Frequently Asked Questions
Q: Do the VOC (volatile organic compounds) in CALGreen apply to the exterior of a low- rise residential building?
A: Not in all cases. Specific CALGreen sections addressing exterior VOC requirements are noted below.
Section 4.504.2. Finish material pollutant control. CALGreen VOC limits apply to interior and exterior conditions. As noted in Tables 4.504.1, 4.504.2 and 4.504.3, some applications are specifically identified as “indoor” or “outdoor”; other applications (e.g., Structural Glazing Adhesives) are defined within the referenced Rule 1168 as used for adherence to exterior building frames; other specified applications can be used for both interior and exterior purposes.
Section 4.504.5. Composite wood products. This section addresses formaldehyde (a type of VOC) in hardwood plywood, particleboard and medium density fiberboard composite wood products used for either interior or exterior purposes. Limits for formaldehyde are specified in Table 4.504.5.
Q: What is the difference between a vapor retarder and a vapor barrier? What is the importance of a capillary break?
A: Concrete under-slab vapor retarders are designed to intercept and block moisture vapor before it can reach the slab. They are always installed below the slab, either below or on top of the capillary break. This positioning is critical, as no concrete top coat can protect slabs from moisture migrating from beneath the concrete. The terms “vapor retarder,” “vapor barrier,” and “moisture barrier” are often used interchangeably; however, there are differences.
The California Building Code provides the definition for “vapor retarder class” as follows: (A similar definition is included in the California Residential Code.)
A measure of a material or assembly’s ability to limit the amount of moisture that passes through that material or assembly. Vapor retarder class shall be defined using the desiccant method of ASTM E 96 as follows:
Class I: 0.1 perm or less.
Class II: 0.1 < perm < 1.0 perm. Class III: 1.0 < perm < 10 perm.
The CALGreen Code defines “vapor barrier” as follows:
Material that has a permeance of one perm or less and that provides resistance to the transmission of water vapor.
A “capillary break” as used in this section provides a separation by which capillary action in the soil or rock is disrupted. “Capillary action” is generally defined by the U. S. Geological Survey as the movement of water within the spaces of a porous material due to the forces of adhesion, cohesion, and surface tension.
Q: Does the requirement for 19 percent maximum moisture content of building materials (Section 4.505.3) apply to pressure treated wood and fire-retardant treated wood?
A: Yes. In general, as per the manufacturers’ specifications, the moisture content for treated lumber is high – over 35 percent (sometimes as high as 75 percent) – and the wood is still wet when it arrives at the job site. CALGreen and the California Building Code do not make distinctions between regular lumber and pressure treated lumber. Pursuant to 2010 CBC (Section 2303.1.8.2), where preservative-treated wood is used in enclosed locations where drying in service cannot readily occur, such wood shall be at a moisture content of 19 percent or less before being covered with insulation, interior wall finish, floor covering or other materials. One way to comply with this requirement is by using kiln-dried after treatment (KDAT) material, with moisture content of 19 percent or less. Another option is to air-dry the treated lumber on the job site (or in the lumberyard). This process will take time depending on the type of weather and the extent to which the lumber is exposed. The requirement for fire- retardant treated wood is the same: for interior application, it shall be dried to a moisture content of 19 percent or less for lumber, and 15 percent less for wood structural panels, before use.
Q: CALGreen includes requirements for mechanical exhaust fans for bathrooms. Does CALGreen require mechanical exhaust fans for each bathroom?
A: Yes. The text in Section 4.506, effective July 1, 2012, requires exhaust fans in each bathroom.
This intent was initially stated only in the Residential Occupancies Application Checklist in CALGreen, Section A4.602, and identified as a mandatory feature. However, the requirement for mechanical ventilation is also required/mandated in other building codes.
Q: The code states “Building materials with visible signs of water damage shall not be installed.” What is the definition of “visible signs”?
A: “Visible signs” of water damage means an obvious presence of water damage or decay, which would affect the structural integrity of the dwelling. Discoloration, by itself, does not constitute “water damage”. However, warping, splitting or softness due to decay can be considered “visible signs of water damage” if it is present to the extent that it would affect the structural integrity of the framing members.
Q: What does “enclosed” mean?
A: “Enclosed” is not defined in the CALGreen code. As used in this section, “enclosed” refers to enclosure or covering of the framing lumber with drywall, flooring, etc. Enclosure occurs when both sides of a framing member are covered. Enclosing wall or floor framing members exceeding 19 percent moisture content would reduce air circulation and impede or prolong the drying of green lumber. Moisture content in excess of 19 percent can provide conditions conducive to mold growth and create reduced performance variations in framing lumber. Enclosed typically means the covering of the framing with drywall and occurs when both sides of a framing member are covered. Lathing, flooring sheathing, roof sheathing, shear panel or siding that is installed on one side during framing is not considered “enclosed” framing under this section.
Q: Does this section require the use of “kiln dried” lumber?
A: No. This section does not specify the lumber grade and allows the use of “green” lumber. The only requirement is that the moisture content of the lumber is verified to be at or below 19 percent prior to enclosure.
Q: Is the use of “green lumber” allowed under HCD’s green building standards?
A: Yes. The moisture reading is not taken at time of initial framing construction. This section only requires the reading to be taken prior to the wall or floor cavity being enclosed.
Q: Who is required to complete and document the moisture testing?
A: The code does not specify who does the testing. It can be done by the builder, trade contractor, building inspector or a third party prior to enclosing the wall and floor cavity. The testing can be documented by using an inspection check list or other means acceptable to the local jurisdiction to indicate that the testing was successfully completed. Methods of verification could vary from jurisdiction to jurisdiction as approved by the enforcing agency pursuant to Section 101.8 of CALGreen.
Q: Does every piece of installed lumber need to be verified for moisture content?
A: No. Each piece of lumber does not need to be verified for moisture content. This section specifically states that “at least three random moisture readings shall be performed on wall and floor framing …” This means that if the three random readings are at or below 19 percent, the walls and floors can be enclosed.
Q: At what phase of the construction schedule should the moisture readings be taken?
A: It is the intent of this section that the moisture readings are to be taken just prior to the enclosure of the interior wall and floor cavities. This will typically occur during the frame inspection prior to approval to insulate. At this stage, the exterior side of the dwelling envelope is covered, floor sheathing, roof sheathing, and shear walls may have been installed and the building is ready for sheetrock. The measurement must be taken prior to enclosure of the interior side of the dwelling envelope.
Q: During the winter months, a project may be subjected to a substantial amount of rainfall. Are subsequent moisture readings allowed under the requirements of this section?
A: Yes. At the time of frame inspection, the building envelope should be weather tight. In the case of severe rainstorms, entire jobsites will experience delays affecting grading operations, concrete installation, framing, stucco, painting, roof, and framing. Projects, which have not taken appropriate measures to ensure the framing lumber is protected from the weather during storage or for a sufficient time prior to testing, may need additional time to allow the framing members to reach 19 percent. Enclosure of the interior of the dwelling wall and floor may not commence until a passing test showing moisture readings at or below 19 percent has been verified.
Q: If lumber gets wet and stained, can it be installed and then allowed to dry?
A: Yes. Section 4.505.3 requires that the moisture level prior to enclosure be 19 percent or less.
Q: If rainy weather sets in and the structure is ready for its framing inspection, and a moisture reading is received that exceeds 19 percent, how long must the subcontractor wait before getting another inspection?
A: The time will vary based on location, air circulation and the administrative procedures of the particular jurisdiction. There is no requirement to wait a certain period of time to re-test for moisture content contained in this section.
Q: Is it a requirement to cover stored material while it is on-site prior to installation?
A: No. Covering of stored lumber is not required unless the local jurisdiction has adopted the “Tier 2” requirements.
Q: Does the requirement for 19 percent maximum moisture content of building materials (Section 4.505.3) apply to pressure treated wood and fire-retardant treated wood?
A: Yes. In general, as per the manufacturers’ specifications, the moisture content for treated lumber is high – over 35 percent (sometimes as high as 75 percent), and the wood is still wet when it arrives at the job site. However, the CALGreen code, as well as the California Building Code, does not make distinctions between regular lumber and pressure treated lumber. Pursuant to 2010 CBC (Section 2303.1.8.2), where preservative-treated wood is used in enclosed locations where drying in service cannot readily occur, such wood shall be a moisture content of 19 percent or less before being covered with insulation, interior wall finish, floor covering or other materials. One way for complying with this requirement is by using kiln- dried after treatment (KDAT) material with moisture content of 19 percent or less. Another option is to air-dry the treated lumber on the job site (or in the lumberyard.) This process will take time depending on the type of weather and the extent to which the lumber is exposed.
The requirement for fire-retardant treated wood is the same; for interior application, it shall be dried to a moisture content of 19 percent or less for lumber, and 15 percent or less for wood structural panels before use.
Q: Do local jurisdictions have the authority to require moisture control building standards more stringent than those adopted by the Department of Housing and Community Development?
A: Yes. Health and Safety Code Section 17958.7 indicates that local jurisdictions have the authority to adopt building standards, including green building standards, which are more stringent than those contained in the state building code. However, this statute also requires the local jurisdiction to make a finding that such a change is needed based upon local climatic, geological or topographical conditions. The local modification (and find) must be adopted via open public proceedings and the local amendment cannot take effect until both the ordinance and finding of local conditions have been duly filed with the California Building Standards Commission.
Q: Can an enforcing agency eliminate the need for a moisture meter testing of the lumber?
A: An enforcing agency may modify the requirements if it is reasonably necessary due to climatic, geological or topographical conditions. Any amendments made by the enforcing agency must include findings, be approved through a public process, and filed with the California Building Standards Commission.
Q: Why did the Department of Housing and Community Development (HCD) choose 19 percent for the maximum allowed moisture content of building materials?
A: After much stakeholder input and research, HCD has cited many references supporting the adoption of a 19 percent maximum allowable moisture content:
Source #1: National Association ofHomebuildersModelGREENHomeBuilding Guidelines, Section 5 {Page 147}:
Section 5.3.8 Check moisture content of wood before enclosing on both sides. Because wood’s ability to dry is compromised when it is not subject to free airflow, moisture content should be acceptable before the wood is enclosed in a wall or floor joist cavity. Reduce the risk of shrinkage and mold on lumber by ensuring the moisture content of dimensional lumber is below 19 percent before enclosing.
Source #2: 2008 National Green Building Standard Commentary, Indoor Environmental Quality {Page 159}:
Section 903.4 Moisture Control Measures. The moisture content of lumber is sampled to ensure it does not exceed 19 percent prior to the surface/wall cavity being enclosed.
Source #3: American Softwood Lumber Standards, Doc PS 20, June 2010 {Page 2}: Section 2.7 Dry Lumber.
Lumber of less than nominal 5-inch thickness which has been seasoned or dried to a maximum moisture content of 19 percent.
Source #4: A California Builder’s Guide to Reducing Mold Risk, Construction {Page 40}: Section 4 Measure moisture in wood framing before ‘rocking walls’.
To avoid mold growth in gypsum board caused by wet framing lumber, it would be prudent to make sure the maximum moisture content of the framing is below 19 percent before the wall board is placed in the home.
Source #5: Indoor airPLUS, Construction Specifications {Page 3}: Section 1.13 Do not install building materials that have visible signs of water damage or mold. In addition, interior walls shall not be enclosed (e.g., with drywall) if either the framing members or insulation has a high moisture content. For wet applied insulation, follow the manufacturer’s drying recommendations.
Advisory: Lumber should not exceed 18 percent moisture content