Confusing Code Issues: Mandatory Rigid Insulation

There are certain portions of the code that can be a bit confusing, or perhaps have been hastily added without the proper review to determine their clarity on intent. Two such code sections are Table 502.2(1) of the IECC, and Table 1015.1 of the IBC. 

Table 502.2(1) of the IECC evolved recently from having one easy to read R-Value for walls in most types of construction, to the mysterious appearance of an additional R-Value with a ci subtext notation. Further explanation can be found in Table 502.2(2), which indicates that this ci or continuous insulation means that rigid insulation should be provided on many exterior walls in addition to the normal cavity insulation; however, the logic is never fully explained, even in the commentary. This has led to confusing requests from designers, builders, etc. to code officials as to whether or not they could simply provide more cavity insulation in lieu of completely "sealing up" the structure. The correct answer is no. The idea behind this continuous layer of ridged insulation is to cut down on what is known as a thermal bridge. In construction the framing members or small mass walls can act as a thermal bridge conducting heat from inside the structure to the cool exterior. The ridgid insualtion in essence raises the drawbridge on these thermal highways, and in addition may help keep moisture where it belongs on the outside of the structure; thus, these effects cannot be achieved by simply further insualting the wall cavity.

Table 1015.1 is a fairly straightforward summary of spaces which only require one means of egress. Studying the table one can determine that a group E occupancy may have up to 49 people before a secondary egress is required based strictly upon the occupant load, but there is a footnote indicating that daycares are limited to 10 unless a secondary means of egress is provided. This would also seem very clear; however, when inquiring minds scour the commentary for the impetus behind this slight change, this issue becomes a bit hazy. The commentary goes on to explain that this provision was actually added to increase the safety of occupancies that were actually I-4, but were permitted to elude the stringent requirements of IBC Chapter 9 due to their grade level location and access. Instead of making this a separate requirement for these particular situations, the code as written seems to make this a blanket requirement for all group E daycare spaces. As a result even daycares for older children that have classrooms as small as 400 square feet, are now technically required to have two means of egress. A code official may decide to apply some logic to the code and not require such situations to comply with this requirement. Although I personally wouldn't want to be preaching logic and the commentary, if something unfortunate were to happen in such a building; however, the 2012 code has removed/clarified this requirement, so PA will hopefuly be able to enforce this logically sometime in the next decade.