How to Install Batt Insulation Fastbuild Supplies

Whether renovating an old home or creating a new space, insulation is one of the most important aspects to consider. While it’s not the most glamorous job, quality insulation can save you a ton of money on heating bills.

Batt insulation – usually sold in boards or rolls – is simple to install in cavity walls and roofs. However, installing it correctly is key, as even the slightest gap or loose end can seriously impact the quality of the insulation. Following this guide will help ensure you do quality work every time.

What You’ll Need

  • Batt insulation
  • Sharp utility knife
  • Tape measure
  • Long straight edge
  • PPE (dust mask, safety goggles, gloves etc.)
  • Step ladder (particularly if working on roofs)

Comparing Fibreglass, Cellulose, and Foam Insulation Fastbuild Supplies Knowledge Centre

1. Measure Your Cavities

First things first, it pays to have an accurate idea of how much cavity space you’ll need the insulation to fill. Getting this right won’t only ensure your insulation fits snugly but it can also help you avoid having to buy too much (or have to order more because you got the dimensions wrong).

Insulation batts are often available at different lengths, widths and depths (for the depth of your cavity), so having this information to hand will be really useful when looking for the right insulation.

Insulation FAQs Fastbuild Supplies Knowledge Centre

2. Prepare the Space

When you’re ready to work, clear out the space where you’re working and ensure everything’s in place so the insulation can be fitted.

Make sure you’re wearing PPE and, if working close to wires, make sure the power is off. If your insulation is tightly packed, you may want to release and knock them a few times so it expands to the recommended depth for optimum performance.

3. Cut Batts Slightly Long

Lots of batts are designed to fit the standard cavity width. However, every job will come across a moment where batts need to be cut to size.

Always cut your batts slightly longer than the space. Doing this ensures the batts fit nicely and you won’t leave any gaps at the edges for cold air to pass through.

A general rule is that you should add an extra inch to your measurements if cutting for a standard cavity, and around half an inch is cutting around fixtures (such as boxes) or into unique spaces.

You can use a long straight edge, such as a plank of wood, to help cut your batts straight. Alternatively, you can cut in place by holding the batt against the space and cutting along the edges (remembering to add a little extra).

4. Install Batts into Cavities

Installing insulation batts at this stage is super simple – they should slot in fairly comfortably.

Use a stick to push in the edges, but don’t try to compact it too much or it can lose its effectiveness at storing heat. The insulation should sit in line with the cavity face, providing a good surface for plastering.

5. Installing Batts Around Pipes, Wires and Fittings

Installing batts into empty cavities is a breeze, but installing them into cavities containing other fixtures requires a little more attention.

It’s best to put insulation behind pipes and wires for multiple reasons, particularly so they can be easily reached in future and, in terms of pipes, the property can help keep them warm during the winter. 

If things like pipes and electrical boxes are too large to fit insulation behind, then try to cut the insulation around the fixtures. Batts can be partially cut to leave a sleeve for a pipe, while small squares can be cut out to leave room for boxes (as explained above).

6. Fill Small Gaps

Finally, ensure all small gaps are also insulated or filled to ensure there’s no space for possible heat loss (taking into consideration condensation and air flow needs). Small strips of insulation can be fitted into small areas, while things such as expanding foam can also be used to insulate the final edges around fixtures like doors and windows.

After that, you should have a complete, nicely insulated space. It’s recommended that you keep a record of the insulation used in case any questions or problems arise in future.

Whether you’re working on a new project or need some new materials for the next job, keep yourself stocked with everything you need here at Fastbuild.