## Brief Overview of 2015 IECC Compliance Options The 2015 IECC has 3 main compliance options: Prescriptive ; Performance ; and Energy Rating Index

. 

### 1. Prescriptive Path This is the primary means of compliance with the IECC, and it incorporates three different means of calculating the efficiency of the thermal envelope : R

- value, U

- factor, or Total UA. Each path starts with the same reasonable model home with common thermal envelope components, and adds varying degrees of flexibility (and complexity). All three paths also require compliance with a number of specific requirements an d mandatory backstops

. R
- value
. Compliance is based on meeting a recipe

- like table of requirements for specific thermal envelope components , along with a more detailed list of re quirements for materials and systems

. This is the simplest compliance option, but also the least flexible.

• Building components must meet the R

- values and fenestration U

- factors in the prescriptive table (R402.1.2).

• Other requirements and exceptions ap ply, including requirements specific to heating, cooling, and water heating systems, ducts, pipe insulation, mechanical ventilation, air tightness, and lighting. The code also lists specific air barrier criteria, insulation installation requirements, etc.

• Certain mandatory backstops apply (e.g. air leakage and testing, duct testing, fenestration trade

- off maximums, etc.)
U
- Factor Alternative
. This is similar to R

- value compliance, except that the building complies when an area

- weighted average of the whol e assembly (such as wall assembly, fenestration, etc.) achieves a U

- factor less than or equal to the assembly values listed in the Equivalent U

- factors Table (R402.1.4).• As with the R

- value option, the other specific requirements and mandatory backstops apply. This option is more flexible because it permits trading within assemblies. Different parts of the ceiling can have different levels of insulation, so long as the U

factor of all ceiling area is less than the value in Table R402.1.4.
Tota l UA Alternative
. Compliance is achieved if the total proposed building thermal envelope UA (sum of U

- factor times assembly area) is less than or equal to the total UA resulting from the U

- factor table, based on the same assembly areas as the proposed bui lding. This is different from a U o calculation because the Total UA is a modeled comparison between two buildings with the same assembly areas, rather than a single number that is applied to all buildings, regardless of the glazing area percentage

. As an example, i n the Total UA, g lazing area is the same on both sides of the equation, so there are no built

- in “credits” or “penalties” for different glazing area percentages.

• Assembly areas are the same for base case and proposed home. Assembly areas are multiplied by U

- factors, then added together for a total UA number. For example:
o ( Wall area x IECC U

- factor ) + ( ceiling area x IECC U

- factor ) + ( fenestration area x code U

- factor ), etc

. = Base case UA
o Wall area x proposed U

- factor + cei ling area x proposed U

- factor + fenestration
area x proposed U

- factor , etc. = Proposed UA . The proposed UA must be ≤ the base case UA

. • U.S. DOE’s REScheck is a very commonly

- used code compliance software that calculates Total UA

.• As with the R

- value and U

- factor options , o ther requirements specific to inst allation and construction apply, such as air barrier criteria, insulation installation requirements, etc.

• Fenestration SHGC requirements must also be met, and c ertain mandatory backstops apply (air leakage and testing, duct testing, fenestration trade

- off maximums, etc.)

. 

### 2. Performance Path
The Simulated Performance Alternative is another outgrowth in Section R405 begins with a similar model home, but permits a wider range of trade

- offs. In addition to trade

- offs among thermal envelope components, the performance path includes the ability to trade among air leakage and duct tightness, etc. The p rop osed design must be shown to have an annual energy cost less than or equal to the annual energy cost of the IECC standard reference design (which is a model home based on the U

- factor table). This is more flexiblethan the prescriptive or Total UA paths b ecause it includes a broader range of components and systems in the calculation.

• Fenestration area assumption is set at 15%, unless the proposed design is less than 15%

-- in which case, the standard reference and proposed design use the same glazing area assumption. Thus a proposed home with 12% glazing is compared against a standard reference home with 12% glazing. Again, this eliminates the built

- in “credit” for reduction in glazing area.

• Like the prescriptive path, c ertain mandatory backstops apply (a ir leakage and testing, duct testing, fenestration maximums, etc.).

• DOE’s REScheck also contains a truncated version of the performance path.

• Note: The performance path does not award “credit” for heating, cooling, or water heating equipment more efficient than the mandatory federal minimum efficiency levels, and the performance path does not include appliances or other plug loads.


### 3. Energy Rating In dex ( New in 2015 IECC ) This is the most complex of the options, but it also offers the most flexibility.

• The home undergoes an analysis to dete rmine an energy rating score, or index number. The b aseline standard reference home generally reflects the 200 6 IECC requirements, Scored from 0

- 100 or more; buildings comparable to a 2006 IECC baseline earn a score of approximately 100, and buildings with no net purchased energy use achieve a score of 0.

• Calculation is based on a methodology called “Normalized Modified End

- Use Loads” for all energy used in the building, including heating and cooling equipment, water heating, lighting, and certain appliances.

• The ERI is d esigned to mirror the Home Energy Rating Index developed by RESNET , but like other IECC compliance options, it contains a few key backstops:
o Building thermal envelope shall be at least as efficient as the prescriptive tables in the 2009 IECC
o All mandatory requirements of the 2015 IECC shall be met
o Maximum ERI scores by climat e zone are listed in IECC Table R406.4

.Notes:

• T he IECC does not control the size or configuration of the house. It establishes a reasonable baseline home, and all compliance options are outgrowths from that baseline home , based on the assembly areas

. • When the prescriptive or performance path is used to achieve compliance with thermal envelope R

- values or U

- factors, a list of other specific requirements applies, including:
o Fenestration SHGC,
o requirements related to heating, cooling, and water heating s ystems,
o duct systems, including duct testing,
o air tightness and testing,
o pipe insulation,
o mechanical ventilation,
o lighting

• The ERI option has its own set of assumptions and a different baseline, and its own backstops, but it still requires compliance with the mandatory measures of the IECC.

• This overview is not intended to be a complete summary of all code requirements, but a simplified list of a few key elements in the IECC’s various compliance paths.