Licensed Architect - Summer 2017 - 31

Original roof with theoretical venting illustrated by red arrows.

Water staining was visible on ceiling
tiles and interior wall surfaces.
The owner stated that numerous
ceiling tiles were replaced after the
previous year's snows and were
again damaged over the recent
season when snow melted away.
Damaged tiles and water stains
did not correspond with locations
of ice accumulation, indicating an
alternate moisture source(s) likely
existed. From the attic, numerous
gaps and voids in the batt insulation
were observed and no continuous
vapor barrier was provided at the
ceiling. Insulated ductwork also ran
through the attic that fed into the
space below. The attic temperatures
were warm near the middle of the
roof and cooler above storage areas
near the roof edge. See Table below
for temperature and relative humidity
values taken during the inspection.

Findings
The 1996 design intended soffit-toridge venting of the roof above the
metal deck, between the insulation and
sheathing. This system ideally allows
air to escape from beneath the shingles
(during hot exterior temperatures)
to prevent overheating the shingles.
However, the air-flow through this
cavity is not adequate to maintain cool
temperatures (avoiding snow-melt)
during colder months. The efficacy of
the insulation was compromised, being
separated between the ceiling and
roof levels. In addition, the presence of
ductwork (even insulated) separated
from interior conditioned spaces with
ceiling insulation, is not advisable, as
warm air escaping ductwork joints can
add unwanted heat and humidity into
this space. These conditions lead to
condensation and ice dam formation at
the building.

Temperature
Dry Bulb
(Degrees F)

Relative
Humidity (%)

Dew-point
Temperature
(Degrees F)

Assembly area

69.0

25.0

31.8

Bathrooms

66.5

27.7

31.6

Storage

68.4

26.7

32.2

South Storage

66.6

25.5

30.0

Attic (central)

68.4

28.8

34.1

Attic (above storage)

64.0

32.0

33.6

Exterior Reference

26.6

93.0

24.8

Location

Condensation: Gaps between the
sheathing panels and corresponding
rigid insulation compromised the
continuous layer of insulation and
allowed exterior air to contact the
metal deck. In addition, the segmental
layer of batt insulation, separating the
attic from conditioned spaces below,
lacks a continuous air/vapor barrier
and allows conditioned air from below
to enter the attic. Warm air was also
free to enter the attic through joints
in the insulated ductwork above
the ceiling. With colder exterior
temperatures, the deck was cooled
below the dew-point temperature of
the interior air. As deck temperatures
dip below this dew point,
condensation occurs. When deck
temperatures are below freezing, frost
can built-up in areas where interior air
flow is more stagnant and later melt
during warmer periods. This melting
resulted in observed water stains on
interior finishes.
Ice Damming: Where interior air
circulation within the attic was greater
(near ducts), conditioned air could
warm the roof deck, melting snow
at upper roof portions which would
then refreeze further down the roof.
Adding holes in the soffit and into
the attic was not consistent with the
intended ventilation path, and allowed
air to bypass the already un-insulated
wall. This cooled the roof edges in
colder weather exacerbating ice
dam formation. Accumulated ice on
lower roof portions can trap snow
melt, allowing it to collect/pond up
the roof, beneath the shingles and
underlayment, and into the building.
Repairs
To prevent condensation and ice
dams, a continuous layer of insulation
and air and vapor barriers along the
roof was recommended. The warm air
seepage within the attic exacerbated
these conditions, thus the ceiling
insulation was removed and the
attic was treated as a conditioned
space. This included insulating and
integrating the upper wall portions
with the roof to create a continuous
air and vapor barrier. Two options

Summer 2017 | Licensed Architect | 31



Table of Contents for the Digital Edition of Licensed Architect - Summer 2017

President’s Message
ADA Advice Accessibility: Handrail Details for Stairways and Ramps
Continuing Education A Review of Window, Door and Skylight Standards and Certification
Buyer’s Guide
Feature Article The Necessary Accessory: Hardware
Continuing Education Providers/ ALA New Members
Insurance Design Professionals and Cyber Risk - Part 2
Second Chances for Buildings The New Roof is Still Leaking?
Feature Article What Do Clients Want? Amenities, style and function
Firm Management Tools for Small Firms: Time Management
Index of Advertisers
Licensed Architect - Summer 2017 - Intro
Licensed Architect - Summer 2017 - cover1
Licensed Architect - Summer 2017 - cover2
Licensed Architect - Summer 2017 - 3
Licensed Architect - Summer 2017 - 4
Licensed Architect - Summer 2017 - 5
Licensed Architect - Summer 2017 - President’s Message
Licensed Architect - Summer 2017 - 7
Licensed Architect - Summer 2017 - ADA Advice Accessibility: Handrail Details for Stairways and Ramps
Licensed Architect - Summer 2017 - 9
Licensed Architect - Summer 2017 - 10
Licensed Architect - Summer 2017 - 11
Licensed Architect - Summer 2017 - 12
Licensed Architect - Summer 2017 - 13
Licensed Architect - Summer 2017 - 14
Licensed Architect - Summer 2017 - 15
Licensed Architect - Summer 2017 - Continuing Education A Review of Window, Door and Skylight Standards and Certification
Licensed Architect - Summer 2017 - 17
Licensed Architect - Summer 2017 - 18
Licensed Architect - Summer 2017 - 19
Licensed Architect - Summer 2017 - 20
Licensed Architect - Summer 2017 - Buyer’s Guide
Licensed Architect - Summer 2017 - 22
Licensed Architect - Summer 2017 - 23
Licensed Architect - Summer 2017 - 24
Licensed Architect - Summer 2017 - Feature Article The Necessary Accessory: Hardware
Licensed Architect - Summer 2017 - Continuing Education Providers/ ALA New Members
Licensed Architect - Summer 2017 - Insurance Design Professionals and Cyber Risk - Part 2
Licensed Architect - Summer 2017 - 28
Licensed Architect - Summer 2017 - 29
Licensed Architect - Summer 2017 - Second Chances for Buildings The New Roof is Still Leaking?
Licensed Architect - Summer 2017 - 31
Licensed Architect - Summer 2017 - 32
Licensed Architect - Summer 2017 - Feature Article What Do Clients Want? Amenities, style and function
Licensed Architect - Summer 2017 - 34
Licensed Architect - Summer 2017 - 35
Licensed Architect - Summer 2017 - Firm Management Tools for Small Firms: Time Management
Licensed Architect - Summer 2017 - 37
Licensed Architect - Summer 2017 - Index of Advertisers
Licensed Architect - Summer 2017 - cover3
Licensed Architect - Summer 2017 - cover4
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