Wall Insulation For Existing Homes

Wall Insulation For Existing Homes

Many older Australian homes are missing wall insulation. If you experience costly power bills, a cold home in winter and hot conditions in summer you may need to turn your attention your walls. Without wall insulation you may be losing as much as 25% of your homes heating in winter and cooling in summer. Installing wall insulation will reduce your reliance on heating and cooling appliances and save you money on your next energy bill.

Should I Replace My Wall Insulation?

Wall Insulation is built to last for years however insulation that is 10 years or older may need to be checked for damage, mould or rodents. Over time, insulation may lose its effectiveness and the R-value reduced due to compression, moisture or movement creating gaps in the insulation.  Rotting or damaged insulation may require replacement and installing new insulation into the area required. There are a number of retrofit options for an existing home, including a variety of insulating materials such as; fiberglass, blow in cellulose and spray foam.

Fiberglass vs Cellulose vs Spray Foam For Wall Insulation

The application of retrofitting wall insulation using spray foam, fiberglass and cellulose is the same, however the material used differs between these applications.

Fiberglass insulation the most common insulating material and is available in batts, rolls or loose fill which can be easily sprayed into place. This insulation type in inexpensive, effective and has a high fire rating.

Blow in cellulose insulation in an inexpensive product however it requires more effort than fiberglass installation as training is required before using the blow machine. As cellulose insulation is manufactured from ground up paper it has a lower fire rating. Overall, this product is quite effective however but has a short lifespan and can get blown around leaving gaps between the insulation material.

Spray foams are more expensive compared to the other options, and as it must be installed by a professional, this increases the overall cost of the product. In general, spray foams have a longer lifespan, are permanent and will not sag or loose its R-value over time.

Spray foams comes in two forms; open and closed cell structure. Open cell foam has air gaps inside the material and occupies more space per weight, it can be easily installed and has a lower cost than closed cell foam. As the foam expands it is effective at filling air spaces and preventing air draughts. Closed-cell foam is more common and denser giving it a higher R-value rating.

Wall insulation Batts Vs Blown-In

A major renovation project or extension with brick-veneer or weatherboard walls, provides the perfect opportunity for wall insulation batts to be easily installed. However, when the wall lining is not being removed it becomes more complicated to install insulation. In this case, pump-in cavity wall insulation can be used as it is made of small insulation particles which easily conforms to any space. The R-value achieved by blown-in insulation, depends on the material used and the thickness of the wall cavity. During installation of blown-in, it is important to ensure that the insulation material does not collect any moisture as it passes into the wall cavity as this can compromise its performance.

How to retrofit Wall Insulation?

Installing blown-in wall insulation into existing walls, can be done with brick veneer, cavity brick or weatherboard walls. A blowing machine is used to insulate the walls and access to the cavity space is achieved by lifting tiles above the cavity. A special hose is then dropped into it, and gradually lifted as the cavity fills. If the cavity is not accessible in this way, then a small hole is made in each cavity (from the outside) and material is pumped through to fill each wall space. Installing insulation into existing walls can be a tricky and complex process, therefore we recommend you seek professional support and advice before commencing. Visit our “How to install insulation” page for more information and videos.

Wall Insulation Batts – Brand Comparison

Insert Video – Pink Batts vs Earthwool vs Bradford Insulation

Pink Batts made by Fletcher insulation is a glasswool insulation batt, made from up to 80% recycled glass material. Its new soft touch technology gives the insulation a low-itch feel making it easy to install. It is a lightweight and firm batt which keeps its shape once installed and has a life span of up to 50 years.

Knauf Earthwool is a glasswool insulation product and is the least itchy of the three brands. It is made of 80% recycled glass and has no added formaldehyde. It is odourless, rot proof and does not sustain vermin, thus being an attractive product for older houses.

CSR Bradford has been manufacturing insulation in Australian for over 80 years and has a large variety of insulation products on offer. When properly installed Bradford insulation can be expected to last as long as your home!

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15 thoughts on “Wall Insulation For Existing Homes

    • Pricewise Insulation says:

      Hi Sally, insulating existing walls with blow-in insulation is difficult because of all the timber joists that are in the way. There are companies that do this (such as Enviroflex in Melbourne), however it is quite expensive. If you are renovating then one option is to remove the plasterboard or weatherboards, install R2.5HD Knauf Earthwool Insulation Sound Shield Batts and then install new plaster and weatherboards. We understand that this is not an easy or cheap solution, however once it’s complete the insulation is designed to work effectively for decades. Feel free to give our team a call on 1300 729 639 if you have any questions.

      Pricewise Insulation

  1. Rose says:

    I would like to upgrade my external wall insulation in my existing home without needing to remove plaster walls. My main aim is to reduce traffic noise from outside. Is that possible?
    If so is there any concerns and would it affect the wiring in the walls
    Also would it void my structural guarantee?


    • Pricewise Insulation says:

      Hi Rose,

      Thanks for your question! If you have timber cladding on the exterior of your home then this could be removed and the insulation can be installed this way. Another option would be to get the insulation blown into the wall cavities, but this is an expensive option and not so common in Australia. In terms of the structural guarantee, you would need to talk to a builder or engineer about this. Feel free to contact us on 1300 729 639 if you have any questions!


  2. Chris Mitchell says:

    Hello, what is the best way to reduce as much noise as possible coming through the internal plasterboard walls I share with the townhouse next to me. I plan on staying here for 5+ years, so want to get a solution to the noise problems I am having!

    • Pricewise Insulation says:

      Hi Chris,

      This is a great question. We would recommend removing the plaster on the partitions wall and installing R2.7HD Knauf Earthwool Sound Shield Insulation. For added benefits you could also install new soundproofing plaster instead of regular plaster along the partition walls. You could also look at installing R4.0 Sound Shield Insulation in your roof space, as this will help to reduce noise travelling into your townhouse this way. Feel free to contact our team on 1300 729 639 if you have any further questions. Cheers!

  3. Jen says:

    I live in an apartment on a main road and although I can hardly hear my neighbours, the traffic noise from outside is quite audible. I have double glazed windows including sliding doors to the balcony that faces the main road. Unsure if it’s the sliding glass doors that need to be upgraded or if I need to insulate my walls. Ideas on how to check?

    • Pricewise Insulation says:

      Hi Jen,

      Thanks for your question. If you already have double glazed windows along the side of the house facing the road, I would start by trying to improve the quality of the seals around the windows and doors. This is typically an area where you can get a sound entering the house. You might want to look at taking the architraves off around the doors and windows and sealing those as well to stop noise leakage.

      If you have weatherboards or other light weight cladding on the outside of the house, putting insulation in the walls will help with the sound of the traffic, however if your house if brick then insulation won’t make a huge difference. I would suggest that you start with the windows before considering other options.

      Kind regards,

  4. Wendy says:

    Can you recommend 3 companies for quotes to retrofit a weather board house cavity walls with blow in insulation please.

  5. George says:

    Our house in North Western Sydney was built in 1999. It doesn’t have any kind of insulation (sarking, ceiling and wall). Can you please suggest some ideas to insulate our house? Does the foil insulation underneath the tiles (without removing the tiling) help? I am planning to install ceiling insulation. What should be the R value. I believe the wall insulation is nearly impossible without removing the plaster board. Thanks.

    • Pricewise Insulation says:

      Hello George,

      Generally if you want a good result in the ceiling, we would look at installing bulk insulation batts, or a combination of the sarking with bulk insulation batts. We recommend installing R4.0 ceiling insulation or higher in Sydney. For the best thermal results we would recommend R5.0 or R6.0 batts.

      You can retrofit sarking, and this will help with radiant heat, you can also look at roofing blanket with foil facing. As for the walls you can look for someone that install blow-in insulation, however this is generally quite an expensive option. If you wanted to use batts you would have to remove the plasterboard, so this is best to do when completing other renovation works. Feel free to give our team a call on 1300 722 639 if you have any further questions.

  6. Jay says:

    We have 25 years old modern brick veneer double story home which we built. How can we insulate our walls? We plan to live here for another 20 years. What options we have?

    • Pricewise Insulation says:

      Hi Jay,

      Thanks for your question. Insulating walls in an existing home is never easy, especially in Australia where blow-in wall insulation is both uncommon and very expensive. Basically your best option would be to remove the plasterboard, install R2.5HD Earthwool Sound Shield Wall Insulation and then install new plaster. The best time to do this would be during renovations when all the furniture and other items have been removed. We hope this helps! Feel free to contact us on 1300 729 639 if you have any further questions. Cheers!

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