The benefits of improving your thermal performance of your home are well known - lower energy bills, warmer in winter and cooler in summer. Not to mention that your home is actually more comfortable all this time too, without cold spots throughout the home.
As Melbourne's home stock is a mix of styles, ages and an ever evolving minimum building standard (and changing attitudes from 'just turn the heater up' to 'insulate better so you don't need to turn the heater up') - knowing what upgrade to do first is increasing a common question.
This is a surprisingly easy question to answer, when you have all the information on cost vs benefit of both. Every home is different, so you just need to do a quick assessment of your home first. Don't worry, this is an easy task.
How Heat Moves through your home
Let's start with how you home cools or heats to the external elements. ie where heat loss or gain actually happens a standard residential home in Melbourne.
| Part of Home | Approx. Heat Loss/ Gain |
| Ceiling / roof | ~40% |
| Underfloor | ~15% |
| Walls | ~15% |
| Windows | ~25% |
| Gaps & Air leakage | ~5% |
As you can see, the ceiling is the largest single point in the home. However, from a comfort perspective, windows are actually responsible for the majority of the uncomfortable temperature feelings within the home due to radiant heat gain or loss. This is because you are often right next to a window while living in your home, whereas the ceiling is often a meter away.
What Bulk Insulation Does
Bulk insulation, typically a glasswool or sometimes polyester batts, are installed in the ceiling, walls, and sometimes underfloor, and works by trapping air in pockets that slow down heat transfer.
Pro's
- Very cheap to install - a typical home is only $1,500-$4,000 depending on size and specification of insulation
- Can be installed yourself in a day
Con's
- Often there is existing insulation that needs to be removed, which while not hard, can be a thankless task
- Does not specifically address "cold spots" in the home, ie single points of heating/ cooling loss
What Retrofit Double Glazing Does
Retrofit double glazing means removing the existing glass and installing a Insulated Glass Unit (IGU). These are fully sealed units that have an insulating gap of argon gas between the panes, and most typically these days a low-e coating. Together they block radiant heat (the low-e coating) and conduction (the argon gap), as well as noise.
These are installed without having to rip out your old windows, just the glass.
Pro's
- Effective at creating a more consistent temperature throughout the home - removes that "cold radiant" feeling when walking past a window
- Major reduction in noise entering through the windows (the weakest point for sound to enter your home)
- Improves security as the two panels are harder to smash through
- Prevents condensation on windows, which can lead to a colder feeling home and mould growth over time
Con's
- Significantly higher cost than ceiling insulation, usually $8,000 to $12,000 for all windows in a three bedroom home.
- Install is best suited to trained professionals (we recommend Retrofit Double Glaze here) or skilled DIY enthusiasts (in which case you can buy the glass from DIY Double Glaze)!
So Which to Choose First?
Easy! First, look in your roof cavity through your manhole. If there is no insulation, blow in insulation, or the insulation batts are compressed, dirty or less than 150mm thick - then do the ceiling! The cost/ benefit is undeniable.
However, if your already have decent ceiling insulation, then tackle the windows, as this will be the major source of heat loss/ gain.
So, ask yourself:
- Is my ceiling insulated? If no - insulate first.
- Do I feel cold near my windows or hear a lot of outside noise, even with insulation in place? If yes - retrofit double glazing is likely your next priority.
- Is condensation forming on the inside of my windows in winter? That's a glazing problem, not an insulation problem.
Still Unsure?
The honest answer is that the right choice depends on your home with respect to its age, orientation, existing insulation levels, and window construction. A proper in-home assessment will identify exactly where you're losing the most comfort and dollars, so you're not guessing. Most local councils can point you in the direction to have an energy assessor visit your home and let you know the best approach.