For new builds or if you are renovating, you may be asking yourself if you should insulate your ceiling or walls first.
The best answer is both. Insulation is a once-only cost that makes your house more comfortable for it’s entire lifespan, without another cent having to be spent. But life, and our budget, does not always allow us to afford both. If you were on a very skinny budget and had to make a choice, you would insulate your ceiling first. Installing ceiling insulation can save around 35% on heating and cooling energy.
Compare this to insulating your walls. Insulating your walls saves around 15% on heating and cooling energy.
The below diagram helps show the difference:
Source: SEAV 2002
Now that we have established that ceiling insulation is more effective than wall insulation, the next question is what R-value to use.
The best answer is the highest R-value you can afford. Remember, this is a once only cost that lasts the life of the house. We recommend R6.0 for ceilings.
In alpine climates it is recommended that two layers of insulation be used in the ceiling. One between the joists and the other on top.
When installing insulation in the ceiling you want to maximise coverage BUT be mindful of ceiling lights. Downlights generate a lot of heat and a minimum
clearance of 50mm is recommended for light transformers. If you are buying lights, ask your lighting specialist if they have a fire safety barrier for the light.
So there you have it.
When insulating, install both the ceiling and wall insulation if you can. If not, then make sure you start with the ceiling and get the highest R-value product you can afford.