How to Top Up Loft Insulation

Topping up insulation that has previously been installed in a loft can ensure maximum efficiency for preventing heat loss from the home, or heat penetration from outside. There are several reasons why topping up your insulation may be necessary. These range from the material settling over time and losing some of its thermal capability to the insulation becoming damaged.

Unfaced Fiberglass batts
Utility Knife
Staple gun

Instructions

- 1
  Check that you need extra loft insulation. The U.S. Department of Energy states that most homes should have between R-30 and R-60 insulation in the loft. The R-value refers to the effectiveness of a material at preventing heat passing through it.
- 2
  Use the Department of Energy’s Zip Code Calculator for an accurate recommendation of insulation levels for your location and house type.
- 3
  Cut lengths of fiberglass batt to fit snugly between the joists of the loft.
- 4
  Use a staple gun to affix the batts to the wooden joists.
- 5
  Avoid compressing the batts when installing them. Compressing the fiberglass can reduce its R-value.
- 6
  Place the batts crosswise across the joists only if the previous insulation sits flush with the top of the joists. Having the weave of the batt run in a different direction helps prevent air flow through the insulation.
  
  Don’t do this if the insulation is not flush, as it will leave an air gap between the layers, which will allow air flow and reduce insulation effectiveness.

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