Tag Archives: Renovation

Energy Cost Calculator

How can a renovation help to save money?

Imagine the house’s external walls as a continuous shell, and every little gap you have in this shell will result in heat loss, or the other way around in summer.
Hence, every time you stop this unwanted heat transfer, you can reduce your energy bill.

Energy Cost Calculator

With the FirstRate5 energy rating assessment tool, we can determine the Total Energy Usage per year of the different Star Rated versions of our home.
Once we have the annual energy costs, we can factor in the effects of inflation to understand how much  money the renovation can save us over a period of 7 years.

The existing house, with 0.8 Stars, will cost us more than $33.500 over the 7 years.

Insulating our house, sealing all wall and ceiling vents, putting in self-closing exhaust fans and weather-stripping windows and doors brings us to 3.6 Stars and we will use 38% of the energy – saving approximately $20,000.

Putting in an air-lock and replacing some single glazing aluminium windows with good performing double glazing windows will increase the energy rating to 5.6 Stars. We will use 19% of the energy – a saving of more than $27,000.

5.6 Stars: It’s not that hard

Now, after we have retrofitted the insulation and sealed all the gaps,  it’s time to look into other options on how to improve the energy efficiency. But also we want to optimise the floor plan.
We think there is potential to utilise the floor area more efficient. We decided to reorganise the kitchen/living/dining area and also that an European laundry would be enough for us. That means we will be able to transform the 2 bedroom unit into a 3 bedroom unit. But that’s not all, we will even manage to fit in an extra ensuite for the new master bedroom.

But what are we planning to do to that will improve the energy efficiency?



One of the first things you should do is to put in an air-lock. With the extra door you can close of the entry area. This is especially important in Winter, then
the moment you open the front door the warm air gets sucked out and you have to start afresh. In summer it can be open all the time, but there should be a way in winter to close it off.

Replace Windows/Doors

Many might think, there is no point replacing one or 2 windows, it won’t make a difference. But you would be surprised what you can achieve. Especially big windows lead to unwanted heat gains or losses. Even just replacing some windows can make a massive difference.
We want to put in a new french door towards the new deck, also we will put in a new door and new windows in the new master bedroom. So altogether we will put in 2 new windows and 2 new doors. Keep in mind, the lower the U-value the better performing the window. In our case, we will try to get the best windows/doors we can get; double glazed, uPVC or timber windows, with a  U-value of 1.99 or lower.

Energy Savings

Just putting in the air-lock and a few new windows/doors increases our energy rating to 5.6 Stars. This means the renovated house will need 81% less energy, meaning instead of $4,300, we will just pay $829 per year.

Imagine how much energy you could save!!!

3.6 Stars: How to make an existing home more energy efficient without spending a lot of money

There are a few simple things you can do that will make a huge difference to your energy bill, without spending a lot of money.
In our case, it brings us already up to 3.6 stars. This means that we will need 62% less energy than before the renovation. Instead of paying more than $4,300 per year, we can reduce our energy bill to approximately $1,600.

So what did we do?

Seal your house

Every little gap causes unwanted heat losses and heat gains, therefore, one of the first things you can do to make your house more energy efficient are:

– Close off wall and ceiling vents

– Replace existing exhaust fans with self-closing ones

– Weather-stripe existing windows and doors

– Don’t use standard down lights in the ceiling as they leave gaps/holes in the insulation

Insulate your home as much as possible

The more insulation the better. Put in as much insulation as you can
In our case, we’re going to install insulation to the ceiling and to the roof, with a combined overall R-value of  R6.0 and insulation to the timber sub-floor of R2.0.

– Insulate the sub floor using waterproof rigid insulation and ensure there are no gaps around the insulation – for example, use expandable foam.

– Update roof/ceiling insulation using both reflective and bulk insulation, the higher the R-value the better. Aim for a combined R-value for the roof and the ceiling insulation of min. R.5.0

Retrofitting an existing brick veneer wall is a bit more tricky.  It is a pretty time intense and messy job. Therefore we decided not to insulate the walls, at least not at this stage.
Taking off the plasterboard to install bulk insulation may be the most obvious way, but you can also bore holes in between studs and pump in cellulose fibre. But if you do this you have to ensure that the walls are closed at the bottom and that the insulation can’t fall though.

3.6 stars is a good start, but we can do better.