9th N1108 convert spaceN1108.1.1.1 (R502.1.1.1) Building envelope. New building
envelope assemblies that are part of the addition shall comply
with Sections N1102.1, N1102.2, N1102.3.1 through
N1102.3.5, and N1102.4.
Exception: Where nonconditioned space is changed to
conditioned space, the building envelope of the addition
shall comply where the UA, as determined in Section
N1102.1.5, of the existing building and the addition, and
any alterations that are part of the project, is less than or
equal to UA generated for the existing building.
(Essentially, HERS raters are the only people able to evaluate the UA values of the existing
building)
❖ The exception is the key to this section. Again, the
insulation, sealing and air infiltration barriers required
in the code for new construction apply to the addition.
However, the exception provides some guidance
regarding the circumstance where nonconditioned
space becomes conditioned space. A typical example
of this would be enclosing an attached garage to
become a family room. The baseline for the entire
building including the existing building would be the UA
of the existing building. That is the sum of the U-values
for the walls, windows and doors multiplied times the
respective areas of each of those components.
Accordingly, the total sum of the UA for the completed
building including the newly conditioned garage must
be less than the UA for the existing building. This
ensures that, regardless of how well insulated the
existing building is, the addition will not make the building
envelope less energy efficient.
Example: An existing house has a total UA of 222.
(Using the “Standard” Design as the existing house
from the example in commentary Section N1102.1.4.
A 20-foot by 10-foot garage is proposed to be converted
to a family room. For the example, assume the
newly renovated garage has a 20-square-footwindow.
The total UA of the existing building is 222 as calculated
in Section N1102.1.4. For the building with the
new family room, we are using R-20 wall insulation in
the cavity, with R-13 continuous insulation. Floor insulation
is increased to R-38. The total UA for that combination
of exterior wall values is 234, which is greater
than 222. Therefore, some additional insulation will be
required in order for the newly created conditioned
space to meet the code.
Climate Zone 5 and Marine 4 Fenestration U Factor shall be “0.30”.