The Difference Between Wall and Ceiling Insulation – Can You Use Wall Insulation Under Floors?

ceiling insulation

Home insulation is designed for the four main areas of your house: ceiling, walls, underfloor and between floors. Insulation products are designed specifically for each area to ensure they fit the required stud spacing, cavity depth and thermal ratings (R-values). Although two products may be made from the same materials, it may not be ideal to use them exchangeably throughout the home.

Read on to find out the difference between wall and ceiling batts, and whether you can use wall insulation in your ceiling or under your floors.

What’s the Difference Between Wall and Ceiling Batts?

Ceiling batts tend to be thicker and less rigid than wall batts so that there are no gaps when they’re installed between the ceiling rafters. On the other hand, the depth of wall cavities tends to be significantly smaller than you find in the ceiling space. Therefore, wall batts need to be thinner to ensure they fit snugly between wall studs.

Since wall batts stand vertically in the wall cavity, they need to be more rigid to avoid slumping under the influence of gravity. Additionally, wall insulation usually has a water repellent added to it whereas ceiling insulation doesn’t.

This comparison refers to bulk insulation products. Keep in mind there are other types of insulation, including reflective insulation and foam insulation, which have a range of unique properties that make them ideal for particular applications.

Can You Use Wall Insulation in the Ceiling?

In general, we recommend using the insulation type designed for its specified area for the best thermal performance and energy savings. However, for some homes this may not be possible.

Two factors you should consider when choosing insulation for your ceiling area are R Values and amount of clearance.

R Values

Depending on the area of your home that you are insulating, you will be required to meet minimum R-Value guidelines according to the Building Code of Australia (BCA).

We recommend a minimum of R4.0 for ceilings. However, the highest R-value that wall batts reach is an R2.7HD. In contrast, ceiling insulation batts go up to R7.0 and are designed to perform well even in alpine conditions and very hot climates.


In homes where there is not enough clearance for ceiling insulation, there may be no other option than to install wall or midfloor insulation.

If you have very little clearance in your ceiling space then you could use an R2.5HD or R2.7HD wall insulation product. However, if you have enough space then we would recommend installing midfloor insulation rather than wall insulation.

Some of our bestselling products for this purpose include:

These insulation batts achieve higher ratings in less space than typical ceiling insulation batts and are better than R2.7 wall batts.

If you need advice, our insulation specialists are happy to help you find the best solution for your project.

Can You Use Wall Insulation Under Floors?

In many circumstances, it is possible to use wall insulation in underfloor applications. If you choose to do so, we recommend installing an R2.0 or R2.5 high density or acoustic product. These products are more rigid which means they will stay in place over time.

We also recommend that you strap the insulation in place as shown in our video tutorial How to Install Knauf Earthwool FloorShield Insulation Batts.

R2.5HD Knauf Earthwool Sound Shield Insulation is a great choice for underfloor applications because of its rigidity, accessibility and price.

Find out more about which underfloor insulation you should use.

What Insulation Should I Use in My Ceiling?

One of the most important considerations for insulating your ceiling is R-Value or the thermal performance of the product.

The table below outlines the minimum recommendations based on location.



Perth, Brisbane, Northern NSW


Melbourne, Sydney, Adelaide

R5.0 or R6.0

Alpine regions

R6.0 or R7.0

Keep in mind that the above values are minimum requirements. Upgrading to the highest R Value you can afford will boost thermal performance and reduce your energy bills.

When choosing your ceiling insulation products, don’t forget to also consider materials, cost and brand reputation. Find out more in our guide to the best ceiling insulation in Australia.

What Is the Best Insulation for Walls?

When choosing insulation for your walls, it’s important to consider both the acoustic and thermal capabilities of the product.

All insulation provides a level of thermal resistance (this is their R-value) but choosing insulation that can minimise noise levels within your home will also help you create a more comfortable home.

There are two types of wall insulation we would recommend you install in your home: external and internal wall insulation.

External Wall Insulation

The main purpose of external wall insulation is to reduce heat transfer from outside to inside and vice versa.

Choosing an acoustic insulation product can also prevent noises like traffic and neighbours from entering your home – and prevent noises inside your home from disturbing your neighbours.

Read our external wall insulation guide for more information.

Internal Wall Insulation

Internal wall insulation reduces heat flow between rooms of your home which helps make heating and cooling more energy efficient.

Acoustic insulation products are recommended for internal walls to prevent unwanted sound travel between adjoining rooms.

We recommend installing a minimum of R2.5 wall insulation in Melbourne, Sydney and Adelaide and at least R2.0 for warmer climates like Perth and Brisbane.

Read our internal wall insulation guide for more information.

Buy the Right Type of Insulation for Your Project

Whether you need high performing thermal insulation in your ceiling or acoustic batts to reduce sound transfer between rooms, Pricewise Insulation has a wide range of products to suit your needs.

If you need further information about the difference between wall and ceiling batts and whether you can use products interchangeably, our team is here to help.

Buy affordable and high performing insulation online today or give us a call on 1300 729 639 for free expert advice about your project.

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