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Avid students of the Chicago Energy Conservation Code

Reading code books is arguably one of the more arduous and boring parts of the construction process. One reason is that the building codes are legal documents, and so they carry a certain ponderous barrier of legalese which can repel the uninitiated.

Another reason is that they are documents of governments, and so they carry another ponderous barrier of legalese which can repel the uninitiated.

Finally, if you are not repelled enough, they cover a complex, interrelated set of topics and use lengthy numerical paragraph numbers for referencing purposes. It’s not hard to find paragraphs such as these in most code books. Try reading this to your kids at night:

Building code-speak.

18-13-101.2
The Chicago Energy Code applies to residential and commercial buildings.

18-13-101-4
The Chicago Energy Code is for new construction, or the rehabbed area only of an existing building, or for an existing building which undergoes a change of usage. Landmarks and historic structures are exempt with regard to the exterior envelope. Low-energy buildings (buildings that don’t need heat) are exempted.

18-13-101-5
Article 4 pertains to residential. Article 5 pertains to commercial.

18-13-102
Where performance ratings derived from NFRC certification are available, they can be used in energy calculations. When not available, this section provides charts with default values that can be used.

18-13-302
This section defines design conditions for Chicago as follows: Winter: -10 degrees F Summer: +92 degrees F (both dry bulb)

Residential (Article 4)

18-13-401.3
The builder or registered design professional must place a certificate of building insulation types, U-values and SHGC values in the electrical distribution panel.

18-13-402-1.1
Chart showing maximum allowed U value for fenestration .35. Maximum allowed U value for skylights: .60.

18-13-402.3
Provisions for averaging or “area-weighting” the U-values and SHGC’s for various glazed products in the building.

18-13-402.3.6
Replacement of sash and glazing must meet requirements of code as if it were new construction, however 18-13-101.4.3 states that replacement of glass only is exempted.

18-13-402.4
All building components must be sealed with an air barrier material. Windows, skylights and sliding doors shall have an air infiltration rate of no more than 0.3 cfm/sf when tested per NFRC 400 or AAMA/WDMA/CSA101/I.S.2/A440.

18-13-402.5
Vapor retarder is mandatory, to be placed on the “warm-in-winter” side of the thermal insulation.
 
18-13-402.6
Mandatory maximum area-weighted U factor is .40 for vertical fenestration and .75 for skylights.

18-13-404
Provisions for the use of a simulated energy performance analysis.

18-13-404.5.2
This chart offers specifications for standard reference and proposed designs for all major building components. It refers to previous table 18-13-402.1.1 for U factor and adds that SHGC maximum = .40

Insulation and Fenestration Requirements by Component 18-13-402-1.1

18-13-502.1.1
The building thermal envelope shall meet the requirements of Tables 18-13-502.2(1) for opaque walls and 18-13-502.3 for walls with fenestration (windows). If the building has a fenestration or skylight area that exceeds that which is allowed in Table 18-13-502.3, shall comply with building envelope provisions of ASHRAE/IESNA 90.1

18-13-502.2(1)
This is the table for opaque walls referred to above. In part, it says:
Metal framed walls inside mass walls (such as concrete) above grade: R-13 insulation plus R-3.8 for the mass wall portion.
Wood framed walls: R-13

18-13-502.3
This is the table for fenestrated walls referred to above. In part, it says:
Metal framed curtain wall/storefront U-Factor: 0.45
Solar heat gain coefficient (SHGC) for walls where projection factor (see below) is less than 25%: 0.40, no requirement where projection factor is greater than 25%.
Glass skylights U-Factor 0.60, SHGC: 0.40
Air infiltration maximum for curtainwalls and storefront: 0.3 cfm per square foot. Per 18-13-502.4.2 the test pressure is 1.56 psf.

18-13-502.3 Commercial Building Envelope Requirements - Fenestration

18-13-502 thru 505
Extensive section on HVAC and electrical requirements.

18-13-506
This section discusses guidelines for performing a full building, year round energy consumption simulation, also called “Total Building Performance”

For more on the Chicago Energy Conservation Code, go here.

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