Design Information

Criteria

2018 IECC Compliance and Design Criteria for Homes in Douglas County

New residential; construction, additions, alterations, renovations or repairs shall comply with one of the following three paths for energy conservation:

Prescriptive – Just like it sounds, you need to follow the code to the letter (while you can do better, you can’t do any type of trade-offs).

Performance – aka UA/insulation trade-off option – Example – architect uses ResCheck or something similar to show compliance such as skipping under slab and/or exterior continuous insulation in favor of adding more insulation in the attic.

Energy Rating Index (ERI) option aka the HERS path where one has to meet or be less than a target HERS score where you can use higher efficient appliances to comply.

A permanent certificate provided by the builder, shall be posted in the room where the mechanical equipment is housed. The certificate shall list the R-values of insulation used in the walls, ceiling, floor, foundation and ducts along with the U-factors of the windows. The certificate shall list the type and efficiency of the heating, cooling and service water heating equipment installed.

View more information about Energy Efficiency.

**All International Code Books can be purchased at any major bookstore, online at the International Code Council website or viewed at your local library.**

Design Criteria for the Douglas County Building Division

Wind Speeds

Wind Speeds under the 2021 IRC

115 ultimate wind speed exposure “C” for elevations less than 7000 ft. U.S.G.S.
130 ultimate wind speed exposure “C” for elevations 7000 ft. and above U.S.G.S.

Wind Speeds under the 2021 IBC

Category I – Figure 1609.3 with (4) equals 105 mph
Category II – Figure 1609.3 with (1) equals 115 mph
Category III – Figure 1609.3 with (2) equals 120 mph
Category IV – Figure 1609.3 with (3) equals 120 mph

The design wind exposure category for unincorporated Douglas County shall be exposure “C”.

Seismic

Site Class – B

Foundation Standard

ACI 318 Foundation walls over four feet in height shall have deformed bars not smaller than No. 4 in size with a specified yield strength of not less than 60,000 psi placed both vertically and horizontally with a maximum spacing of 18 inches. Foundation walls four feet in height or less shall have two horizontal deformed bars both top and bottom as specified in the following paragraph. All walls shall have two bars not smaller than No. 5 in size with a specified yield strength of not less than 60,000 psi placed horizontally at the top and bottom of the wall.

Frost Depth

Minimum 36 inches below finished grade

Snow Loads are determined according to elevation

ELEVATION RANGES (Feet)	SNOW LOAD (PSF)
5152 – 5999	30
6000 – 6499	35
6500 – 6999	40
7000 – 7499	45
7500 – 7999	50
8000 – 8499	55
8500 – 8999	60
9000 – 9499	65
>=9500	70

* Ground Snow Load = Roof Snow Load, reductions for Snow Loads are not allowed.

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