How To Install Ceiling Insulation in your Existing Home in Melbourne - Step by Step

Replacing old insulation in your Melbourne home is one of the easiest and cost effective ways to reduce your energy consumption. This means, lower bills, warmer house in winter, cooler in summer and less noise. This guide takes you through the steps to easily do it! 

While the process is very straight forward and within the capabilities of any handyman, there are a few tips and tricks to make the process fast and easy and achieve a fantastic result for decades to come.

If you're new to insulation, then the Australian Government sustainability website YourHome has some great resources.  

In this guide

1. Why Melbourne Homes Need Better Insulation

Historically, Melbourne homes have given little thought to ceiling insulation. Our cheap, abundant gas (now a thing of the past), meant that our approach to a cold home was to turn the heating up! Melbourne's housing stock until perhaps 10-15 years ago was built on this concept, and so many homes still do not have adequate insulation in them! This is not the beast approach today, as we want to keep the warmth in so we use less energy in heating our homes.

2. Choosing the R-Rating

The R-rating is how well the insulation performs. Higher is better. Let's not overcomplicate things, put simply you should choose the highest rating your budget and space permits, as the incremental costs of improved insulation are paid back faster. We have an entire blog on R-Value, but the take away is below: 

Choosing Batt Insulation R-Rating

Takeaway: Choose R5 to R7, depending on your budget and space.

Pro Tip: If you are topping up insulation, ie laying batts over existing insulation, the r-value simply add up.

3. Measuring and Assessing Your Roof Space

Before you buy anything, get into your roof space via your manhole with a good torch. Measure the distance between the roof joists (the timber running length ways), and measure the depth of the joists too. Note the location of down lights, ceiling fans and a/c vents too. Also check for any existing insulation, signs of moisture or mould and any obvious hazards like electrical wires. 

Pro Tip: Roof joists are nearly always 450mm or 600mm apart. This corresponds to the pre-cut batts thickness of 430mm or 580mm, which is the size of the cavity. Choose the right size means you don't have to cut them as much, making install faster.

Measure the length and width of your ceiling space to work out the total sqm needed. 

4. Ordering Your Insulation 

You can use our calculator on each product page to work out the material to purchase, as you will need less than the total area you measure, because of the joists.

Pick a day before you plan to install for delivery, and pick a date where it is not expected to be too hot to be in the roof space. Remember if you purchase too much, you can always return full bags to us for for no cost. 

5. Dealing with old insulation

If you have existing insulation (be it blow in or old batts), you have a choice to keep or remove it. The key consideration in retailing old insulation is GAPS! It's important for insulation to have a tight fit, devoid of gaps, for the best performance. If your existing insulation is blow in, it may have blown around the roof cavity and settled at different heights and be hiding gaps. You will need to remove it. This can be done by hand or by other professionals. If you're doing it yourself, remember to wear a P2 N95 respirator mask as minimum. 

If you have existing batts with a lower spec, if they are in good condition you can simply lay the new batts on top. Again, providing they are in good condition and don't have any visible gaps or inconsistent heights.

6. Laying New Batts

Push up each batt still in it's packet into the manhole. Enlisting the help of a friend of spouse makes this much easier! Don't cut the bag open until you need to, as batts are compressed and will expand once removed from their packaging, which makes handling them a little more work. Cut open only 1 bag at a time. If you manhole is too small for a bag to fit up, then you will need to cut them open and pass up each batt individually. Not the end of the world, just a little more work. 

Start at the eaves (the furthest point from your access point) and work back towards the man hole. Place batts snugly but not compressed  into the joists. Compression reduces performance. For irregular areas, simply cut the batt with your utility knife on a ceiling joist. Batts cut easily with a couple of passes with the stanley knife! 

Pro Tp: Be careful of electrical wires when cutting! 

7. Air Sealing and Edge Details

Insulation works best when there are no gaps. Check for gaps around pipes, light fittings, and the manhole frame as these are significant heat loss points. Ensure eave ventilation is not blocked by pushing insulation hard to the eave ends. Use off cuts to block holes.  

Don't forget to also cover the manhole with a cut to size batt too. 

Ensure a clearance of 20mm or more between batts and the roof sarking or roofing, so moisture does not wick from the roof onto your batts. 

8. Final Check and Clean Up 

Before leaving the roof space, do a final sweep to confirm all areas are covered, none of the batts are compressed, and all vents, downlight and electrical equipment is not covered.

Frequently asked questions