Attic Insulation Basics

Attic Insulation

       In comparison to the rest of the building envelope, attic spaces have more complicated heat and mass transport. Due to complex geometries, multi-layered material components, non-linear material properties, and geographic locations, the thermal energy evolution of these unique spaces is further complicated. The quantity of thermal energy transported through the ceiling to the occupied space and the energy usage of the building envelope are both affected by attic design. This is especially significant in light of changing climatic circumstances, which have an impact on the energy demand of both residential and commercial structures.

        Experiments and computer simulations were used to assess the efficacy of radiant barriers in residential applications under three different insulation levels. The tests were carried out in central Texas, USA, and involved side-by-side examinations of two identical houses with identical floor designs and thermal profiles. The homes were equipped, calibrated, and the heat transfer rates over the ceilings were measured and recorded. The computer simulations were done using a heat and mass transport model. The findings imply that when the attic insulation resistance increases, the radiant barrier decreases in heat transfer (on a percentage basis) decrease. The radiant barriers in combination with attic insulation resistance levels of 1.94, 3.35, and 5.28 resulted in average summer heat flow reductions of 1.94, 3.35, and 5.28.

       High ambient temperatures, along with high humidity, create unwelcoming conditions that are detrimental to human comfort and productivity. Insulation in the attic under the roof or above the ceiling could limit heat transmission through the roof. In the attic, a solar collector on the roof might supply both ventilation and cooling.

       A finished attic can be insulated in one of two ways. If you're simply going to insulate the living space, wrap the insulation around the room's walls and ceiling before continuing along the non-living section's floor. The area behind the knee wall will be uncomfortably hot or chilly in this instance. Apply insulation from the roofline all the way down to the floor to keep the area behind the sidewalls from freezing in the winter.

       A roof should be able to "breathe," that is, air should be able to flow from the eaves to the roof above. In the winter, this ventilation keeps the roof cool, preventing ice dams that can damage your roof and potentially your house.

       To provide ventilation in a roof that is insulated, install special rafter vents. These are stapled to the underside of the roof sheathing, between rafters. They allow air to move behind the insulation so the roof stays nice and cold while the room inside is insulated against the cold. Make sure the eave vents at the bottom of the rafter and the ridge vent or other vents at the top are free of obstructions so air can move freely.

How much insulation should you install?

      The amount of insulation recommended for your home will vary depending on a number of factors:

Where you live—Different climates require different insulation R-values. You will need a higher R-value of insulation if you live in the Northeast than if you live in Southern California.

Your home’s age—If your home is more than 10 years old, you likely need more insulation. There are many ways to retrofit a home with fiberglass and mineral wool insulation.





       Anthony D. F., Kahntinetta M. P., Jan K., Baskar G. (July 2016). Exploring future climate trends on the thermal performance of attics: Part 1 – Standard roofs. Energy and Buildings. Volume 129. Pages 32-45. Retrieved from:

       Don V. (February 28, 2022). How to Insulate an Attic. HomeTips. Retrieved from:

       How Much Attic Insulation Do I Need? Insulation Institute. Retrieved from:

       K.S. Ong (June 2011). Temperature reduction in attic and ceiling via insulation of several passive roof designs. Energy Conversion and Management. Volume 52. Issue 6. Pages 2405-2411. Retrieved from:

       Mario A. M. (May 1, 2000). On the performance of radiant barriers in combination with different attic insulation levels. Energy and Buildings. Volume 33. Issue 1. Pages 31-40. Retrieved from: