Mark Meshulam is an expert witness and consultant for windows, glazing and building exteriors.
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:
And so, dear reader, Chicago Window Expert has bravely waded into the Chicago Energy Conservation Code armed only with many cups of coffee to maintain focus, and has extracted points of interest, summarized here, so you won’t have to. Think of this as the “Cliff Notes” of the Chicago Energy Conservation Code. You would never want to build a building using this distilled overview, but at least you can get an idea of what’s in there.
Extracts from the Chicago Energy Conservation Code, amended April 22, 2009
Points of Interest and Window-Related Items
Chapter 18-13 of the Chicago Building Code shall be known as the “International Energy Conservation Code of the City of Chicago”. This is also called the “Chicago Energy Code”.
The Chicago Energy Code applies to residential and commercial buildings.
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.
Article 4 pertains to residential. Article 5 pertains to commercial.
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.
Residential (Article 4)
The builder or registered design professional must place a certificate of building insulation types, U-values and SHGC values in the electrical distribution panel.
Chart showing maximum allowed U value for fenestration .35. Maximum allowed U value for skylights: .60.
Provisions for averaging or “area-weighting” the U-values and SHGC’s for various glazed products in the building.
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.
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.
Vapor retarder is mandatory, to be placed on the “warm-in-winter” side of the thermal insulation.
Mandatory maximum area-weighted U factor is .40 for vertical fenestration and .75 for skylights.
Provisions for the use of a simulated energy performance analysis.
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
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
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
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.
Projection factor (PF) is A divided by B, where:
A is the maximum overhang of a continuous element that provides shade – this is measured horizontally, and
B is the vertical distance from bottom of shading element to bottom of glazing.
Therefore, if no shading devices or projections exist, the projection factor will be 0, and SHGC will be maximum 0.40.
All framed walls, floors and ceilings not ventilated to allow moisture to escape shall be provided with an approved vapor retarder installed on the warm-in-winter side of the insulation.
18-13-502 thru 505
Extensive section on HVAC and electrical requirements.
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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