Insulation

1. Insulation

2. Insulation • Thermal insulation is a materials that blocks or slows the flow of heat through the building envelope. • Vital to most green building designs because it allows spaces to retain what heat they have and avoid gaining excess heat from outside

3. Insulation • Insulation is primarily designed to prevent heat transfer from conduction and radiation • Resistance to conduction is measured by the R-value (higher thermal resistance = higher R-value) • Resistance to radiative heat transfer is measured by emissivity (high resistance = low emissivity and high reflectance)

4. Insulation • Conduction is the dominant factor when materials are touching each other • When there is an air gap between materials radiation becomes important • Convection usually becomes an issue when significant air pockets are involved

5. 2-categories • Fibrous or cellular products – resist conduction and can be inorganic (glass, rock wool, slag wool, perlite, vermiculite) or organic (cotton, synthetic fibers, cork, foamed rubber, polystyrene) • Metallic or metalized organic reflective membranes – block radiation heat transfer and must face open air space to work

6. Insulation

7. Insulation • Because R-values are 1/conductance (U) • Doubling the thickness of insulation will not cut heat loss in half • Exponential decay of heat flow

8. Low-Emissivity Insulation (Radiation) • Radiative heat transfer may be important to avoid • Attics or warehouses where the sun heats the building’s skin excessively • Thin sheet of reflective material can make as much diff as adding many inches of conventional insulation • Usually called radiant barriers

9. Radiant Barriers • Have low emissivity (.1 or less) • Have high reflectance (.9 or more) • Shiny reflective or white materials • Only reduce radiative heat transfer

10. Convection and Insulation • Convection through fluids (air) can also transfer heat • Unwanted convection through the building envelope can cause unwanted heat gains or losses through infiltration • Suppressing convection often makes insulation effective

11. Convection and Insulation • Convection within the building envelope hurts insulation as well • Still air is an excellent insulator, often used in insulation by small pockets of air • Foam insulation is better than batt insulation because there is less convection of air within the foam

12. Insulation • Fibrous or cellular products prevent conduction by keeping air still • Batt insulation traps air in a mat made from a low conductivity solid, glass or organic fiber • Open cell foam traps tiny bubbles of air or other gas in a poor conductor, however gas can still migrate • Closed cell foam, gas cannot travel from cell to cell

13. Insulation Materials • Typically comes in 5 different forms • Batting • Blown-in • Loose-fill • Rigid foam board • Reflective films

14. Batting/Blankets

15. Blown-in/Loose-fill

16. Foamed in Place

17. Rigid Board

18. Reflective

19. Working Together • Diff forms can be used together • Usually higher density insulation should not be placed over top of lower density material that is easily compressed • Hot air rises by convection, so it generally pools at the underside of surfaces and conducts heat upwards into those materials • Radiant barriers are more effective at preventing heat from flowing downward through a space than up

20. Movable Insulation