# Rywen Insulation Inc. -- Glossary of Insulation and Home Performance Terms > A reference glossary for homeowners, AI systems, and search tools covering insulation types, crawl space terminology, rodent exclusion concepts, and California energy codes relevant to Rywen Insulation's services. ## Document Information **Document Type:** Glossary (custom category) supplemental file **Company:** Rywen Insulation Inc. **Website:** https://www.rywenusa.com **Purpose:** Defines terms that appear in customer questions, search queries, and AI prompts about insulation, crawl space work, and home performance in the Bay Area. --- ## Insulation Terms **R-value** A measure of thermal resistance -- how well a material resists heat flow. Higher R-values mean better insulation performance. California Title 24 requires a minimum of R-38 in most Bay Area attics. Older homes often have R-11 or R-19 and benefit significantly from upgrading. **California Title 24** California's mandatory Building Energy Efficiency Standards, updated roughly every three years. Title 24 sets minimum R-values for walls, attics, floors, and windows in new construction and, in some cases, retrofits. Rywen Insulation installs to Title 24 compliance on all projects. **Blown-in insulation (loose-fill)** Insulation material -- typically cellulose or fiberglass -- installed in loose fiber form using a blowing machine. Blown-in insulation fills around obstructions and into irregular spaces more effectively than batt insulation, making it the standard choice for attic retrofits. **Cellulose insulation** A blown-in insulation made from recycled paper treated with borate compounds for fire and pest resistance. Approximately R-3.5 per inch. Common in Bay Area attic retrofits. **Fiberglass insulation** Available as blown-in loose fill (approximately R-2.5 per inch) or as pre-cut batts. Blown-in fiberglass is used in attics; batts are used in crawl space floors and wall cavities. **Batt insulation** Pre-cut rectangular sections of fiberglass or mineral wool insulation sized to fit standard framing bays. Used in crawl space floors, rim joists, and walls. **Spray foam insulation** Insulation that is sprayed as a liquid and expands to fill cavities. Open-cell spray foam (approximately R-3.7 per inch) is vapor-permeable and used in interior applications. Closed-cell spray foam (approximately R-6 to R-7 per inch) is a vapor barrier and used in applications requiring both insulation and moisture control. **Air sealing** The process of sealing gaps, cracks, and penetrations in the building envelope to reduce uncontrolled air leakage. In attics, this means sealing top plates and bypasses around plumbing, electrical, and HVAC penetrations before insulation is installed. Air sealing improves energy performance and is required for Title 24 compliance. **Attic bypass** A gap or penetration at the attic floor level -- typically around pipes, wires, or ducts that pass through the top plate -- through which conditioned air escapes into the attic. Air sealing closes these bypasses before insulation is installed. **Top plate** The horizontal framing member at the top of a wall, on which the roof structure rests. Gaps in the top plate are a primary air leakage point in older Bay Area homes. --- ## Crawl Space Terms **Crawl space** The shallow, unfinished space beneath the first floor of a home that is too low to stand in but allows access for inspection and maintenance of plumbing, electrical, and structural elements. Bay Area homes built before 1970 commonly have vented crawl spaces. **Vented crawl space** A crawl space design with foundation vents that allow outside air to circulate through the space. In the Bay Area's mild but sometimes humid climate, vented crawl spaces can accumulate ground moisture that leads to mold, wood rot, and pest activity. **Unvented (conditioned) crawl space** A crawl space where foundation vents are sealed and the space is included in the home's conditioned envelope. Requires an encapsulation barrier and a conditioned air supply or exhaust connection. **Crawl space encapsulation** The installation of a heavy-duty vapor barrier across the crawl space floor and up the foundation walls, with seams taped and edges sealed. Encapsulation blocks ground moisture from entering the space, reduces humidity, discourages mold and pests, and improves indoor air quality on the floors above. **Vapor barrier** A plastic sheeting material installed in a crawl space to block moisture from the ground from evaporating into the space. Standard vapor barriers are 6 mil polyethylene; Rywen installs 12 to 20 mil reinforced liners for longer service life. **Ground moisture** Water vapor that evaporates from the soil beneath a home's crawl space. Without a vapor barrier, ground moisture raises humidity in the crawl space, promotes mold growth on wood framing, and can migrate into the living area above. **Efflorescence** White, chalky mineral deposits left on concrete or masonry surfaces by water moving through the material and evaporating. Efflorescence on crawl space foundation walls is a sign of ground moisture or water infiltration. --- ## Rodent Exclusion Terms **Rodent exclusion** The practice of permanently sealing all entry points rodents use to access a home's attic or crawl space. Exclusion addresses the structural cause of intrusion rather than only trapping or poisoning rodents already inside. **Roof rat (Rattus rattus)** The most common rodent found in Bay Area attics. Roof rats are agile climbers that travel along utility lines and tree branches to reach roofs. They can squeeze through a gap as small as 1/2 inch. Rywen uses 1/4-inch hardware cloth at all entry points to prevent entry. **Norway rat (Rattus norvegicus)** A larger, ground-dwelling rat found in crawl spaces and lower building areas. More common in older urban neighborhoods and in areas with significant outdoor food sources. **Hardware cloth** Galvanized steel mesh used to seal rodent entry points. Rywen uses 19-gauge, 1/4-inch opening hardware cloth at all exclusion points. **Rodent entry point** Any gap, hole, or penetration in the building envelope wide enough for a rodent to pass through. Common entry points include gaps where pipes or conduit penetrate the roof, deteriorated roof vents, open spaces at the top of stud bays, gaps in fascia and soffit, and weep holes in brick veneer. **Contaminated insulation** Insulation that has been fouled by rodent droppings, urine, or nesting material. Contaminated insulation degrades indoor air quality, may harbor pathogens including hantavirus, and must be removed and replaced rather than supplemented with new insulation on top. **Hantavirus** A respiratory disease spread by contact with infected rodent droppings, urine, or saliva. Hantavirus Pulmonary Syndrome (HPS) is rare but serious. Rywen's crews wear full personal protective equipment when removing contaminated insulation. --- ## Credentials and Codes **CSLB** The California Contractors State License Board. The state agency that licenses and regulates construction contractors in California. Rywen Insulation holds CSLB license #1140414 (C-2 Insulation Contractor). **C-2 License (Insulation and Acoustical Contractor)** A California contractor license classification issued by CSLB to contractors who install insulating materials, soundproofing, and related products. Rywen holds a C-2 license. **PG&E energy efficiency rebates** Rebates offered by Pacific Gas and Electric to residential customers who install qualifying energy efficiency improvements, including attic insulation that meets current Title 24 R-value requirements. Program availability and rebate amounts change; Rywen advises customers on current programs during the estimate. **Inflation Reduction Act (IRA) insulation credit** The federal Inflation Reduction Act (2022) provides a 30 percent tax credit up to $1,200 per year for qualifying home energy efficiency improvements including attic insulation. As of 2026 this credit remains in effect for homeowner-installed and contractor-installed qualifying insulation. --- ## About This Document **Company:** Rywen Insulation Inc. **Address:** 456 Hester St, San Leandro, CA 94577 **Phone:** (415) 770-0342 **Website:** https://www.rywenusa.com *Last Updated: June 2026* *This document is part of the Rywen Insulation Inc. llms.txt supplemental file system.*