTLING RANGE = 4.1
PERCENT OF HOURS ANY PLANT LOAD NOT
SATISFIED = 0.0
NOTE: ENERGY IS APPORTIONED HOURLY TO ALL END-USE
CATEGORIES.
Table 1b summarizes the energy distribution in the
building for the ECB case, as follows:
Table 1b. ECB/BEPU
excerpt from 120-ECB.SIM.txt.
120 - LEED
EAc1 Final Submittal
PSZ/Furnace/NFS/Eff Mods to ECB Sim
DOE-2.2-44e4 10/01/2007 6:20:06
BDL RUN 1
Modeler: Don
Cott; don.cott@ak.net;
http://home.gci.net/~tse/
REPORT-
BEPU Building Utility Performance
WEATHER FILE- Fairbanks AK TMY2
---------------------------------------------------------------------------------------------------------------------------------
TASK MISC
SPACE SPACE HEAT
PUMPS VENT REFRIG
HT PUMP DOMEST EXT
LIGHTS LIGHTS
EQUIP HEATING COOLING
REJECT & AUX FANS
DISPLAY SUPPLEM HOT WTR
USAGE TOTAL
------- -------
------- ------- -------
------- ------- -------
------- ------- -------
------- --------
EM1 ELECTRICITY
KWH
27894. 1446. 82059.
0. 7734. 0.
2890. 5840. 0.
0. 1377. 0.
129240.
FM1 FUEL-OIL
GAL 0. 0.
0. 267. 0.
0. 49. 0.
0. 0. 0.
0. 316.
BFOM
FUEL-OIL
GAL 0. 0.
0. 845. 0.
0. 81. 0.
0. 0. 0.
0. 926.
GFOM
FUEL-OIL
GAL 0. 0.
0. 4574. 0.
0. 216. 0.
0. 0. 0.
0. 4790.
TFOM
FUEL-OIL
GAL 0. 0.
0. 401. 0.
0. 48. 0.
0. 0. 0.
0. 450.
TOTAL ELECTRICITY 129240. KWH 9.486 KWH /SQFT-YR GROSS-AREA 9.486 KWH /SQFT-YR NET-AREA
TOTAL FUEL-OIL 6482.
GAL 0.476 GAL
/SQFT-YR GROSS-AREA 0.476 GAL
/SQFT-YR NET-AREA
PERCENT OF HOURS ANY SYSTEM ZONE
OUTSIDE OF THROTTLING RANGE = 3.3
PERCENT OF HOURS ANY PLANT LOAD NOT
SATISFIED = 0.0
NOTE: ENERGY IS APPORTIONED HOURLY TO ALL END-USE
CATEGORIES.
Oil gallons and electric KWH are combined for the
above two tables into present value US$ by Table ES-D in the above referenced
data files, as follows for the DEC case:
Table 1c. DEC/ES-D
excerpt from 118-DEC.SIM.txt.
118 - LEED EAc1 Final Submittal Fan Tuning HRVs DEC Sim DOE-2.2-44e4 9/24/2007
2:02:57 BDL RUN 1
Modeler: Don Cott;
don.cott@ak.net;
http://home.gci.net/~tse/
REPORT- ES-D Energy Cost Summary WEATHER
FILE- Fairbanks AK TMY2
---------------------------------------------------------------------------------------------------------------------------------
METERED TOTAL VIRTUAL
ENERGY CHARGE RATE
RATE USED
UTILITY-RATE RESOURCE METERS UNITS/YR ($) ($/UNIT)
ALL YEAR?
-------------------------------- ---------------- -----------
------------------- ---------- ----------
---------
GVEA Gen Serv 2(1) ELECTRICITY EM1 145404. KWH 20811. 0.1431 YES
Fuel Oil Rate FUEL-OIL FM1
BFOM 2057. GAL
5142. 2.5000 YES
GFOM TFOM
==========
25953.
ENERGY COST/GROSS BLDG AREA:
1.90
ENERGY COST/NET BLDG AREA:
1.90
And for the ECB case:
Table 1d. ECB/ES-D
excerpt from 120-ECB.SIM.txt.
120 - LEED
EAc1 Final Submittal
PSZ/Furnace/NFS/Eff Mods to ECB Sim
DOE-2.2-44e4 10/01/2007 6:20:06
BDL RUN 1
Modeler:
Don Cott; don.cott@ak.net;
http://home.gci.net/~tse/
REPORT-
ES-D Energy Cost Summary
WEATHER FILE- Fairbanks AK TMY2
---------------------------------------------------------------------------------------------------------------------------------
METERED TOTAL VIRTUAL
ENERGY CHARGE RATE
RATE USED
UTILITY-RATE RESOURCE METERS UNITS/YR ($) ($/UNIT)
ALL YEAR?
-------------------------------- ---------------- -----------
------------------- ---------- ----------
---------
GVEA Gen
Serv 2(1) ELECTRICITY EM1 129240. KWH 18835. 0.1457 YES
Fuel Oil
Rate FUEL-OIL FM1
BFOM 6482. GAL
16205. 2.5000 YES
GFOM TFOM
==========
35041.
ENERGY COST/GROSS BLDG
AREA: 2.57
For DEC vs. ECB comparison purposes, the data from
the above Tables 1a – 1d are transferred into Table 1e for further comparison
and adjustment:
|
Table 1e. Adjusting eQUEST / DOE-2 Output to LEED NC
2.1 Requirements. |
|||
|
Annual Energy End Use |
ECB |
DEC |
Comments |
|
Ceiling
Lights (kWh) |
27,894 |
21,113 |
BEPU1 (difference is daylighting
controls in DEC but not ECB) |
|
Task
Lighting (kWh) |
1,446 |
1,446 |
BEPU1 |
|
Plug
& Process Load (kWh) |
82,059 |
82,059 |
LEED NC 2.1 Table 3 Plug Load from BEPU1,
includes Information Technology (IT) Room Load of 6 kW continuous to be
removed from both ECB & DEC below |
|
Space
Cooling (kWh) |
7,734 |
20,252 |
BEPU1 (more cooling required for DEC
because it’s better insulation holds the solar heat better than the ECB, both
of which receive about the same solar heat despite the longer overhangs on
the DEC |
|
Pumps
& Auxiliary Equipment (kWh) |
2,890 |
6,811 |
BEPU1 (comparing hydronic pumping
required in DEC to combustion furnace unit heaters in each zone for ECB,
actual ECB would be a central furnace with lots of duct losses, not included
here) |
|
Ventilation
& Unit Heater Fans (kWh) |
5,840 |
12,349 |
BEPU1 (HRV fan losses for DEC, no
HRV’s in ECB) |
|
Domestic
Hot Water (kWh) |
1,377 |
1,374 |
BEPU1 (slight difference due to less
Hot Water system heat loss to slightly warmer average air temperature in DEC) |
|
Total
Annual Electrical Load (kWh) |
129,240 |
145,404 |
BEPU1 (this still contains the 6 kW
continuous IT room load, which is non-regulated, LEED NC 2.1 pg 146) |
|
IT
Room Load (6 kW continuous non-regulated) |
-52,596 |
-52,596 |
(6 kW)(24 hr/day)(365.25 day) = 52,596 kWh |
|
|
ECB’ |
DEC’ |
|
|
Total
Regulated Annual Building Electrical Load (kWh) |
76,644 |
92,808 |
(prime means non-regulated load subtracted out,
LEED NC 2.1 pg 145) |
|
Regulated
Annual Electricity Cost |
$11,167 |
$13,281 |
Multiplying the Regulated Electrical Load above
by the rates of $.1457/KWH for the ECB and $.1431/KWH for the DEC (main
reason for rate difference is that the base service charge is spread over
more KWH for the DEC) |
|
PV
Contribution for DEC but not ECB |
-$0 |
-$19242 |
=$1924, 4.7 for 2-axis tracker [Fairbanks
weather & insolation per WBAN #26411 (Solar
Data)], 16% panel eff, 77% inverter eff, no on-site battery storage at
present - net metering with GVEA. |
|
Adjusted
Regulated Annual Electricity Cost |
$11,167 |
$11,357 |
|
|
Space
Heating Fuel Oil (gal) |
6,482 |
2,057 |
BEPU1, Tables 1a & 1b. |
|
Solar
heat for DEC but not ECB (gal oil equiv.) |
-0 |
-235 |
Three south-facing solar/hydronic heating panels
angled back at about 50º on Atrium roof including piping & pumping losses
in 85% efficiency, 3.4 from Fairbanks weather table, WBAN #26411 (Solar
Data), latitude-15º from horizontal, south azimuth. 3 |
|
|
ECB’ |
DEC’’ |
(double-prime means renewable energy
contribution included) |
|
Space
Heating Fuel Oil corrected by Solar Heat (gal) |
6,482 |
1,822 |
Solar-Adjusted
heating oil equivalent |
|
Space
Heating Fuel Oil adjusted Cost |
$16,205 |
$4,555 |
Solar-Adjusted Heating Oil Cost, (gals above x
$2.50/gal) |
|
Total
Annual Energy Cost |
$27,372 |
$15,912 |
Adjusted Regulated Electricity Cost + Solar-Adjusted
Heating Oil Cost |
|
% Savings |
42% |
Equation 1, LEED NC 2.1 pg 145 |
|
|
EAc1 LEED Points |
6 |
LEED NC 2.1 pg 133 |
|
|
1 BEPU Table from DEC & ECB runs reproduced
herein as Tables 1a & 1b. 2Unknown why this value is about $300
above that calculated by Greg Egan in EAc2.
The efficiencies came from him.
As a full-time solar specialist, he may know something this
generalized modeler doesn’t regarding what GVEA charges vs. what it pays for
net metering. See http://www.gvea.com/alternative-energy/snap/producer.php
for an overload of feel-good PR and Obfuscatory Legalese, but no “SNAP No. 1
– Producer Schedule”, which supposedly contains the formula for calculating
the payments or offsets to producers.
It is herein assumed that only the 77% conversion/storage/offset
efficiency is applicable to PV power produced on-site. The % of PV produced energy is presently
low enough that plenty of other options exist for re-directing the PV power
without trading it to GVEA, if justified by developing economics. 3One panel is actually domestic water, but
that heat goes to the building space heat through leakage from the propylene
glycol to potable water heat exchanger, hot water plumbing and the inside
septic tank in the atrium basement.
The 85% assumed efficiency is speculative and subject to experimental
verification. It assumes the
solar-thermal panels will be used for the low-temperature preheat only of the
entire hydronic flow (~95F), with the higher-temperature heat supplied by the
oil-fired boilers. |
|||
where the tabulated
performance data for the ECB and DEC cases is taken from Tables 1a – 1d. Note each of these files prints out from 1600
to 1900 pages long, so it isn’t trivial for a new user to find the desired data. Search on the reference in the Comments
column above (BEPU or ES-D) to find the referenced datum. If you have downloaded eQUEST, then drop the
.txt and the SIM Viewer bundled with eQUEST will display the lengthy tabular
output in a formatted & organized manner.
Since the preliminary submission of this document in 2006,
four 2-axis tracking solar panels are being added as illustrated in Figure 1,
and three fixed solar thermal panels are being added to the Atrium Roof. Note this is a retouched photograph. The masts are as shown, but the panels were
added for PR purposes. I visited today
(10/8/07) and the first panel was actually being attached. All are being assembled in the North Lab.
On the Atrium roof two of the three panels are in
place, but not yet tied into the hydronic system. The base for the third is in place, and I
found the mirrors in the North Lab. So
it is actually coming together, and the calculations in Table 1e utilize the
best estimates we have at present for expected performance.
In addition to displaying the required ECB and DEC
end-use energy data, Table 1e adjusts the data to correct for process loads not
90.1-regulated, and auxiliary power generation, as required by LEED-NC 2.1 pg
145. In this case the computer rack
Information Technology (IT) Room load of 6 KW-continuous released as heat in
the Office Basement Zone is adjusted out of both the ECB and DEC columns.
Once IT room, solar-PV, and active-solar-thermal
adjustments are made, the bottom line in Table 1e is an Energy Savings of 42%
for the DEC over the ECB. This
translates to 6 of a possible 10 points claimed under EAC1 of LEED-NC 2.1, pg
133. In accordance with this the project
Mechanical Engineer, Donald W. Cott, hereby attests to the accuracy of this
comparison, as follows:
The required Energy Cost Budget Compliance Report
from ASHRAE 90.1-1999 User’s Manual is as follows:
Energy Cost Budget (ECB)
Compliance Report Page 1
|
Project
Name: Cold Climate Housing Research Center Research and Test Facility |
|
|
Project Address: 1000 Fairbanks St. |
Date: November 6, 2006 |
|
Designer of Record: N. C. Porter, Jr. |
Telephone: 907-562-2283 |
|
Contact Person: D. W. Cott |
Telephone: 907-488-0873 |
|
City: Fairbanks, AK |
Principle Heating Source: Fossil Fuel |
|
Weather
Data: Fairbanks, AK (FAIRBAAK.bin) |
|
|
Energy Code: ASHRAE 90.1-1999 |
Space
Summary
|
Building
Use |
Conditioned
Area (sf) |
Unconditioned
(sf) |
Total (sf) |
|
1. Office |
4032 |
0 |
4032 |
|
2. Laboratory |
4608 |
0 |
4608 |
|
3. Mechanical/Electrical/Utility |
2688 |
0 |
2688 |
|
4. Hallway & Elevator Lobby |
2128 |
0 |
2128 |
|
5. Green Roof |
0 |
4608 |
4608 |
|
6. Atrium |
672 |
0 |
672 |
|
7. Indoor Stairwell |
335 |
0 |
335 |
|
Totals: |
14,463 |
4,608 |
19,071 |
Advisory
Messages
|
|
Proposed Building Design |
Budget Building |
Difference (Proposed – Budget) |
|
Percent
of hours system load out of throttling range (see Tables 1a & 1b, note
throttling range was the default value of 2F in all cases) |
4.1% |
3.3% |
0.8% |
|
Percent
of hours plant load not met (see Tables 1a & 1b) |
0% |
0% |
0% |
|
Number
of Warnings (condensation in all HRVs, no HRVs for ECB, no other
warnings. In Interior Alaska all HRVs
need to be run in a defrost cycling mode) |
9 |
0 |
9 |
|
Number
of Errors |
0 |
0 |
0 |
|
Number
of Defaults Overridden (10 here mostly severe climate & solar heating
related, i.e. zone or system HVAC sizing factors) |
Approx 10 |
Same 10 |
0 |
|
Description
of differences between the budget building and proposed design not documented
on other forms: Attached (See Simulation Validation section of EAc1 Summary) |
|||
Compliance
Result
The design detailed in the above referenced plans
complies with the mandatory requirements of ASHRAE 90.1-1999 and the Design
Energy Cost does not exceed the Energy Cost Budget. Therefore, this design DOES COMPLY with the
ASHRAE 90.1-1999 ECB Compliance Methodology.
Individual certifying authenticity of this data
provided in this analysis:
|
Signature:
|
Title: Mechanical Engineer (AK PE# M10358) |
ENERGY MODEL
The building itself is described on the CCHRC web
page (http://www.cchrc.org/). Check that for beautiful architectural
renderings and photographs. Here what
you get is the energy model, beautiful only to mechanical engineers. 3-D representations of the eQUEST building
envelope model are as follows:
Figure 2. RTF Envelope Model as viewed from the
Southeast.
as viewed from the southeast. The near wing is the Office Wing, consisting
of two above-grade stories and a full basement.
The black structure at the left is a tree line, which is actually considerably
taller than shown, but during the shoulder and winter seasons, when it would
shade the south windows, the birch trees are bare of foliage. The remaining conifer trees were eyeballed to
shade at 100% to only about an 11’ height above grade. In the summer when the birch foliage provides
near 100% shade to much higher, the sun angle is such that the still shadow
falls short of the S Lab Wing windows.
In winter the noontime sun is only about 1.5º above the horizon (~65º N
Latitude), and some solar blockage occurs to the lowest S Lab windows. This is accounted for in the eQUEST model for
each hour of the year.
Behind the Office Wing the Elevator Lobby stack
and Elevator Shaft are shown. The actual
roofs for all the building components except the Laboratory Wings consists of
wood trusses and cold 3tab-shingle roofs, which are unimportant from a heat
transfer standpoint, and so are non-existent in the energy model. These roofs are only thermally represented as
a 2’ deep tubs of fluff, as shown.
The laboratory end of the building is better shown
in Figure 3, as follows:
Figure 3. Building Envelope Model as viewed from the
Southwest.
From Figure 3 the high-bay laboratory end the
North and South Lab Wings are evident, connected to the Office Wing by the Utility
Spine of the building. The spine
consists of a full basement, containing sewage treatment and flush water
recycle equipment, a ground floor which is mainly a connecting hallway among
the Office, Lab, and Mechanical Rooms in the N Lab, and a nearly 2-story
Atrium, connecting to offices that may gradually evolve into a Tool Crib and
Instrument Calibration Lab in the future.
The flat roofs of both labs are green roofs, insulated with 12” of EPS
foam above the roof deck, and 4” of soil above that. The green roofs are accessed from the 4th
floor elevator lobby, which offers a sunny view through the tree tops (to be)
in the Atrium.
The laboratory roofs are snow-covered during all
but the summer. The insulating value of
the snow is ignored in the model, although the radiant properties are that of
snow when the weather model indicates snow coverage.
Solar heating and daylighting are important in the
South Lab, the Atrium, the Top and Ground Floor of the Office Wing. Limited daylighting and solar heating are
provided by the skylight on the N Lab roof.
All are accounted for in the model.
The DEC monthly end-use energy breakdown, from the
information contained in the DOE-2 output file RTF-DEC.SIM.txt,
is displayed graphically from eQUEST as follows in Figure 4:
Figure
4. Monthly breakdown of
RTF DEC energy by end-use. Red bars are
fuel oil, not gas, where the heating value is 138,000 Btu/gal. Blue is
DX-cooling, and red is oil-fired heating, somehow cut off the legend.
Note that the heating and cooling overlap during
the summer due to cool nights, cold seasonal frost and permafrost around and
under the basement, and cool-cloudy days requiring heat on some days of the
month, while warm sunny days require cooling in the solar heated spaces on
other days. More fine tuning could have
been done to eliminate the cooling (blue) through the winter when the passive
solar tends to overheat several of the zones, but the point of diminishing
returns precluded actually saving enough to make the next break in LEED Points. Note
also that the green “Misc. Equipment” bars do include the process load of 6 KW
dissipated from the computer racks in the Information Technology Room in the
Office Wing Basement. That effect is
subtracted out in the annual comparisons of Table 1e.
The
above graphical display is quantified in the following Table 2:
Table 2.
DEC data displayed in Figure 5 by month and end-use, and transferred to
the DEC Column of Table 1 from the Total Column above. Again, the fuel is oil, not gas as shown
above from the eQUEST format.
For comparison, similar charts and tables for the
ECB case are displayed in Figure 5 and Table 3 as follows:
Figure
5. Monthly breakdown of
RTF ECB energy by end-use. Red bars are
fuel oil, not gas, where the heating value is 138,000 Btu/gal.
Table 3.
ECB data displayed in Figure 5 by month and end-use, and transferred to
the ECB Column of Table 1 from the Total Column above. Again, the fuel is oil, not gas as shown
above from the eQUEST format.
Note the much higher summer oil consumption in
Figure 5 is partially because ASHRAE 90.1-1999 Table B-24 requires no
insulation below the central Basement and Laboratory Slabs, despite the fact
these slabs are sitting on permafrost!
In the corresponding DEC and ECB simulations we did not use the ASHRAE-recommended
F-factor approach of neglecting heat transfer through the central slabs (ASHRAE
90.1-1999 Sec 5.3.1.5 & Sec A6).
That’s for buildings built on warm soils, and would result in totally
erroneous heat loss calculations for our situation. When on-grade and below-grade slabs below
heated spaces are placed on permafrost they must be insulated for structural
reasons. Otherwise foundation support
below the building will rapidly be lost as the ground melts non-uniformly, and
the subsequent building breakup is the stuff of thousands of hard-earned
lessons in polar architecture. So the
DEC building modeled herein uses 4” of EPS insulation below the central slab at
R-4.5/in, in conformity with good sub-arctic design practice, with heat-loss
calculated using U-factors in the central slabs. The ECB building modeled herein – for energy comparison
purposes only - uses no insulation below the central slab, in conformity with
ASHRAE 90.1-1999 Table B-24, and uses U-factors, not F-factors, for estimating
heat-loss. In both cases the thermal
resistance of the Non-Frost-Susceptible (NFS) fill is included in the thicknesses
used under each basement slab for the DEC case.
SLAB
HEAT TRANSFER OVER PERMAFROST
The above deviation from commonly accepted ASHRAE
heat transfer modeling techniques requires some justification. The geotech well log from April 2003, before
the ground had been disturbed at all for RTF construction, appears in Table 4
for the hole adjacent to the eventual location of the south wall of the South
Laboratory (Subsurface Soil Investigation, Soils Alaska, P.C., Fairbanks,
AK, April 1, 2003, unpublished report by Tom Berglin):
Table
4. Geotech Well Log before construction.
The winter of ‘02-’03 featured good snow cover, so
the seasonal frost from that year was only 5’ deep on April 1, 2003. The solid bar near the left denotes the
depths at which the soil was frozen. The
summer of ’02 shows in the thawed silt from 5’ to 7.5’. The winter of ’01-’02 shows in the residual
seasonal frost from 7.5’ to 9’. And
permafrost begins at the 15’ level. The
unfrozen silt between frost layers looked and behaved like chocolate pudding,
just after cooking, while being poured hot into bowls. Very marginal stuff for supporting a
building.
So Table 4 makes the structural case for the
desirability of digging to the frost table and filling with non-frost-susceptible
(NFS) fill to the slab and footings, and for insulating well enough to maintain
the permafrost if possible in the face of global warming. This subsurface situation was numerically
modeled for the RTF (2-D transient) in the paper:
Cott, Don, "Shallow Foundation Design in Deep Silt over Decaying
Permafrost using Embedded Computer Monitoring and Control of Subgrade Moisture
and Temperature," Cold Regions Engineering Session, 54th Arctic
Sciences Conference – Extreme Events, American Association for the Advancement
of Science, Fairbanks, Alaska, Sept. 23-24, 2003.
From which the following contour solution is taken,
and displayed as Figure 6:
Figure 6. Seasonal Temperature Distribution at end of a
Fairbanks Winter (5500 freezing ºF-Day), beneath the edge of the RTF Office
Basement.
The
contour diagram above is good for visualizing the interaction between
permafrost and seasonal frost in springtime, but the contour interval is too
coarse to show the permafrost freeze contour.
That shows a little better with the node temperature diagram of Figure 7,
where the node temperatures are in ºF:
Figure 7. Node temperatures in ºF for the contour
diagram of Figure 6.
Note there is a permanent thaw bulb immediately
beneath the slab, which extended about a foot into the silt underlayer for this
preliminary foundation design. The
eventual design utilized more NFS fill, so that the thaw bulb is entirely
within that fill for at least the first decade following building
construction. If the local climate
warming trend continues, however, there is little doubt that the permafrost
support will be lost sometime during the life of the building. Structural provisions are in place for that,
but are beyond the scope of this heat transfer explanation.
The geotech bore hole of Table 4 was permanently
instrumented for temperature profiles.
Those Subsurface
Profiles are displayed near-real-time and linked from the CCHRC web site (www.cchrc.org). Typical subsurface thermister string data is
shown in the Figure 8 plot as follows:
Figure 8. Deep thermister string data from the original
met station hole, before data interrupted for excavation.
The web URL for Figure 8 as of 3 October 2006 is http://www.tanana-watershed.org/mesonet/stations/cchrc/data/CCHTH3_L.gif. At the date of this writing the thermister
string is disconnected, pending re-connection, along with the connecting of
several other thermister strings through the same panel. And so the data is temporarily truncated at
Dec of 2005. Note that while the
shallower thermisters show seasonal temperature variation above freezing, the
deeper thermisters stay fairly constant at below freezing. Note that water content varies from 23% to
40% by mass.
DEC
/ ECB COMPARISON DETAILS
Because
the Reviewer Comments on the original RTF EAc1 Submittal of Oct 2006 required
that the model be re-worked with the ECB case HVAC be “Packaged Single Zone A/C
with Fossil Fuel Furnace”; and the DEC case HVAC to be “Packaged Single Zone
with Hot Water Heating”; it was not possible to run both cases in tandem as
parametric variations on each other as had been done in the original
submittal. Therefore the cases were run
on a stand-alone basis. As before, the
only differences were those directed by the 2003-LEED NC-2.1 Reference Guide,
and 1999-ASHRAE Standard 90.1. This is
another reason why the results shown in Figure 4 and Table 2 show space cooling
through the winter, where Figure 5 and Table 3 don’t. If the modeler had gone back through and
individually tuned one case and not the other, then they wouldn’t have been
equivalent in the LEED sense.
Regardless, the That these
parametric values have been properly reflected in the envelope components can
be verified from Table LV-D, “Details of Exterior Surfaces” in the
.SIM files for the DEC and ECB cases, respectively (118-DEC.SIM.txt
& 120-ECB.SIM.txt).
Details
of the HVAC systems for each case may be found in Tables SV-A for each case (118-DEC.SIM.txt
& 120-ECB.SIM.txt).
For Area Lighting the difference is due to
daylighting controls in the DEC, which don’t exist in the ECB. Ventilation and Pumping cost more for the ECB
because so much more heating is needed, with it’s attendant fan and hydronic
pump power penalties. Space Cooling
costs more for the DEC because the DEC tends to hold the solar heat better,
such that on warm afternoons air cooling is needed to dissipate the heat. For Space Heating, the ECB is much more
expensive, because of the much higher U-values associated with the ASHRAE 90.1
envelope components, compared to the actual components used in the DEC.
The daily end-use profiles for the DEC are
displayed in Figure 11:
Figure 9. DEC Daily End Use
profiles for typical winter and summer month.
Note that in February, daylighting is obvious from
the yellow profile, where lighting power is reduced considerably in the middle
of the short sub-arctic day. Daylighting
also exists in July, but the day is 22-hours long, so it reduces the whole
profile uniformly, rather than just in the midday hours. Note the lighting peak in the afternoon is
because the basement lights are on automatic personnel-sensor switches. For both DEC and ECB this was approximated by
only turning the lights on for two-hours in the afternoon.
For comparison with Figure 11, Figure 12
represents the daily profiles for Feb and July for the ECB:
Figure 10. ECB Daily End Use profiles for typical winter
and summer month.
Note there is no daylighting at all for the ECB,
but the basement occupant sensing switches are identical to the DEC (ASHRAE
90.1-1999 Sec 11.4.5, i.e. approximated using identical schedules).
SIMULATION VALIDITY
eQUEST and DOE-2 include a number of self-checking
and diagnostic redundancies for the purpose of establishing the validity of the
simulations. Sec 11.1.5(d) of ASHRAE
Standard 90.1-1999 requires that any error messages be reported and
explained. There were no “errors”
reported in either the DEC or the ECB simulations. But “warnings” were copiously reported. There are 11 warnings reported in 118-DEC.SIM.txt.
All these warnings concern condensation events in the exhaust leg of the
various Heat Recovery Ventilators (HRV).
The first of these is repeated as follows, and it is typical:
**WARNING**********************************************************************
Energy-recovery ventilator: SL
HVAC Sys has
condensation on the exhaust
outlet. First occurrence: 1 1 1
OA T&W: -33.4 0.0001
Return T&W: 65.1 0.0080
The others may
be examined by following the above link, and searching on “warning.” The ECB simulation, 120-ECB.SIM.txt,
contained no errors and no warnings. There are no HRVs in the ECB case, hence no
condensation events in the exhaust duct.
Note that both simulations meet the Comfort Criterion of Table 2, pg
140, LEED-NC 2.1.
By way of
explanation, it should be pointed out that HRV’s do routinely frost up in the
winter in Fairbanks because of the extremely low outside temperatures. All incorporate some sort of defrost cycle,
usually a supply air bypass, sometimes modulated, sometimes not. DOE-2 does a first law solution of the entire
building once an hour. The defrost cycle
of the HRV’s is significantly less than 1 hour.
So by it’s very nature, DOE-2 cannot follow the transient solution of an
HRV defrost cycle. There are
approximately ten quasi-steady-state combinations of HRV defrost configuration
in eQUEST Vers 3.6. A few cannot find
solutions and crash the simulation. The
others frost up and generate warnings.
These solutions utilize the supply air modulated bypass with modulation
reset each hour by setting exhaust outlet temperature to just above
condensation, if the exhaust outlet would be wet without any bypass. When no non-condensing solution exists then
the model generates a warning, as sampled above. This condition will result in some inaccuracy
in the simulation compared to a properly cycling HRV, but the energy is not
large, as can be seen from examination of the ERV reports in the .SIM
files. Also any HRV-related energy is
quite similar for the DEC and ECB simulations, again comparing ERV reports for
the two .sim files. Thus it is concluded
that the warnings are not indicators of any serious inaccuracies in the
simulations.
The other
indicator of simulation accuracy is the BEPU reports in the .sim files, where
the “percent hours outside throttling range” and “percent hours plant loads not
satisfied” are reported (LEED-NC 2.1 pg 141).
Loads are satisfied in all cases, but the default throttling range of 2F
was utilized, and 3 to 4% of the zone-hours do fall outside the throttling
range. However in all zone hours the
temperatures are still within the bounds of Table 2, pg 140, LEED-NC 2.1. Inspection of the SS-O reports in the .sim
files establish this. So the BEPU out of
range reports are not a significant source of simulation inaccuracy either.
Note these
considerations by no means constitute a formal validation suite. They only eliminate the most common errors.
PLANT, HVAC,
and ELECTRICAL SYSTEMS
The building is
heated by three independent hydronic systems, supplying water to fintube
heaters, unit heaters, supply air coils, and radiant slabs throughout the
building in nine controlled zones. All
the south-facing above grade zones utilize passive solar heating and daylighting
through intensity sensors and dimming ballasts.
All but emergency lighting circuits employ occupant detection sensors
for automatic cutoff. Lighting intensity
is detailed for each space in report LV-C of the .sim files (118-DEC.SIM.txt
& 120-ECB.SIM.txt), and is 1.0 W/ft2 in all but the Elevator Shaft (0.14) and
Atrium Ground Floor (0.7). The lighting
intensity is identical for the DEC and ECB cases. Plant and zone equipment is as follows in
Table 6:
|
Table 6. RTF Plant,
Zone, & Electrical Equipment breakdown for original design (Some substitutions have been made as-built; in all cases resulting
in efficiency improvements except for the deletion of one underutilized HRV;
but this is what was designed & modeled except for autosizing & using
baseboards/inertia floors to approximate radiant slabs – which DOE-2 handles
very poorly). |
||
|
Plant Loop |
Zone Served |
Zone Equipment |
|
B-1, Viesmann VR2-40, Oil-fired, 140,000
Btu/hr, 1-1/2” Main Loop, heater incl. domestic water winter preheat loop (in
parallel with summer solar water preheat panel to be added later – not
modeled). ¾ hp,
17 gpm, 27’ head, Grundfos UP 40-50/2 Circ Pump |
UCB – Utility Corridor Basement |
21’-3/4” Fintube Vulcan Linovector
DS-312, 1010 Btu/hr/ft, 1 GPM. ~200 cfm Lifebreath 300DCS HRV shared
with OB (incl MERV-13 filters). |
|
OB – Office Basement |
40.5’-3/4” Fintube Vulcan Linovector Bare
Element Single Tier, 630 Btu/hr/ft, 1 GPM. ~200 cfm Lifebreath 300DCS HRV shared
with UCB (incl MERV-13 filters). 6 KW continuous electrical load in the
Information Technology subzone. |
|
|
OGF – Office Ground Floor |
Radiant Floor, 2715’-1/2” PEX in 8
parallel loops, 0.5 GPM. ~250 cfm Lifebreath 300DCS HRV shared
with two restroom & one kitchenette subzones (incl MERV-13 filters). |
|
|
OTF – Office Top Floor |
Radiant Floor, 2715’-1/2” PEX in 8
parallel loops, 0.5 GPM. ~250 cfm Lifebreath 300DCS HRV shared
with two restroom & one kitchenette subzones (incl MERV-13 filters). |
|
|
B-2, Viesmann VR2-40, Oil-fired, 140,000
Btu/hr, 1-1/2” Main Loop Heater. 1/6
hp, 17 gpm, 17’ head, Grundfos UP 43-75 Circ Pump |
NL – North
Lab |
2 – 40,000
Btu/hr, 4 gpm, 1760 cfm, 1/6 hp, Unit Heaters, Trane 126-S. ~250 cfm Lifebreath 300DCS HRV shared
with three restroom subzones and adjacent GFH zone (incl MERV-13 filters). |
|
GFH – Ground Floor Hallway |
26’ – ¾”
Fintube, 2-tier, 1730 Btu/hr/ft, 2 gpm, Vulcan Linovector DS-324. No HRV
coverage, but 4 doors without airlocks opening to outside (transient
occupancy only). |
|
|
ATF – Atrium Top Floor |
16’ - ¾”
Fintube, 2-tier, 1730 Btu/hr/ft, 2 gpm, Vulcan Linovector DS-324. ~250 cfm
Lifebreath 300DCS HRV shared with three restroom subzones and adjacent NL
zone (incl MERV-13 filters). |
|
|
B-3, Viesmann VR2-40, Oil-fired, 140,000
Btu/hr, 1-1/2” Main Loop Heater. 1/6
hp, 17 gpm, 17’ head, Grundfos UP 43-75 Circ Pump |
SL – South
Lab |
2 – 70,000
Btu/hr, 6 gpm, 3300 cfm, ¼ hp, Unit Heaters, Trane 230-S. ~250 cfm
Lifebreath 300DCS HRV shared with one restroom & 3 office subzones and
adjacent ATF zone (incl MERV-13 filters). |
|
Main Power
Drop: 3-P, 400 A, 480 V; Lighting: F32-T8-6P35, all but basement continuous
dimming in response to daylight down to 20% intensity (unsure of ballast
factor at cutoff, used DOE-2.2 default), then switch off. Switch off if no occupants detected (all
zones incl. basement. |
||
The cooling
Energy Input Ratios are 0.338 Btu/Btu for all zones in both the ECB and DEC
cases, and can be confirmed from Table SV-A of the simulation output files (118-DEC.SIM.txt
& 120-ECB.SIM.txt).
The heating Energy Input Ratios are 1.28 Btu/Btu for each zone in the
ECB forced-air furnace case. That
doesn’t seem to be listed in the .sim file, but it can be confirmed by opening 120-ECB.inp.txt and searching for “FURNACE-HIR” for
each zone. The heating Energy Input
Ratios in the DEC case are 1.253, 1.253, and 1.080 (fully condensing) Btu/Btu
for the three boilers, respectively (Table PV-A).
DIRECT DIGITAL
CONTROL
The RTF is
being equipped with by Siemens with a Apogee full building monitoring and
control system utilizing Insight software.
All building data will be available to anyone who is interested over the
Internet. In addition to routine
building operations, the system will be used as a data acquisition system for
testing HVAC, Plant, and Envelope components and systems (many of which have
been donated in return for future performance data).
SCHEDULES
The imposed
schedules are reported in LV-G of the ECB and DEC simulation files (118-DEC.SIM.txt
& 120-ECB.SIM.txt).
All schedules for DEC and ECB cases are identical. Everything related to occupancy ramps up to
nominal from 7 to 9 AM, and back down to zero from 4 to 6 PM on weekdays. Nominal zone occupant loadings appear in
report SV-A of the .sim files, and are summarized in Table 7:
|
Table 7. Nominal Zone
Occupant Loadings during office hours on weekdays. |
|||
|
Zone |
Occupants |
Zone |
Occupants |
|
UCB – Utility
Corridor Basement |
1 |
AT - Atrium |
2 |
|
NL – North
Lab |
2 |
OGF – Office
Ground Floor |
5 |
|
SL – South
Lab |
2 |
GFH – Ground
Floor Hallway |
1 |
|
OB – Office
Basement |
1 |
ES - Elevator
Shaft |
1 |
|
OTF – Office
Top Floor |
6 |
Total
Building Occupants: |
21 |