BASIX, NatHERS and energy efficiency

I am by no means a tree hugging hippy, but I do value energy efficiency in a home.

Part of the reason why we are knocking down and rebuilding is the incredibly poor thermal performance of our current uninsulated double brick home. The energy wastage in heating and cooling our home does annoy me, and ultimately the inability of the home to maintain a pleasant temperature all year round makes it not particularly nice to live in.

I had naively assumed that new homes would be built to a high energy efficiency standard.

News flash for the non-cynical: your builder will build your home to the lowest minimum standard dictated by BASIX and NatHERS.

So when a salesperson promotes the fact that your building is now giving you R4.1 ceiling insulation as an upgrade, that’s salesperson bullshit for the regulations have changed and they’re required to do that. I didn’t know this until I got bored on the train and started to Google NatHERS standards.

The initial plans for the house actually failed BASIX, and so we were forced to adopt low-e glass and tiles in the study to pass – presumably barely pass. Does that mean our house is the D- student of the class?

Recently, we’ve been thinking about how there is nowhere to put a towel rack in ensuite 4 (why hasn’t the architect thought of this??). The solution was to replace the 1.8m tall window with another that is short but wide, leaving enough wall space underneath for a towel rack.

I was informed that a change in window size would require a BASIX and NatHERS reassessment, and our Eden Brae attaché sent me the NatHERS assessment for good measure.

Turns out the house will have a 5.4 star NatHERS rating.

Not all that interesting until you realise that:

1. The rating is out of 10. I’d be gutted if I scored 54% in an exam, and I would avoid a a movie rated 5.4 on IMDB, so why is a 5.4 NatHERS rating ok?

2. The NatHERS website says that a 6 star home is only considered “good”. Meanwhile, some websites state that the minimum for new builds in 6 stars.

This led me down my latest rabbit hole: can we cheaply upgrade a few things to achieve a bare minimum “good” NatHERS rating?

Turns out the answer is a big fat NO. Unless of course, you consider $4990 to upgrade ceiling insulation from R4.1 to R6 as cheap. Yeah, $5k to use thicker bats during an installation process they’d be doing anyway. How does that make sense?

Even if we upgraded the insulation, I don’t know if this would have achieved my desired NatHERS rating. It’s a bit of a black box calculation, and a sensible solution like providing an online NatHERS calculator is far too sensible for the government to adopt.

Why allow people the tools to self-assess energy saving initiatives around their home when you can keep the calculation opaque with the result that no one bothers?

In the end, I’ve decided to live with my less than good rating. I’ve read an article that argued the marginal cost of improving the NatHERS rating beyond 5 outweighed the benefits. It may not be true, but whatever helps me sleep at night.

I’ve also decided to upgrade the solar package from a measly 1.5kW to 8.5kW. That’ll definitely help me sleep at night, especially if I hook up a battery that charges during the sun-shining day to power my fan through those long hot summer nights.