Insulating your home with spray foam is a popular and effective solution to create a warm attic environment. Warm attics are ideal when a conversion is planned further down the road.
What is Spray Foam?
Spray foam is a material made up of two chemical liquid mixtures (Isocyanate & Polyol) which quickly expands, then hardens into a solid. After spraying, the foam expands rapidly to fill the area where it has been applied.
Open-Cell Foam
- Contains less Isocyanate, resulting in a lighter, more flexible foam.
- The cells within the foam are left open, making the material breathable.
- Has a lower R-value per mm than closed-cell foam, however it expands more.
- Allows some airflow through which helps with airflow.
Closed-Cell Foam
- Contains more Isocyanate, resulting in a denser, more rigid foam.
- The cells are completely sealed, making it impermeable to air and water.
- Greater R-value per inch, making it ideal when space is limited.
- Adds increased rigidity to the surface it's applied to.
Can You Pump Spray Foam?
This is a common question, and the answer is no—spray foam cannot be pumped like concrete or blown insulation. Instead, it's applied similarly to spray paint, using specialised spray guns connected to heated hoses. These tools mix the foam’s two components at the nozzle, causing it to expand instantly on contact with the sprayed surface Because of this application method, the foam must be sprayed directly onto the desired surface.
Where Do We Use Spray Foam?
A Rate.ie focuses on using the right product in the correct situation. We typically use open-cell foam at rafter level in the attic. Open-cell can, however, be used in a wide range of areas such as walls and floors, where sound dampening, flexibility, and breathability are beneficial.
We also use closed-cell foam, commonly found in commercial settings, shipping containers, metal buildings, or anywhere that moisture ingress must be prevented. Closed-cell foam can also be used for asbestos encapsulation, helping to seal in hazardous fibres and prevent disturbance.
What Are the Ventilation Requirements?
Spray Foam requires that a 50mm ventilation gap is left between the roof felt and the foam. A Ventilation Cards are used as a barrier to ensure this gap remains consistent across the roof joists. Soffit or Roof tile Vents should also be included in order to ensure this space receives enough airflow.
SEAI Grant Standard Spray Foam Depth
To meet the current building regulations for a U-value of 0.20 in a pitched roof, spray foam insulation typically needs to be installed to a depth of 200mm. However, standard roof joists are often only around 110mm deep, which presents a challenge. When using spray foam, you also need to install ventilation cards behind the insulation to maintain proper airflow. Fitting both the vent card and 200mm of spray foam into a 110mm space means the foam would need to extend beyond the rafter line—which is typically where plasterboard would be installed if you were converting the attic. Because of this, many homeowners opt for a high-performance insulation board, such as PIR (polyisocyanurate). PIR insulation offers excellent thermal performance in thinner profiles, allowing you to achieve the required U-value, maintain proper ventilation, and keep within the structural limits of the rafters—all while staying eligible for SEAI grants and setting the space up for a future attic conversion.
How Much Does It Cost?
Our online calculator can provide an exact quote for spray foam insulation. Visit: https://estimate.arate.ie/attic
For any commercial projects, please call: 01 960 1001
