Just a few weeks ago, George – a great builder in Perth (name changed) – called. He’s half way through building a spectacular ~$5 million-dollar house with fantastic views.

George’s client wanted not only a beautiful home, but also an energy efficient building.

So along with the heavily travertine clad floors and walls (with hand-picked Italian travertine), George had gone to plenty of trouble to include a lot of thick insulation in the walls, ceiling and roof to limit heat gains in summer and heat losses in winter. Double glazing throughout. And sealing of the building (to stop air infiltration).

And the client had from the very start of the project, said that he wanted a geothermal heating and cooling system for his house.

George found a contractor that seemed to offer what they needed, so the client gave them to go-ahead, and everything seemed to be off to a great start.

(The builder told me all of this a few weeks ago when I met him on site – about 14 months since they had first engaged the original contractor).

But George and the client had recently given the original contractor the axe, and called us upon a recommendation from a colleague.

On site George walked me through what had been already installed, and then sat me down to show me the system design.

And this was where the penny dropped.

There really was no design.

Just a few emails and some coloured lines drawn over a PDF site plan.

It was being put together on-the-go… The company was ‘winging’ a $429,000 project (what they had quoted).

So we sat down and went through the emails. We put together a drawing showing the proposed system design. And we did our own calculations.

The main things found were:

1. The geothermal system was undersized by 41%. This means that there would not be enough energy available to heat and cool when really needed during the peak of winter and summer.
2. There were 7 heat pumps when 1 (at max 2) were required. Some machines were oversized. Some undersized. But this increased the overall power draw, decreased efficiency, and meant many of the machines were working against each other when operating simultaneously.
3. The geothermal system had been configured in a basic ‘primary-loop’ configuration. Meaning every heat pump connected to the primary-loop after the first heat pump was working harder and harder at lower efficiency (Think of breathing into a bag… After every breath there is less oxygen available for the next breath).
4. The aircon was OK. This was pretty much the only thing that was done right – because the subcontractor doing this part had done some planning.
5. The list (unfortunately) goes on…

Now, this isn’t a total throwaway system. We are salvaging what we can for George and the client. But it’s going to cost the owner an extra $90K, and there are some elements of the system which are built-in and cannot be changed (unless there is some serious demolition work), meaning some efficiency is permanently lost.

But if the appropriate calculations were performed, and a detailed system design completed, the system would be not only sufficient for its purpose, but also much more energy efficient, and would have cost the client less money now (and at the beginning), and in future running costs.

Make sure there is a detailed system design (drawings), based on specific data (calculations). Otherwise the contractor is basing your system on guesses, hopes (and maybe even dreams), and risking your money and future peace-of-mind.

But how much does getting a system calculation and design cost?

Well, it depends on the type and size of the system… There doesn’t have to be an up-front cost associated (but often for large or complex systems there can be a design fee).

There are 2 key factors to consider:

1. The entire system should be designed by one engineer/company. Most often we see issues where a supplier/manufacturer provides a design for one part of the system (which may be technically sound), but then the other parts of the system are designed/calculated by someone else (and they don’t marry together), or worse, not designed or calculated at all… and the chain is only ever as strong as its weakest link.
2. From experience, we recommend your system be designed by a professional that is suitably ‘qualified’ (tertiary degree), not just ‘certified’ (usually a 1-day training course). Every week we talk to people in our industry that don’t understand basic physics 🙁

Importantly: Ask to see the calculations and design before you commence with your project. From this you’ll get a good feeling of whether your contractor is on the right track.