Envelope Assessment
Jaffrey Grade School
Prepared for Design Day Mechanicals
May 2015
Table of Contents
Introduction
2
Historic Energy Usage
3-4
Envelope Analysis Summary
5-6
Summary of Recommendations
7
Construction Eras and Orientations
8
Floor Plan Schematics
9-10
Roof and Attic Performance Assessments
11-18
Wall Types
19-25
Doors and Air Leakage
26-27
Window Types
28-30
Blower Door Testing
31
Heating Systems
32-33
Introduction
This envelope assessment report has four goals:
1. To describe the Jaffrey Elementary School’s (JGS) thermal envelope in term of each component’s
existing effective performance and specific weaknesses.
2. To identify cost effective envelope improvement strategies which can reduce the total heating
load in a meaningful way.
3. To present this and other pertinent information in a way that facilitates energy modeling by another team member.
4. To create a document which may be helpful to school personnel in gaining a better understanding of heat loss and the importance of an effective thermal envelope.
The original JGS building was built in 1938. There have been at three major additions to the school. It is
presumed that a gym and cafeteria was added at some point after 1938, followed by a classroom building
designed in 1986 and a smaller classroom wing designed in 2003. Part of the bus port was enclosed for offices in 2004 and many windows were replaced at that time. This Envelope Assessment has attempted to
describe existing components of the thermal envelope in terms of their effective performance in conserving
heat generated by the existing oil fired boiler. This is considered the “demand side” of the building energy
equation: the more effective the thermal envelope in conserving heat, the less energy (heating fuel) needed
for supply.
The primary goal of the assessment was to identify opportunities for cost effective improvements to the
thermal envelope. The goal of this report is to present a summary of the existing conditions and a breakdown of the building’s thermal envelope for the rest of the energy audit team as well as the School’s facility
managers and decision makers. Therefore, it has been written and organized with that goal in mind.
The most cost effective time to make an energy efficient building is during the initial design and construction phase. It is hoped that this document will serve all parties, for the purposes of completing this energy
audit, but also during the planning and implementation of future construction and capital improvements.
2
Historic Energy Usage
Energy
Heating Oil
Propane - Cooking
Electricity
Totals
EUI KBtu/ft2
Unit
17,100
468
221,280
Site Btu's
2,368,350,000
42,728,400
755,007,360
3,166,085,760
57,830
54.75
Floor Area
KBtu/ft2
Source Btu's
2,723,602,500
49,137,660
1,920,710,400
4,693,450,560
81.16
KBtu/ft2
Cost
$54,891
$922
$38,572
$94,385
$1.63
$ per ft2
The usage chart above represents the average heating oil and propane use based on calendar years 2013 and
2014. It also represents the annual average electric usage, based on 24 months, from July 2013 through
June, 2014. The monthly data can be found on the next page.
Electric and propane costs are based on actual costs, and fuel costs are based on the SAU’s contract prices
with Rymes Oil through June 2015: $3.21 per gallon of oil. The cost of heating fuels has historically been
very volatile, and increasingly so in this century. NHOEP’s “Current Heating Fuel Values” as of January 15,
2015 is $2.85 for oil and $3.19 for propane, and predicting future costs is always a gamble. For estimating
predicted savings from improvements—this report uses the current contracted prices, but please note that
too, involves the same gambling.
Therefore, converting energy sources to their Btu content is the more reliable way to determine a building’s
Energy Utilization Index (EUI). And it allows for a ‘snap shot’ comparison between a building’s overall energy usage and efficiency and other buildings of similar sizes and functional uses. There are NH school
buildings with EUI’s ranging from 119 KBtu’s per square foot down to newly constructed, very high performing 29KBtu’s per square foot. At 54.75 KBtu per ft2 floor area, JGS is somewhere in between. This
assessment addresses the specific opportunities available to the School to lower that EUI.
From both a cost, and source energy use, perspective, heating fuel represents 58% of total energy delivered.
This assessment focuses on the demand side aspect for heating costs in terms of heat lost to the outside
through foundation, walls, windows, doors, and the ceiling or roof. The supply side—that is the heating and
ventilation equipment and distribution, accounts for anywhere from 25—45% of the heating costs. So improvements to the envelope and mechanical systems should be analyzed as one whole building system.
3
Heating Oil
Delivery
Date
11/19/12
12/12/12
01/04/13
02/01/13
02/21/13
03/20/13
04/24/13
05/29/13
11/13/13
12/05/13
12/19/13
01/10/14
01/24/14
01/31/14
02/11/14
02/21/14
03/06/14
03/14/14
03/26/14
04/04/14
04/24/14
05/22/14
10/20/14
11/11/14
11/25/14
12/10/14
12/31/14
01/08/15
01/16/15
Gallons
Totals 2013
Heating Oil and 2014
2010
1500
2000
2000
2000
1000.1
1000.1
1920.1
1,500.5
1,500.2
1,000.0
3,041.3
14,962.3
1,200.1
3,041.3
1,209.3
1,161.0
1,610.0
765.0
1,000.0
836.1
1,000.0
1,000.0
1,200.0
1,200.0
1,200.0
1,315.6
1,500.0
19,238.4
600.0
1,100.0
Propane—Cooking
Gallons
$ Cost
LP
129
$211
Delivery
10/4/2012
1/3/2013
4/4/2013
7/3/2013
8/22/2013
11/21/2013
2/20/2014
5/15/2014
11/21/2014
101
115
111
22
152
$174
$206
$182
$45
$327
501
135
142
160
$934
$415
$259
$245
436
$920
Electric
Period
Ending
July
August
September
October
November
2011-2012
kWh
10,480
13,920
18,960
19,600
20,080
Cost
$2,191.54
$2,839.15
$3,417.80
$3,539.94
$3,613.60
2012-2013
kWh
9,760
15,280
20,080
24,960
18,160
Cost
$1,754.24
$2,752.59
$3,289.72
$3,825.22
$3,092.03
December
January
February
March
April
May
June
18,400
17,600
18,720
21,120
19,360
20,160
16,080
$3,360.85
$3,231.32
$3,353.79
$3,646.99
$3,495.46
$3,593.20
$2,917.05
20,000
20,720
21,840
22,000
18,560
22,000
14,720
$3,325.05
$3,412.13
$3,580.80
$3,539.13
$3,274.55
$3,519.95
$2,576.35
214,480
$39,201
228,080
$37,942
Fuel usage was updated in January 2015, but electric use data ended in spring 2014, so the 24 months above
represents the fiscal years 2011-2013.
The EUI on the previous page was based on two year averages for oil, propane, and electric.
4
Envelope Analysis Summary
Fundamental thermodynamics informs us that heat moves in three ways: conduction, convection, and radiation. These three transfer mechanisms typically occur at the same time, though one usually dominates in a
given situation. A building’s thermal envelope consists of control layers to slow conduction, limit convection, and manage radiative transfer—while at the same time managing water and vapor. Simplistically, insulation slows conductive losses, air barriers slows or stops convective losses, and opaque surfaces eliminate
radiative losses (and gains). Since heat moves to cold and warm air rises, conductive losses can occur in any
direction, while convective losses are often a matter of air infiltration at lower levels and exfiltrating nearer
the top of a building.
A continuous air barrier (stopping air leakage) not only saves heating and cooling energy, but is also a very
important method of vapor control. It is also important to understand that the effectiveness of insulating
materials is largely dependent on its being in contact with an air barrier—most especially at the ceiling plane.
The R-values listed by the manufacturer were calculated in a laboratory under optimal installation conditions. Unfortunately, this has not been understood over decades of installations, so ‘field’ performance is
often 25-75% less effective than the manufacturer’s ratings.
The rate of conductive heat loss depends on three factors: The conductivity of the materials in an assembly,
the surface area of the material or assembly, and the temperature difference between inside and outside.
Therefore, assessing the thermal performance of a building’s envelope includes, among other things, measuring the surface area of all surfaces, assessing the conductivity of each surface or assembly. The chart below offers a summary snapshot of RMS surfaces areas, categorized by construction era. A spreadsheet with
room by room details accompanies this report as a pdf.
Building
Era
Exterior
Wall
Surface
Area Ft2 Area Ft2
Glazing
Area Ft2
Ceiling
SA Ft2
Door Volume
SA Ft2
Ft3
UA
Btu's
UA
Ratio
1938
9,765
4,639
1,533
4,876
32
117,104
3,488
26%
Gym
8,907
4,330
624
4,552
137
133,953
3,613
27%
1986 17,213
6,658
1,027
9,191
108
297,039
5,238
39%
5,833
4,104
228
2,906
20
65,046
1,210
9%
3,413
21,525
297
613,142
2003
TOTALS
41,717
19,731
13,549 100%
Conductivity is described as a material or assembly’s “u” value, which happens to be the inverse of the more
familiar “R” value. The UA of a building is calculated by multiplying an assembly’s u-value by the surface
area of that assembly. Breaking JGS down into the three construction era’s, or four ‘buildings’, we can see
that the 1986 building represents both the largest floor area and the largest heating demand at 39%. Another interesting thing to note is that the original classroom and gym are similar in both exterior surface area
and heating demand or load.
5
The chart to the right summarizes the building’s heat loss
Component
UA
ratios based on envelope component. Estimated air leakage
Air Leakage
5,107
in winter months accounts for almost 38% of the building’s
Windows
2,131
heat loss. Walls are responsible for an estimated 18%, folRoof/Attic
1,918
lowed by windows at 16% and the ceiling plane at 14%.
Walls
2,485
The foundation and slab less at 12%, and the doors just
Floor/Slab
1,631
over 2%. These calculations are, again, largely based on
278
Doors
estimated thermal conductivity performance and surface
13,549
TOTAL UA
area. Even more complicating is the fact that the windows,
doors, ceilings, all share responsibility for convective losses represented as “air leakage”.
Ratio
37.7%
15.7%
14.2%
18.3%
12.0%
2.1%
100%
This is especially relevant because even though there may be a lot of insulating material above a ceiling,
thereby suggesting low conductivity, if warm air is allowed to rise through the insulation—then the performance of the entire ceiling is compromised. This dynamic is stated several times in this report because
common practice throughout the industry has been to keep adding more and more low density, loose fill,
insulation over time—but with minimal, or less than optimal, improvement because establishing the more
costly air barrier is ignored. At JGS, this is especially the case in the attic of the 1938 and 1956 buildings, as
indicated in the infra red images on page 12. Warm air rising through a ceiling plane plays a role in the creation of icicles and ice dams—and the $5,000 cost each time ice has to be removed from eaves.
It should also be noted that heating or ventilation equipment and duct work in an attic, above the ‘thermal
barrier’ also contributes to heating distribution losses and attic warming—therefore also contributing to icicles and ice dams.
These and other dynamics create a more complicated story than can be expressed in a simple chart as above,
however “snap shots” can be helpful in creating realistic expectations around costly improvement strategies.
For greater detail and a room by room envelope “UA analysis”, please refer to the spreadsheet accompanying this report.
Based on an estimated UA of about 13,549, or building’s total conductance, and the relatively constant
thermostat settings of close to 70 degrees throughout the school 24 hours a day, seven days a week, it can
be estimated that the building’s envelope load—that is, the amount of heating btu’s required to maintain an
indoor temperature of 70 degrees in the winter—is about 1,561,000,000 Btu’s or 1,561MMBtu’s.
Since the school uses an average of 2,394 MMBtu’s worth of heating oil each winter, it can be further estimated that the heating and ventilation equipment may be responsible for up to 40% of the school’s fuel use.
Reducing energy costs requires reducing the building’s heating load through improvements to the envelope
and/or reducing the “supply losses” by improving the efficiency
Building UA
13,549
of the heating and ventilation equipment and distribution sysTotal PHL
975,564 Btu/hr
tems.
Envelope load
Boiler at .75 AFUE
Ventilation losses
Actual Usage
This report explores the demand side part of that equation, in
full acknowledgement that there are great opportunities on the
supply side as well. The third component of the full audit is a
comprehensive energy model which considers all factors for a Difference
cost—benefit financial analysis of all improvements.
Model Error
6
1,561
1,951
2,244
2,394
MMBtu
MMBtu
MMBtu
MMBtu
(150) MMBtu
-6.27%
Summary of Recommendations
The following recommendations are based on the assessment of the existing envelope and opportunities
for envelope improvements which is believed to have a significant impact on comfort, heating energy demand, and issues of air quality, maintenance and durability. . The are listed in order of impact more than
installed costs. The financial analysis will be based on energy modeling performed by another member of
this team.
1. Replace the three sets of double doors which serve as entrances to the gym with insulated steel doors
which close and air seal completely. (If approved by the fire marshall, an alternate approach might be to
sealed closed two of the door sets.) Allowance $6500
2. Weatherstrip all remaining exterior doors. Estimated cost: $1800
3. Add weather-stripping to all Type 3 windows, which were installed to close below the sill, so care must
be taken for them to remain operable. $2200
4. In conjunction with replacing the ventilation equipment (including duct work) in the 1986 building with
ERV’s located above the suspended ceiling in the hallways, remove all insulation material and establish
a continuous air barrier at the floor plane of the attic. This will also involve removing an unused chimney which penetrates the attic near the valley over the bus port. Blow in 15 inches of cellulose. No
estimate is available for the total project at this time, though installing a plywood floor, air sealing and
adding 15 inches cellulose over 10,000 square feet could cost in the range of $30-$40K.
5. In conjunction with installing ERV’s in the 2003 addition, permanently seal intake registers for the Unit
Ventilators. $600
6. Surgically air seal the attic floor of the gym. $2200
7. Remove fiberglass batts above the stage and after inspecting the floor and wiring for safety, surgically
air seal the horizontal decking and spray 4” closed cell foam on all vertical walls and 6” spray foam on
all roof slopes. $5500
8. Air sealing the 1938 ceiling plane is also recommended though the strategy will depend , in part, on
whether the ventilation equipment will be replaced as well.
7
10º N
290º W
115º E
195º S
2003
Unit Ventilators
1938
Baseboard
1987
Baseboard
? - window opening bricked in suggests the gym and cafeteria below
may have been built after 1956
Radiators
Part of the Bus Port was enclosed for offices, I believe during—or close to—the
2003 construction.
8
All rooms are heated with baseboard except for the 2003 addition
which have six unit ventilators.
151 Library
Computer lab
9
10
1938 Attic / Ceiling Planes
While there is considerable depth of “insulating material”, the lack of a continuous air barrier reduces the
effectiveness of low density loose fill insulation such as fiberglass. Of equal or more significance is the condition of the duct work and insulation. Note, bright areas indicate heat loss into the attic.
11
1938 Attic / Ceiling Planes
The challenge here, as above the gym and the 1987 addition, is that ventilation equipment is outside the
thermal envelope, unsealed and poorly insulated—and without a rigid surface to air seal, it is impossible to
effect a continuous air barrier, making the insulation above less than effective. All of these conditions conspire to waste considerable energy.
12
Gym and Stage Attic / Ceiling Planes
The gym attic is a similar situation, though somewhat less congested with duct work and other ceiling penetrations, it has considerable debris which compresses the fiberglass, further degrading its insulation value. The
stage ceiling has large areas without any insulation, including the vertical wall ‘riser’ which serves as a major
thermal bypass. (Excessive heat loss)
13
Gym and Stage Attic / Ceiling Planes
Bright areas indicate heat loss from conditioned space below into the attic—in this case through the uninsulated vertical ‘riser’, gaps and disturbed loose fill, and ceiling penetrations of an ‘air barrier’.
There are fewer duct runs above the gym, yet they not air
sealed and the minimal insulation covering has been compromised.
14
Ceiling Planes and Attics
Looking up at the ceiling from the gym balcony. Dark areas indicate insulation voids.
15
1987 Attic / Ceiling Planes
The 1987 attic / ceiling plane is perhaps in the roughest shape. Again, no rigid surface exists to air seal, with
many wiring and duct penetrations, in addition to two chimney’s—one active, one inactive. The image below shows an area with no insulation at all—and missing structure.
Former
roof encapsulated
by the
addition.
16
1987 Attic / Ceiling Planes
It appears as if there was an attempt to enclose at least the air handler within a thermal envelope by constructing walls and a ceiling plane. Fiberglass batts had been place in the bays under the relatively flat deck.
Evidently a wind and rain storm came up while the roof membrane was being installed; the workers pinned
the membrane and left. Returning the next day, the membrane had lifted off and the insulation was soaked
through and hung dripping. It was eventually removed and the plywood treated for mold. The remaining
structure further complicates efforts to establish an air barrier at the attic floor plane.
Six plus inches fiberglass batts are stapled to the joists 18” below this walking deck. Some batts are foil
faced which slows vapor migration by diffusion, though far more vapor moves with warm air rising through
air gaps, cracks, and large holes.
17
2003 Ceiling Plane
The 2003 ceiling plane is constructed as a rigid air barrier—installed as sheetrock with seams taped—
though the transition to the CMU was not sealed, but stuffed (or not) with air permeable fiberglass as has
been conventional practice—though the convention is slowly shifting to using spray foam for a continuous seal.
This reflects current best practices and
worth the small cost premium during construction, as it is exponentially more costly
to try and construct an air barrier later.
It is believed that the water stained tiles are the result of a past roof leak in the corner transition from the
1938 to 2003 building. Below right shows fiberglass stuffing and air gap between the wall and the sheetrock
air barrier.
18
Wall Types
1938:
Rare peaks at the ceramic tiles used on the interior of the
brick walls. Above are two images of a chase with access
near the floor of the library’s northwest wall. To the left
was taken at an interior wall and the entrance up into the
attic—but it is likely these were also used to the interior of
the brick and finished with plaster.
Adding the value of the 10” brick, tile, plaster, and air films,
the estimated performance of the 1938 walls is R6.
19
Wall Types
1938: Brick with plaster surfaces.
Thermographic images of un-insulated walls, air infiltration at windows, and the baseboards hard at work to
add enough supply to keep up with those losses.
20
Wall Types
2. Gym Above Grade
The gym walls mat have been constructed after the original 1938 building, but are of similar construction. It appears some kind of insulating material was added in between furring strips, or perhaps it is only variations in thickness of plaster and the contrast is due to the high temperature of
the wall radiator.
21
Wall Types
3. Below Grade—Cafeteria and Kitchen
22
Wall Types
4. 1987
The 1987 addition was designed by John Jordan. Typical
wall section of a another Jordon building of the same vintage to the right shows CMU structure with 2” rigid foam
insulation, an air space / drainage plane and brick veneer.
While the rigid foam was not specified to type, variations
in surface temperature suggest the possibility that it is
polyisocyanurate which—on the southern wall— has
been ‘wetted’ over the years. (Images next page). Overall
assessment of the wall performance ranges from R6 to
R13, with a majority of the wall valued at R11 as below.
37ºF
64ºF
Indoor temperature: 68ºF Estimated R-value: R11
23
4. 1987
The plans called for 2” rigid foam insulation. Assuming it was installed as designed, the thermographic patterns suggest the possibility that the insulation boards may have become wet - likely from sun driven moisture—which has compromised their original thermal performance, resulting in varying degrees of heat loss.
If this is the case, it is likely that the insulation was a polyisocyanurate, possibly with a fiberglass matt covering, which does not act as a weather barrier. It is ALSO possible, though less likely, that these surface temperature anomalies are caused by exterior surface variations.
Note the distinct line at the ceiling plane, indicating less heat lost from
the cooler, vented attic.
24
5. 2003 Addition
The 2003 wall is constructed similarly as the 1987 addition, though—according to the plans - with 1.5” rigid
foam. T his foam board appears to be performing far better and more consistently than its predecessor. The
heat loss shown below is from exhausted conditioned air.
Bath exhaust fans
Ducted exhaust air
above the ceiling.
Unit ventilators
intake
25
Doors and Air Leakage
By far the highest replacement priority are the three sets of wood and single double doors to the gym. Not
only is the total surface area assessed at an overall R1, but the doors do not close properly so are a large
source of air infiltration and heat loss.
26
27
Windows or Glazing
The chart below offers a reference for whole window u-values (as opposed to center of glass values) when
manufacturer data is not available.
Another important factor is about air leakage. Assuming the window still operates enough to close properly
(not all do), tightness of a unit varies with operational design: the tightness is typically windows which are
not operational, or ‘fixed.’ Followed by casement, awning style with effective locking mechanism, double
hung, and—leakiest of all—sliders.
Emittance
of low e
coating
Single Glass
none
Double glass, clear, 1/2" air space
none
Double glass, low-e, 1/2" air space
0.2
Double glass, low-e, 1/2" air space
0.1
Double glass, low-e, 1/2" air space
0.2
Triple glass, low-e on 2 panes, 1/2" AS
n/a
Quadruple glass, low-e on 2 panes 1/4"
0.1
Gas between
panes
none
none
none
none
argon
argon
krypton
Aluminum
Aluminum Wood or
Frame w/out Frame with
Vinyl
thermal break thermal break Frame
1.3
1.07
n/a
0.81
0.62
0.48
0.7
0.52
0.39
0.67
0.49
0.37
0.64
0.46
0.34
0.53
0.36
0.23
n/a
n/a
0.22
The wall of windows below have a steel beam above for structural support.
28
Window Types
1. Double Pane, 1/8” glass, 1/2”
air space; Low e coating on outer
surface #3 or #4 ; double hung
on ‘metal track’ - no thermal
break. Rated at u=0.7
2. Eagle, double pane, 1/2” air
space Low E 272—found in 0ffice expansion and 2003 addition.
LoE 272 is a Cardinal Glass
Trademark with a stated whole
window performance of u=0.30
without gas between panes and
u=0.25 with argon.
3. Narrower window, also found
in pairs or multiples as in fill for
1938 rough openings. Double
pane, 3/8”, clear glass, in double
hung pairs with fixed pane unit
above. Found in Library, computer lab, and 1938 classrooms.
29
4. “Rescue” window egress. Clear double pane glass, 1” air space”, wide metal frame with no thermal break
and very leaky. Fixed side lite may have low e coating on 2nd surface but high solar heat gain.
5. Eagle sliders, egress—found
in 2003 addition, first floor.
3/4” air space in double pane.
6. Basement Awning—found
in cafeteria.
30
Pressure testing in 2008
Efforts were made in 2008 to estimate air leakage from
pressure testing isolated areas of the building. The conclusions from a variety of testing conditions were that 1) the
ceiling planes of the 1938 and 1985 buildings did not constitute an air barrier 2) the ventilation duct work is very
leaky and 3) the masonry walls do constitute an air barrier,
though the window and door openings also contribute to
air leakage considerably. The three day testing was conducted during vacation and all ventilation systems were
fully operating.
The primary recommendation at that time was to investigate the ventilation system and controls, then consider
envelope upgrades. Uncontrolled air leakage rates have
been included in the full UA analysis.
31
Single oil fired boiler and hydronic distribution with air handler. HVAC is outside the scope of this assessment but images included below.
Stairwell temperature exceeded 85
degrees on day of site visit in 2008.
Improvements to controls (while
this may have been corrected, remains a concern.
32
Heat Emitter Types
33