Save Energy, Save Money, Save the Planet

Energy bills seem to be designed to be difficult to understand. That way, we just pay the bill and don’t ask too many questions! Understanding our energy bills are the first step to reducing them, and ringing your provider to ask them to talk you through it can be helpful. For New Zealand, Canstar Blue has prepared a resource to understanding energy tariffs and Powerswitch helps Kiwis find the energy provider that will be most cost effective for their household.

Below is a diagram from EECA that offers some useful first steps to reducing energy use.

Infographic with tips on saving energy in your home

Approximately a third of the energy a household uses is on heating (and/or cooling). To reduce your need to heat or cool your home, this post about Passive Solar Design and this post about making warm and dry homes can help.

Another third of our energy goes to providing us with hot water. To reduce this component of our energy use, check out Cool Ways To Save On Hot Water.

The final third of our energy use is associated with lighting and appliances.

The Lighting section of the EECA website offers great support for all things relating to lighting, including choosing the right bulbs, looking at down lights, and making the most of natural light.

EECA also have a brilliant section on Appliances, which looks at how to effectively use different appliances, and how to learn about how energy efficient they are.

Each programmable appliance (dishwasher, microwave, computer, etc) or appliance that uses a remote control (TV, stereo, etc) uses approximately $20 NZD a year in standby mode. That is for each appliance. Conducting a simple appliance audit (i.e. walk around your home and note how many electrical appliances you have, and also how many of those are on standby) can help identify sources of electricity inefficiency and wastage.

Tip: Stand up and walk around to do the audit, rather than sitting in one place and trying to do it from memory – it will be much more accurate this way!

And finally, if you want to learn how to monitor the electricity consumption of different appliances or your home in general, check out this video:

Remember: increasing energy efficiency and reducing waste is often about taking a lot of small steps, rather than a few larger ones. But the small steps accumulate into big effects!




Your Home: Cold and Damp, or Warm and Dry?

As someone who was raised in Germany and now lives in New Zealand, I’ve got to say I love this videoclip!

Most of New Zealand’s houses have poor thermal performance. In winter, most of them are cold and damp. The remainder are warm but expensive to run. Ian Mayes says the problem is most Kiwis have not lived in warm, dry homes; poor quality homes have been normalised. It is so common, that  parts of the Census is dedicated to asking whether your home is cold and whether these is mould growing in it.

Thermo-Hygrometer: Modell HM 16We should all have thermo hygrometers in our homes. If everyone had one, there would be riots as people realise they are paying so much for cold, damp, poorly performing homes.

Ian Mayes, 2018

Making our homes warmer

Our homes can be made warmer by heating them well and reducing heat loss.


There are different ways we can heat out homes, and EECA has created a great resource to compare the options, depending on the size and use of the space you want to heat.

Reducing Heat Loss

Tips on insulating and reducing heat loss can be found in this blog post but here’s a little bit of extra info about my favourite topic – windows!

A single pane of glass only has an R-value of between 0.15 and 0.19. Standard double glazing is around R 0.26 and the fanciest double glazing might reach R 0.6.

Because even the best double glazed windows still have low insulating abilities, curtaining is very important.

The 4 rules for good curtaining are:

  • Cover ALL glass. Windows. Doors. Funny glazed spots. The lot.
  • Always 2+ layers. It is the air around and between layers that insulates, rather than the material itself. A single layer doesn’t trap nearly as much heat as a double layer.
  • Energy saving curtains should close off airflow over the window glass
    Image from

    Stop reverse convection currents. By having curtains touching the floor, or  pelmets, or both!

  • Good behaviour. Close curtains in the afternoon, to stop daytime heat escaping. Open curtains in the morning to allow heat in during the day.

Making our homes drier

Ventilation and moisture control can help us make homes drier.

Note: Ventilation is different to draughts in that the former is a chosen air exchange, while draughts are uncontrolled air exchanges and heat leakages.

We want less moisture in our homes because it makes them healthier and less prone to mould. Good ventilation combined with other moisture control practices can reduce relative humidity.

Once again, EECA have created a great resource for tackling dampness and reducing indoor moisture, which can be found here:


Three Waters

In Aotearoa New Zealand we like to divide water into three types:

  • Supply water (which can be potable or non-potable)
  • Storm water
  • Waste water

At least 60 million litres of water are abstracted from the Waikato River every day. This is treated to drinking water standard – at great financial cost. Approximately 500,000l will be drunk, so 59,500,000 litres of water made drinkable will not be consumed. One must ask whether this is a good use of resources and money!

rain harvest

What’s more, most homes have a water collection device on them: a roof and pipes! But we do not harvest it; we just send it straight to stormwater.

Stan Abbott is very knowledgeable about rainwater harvesting. His published materials can be useful for people wishing to learn more about rainwater harvesting. Some links to his work include:

Checklist for a good rainwater collecting system:

  • Clean roof (would you lick it?).
  • Clean and clear gutters.
  • Have slopes on the gutters, to avoid water stagnation.
  • Good tank (Plastic can leach. Concrete is self-healing, maintains a good pH and regulates temperature).
  • Minimise bends and curves in the piping if possible.
  • Have a ‘first flush diverter’, which diverts the first 200 (or so) litres of water, as these will contain the most impurities and sludge.
  • Put the tank out of the way, e.g. under garage or drive.
  • Try to get the water as clean as possible before it enters the tank, as then there is less you have to process afterwards.
  • Have a calming inlet (e.g. at the bottom of the tank) so that it does not splash and disturb water/sediment when it enters.
  • Have tap part the way up the tank, so as to avoid sediment. A 1 micron filter should be sufficient.
  • Install overflow at the bottom, as it will self-clean the water by sucking up sediment.


Managing stormwater

  • If you are harvesting rainwater, you are already storing/managing a lot of it
  • Avoid concrete and impenetrable surfaces, as these result in surface run off and erosion.
  • Only gather the water you will use – let the rest go into the ground.
  • Keep it on land as long as possible. Our modern stormwater management systems try to get stormwater into rivers as quickly as possible, leading to flooding and erosion. If we can slow the rate it enters waterways, the results are less extreme.
waikato river
Waikato River (image from Pixabay)

Managing ‘Waste’ water (‘waste’, because we should reconceptualise it to ‘nutrient-inriched-water)

It can be useful to separate black and grey water.

  • Grey water has high volumes and low toxicity
  • Black water has low volume and high levels of BODs and suspended solids

Blackwater can be sent to a worm farm for processing, before being sent to a reed bed. Grey water can go straight to reed bed.

waste water

Passive Solar Design – Building an Eco Home

Bigger Picture

In Aotearoa New Zealand, the majority of homes perform to a very poor standard. They are cold, damp, expensive to run, and making us sick. Each year there are 1600 deaths caused or contributed to by poor housing conditions.

New homes are usually also poorly designed; constructed to minimum Building Code standards.

‘The worst house you are legally allowed to build’

In addition, we are building these poor quality homes on some of the world’s best farming land. And not with diverse people and households in mind:

BRANZ is an independent and impartial research, testing, consulting and information company providing services and resources for the building industry – They have created a resource ‘Measuring our sustainability progress: Benchmarking New Zealand’s New Detached Residential Housing Stock’.

According to the World Health Organisation, the following temperatures lead to health implications:

  • Less than 16oC affects respiratory system
  • Less than 12oC affects cardiovascular system

(These values are for healthy adults. Children, elderly and people with illness or disabilities require at least 2 degrees warmer than these values.)

Living areas should not fall below 18 degrees and bedrooms should not fall below 16 degrees. Yet in New Zealand, 17.9% of living rooms are colder than 18 degrees during winter months (despite active heating), and 13.6% of bedrooms are colder than 12 degrees. In addition, 55% of our homes have visible mould.


This is making people sick, but we can do a lot to avoid it.

For example, it has been calculated that for every $1 you invest into insulating your home, you save $6-10 through direct cost savings (e.g. power bill) and indirect savings (e.g. lower medical bills, better school attendance and education, etc.).

When designing or retrofitting a home, it is important to consider the three factors:


If you try to cut on one, you will end up cutting on the others as well. We spend 55% of our lives in our home, so it is important to make sure we make it good.

pexels-photo-280221.jpegPassive Solar Design


There are 5 key principles to Passive Solar Design:

* Orientation

* Insulation

* Thermal Mass

* Airtightness

* Shading and venting

Orientation (inverse North and South if you are in the Northern Hemisphere!)

By getting the shape and size of the building right, and by facing it to Solar North, we are able to harvest ‘free heat’. This is because windows are energy loss and gain points. Some windows lose more than they gain. Too much glazing leads to too much heat loss. Most glazing should be to the North, with moderate amounts to the East and West. There should be as little glazing as possible to the South.


Surface area is also a factor to consider. The greater the surface area, the greater the heat loss; the more compact the shape, the less heat will be lost. We can think about this in terms of volume: perimeter ratio.

surface area

It is also important to be aware of corners, as they are difficult to insulate. Every external corner is a weak point in the structure, and the more corners, the greater the thermal weakness of the building.


energy use

There are 3 sources of heat in the home:

  1. Solar heat that is harvested
  2. Occupant load (heat generated through people living, e.g. bodies, appliances, etc.)
  3. Added heat (e.g. heat pump, etc.)

In New Zealand, our main aim (for most of the year) is to keep warm air inside. To do this, we need to insulate.

In an uninsulated house, heat can be expected to be lost in roughly the following ways:


Insulating different places (e.g. ceiling, underfloor, etc.), reduces the overall heat loss speed. However, it is important to think about the whole thermal envelope of the house. It does not make sense to just insulate one area of the house as the heat will then just escape somewhere else. It can be likened to being naked in the cold: it helps if you put on a jacket, but to get truly warm you will also need trousers, socks, hat, etc. 3 jackets but no trousers/socks/hat is not as useful as one of each.

When insulating, another important factor to consider are thermal bridges. Thermal bridges are materials that connect from the inside to the outside of the house. It is very easy to lose heat through thermal bridges. As with house design, edges are often the weak point of insulation, as well.

Curtaining windows is important because windows allow a lot of heat loss. There are 4 rules to good curtaining:

  • Curtain all glass (or cover it in some way if it is not possible to put a curtain on)
  • Have 2 (or more) layers
  • Stop convection currents through pelmets and having curtains to the floor
  • Good curtain behaviour – close curtains before heat is lost, around 4pm.

The diagram below illustrates the difference between a well and poorly performing curtain:


Shading and Venting (inverse North and South if you are in the Northern Hemisphere!)

shadingNorth facing side needs to have shading that is moveable and non-permanent, because it has to be able to let sun in in winter and shade from sun in summer à otherwise it will be too cold in winter and too hot in summer.

Deciduous trees are not the answer to shading in this climate, as even with no leaves they still shade at least 50% of light and heat.

The ways to keep the home cool in summer are:

  • Insulation (keeps home cool in summer, as well as warm in winter)
  • Shading
  • Ventilation


Generally, we over ventilate New Zealand homes, plus many homes are draughty. Draughts are uncontrolled air exchanges, while ventilation is when it is controlled (i.e. we have taken control over when and how the air change takes place).

We need to change air in the house every day to ensure good health. We want to do it quickly, not trickling (e.g. through draughts and by leaving a window open a little bit). By opening a window in one part of the house and another on the other side, we can create a path of air movement so that the air exchange is quick. This is especially good in winter, as fast air exchange means thermal mass will not cool down, and so the home will remain warm.

Thermal Mass


Further Resources

“Remember, we don’t have to do everything; we just need to do as much as we can. And if more of us do more, that will be enough; we don’t all have to do it all.” – Ian Mayes