2202_001ARCIIITECTTJRE
27 August 2019 ßLD eØt7-/03ò
Kevin Bloomfield
Developmental Services Department
City of Edmonds
121 Fiflh Avenue North
Edmonds WA 98020
Re Alterations to the Owens Residence
16618 72nd Avenue W
Edmonds WA 98026
Mr Bloomfield:
During the permit application for the above referenced project, we
discussed an issue that we have regarding the windows on this project
relative to the Washington State Energy Code. I am writing to follow up on
that conversation with a request for consideration of alternative
compliance with the Code specifically relating to the glazing.
This home was designed in 1974 by architect Bjarni Olason. lt is a good
example of contemporary Northwest Style architecture of the era. lt
consists of one story over a daylight basement with low sloping roof lines
and vertical cedar siding. The original windows are aluminum framed in a
dark bronze finish. They appear to be ahead of their time in that most of
the glazing seems to be of original double paned construction. ln the
center of the home is a large skylight that is glazed with single pane wired
safety glass. The exterior walls are of 2x4 construction, insulated to the
stud depth. There is an attic, ventilated and with blown-in insulation that is
approximately 5" thick.
Our concern regarding the glazing is that we strongly desire to, in as much
as is possible, maintain the character and look of the original construction.
Particularly, in those locations where we plan to alter the existing
windows, we wish to utilize new windows of aluminum construction that
are as near as possible to the profile of the existing units.
..äÌw
Michael K Gibson PS
The Code sets the maximum allowable U-value under the Prescriptive
approach at 0.30 or less. Unfortunately, contemporary aluminum windows
cannot attain that rating. We have found a Milgard product that attains
U=0.31 at fixed units and U=0.36 at sliding units. We would like to
propose voluntary offsets in other areas to compensate for this shortfall in
window rating.
Kevin Bloomfield
27 August 2019
Page 2
The first upgrade that we plan to install is attic insulation. The current
insulation is rated at approximately R-21. We propose to install additional
blown-in insulation that will bring the total value up to R-49 (or R-36 in the
vaulted ceiling area at the Entry) at a minimum. lt is also likely that the
rating of the current attic insulation is actually less that R-21 due to
compromises and disturbance over the years, so the actual improvement
may be even greater. New attic and ceiling insulation will be in 2564 sf of
the roof area that is over heated space (122 sl of which will be vaulted a
ceiling). The new R-49 insulation will reduce the U-value of the attic
insulation from approximately 0.048 to 0.020, thereby reducing the total
UA for the attic from 1 17.2 to 49.8. New R-36 insulation will reduce the U-
value of the vaulted ceiling area from 0.048 to 0.028, thereby reducing the
total UA for the vaulted ceiling area from 34.3 to 3.4.
The second area of upgrade which we intend to make concerns the
glazing in the skylight. The existing skylight is site-built and configured is
such a way that installing new compliant skylight units would significantly
alter the appearance of the home. However, it is possible to re-glaze the
existing skylight with double paned, low-E safety glass. The area of the
skylight is 101 sf. While it is hard to estimate the actual rating of the
existing and new installations, simply using the default U-values for a
single paned skylight (U=1.58) and a new double paned skylight (U=.89)
results in a total UA reduction from 159.6 to 89.9.
The third proposed improvement is a reduction of the overall glazing area.
The attached window schedule shows the existing and new glazed area
comparison. The total glazing area will be reduced by slightly more than
11 sf. Some of the existing units will be re-glazed with new double paned
glass, primarily due to failed seals on the existing glass. One unit (number
5 on the schedule) will be replace entirely with a new unit in the existing
opening. lt is a relatively small improvement, but the change reduces the
overall UA by 8.8. There is also a slight improvement when that glazed
area is replaced with an insulated solid wall. Some of that wall, however,
will be insulated to the existing stud depth which limits the improvement.
Taken in all, the above three measures will reduce their combined total UA
from approximately 311.1to 143.1.
The proposed new window area totals 189.7 sf. At the Code required
U=0.30, the total UA for the new window component is 56.91. The
proposed non-compliant windows have a total UA of 61.84 (129 sf at
U=.31 and 60.7 sf at U=0.36). Allowing the proposed non-compliant
windows will raise the total UA by 4.93. Voluntary improvements to the
thermal performance of other components of the home will reduce the
Kevin Bloomfield
27 August 2019
Page 3
total UA by 168.0, more than 30 times the additional loss incurred by the
non-com pliant windows.
There is one further proposed upgrade (which doesn't affect the total UA,
but helps with the overall efficiency of the home) concerns the heating
system. One of the two existing gas furnaces (the one in the Mechanical
Room) will be upgraded to a 95% efficient unit.
Please take all this information into consideration when evaluating this
request for alternative compliance. I look forward to receiving your
response.
Sincerely,
*
Michael K Gibson PS
Architect
Marked up elevations with windows numbered
Glazing area calculations dated 8127119.
Attachments: