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Week Nine - Insulate

Save 74 kilograms CO2e per person per year

· Weekly experiments


- We have to get rid of that dog door. A hole in the wall is ridiculous in winter. It's practically snowing in here.

My preschooler

- But that's the Baby Door! What if a baby comes to visit?

Baby on doorstep

Renovate, insulate, procrastinate

When we moved in a decade ago, we had no dog door. For us, DIY means Don't Inconvenience Yourself - we love couch time - so my partner knocked out a pane of glass and replaced it with a towel. It allowed two dogs and one baby to get in and out whenever they wanted. Unfortunately, it does the same for the weather.

Why does this matter? A poorly insulated house uses much more energy to stay cool in summer and warm in winter. Some claim a house loses up to 35% of its heat through an uninsulated roof, up to 25% through draughts and up to 10 times more through poorly insulated windows. More energy means more carbon dioxide and equivalent emissions (CO2e).

Three ways to improve home insulation

1) Draught-proofing. It's cheap and simple. Walk around your house and spot places that allow outside air to leak in, like door frames, locks, vents, skirting boards, cracks and holes. You can do proper renovations (draught tape, draught excluder, patching holes etc) or simply use a door snake. If you have a cold bathroom or unused spare room, keep the door shut so warm air doesn't leak through. Don't do a perfect job. You need some air exchange to breathe, otherwise you'll inadvertently slash your carbon footprint to zero (ie. die). But if you live in an older house or apartment, you're almost certainly leaking more air than you should. Green It Yourself has great tips.

2) Walls and roofs. Adding cavity wall and roof insulation can make a big difference. If building from scratch, choose materials with high thermal mass, then add insulation. It can be expensive but most sources agree it pays for itself in 5 - 10 years. There are DIY options if you're keen.

3) Windows. You can add good pelmets and blinds, renshading and awnings. Double glazed windows are much more efficient than single and aren't that expensive when building, but they cost a lot to retrofit later (think thousands or tens of thousands).

Week 9 experiment - adding draught-proof tape and poor woman's double glazing

We installed roof and cavity wall insulation soon after moving in, so I couldn't test those (just as well, they're expensive ). We've also had a family crisis the last fortnight, so I wound back on our efforts.

We added draught-proof tape to a few door frames and a transparent film product to 10% of our windows. You can buy a special plastic film you install in place of double glazing (unfortunately ours peeled off later in a heatwave, which may have been due to faulty installation or the glue itself. It might work better for you and it definitely added thermal insulation, so give it a go).

Installing home insulation; Clear Comfort.

Ready, set, montage! Double-sided tape; plastic film; and as installed on ​window.

Week 9 results

Many extra insulation products claim you can save one tonne of CO2e per year. ACT Government says insulation saves up to 35% of your energy. But manufacturers make exaggerated claims to sell product and governments do the same to sell policy. That's why I like to test things out myself.

I wasn't expecting to see results on my gas meter, given that we only covered 10% of our windows and did the minimum of draught-proofing. We didn't even fix the dog door (but we got to this later). But my gas meter showed we saved 96MJ, avoiding around 6 kilograms of CO2e. Over the whole winter, that would save 74 kilograms CO2e. We will definitely do more draught-proofing.

Once again, our electricity usage also dropped, saving another 8 kilograms CO2e (95 kilograms over the whole winter). With warming temperatures as spring approaches, these changes could be down to the weather rather than our insulation. However, I compared average temperatures this week and last week, and there was little difference (see notes). I'll put the reduction in electricity usage down to Green Virtue (see Week 8 post).

What would the 'average' house save?

Drawing on Week 7 data, the average 3 person Canberra household emits around 500 kilograms of CO2e for natural gas plus either 400 or 1400 kilograms CO2e for electricity (the difference is whether or not you have underfloor heating). Let's call it one tonne per household.

According to the sources above, this average house might save 35% with good roof insulation, 25% by stopping draughts and 35% with faux double glazing. Add in cavity wall insulation, window pelmets and some strategic tree planting and we're surely ahead of the game. We just saved 110% of CO2e!

This shows the danger of accumulating separate measures, rather than considering the whole. Each improvement leaves less capacity for the next. If I use one tonne to heat my house and save 50% by turning down the temperature, I get to 500 kilograms. If I save another 50% with better insulation, I get to 250 kilograms. I don't subtract 100% from my original and get to zero emissions.

We also tend to overestimate the impact of our good deeds. The Rebound Effect is an added danger. People may install insulation and then start running their house at a higher temperature, thus absorbing any savings.

Based on my own weeklong experiment and natural caution, I'll say the average house could reduce its winter heating emissions by one third with some smart insulation and draught-proofing. This would save 330 kilograms over the season. It will also pay off in summer, particularly as climate change brings us hotter temperatures.

broken image

Now that climate change is here, will my preschooler learn the joy of cracking ice on the dog water dish in winter?

Embedded emissions

As well as costing time and money, my faux double-glazing and draught tape has another cost. It took energy and CO2e to mine the raw materials and design, manufacture, sell and transport the products. This represents the 'embodied energy' or 'embedded emissions'.

Until recently, embedded emissions were thought to be a small part of the overall energy that went into running a house, so the focus was on ongoing energy use. More recent research has found this is not always the case. It's particularly relevant for more wasteful renovations, such as removing a single-glazed window to install double or triple-glazed. Can the old glass be reused or recycled? Does the new glass save enough energy to justify its creation?

My Clear Comfort and draught tape contained around 500g of plastic. It won't last very long, but it's not too energy intense and there's very little of it. I estimate its embedded emissions at around 25 kilograms CO2e (see Notes for details). I've deducted five kilograms from Week Nine savings on the basis that these components might last five years.

Spreadsheet calculations, data sources and references in 'Notes' section, Week Nine.