Low-e Storm Windows
Adam Hadley
Regional Technical Forum
July 21, 2015
2
Overview
Today, we are seeking RTF approval of a new
Proven UES measure for Low-e Storm Windows
3
Measure Overview
Measure Developers
BPA, PNNL, RTF
CAT Review
Adam Hadley
Tech Sub-Com Review
No
R&E Sub-Com Review
No
Notes
•
•
•
•
•
•
This is a new measure for the RTF
Low-e coating on storm windows have been commercially available since
2009 (PNNL)
• Low-e pyrolytic coating is a hard ceramic coating (long-lasting,
durable)
• Available at big-box home improvement stores
Installations are permanent
Both Interior and Exterior Storm Windows Qualify
Often a DIY project
Field studies by DOE have shown significant savings
See PNNL Video for more details (Link)
4
From: Cort, K.A. “Low-E Storm Windows: Market Assessment and Pathways to Market Transformation.” PNNL. June 2013.
5
Measure Specifications
•
•
•
•
•
Storm windows must use glazing materials with an emissivity less than or equal to 0.22 and a solar
transmittance greater than 0.55, as listed in the International Glazing Database (IGDB) managed by
Lawrence Berkeley National Laboratory and measured in accordance with NFRC 300-14,NFRC 30114 and NFRC 302-10.
Storm windows must be of the same opening type as the existing prime window.
Storm window shall be permanently installed.
Storm windows shall be oriented with the low-e coating facing toward the interior of the house.
For installations with metal framed prime windows the storm window’s frame shall not be in direct
contact with the prime window frame.
Measure Identifiers
• Existing Window Type
–
–
–
–
–
•
•
Metal Frame, Single-pane
Wood (non-Metal) Frame, Single-pane
Metal Frame, Double-pane
Wood Frame, Double-pane
NFRC-rated U-0.30
Heating Zones (1, 2, and 3)
Heating System Type
–
–
–
Electric FAF
Electric Zonal or DHP
Heat Pump
This presentation gives results for these measures
but CAT does not recommend their approval because
determination of the baseline U-factor would likely
require research (which is probably not worth the
effort since the measures are not cost-effective).
Energy Savings
6
• Same methodology as other weatherization (and windows)
measures
– Calibrated SEEM runs
– Measure interaction accounted for as per guidelines
• Note: No air leakage reduction assumed in savings calculations
• U-factors and SHGC’s generated using NFRC window modeling
software (documented in PNNL Report)1
Window Type
Glazing Frame Type
Metal
Single
Wood
Metal
Double
Wood
NFRC-rated u-0.30
1Cort,
Baseline UFactor
U-Factor With
Low-e Storm
Baseline
SHGC
SHGC with
Low-e Storm
1.09
0.41
0.66
0.52
0.88
0.35
0.61
0.50
0.33
0.63
0.48
0.27
3
0.18
0.59
0.30
0.46
3
0.24
0.69
0.49
0.30
2
KA; SH Widder, TD Culp. 2015. “Thermal and Optical Properties of Low-E Storm Windows and
Panels.” PNNL-24444.
2Assumes no low-e coating, but in practice, there would be windows by this definition with low-e coating.
3U-Factor and SHGC for low-e storm window + NFRC-rated U-0.30 window based on a regression of the
other data in the table.
7
Note: Wood Frame = non-metal frame
8
Note: Wood Frame = non-metal frame
9
Note: Wood Frame = non-metal frame
Wood Frame, Single Glazed
Study
N
Heating
System
Air Leakage
Reduction
10
Gas furnace
(9), FAF (1)
Chicago
4 (1)
Gas furnace
(2) or boiler
(2)
7%
Philadelphia
2 (2)
Central gas
10%
Atlanta
PNNL Lab
Homes
(1) Six
17%
HZ3
30
25
20
15
10
5
0
SEEM, FAF, SEEM,
SEEM, HP,
HZ1
Zonal, HZ1
HZ1
Atlanta
study
SEEM, FAF, SEEM,
SEEM, HP,
HZ2
Zonal, HZ2
HZ2
Chicago
Study
SEEM, FAF, SEEM,
SEEM, HP,
HZ3
Zonal, HZ3
HZ3
Metal Frame, Single Glazed
HZ1
HZ2
HZ3
35
30
25
20
15
10
5
0
SEEM, FAF, SEEM, Zonal, SEEM, HP,
HZ1
HZ1
HZ1
Philidelphia SEEM, FAF, SEEM, Zonal, SEEM, HP,
HZ2
HZ2
HZ2
SEEM, FAF, SEEM, Zonal, SEEM, HP,
HZ3
HZ3
HZ3
Metal Frame, Double Glazed
HZ1
HZ2
HZ3
25
1
FAF
0%
homes in study, but 2 had clear storms
2 multifamily buildings with a
total of 101 units
(2) Featured
Heating Energy Savings (%)
• SEEM results are generally
consistent with results from
field studies for window types
studied
HZ2
35
Heating Energy Savings (%)
Energy Savings:
Other studies
HZ1
40
Heating Energy Savings (%)
10
20
15
10
5
0
SEEM, FAF, SEEM, Zonal, SEEM, HP,
HZ1
HZ1
HZ1
PNNL Lab
Homes
SEEM, FAF, SEEM, Zonal, SEEM, HP,
HZ2
HZ2
HZ2
SEEM, FAF, SEEM, Zonal, SEEM, HP,
HZ3
HZ3
HZ3
11
Measure Life
• 20 years
– PNNL estimate, supported by
• The 20 year warranty provided by the two leading manufacturers
• A follow–up evaluation of 5 homes used in a field study in a lowincome neighborhood in Chicago, 10 years after installation 96 of
106 storm windows were present and in good condition.
– For details, see Culp, Thomas D. memo to Katie Cort. “Low-E storm
window persistence in Chicago case study homes.” January 27, 2015.
• Note: The following measure specification is intended
to help maintain measure life by reducing the chances
of removal (and no subsequent re-installation) by the
current or future occupant
– “Storm windows must be of the same opening type as the
existing prime window.”
12
Energy Savings: Staff Highlighted Area (1)
• Issue: The energy savings calculation assumes the storm
windows are effective 100% of the year. However, storm
windows could be left open (when the prime window is
shut), almost eliminating savings in those instances
• Question: Should the RTF adjust for this?
– Options:
• Yes: Include an adjustment factor in the savings estimate to account
for storm windows not used correctly through the year
– Adjust savings by factor of 93/96 based on: Evaluation in Chicago found that 3
of 96 storm windows (that were still present and in good condition) were not
fully closed in the middle of winter.
• Yes: Add an item in delivery verification to check whether the storm
window is installed (closed where prime window is closed) during the
heating season
– Where storm is open but prime window is closed, impact evaluation
contractor would make an adjustment to the program savings
• No: Based on energy savings comparison with field studies (previous
slide), assume issue is not significant
Staff Recommendation
(Note: savings in this presentation do not reflect this adjustment)
13
Energy Savings: Staff Highlighted Area (2)
• Issue: Cooling savings are -2% to 6% of heating savings
• Question: Why are cooling savings negative? Should they
be included?
– Background
• Field study results were highly variable and sometimes negative
• Ben Larson confirmed
– SEEM shows reduced cooling load with decreased SHGC
» Expected
– SEEM can show increased cooling load with decreased U-factor
» Uh Oh, not expected! Why: House loses heat to the exterior (internal
gains) slower so more mechanical cooling is needed (this happens during
mild conditions, which happens a lot in the PNW)
– Staff Recommendation
• Remove cooling savings from the measure
– They are insignificant and unreliable
– Model assumes a closed house; people open windows during the cooling
season
– Note savings in this presentation include cooling savings
14
Energy Savings: Staff Highlighted Area (3)
• Issue: Savings do not currently reflect a reduction in
whole-house infiltration rate but field studies all
showed reductions
• Question: Should infiltration reduction be included in
the analysis and if so, what value should be used?
– Staff Recommendation
• Include an infiltration reduction of 10%
– Roughly based on known field studies which show 7%, 10%, and 17%
average reductions
• “Back of the Envelope” savings estimate (using the existing UES
values for infiltration reduction): Savings would increase over
those shown here by 2%-10% in HZ 1
• Note: Savings in this presentation do not include infiltration
reduction
15
Measure Cost (2014$’s)
Low-e Storm Window Costs
Material Costs (per sq.ft.)
Professional Installation Costs (per window)
DIY Installation Rate
DIY Instllation Cost (per window)
Average window size (sq.ft.)
Average installation cost (per sq.ft.)
Total Installed Cost (per sq.ft.)
Value (2014$'s)
$7.50
$60
80%
$30
13.5
$2.67
$10.17
Source
PNNL (see memo)
PNNL (Wx installer informal survey)
PNNL (via manufacturer interview)
Assumed as 1/2 professional install
Analyst assumption (3 x 4.5)
Calculated
Calculated
• Not a lot of data available for installation costs
– Primary staff highlighted area is staff’s proposal for
inclusion of costs for DIY installations
• Section 4.1.4 of Cost Guidelines says, “Labor should not
include installation labor provided by residential end users”
• Staff disagrees with this in principle and proposes a DIY cost
of ½ of a professional install
16
Note: Wood Frame = non-metal frame
17
Note: Wood Frame = non-metal frame
18
Note: Wood Frame = non-metal frame
19
Proposed Motion
“I _________ move the RTF approve the measure
specification, savings*, cost, and measure life for the
Residential Low-e Storm Windows UES measures (except
Wood frame, Double-Pane and NFRC-rated 0.30 u-factor
applications) and
• Set the status to Active
• Set the category to Proven
• Set the sunset date to September 2019.”
*Savings methodology and inputs are being approved here. Savings
values will change after removing the cooling savings, adding
infiltration reduction, and making the 93/96 adjustment as discussed
today; staff will bring back the final results in a Management Update
presentation.
Additional Information on Low-E
Storm Window Measure
SH Widder, PNNL
Effect of Mounting Method for Metal
Assumed
Frame Windows
U-Factor
• ~10% increase in U-Factor if metal storm window is
mounted directly on metal prime window
Source: Cort, KA; SH Widder, TD Culp. 2015. “Thermal and Optical Properties of
Low-E Storm Windows and Panels.” PNNL-24444.
based on
thermally
broken
installation
Installation Info for Low-E Storm
Windows
• BASC
– Exterior:
https://basc.pnnl.gov/resourc
e-guides/low-e-exteriorstorm-windows
– Interior:
https://basc.pnnl.gov/resourc
e-guides/low-e-permanentinterior-storm-windows
• Manufacturer Websites
– e.g. Larson:
http://www.larsondoors.com/
storm_windows/how_to_insta
ll_instructions/
International Glazing Database (IGDB)
• The IGDB is a database of measured optical data for glazing
products.
– Maintained/QA’d by LBNL on behalf of DOE for use in NFRC rating of
fenestration products
• NFRC-qualified products subject to periodic verification testing and noted
with a (#) symbol in the database
– Manufacturers of glazing products submit data collected from a
certified laboratory to LBNL for review and inclusion in the database
• Data collected in accordance with NFRC 300 (solar optical properties), 301
(IR properties), and 302 (reporting).
• Submitted data is subject to review by LBNL and a peer-review by other
manufacturers.
– Glazing samples are also retained for later reconfirmation or challenges of the listed
properties.
Optical Properties of Low-E Storm
Windows
• Major manufacturers of low-e storm windows use glazing
with similar optical properties
Manufacturer
Typical Products
Glazing
Emissivity1
Solar Transmittance1
Larson
Exterior and interior
clear and low-e storm
windows and doors
AGC Comfort Select
0.148
0.689
Pilkington Energy
Advantage
0.164
0.748
Pilkington Solar-E
0.166
0.419
AGC Comfort Select
0.148
0.689
Quanta
Exterior and interior
clear and low-e storm
windows
• Other, smaller manufacturers of low-e storm windows include
ProVia, Allied Window, Harvey Building Products, Thermolite
Windows
– Not sure what type of glazing they use
1
As listed in the IGDB, v.41
Solar Heat Gain
• Both low solar heat gain and high solar heat gain
low-e storm windows available
– Low solar gain windows have same emissivity, but
~20-50% lower SHGC
• Low solar heat gain low-e storm windows will
impact savings could impact savings by ~50%
– Will vary based on house size, climate, prime window
sq.ft. and orientation, low-e window optical
properties, etc
Air Leakage
• Air leakage is extremely variable
(studies report 0-50% infiltration
reduction)
• Not well correlated to savings
based on field studies
• RESFEN1 modeling suggests
that air infiltration may
account for approximately 23%
of total HVAC energy savings
1RESFEN is
a residential energy modeling tool maintained by
LBNL to help consumers and builders pick the most energyefficient and cost-effective window for a given application.
See http://windows.lbl.gov/software/resfen/resfen.html
U-Factor Validation
• SEEM U-factor assumptions based on NFRC
modeling using WINDOWS/THERM (see PNNL
Report)1
– Validated based on testing in LBNL’s MoWiTT
thermal chamber test
facility based on
measured heat flux
and correcting for air
infiltration2
1Cort,
KA; SH Widder, TD Culp. 2015. “Thermal and Optical Properties of Low-E Storm Windows and
Panels.” PNNL-24444.
2Klems, JH. 2002. Measured Performance of Storm Windows. Lawrence Berkeley National Lab.
Attachment Energy Rating Council (AERC)
Launched in 2015, an independent rating,
certification, labeling and performance
verification program for fenestration
attachments sponsored by DOE.
• Consortium effort led by Window Covering Manufactures
Association (managed by DOE)
• During the next 4 years AERC activities include:
– Prioritize product types and performance indices (storm
windows are slated to be first product under evaluation)
– Characterize the key material properties of window
attachment products (e.g., transmittance, reflectance, and
emissivity)
– Conduct product performance simulations and evaluate
procedures to used to rate window attachments