How to top up your roof insulation

James, Team member
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How to top up your roof insulation

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Project Overview

If your insulation is more than 15 years old, there is a good chance that gaps and drafts have developed. Topping up with new insulation will keep your home warmer in winter, cooler in summer and save you money on your heating and cooling costs.
Continue to step-by-step instructions

Step by Step Instructions

1 Be prepared
2 Measure your roof space
3 Tips for installing your insulation
4 Installing the insulation
5 Installing insulation in hard to reach places
6 Insulating around lights and electrical cables
7 Insulating the access hole
  • Step 1. Be prepared

    If you’re working up in the roof, the right preparation can save you from constantly climbing up and down the ladder. Start by turning off the power. You will also need a sharp knife for trimming the insulation, a tape measure, a non-conductive insulation stick, a kneeling board and a torch. Make sure you wear rubber soled shoes and suitable loose fitting clothes, including a long sleeved shirt, long pants, cap, gloves and dust mask. 

  • Step 2. Measure your roof space

    Work out how much insulation you’ll need by calculating the square metres of your roof space. Measure the length and width of your roof space then multiply to two. The area each insulation roll covers is usually marked on its packaging. It can also be useful to draw a diagram of your roof space that includes lighting and electrical fittings.

  • Step 3. Tips for installing your insulation

    Lay the crawling board across three joists. This will give you a stable work platform and also somewhere to place your tools. Take the insulation bags up into the ceiling space before you cut them open. Insulation batts come in different sizes, so make sure you choose the one that fits snugly between your roof joists. And unless you have a very small access hole, make sure you measure first prior to cutting.

  • Step 4. Installing the insulation

    Cut open a bag of insulation and let the batts expand to their original size. Cut the batts so they’re the right length and width. Start laying the insulation furthest away from the access hole then work your way back from the outside edges in. Install the insulation between the ceiling joists and butt pieces together at all joins. Save any off-cuts to fill in any remaining spaces.

  • Step 5. Installing insulation in hard to reach places

    The spaces around the edges and in the corners of your roof can be too low to safely install the insulation. When you find yourself in this situation, cut the insulation to size and use the non-conductive stick to put the batt into place and press it down.

  • Step 6. Insulating around lights and electrical cables

    Safety is paramount when you are installing insulation. Make sure you put all your weight on the joists as you work. If you need to install around downlights, cut a semi-circle out of two ends of the insulation and butt them together, leaving a 200mm gap either side of the light. Also make sure that any electrical cords and cables in the roof are sitting on top of the insulation and not under it.

  • Step 7. Insulating the access hole

    To finish the job, insulate the top of your access panel by cutting a batt to size and stapling or gluing it into place. Now it’s time to reap the rewards of your D.I.Y. job, your home will stay warmer in winter and you’ll be saving money on your heating costs.
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