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7 Days to an Energy Efficient Home: Day 3

Heating and Cooling: Your Number 1 Energy Efficiency Priority

Yesterday we looked at this pie chart.

Energy Use In Australian Home

Which makes it obvious that heating/cooling is the first problem we have to tackle in our quest to make our homes more energy efficient.

Now, you can pay an 'energy efficiency expert' to come round your home and advise you on all this, but to be honest with you it really is not rocket science.

So here's my Dummies Guide to making your home thermally efficient throughout the year:

1) In summer you want to stay cooler in your house than the temperature outdoors (Duh!) To achieve this as efficiently as possible you need to do the following:

a) stop heat getting in the house

b) expel any heat that does find its way into your house


c) stop cool air getting out of the house

2) In winter you want the inside to be hotter than the outside (told you it wasn't rocket science). You do this by:

a) letting as much sun in as possible

b) letting as little heat out as possible

That's it.

So how can you do this as economically as possible? Well here's a check list for you:

1) Let's start with keeping the sun out in summer and letting it in when we need the heat, in winter. A lot of people try to do this with internal blinds. Well I've got some bad news if that is you. By the time the sun has come through the window and hit your blind, all the sun has already got into the house.

You need to block the sun before it gets through the glass. So how about an external shutter? Well apart from making your house look like a prison, they block all the light too! So you need to have your lights on in the middle of the day, plus you end up more miserable than a Pommie in midwinter because you get no daylight into your house.

The best solution is to put horizontal eaves over the north facing windows. Two simple DIY designs will keep you shaded in summer and unshaded in winter and always allow light in.

a) Framed eaves with removable shading:

Passive Solar Eave

and my favorite because it is so elegant:

b) horizontal slats angled to let the winter sun in and the summer sun out. This is achievable because the sun is higher in summer and lower in winter.

The pictures below show how effective they can be in both summer and winter (picture source: Sunergy Design)

2) The next thing you need to do is stop the heat from your house leaving through the roof, walls and windows. This is achieved by Insulation, Glazing and Gaps. And you need to fix up all three if you want an efficient home.

a) Insulation: Get your ceiling insulated. In winter, hot air rises and most of it will disappear through your ceiling if it is not insulated. It will cost you about $1500 for a decent firm.

In summer your roof space will act like a big radiator and insulation will minimize how much it heats your house up.

There are very few excuses for owning a house without ceiling insulation.

And while we are talking about your roof. Those whirlybird vents are actually very good for cooling down your roof space in summer. There is a myth that they let lots of hot air out in winter too, and that cools your house down in winter too. That is nonsense. They actually remove a lot of moisture in winter and don't harm your heating efficiency in winter at all. Even better are the mains (or solar powered) roof fans, as they blow about 10 times the volume of air out of your roof and don't require a breeze to operate. They can also be hooked up to a simple thermostat so they only operate on hot days.

b) If you have single glazed windows, you are losing 40% of your heating and cooling through them. They are evil. They have similar insulation properties to a piece of paper.

If you have the cash, get double glazing. It's a great investment. Otherwise there are cheaper alternatives: like these guys.

Again, a single glazed building simply cannot be thermally efficient in any sense of the word.

c) Gaps. The average Aussie home has enough gaps in the building skin make a hole the size of a house brick. The gaps are under doors, around electrical outlets etc.

Imagine knocking a house brick sized hole in your wall. Then imagine how much heat you would lose through it on a winter's day. That should give you the motivation to get a caulking gun and some $10 draught stoppers for the doors!

If you do all the steps above you will find that, if you have air conditioning, you will only have to use it a handful of days per year.

As for heating; here's an interesting graph that compares CO2 intensity of different heating methods, I'll let you make your own mind up:

Heating and CO2 intensity

Sorry that was a bit longer that I had planned! Let's sum up in 5 sentences:

1) Put properly designed awnings on all North facing windows

2) Insulate your ceiling.

3) Install a mains or solar powered roof fan, or a whirlybird.

4) Sort out your windows. Either go for double glazing or a double glazing alternative.

5) Fix up your draughts and gaps.

Do that and you will have fixed 80% of the thermal problems in your home.

Tomorrow we look at your water heating options.

SmartNow - The Current Cost ENVI


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