Underfloor insulation keeps your home warm in winter and cool in summer. It works by creating a barrier that protects your living space from the air flowing beneath your home. This means your floor will be the same temperature as your indoor environment rather than the outdoors.

R Value represents ‘resistance to heat’, and indicates how well insulation can stop heat flow. In this article, insulation expert ecoMaster walks you through the finer aspects of underfloor insulation to help you find the most suitable solution for your home.

What is a good R Value rating?

Keep in mind - the higher the number, the better the rating. An uninsulated timber floor, for instance, is rated at only R0.7; however, by adding insulation, carpet and underlay, this can be increased to as much as R3.5 (with the addition of R2.5 polyester underfloor insulation).

The level of underfloor insulation is calculated based on the climate zone where the building is located. In Victoria, zones fall between Zone 4 and Zone 8. The Building Code of Australia (BCA) recommends the following minimum R Values for suspended timber floors, or floors that allow any air flow beneath the home.

Zone 4 – R2.25

Zone 6 – R2.25

Zone 7 – R2.75

Zone 8 – R3.25

Determining the R Value of your floor

The R Value of your floor is calculated by adding together all of the different components of your floor including floorboards, carpet and underlay and, the level of underfloor insulation.

Timber floor without carpet or insulation

An uninsulated timber floor will achieve a very low R Value rating, as it doesn’t provide any extra protection against heat transfer. At just 19mm thickness, the average timber floor is a very poor insulator, allowing cold temperatures to move through it very easily. In the absence of a carpet above or insulation below, a timber floor will be rated at just R0.7 and be the same temperature as outside.

Uninsulated timber floor with carpet

Topping a timber floor with carpet without installing additional insulation below mostly has an aesthetic benefit rather than increasing the overall R Value – the carpet just provides an additional R Value of R0.3, adding up to a mere R1.0 when combined with the timber floor.

Timber floor with R2.0 insulation

The thermal performance of underfloor insulation is measured in R Value, which makes it very easy to calculate the total rating that can be achieved. Adding R2.0 insulation to a timber floor rated R0.7, can help achieve an overall rating of R2.7, representing a vast improvement to the home’s thermal comfort.

Timber floor with carpet and R2.0 insulation

This is the highest R Value rating achievable with R2.0 underfloor insulation. With the carpeted timber floor rating at R1.0, the addition of R2.0 insulation will offer an overall rating of R3.0. The optimal combination of carpet, insulation and timber floor will keep the winter warmth in and the summer heat out, reducing energy consumption on heating and cooling in the home.

Timber floor with carpet and R2.5 insulation

A premium quality insulation preferred by thermal comfort experts, R2.5 insulation is recommended for households working towards bringing their energy bills down to zero without compromising comfort. Even without carpet, R2.5 insulation can raise your floor’s R Value up to R3.2; with the addition of carpet, a floor that was rated at just R1.0 will become R3.5, which is an improvement of 250%.

ecoMaster recommends...

ecoMaster recommends only polyester underfloor insulation as it’s proven to be far superior to other materials available. When stapled firmly under a floor, polyester won’t sag, move or compress, holding the same R Value as the day it was installed for the lifetime of your home. Additionally, polyester insulation is non-allergenic, rodent- and mildew-resistant, safe for kids and pets, and can be handled without gloves.

ecoMaster offers both R2.0 and R2.5 polyester underfloor insulation.

Architecture & Design Team

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