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·633 words
Felix Andrews
Table of Contents
Home Journey - This article is part of a series.
Part 10: This Article
Costs and benefits.


According to my rough figuring, I spent a total of about $22k on all this work. That vastly understates the true cost because it does not account for my labour.

Here is a breakdown into categories:


In this series I have focused on improvements to the thermal fabric. At the same time we have upgraded appliances:

  • solar panels 12.7kW (8kW inverter)
  • battery 10kWh
  • hydronic heat pump (replacing gas boiler)
  • solar hot water system
  • ceiling fans
  • heat pump clothes dryer
  • electric vehicle

Having solar panels has transformed my relationship to energy. I am very aware of how much we are using and generating. I feel it viscerally when we are forced to draw power from the grid. Unfortunately, that is what we have to do all winter.


I feel better about my house now. Currently it is winter, and the house is a tolerable temperature, at least in afternoons & evenings. Until a few weeks ago, even though I had poured thousands of hours of work in, I felt that it was fundamentally a failure. Draught sealing, wall insulation, secondary glazing, window coverings, slab edge insulation, box gutter insulation, ceiling insulation, and I was still cold. Then I did a big push to complete the remaining bits of ceiling insulation and gap filling. And at last the dial started to shift, maybe.

That’s the problem with the thermal envelope I guess… Heat takes the path of least resistance, especially in the case of air leakage. So the returns from effort may not show up until the end.

Here is an obligatory before / after shot. The “before” day is 19 June 2023. The “after” day is 4 July 2024. Fairly arbitrary choice. There are differences of course, the weather was not the same, the previous days were also not the same, we ran the heating differently etc.

Basically, it was a couple of degrees warmer inside. (It was also warmer outside, but whatever.)


Family room

Energy consumption


OK. Let’s be real. I probably would have gotten a better result, in terms of both air temperature and power consumption, by just installing a reverse cycle air conditioner.

But: the house was designed with in-slab hydronic heating. There is nowhere I can think of that a reverse cycle compressor unit could go without being a nuisance. And if we didn’t run the hydronic heating the floor would be intolerably cold.

So in one sense, my comfort problem is simple: the house is under-heated. If we ran the hydronic system all day I’m sure it would be very comfortable, but who wants to do that? There is a limit to how many kWh are justifiable, either financially or socially / environmentally. At least now I feel like I have done as much as I can to reduce energy waste, i.e. heat leaking through the building fabric.

What I would do differently

  1. At design stage, all the problems could have been easily avoided if they had been understood and prioritised.
  2. Had I understood the problems early on, before starting to fix them, I would have taken a completely different approach.
    • I would have done a deep retrofit: remove the roof and wall cladding, to wrap and insulate the house properly. Maybe even do a floating floor over the concrete and abandon the floor heating.
  3. Mistakes I made:
    • secondary glazing and wall insulation were probably not worth the cost and effort (the mistake here was believing NatHERS);
    • solar hot water was not worth it;
    • solar panels should have all been tilted north on frames.

Sealing gaps is one thing that does obviously make a difference (it can be felt). Speaking of which:

Next #

Stay tuned for the sequel: ventilation and air quality.

Home Journey - This article is part of a series.
Part 10: This Article