The Owner-Builder Guide to DIY Ceiling Insulation Installation

This is a guide for owner builders and home improvement aficionados who want to install their own ceiling insulation batts. Insulation installation is a relatively safe, manageable task provided you do your research and take the necessary safety precautions. In this guide, we will take you through each step of the process. This guide is designed for pitched roofs with flat ceilings, and assumes that air sealing and sarking has already taken place.

 

Part 1: Preparation

Identifying what you need

The two biggest questions you need to ask yourself when deciding on the right ceiling insulation products for your building are:

  1. What R-Value do I need?

In Melbourne, the minimum total R-Value required by the Builders Code of Australia is 4.1 for roof/ceiling insulation. In Victoria’s alpine region, a higher minimum R-Value is required. It is recommended that you choose insulation with an R value above the minimum to improve comfort and energy savings. In a nutshell: the higher the R-Value, the better the thermal performance.

  1. Is a vapour barrier required?

In Melbourne, a vapour barrier is required to prevent condensation in a number of situations including:

  • In roof spaces with a low ventilation rate
  • If the roofing is metal
  • If high amounts of vapour are generated but not exhausted
  • If there is a significant difference between the indoor and outdoor temperature (as in an alpine environment)

A vapour lining should be installed on the ‘warm’ side of the insulation directly above the ceiling lining and all of the vapour barrier’s joints should be taped or glued to ensure moisture is kept at bay.

 

Equipment

To perform a DIY ceiling batt insulation installation, you will need the following:

  • Ceiling insulation batts
  • Protective clothing (including gloves, a face mask, coveralls, protective eyewear)
  • Utility knife
  • Measuring tape
  • A straight edge
  • A ladder

 

Part 2: Technique

Gaps: Where to have them and where to avoid them

Leaving gaps in your insulation will dramatically reduce its performance. Batts should be fitted snugly with no gaps left around ducts or pipes. Pay special attention to the insulation in the corners of your ceiling as these areas are a common source of heat leaks. Any holes or joins in reflective insulation should be taped up and make sure the ends of multi cell and concertina foils are sealed.

Clearances

Minimum clearances or approved enclosures are crucial around ‘hot objects’ which pose a fire hazard including:

  • Recessed downlights
  • Transformers
  • Flues from fires
  • Exhaust fans
  • Appliances
  • Fittings

Refer to the manufacturer’s installation instructions to find out what the minimum clearances are.

Ventilation (not the same as gaps)

Ventilation allows built up moisture to escape. When insulating your tiled roof, leave air gaps along the ridgeline, or between the tiles. For other roof types, using gable or eaves vents is the best option. If you are in a bushfire prone area, use fine stainless steel mesh to cover any openings. This will prevent cinders from entering the roof space.

Electrical wiring

Have an electrician check that any electrical wiring is suitably sized so it doesn’t overheat when covered by insulation. Never use insulation materials containing reflective foil around electrical wiring and fittings. Insulation containing reflective foil should also never be secured with metal staples.

Handling

Bulk insulation should never be compressed as this will reduce its performance. During installation, cut your batts down precisely to ensure there is sufficient space for the insulation. Bulk insulation should also be kept away from moisture wherever possible. If there is a risk of condensation, install a vapour barrier.

Part 3: Process

  1. Put on all your protective clothing as certain types of insulation batts can cause skin irritation and working in a dusty roof cavity can cause respiratory issues.
  2. Measure the distance between your ceiling joists. This distance may vary so make sure you remeasure each space before making a cut.
  3. Using a utility knife and a straight edge, cut the batt to size. Keep offcuts for patching up any gaps or holes which may appear.
  4. Install the batt in between the ceiling joists.
  5. Continue the process until your ceiling is insulated.

 

Need Help?

As this guide illustrates, whilst installing ceiling insulation is a relatively simple task, there are many different factors to consider before you can actually begin the project. If you are unsure about the insulation requirements of your building Insulation Essentials can help. Since 2000, we’ve been helping owner builders find the right insulation solutions for their project. Give us a call on 03 8339 7111 and one of our team will be able to discuss your insulation requirements and help you find the right ceiling insulation batts in our online store. If you are no longer interested in taking the DIY route we also offer installation services.