R-Values Explained

R-Values Explained.

R-Value is often mentioned alongside insulation, and rightly so. But what is it?

Well, the official definition is as follows;

A measure of resistance to the flow of heat through a given thickness of a material (such as insulation) with higher numbers indicating better insulating properties.

If you’re still lost, don’t worry. It’s a strange concept.

Heat is a form of energy, and energy does not like to stay in the same place for too long. When air heats up, it tends to rise upwards. As warm air rises in your home it encounters several barriers. Your ceilings, floors and roof for example. Heat easily passes through these barriers, as they pose no resistance to the movement of the heat. This directly correlates to a low R-Value.

clipart of thermometer

The insulation in your home acts as a barrier to this movement of heat. It makes an effort to prohibit the movement and loss of heat. This table below, taken from www.todayshomeowner.com displays R-Values for different types of insulation.


Insulation Type:

R-Value per Inch:

Fiberglass (loose)

2.2 – 2.9

Fiberglass (batts)

2.9 – 3.8

Cellulose (loose)

3.1 – 3.8

Stone Wool (loose)

2.2 – 3.3

Stone Wool (batts)

3.3 – 4.2

Cotton (batts)

3.0 – 3.7

Cementitious (foam)

2.0 – 3.9

Polyicynene (foam)

3.6 – 4.3

Phenolic (foam)

4.4 – 8.2

Polyisocyanurate (foam)

5.6 – 8.0

Polyurethane (foam)

5.6 – 8.0


The most common forms of insulation used domestically are fiberglass and cellulose. As you can see, these forms of insulation are nowhere near as good as Polyurethane Foam.

Spray foam insulation provides an entirely airtight seal which minimises heat loss. It also adds structural strength and integrity and can act as a sound barrier, resulting in a more peaceful home. You can find a full list of benefits here.

If you would like to find out more about spray foam insulation or get a free quotation you can email us at info@myfoam.ie, freephone 1800 911500 or fill out a contact form on our home page.


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