How to install ceiling, wall & floor insulation
Ceiling insulation can make a huge difference to your home comfort and power bills. On a hot summer day, an uninsulated ceiling can be responsible for as much as 35% of your home’s heat gain. And in winter, the same uninsulated ceiling will let out up to 35% of the warm inside air.
- Bradford Black ceiling insulation batts
- Retractable utility knife and a tool for creating a straight edge
- Step ladder (if needed to access the roof space)
- Torch or lamp for lighting
- Sturdy kneeling board to lay across beams
- Broom handle or other long non-electrical conductive poker (non-metal)
- Dust mask
- Long sleeve clothing to reduce temporary irritation
Measure the distance between your ceiling joists
Measure to the centre of the joists and remember, distances may vary so make sure you measure each and every joist. This will tell you what width of ceiling batts is required. If your joist centres are 450mm wide, purchase 430mm batts. If your joist centres are 600mm, wide purchase 580mm batts. Batts can be easily trimmed using your knife and straight edge to fit odd distances.
Determine what R-Value you need
Generally speaking, the higher the R-value, the better the insulation. Insulation won’t turn your home into a hotbox – in summer and winter, it’ll stop temperature from transferring into your comfortable living areas. However, if you use a high R-Value, the thickness of the batts may mean you’ll need to consider getting some perimeter batts to fully cover the area. See Handy Tips below for more information.
Roughly measure the area you need to insulate
You can either get this from your house plans or you can measure the area and work out the m² required. This will tell you how many packs of batts you need.
Calculate how many packs you need
Divide the area to be insulated by the coverage per pack. Round it up to determine the number of packs you need to buy.
Calculate your requirements
Install the insulation
- Take your sealed packs into the roof and open them there. They’re going to expand a lot and you don’t want to be dragging individual batts up a ladder. Open the packs with your utility knife, drawing it down the side of the pack.
- Don’t stand on the ceiling plasterboard – only on the joists or use your kneeling board. Position your kneeling board over at least two joists for maximum stability.
- Start from the outside of the roof and work your way back to the access point. Don’t forget your perimeter batts if you’re using them.
- Push your batts out towards the eaves so that the first batt is 50mm across the top plate (edge of the outside wall) but remember the 20mm gap between roof and batt. Use your poker to push them into hard-to-reach areas.
- Fit the batts snugly between the ceiling joists onto the ceiling plaster, and butt them up against each so they’re firm but flat.
- Fill in any gaps with offcuts or trim a piece off a fresh batt.
- Wear long sleeve clothing to prevent temporary skin irritation.
- Don’t choose a hot day to do the install. If it’s summer, do the job early in the morning before heat builds up.
- It’s always a good idea to get an extra pack above the minimum required. Nothing is more annoying than finding yourself short of materials halfway through a job. You can always return any unopened packs to your local Mitre 10 store.
- Take a large bottle of water with you so you don’t have to go back to the house for it.
- Insulation should be installed right to the eaves so the batt is 50mm over the outside wall. However, you need to leave an air gap of 20mm between the insulation and your roof. Standard R3.5 ceiling insulation batts are 185mm thick, so depending on the roof pitch the batts may touch the underside of your roof at the edges of your ceiling. If so, we recommend you purchase some higher-density wall batts to fill in around the ceiling perimeter, then use the R3.5 ceiling batts for the rest of the space where there is enough clearance. This will ensure you get the best possible performance from your insulation.
- If you have a very low-pitched roof or reduced access, you may need help from a specialist insulation installer.
- When the job is done, have a shower to wash off any skin irritation, enjoy a cool drink and pat yourself on the back for a job well done.