Why Is continuous insulation better than cavity insulation?
Continuous insulation is the only way to block thermal bridging, according to Dow Buidling Solutions, a leading insulation solutions manufacturer. Wrapping the exterior wall in a continuous layer of rigid foam protects the cavity and the stud, providing high R-value in several ways:
- Continuous insulation minimizes the temperature differential between the cavity and the stud, reducing heat loss and increasing the effective R-value of the wall system
- With continuous insulation, the dew point moves from inside the cavity to the exterior wall, preventing mold and mildew accumulation inside the wall
- When combined with a drainage plane and moisture barrier, continuous insulation provides better protection against water intrusion, reduces material degradation and extends the service life of the home or building
Cavity insulation (or batt insulation) limits thermal protection to the wall cavity and creates a thermal bridge (thermal shorts) for heat transfer through framing studs:
- Exterior walls with their inherent thermal bridging from the wood framing contribute to 17 percent of the total heat loss of the house
- In a steel-framed building, thermal shorts reduce the R-value of cavity-insulated wall systems by more than 50%2
This thermal bridging encourages condensation and moisture build-up between gypsum or conventional wood sheathing and batt insulation. Condensation compromises the wall assembly by:
- Reducing the R-value of cavity batts
- Encouraging mold and mildew
- Shortening the service life of the wall assembly
Continuous insulation offers increased performance. Here's how:
Higher R-value: Whether it's for a commercial or residential structure, building experts consider continuous insulation a best practice. Using closed-cell foam insulation provides a very high level of rated R-value per inch and the highest level of effective R-value per inch.
Thinner wall profile: With roughly twice as much R-value per inch as traditional batt, closed-cell foam insulation maximizes thermal performance while minimizing wall thickness. Continuous insulation is now a prescriptive ASHRAE 90.1-2007 standard for above-grade, steel-frame commercial buildings in six out of eight U.S. climate zones. In residential construction, continuous insulation is a very cost-effective option in climate zones where R-20 or R-13+R-5 is mandated under the International Energy Conservation Code (IECC), 2009.
Less waste: High-performance foam insulation provides durability, moisture resistance, and the highest available R-values per inch – three qualities that help buildings last longer and send less waste to landfills.
Tighter shell: In addition to thermal bridging, batt-insulated walls lose a very large percentage of conditioned air through gaps, cracks and crevices. Sealing the interior wall with spray foam insulation blocks air infiltration, which accounts for 38 percent of heat transfer in a typical building with cavity batts.
Companies: Dow Building Solutions