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Dr Paul's Guide to Saving Energy around the Home
The dynamics of energy use in a house are strongly affected by
climate. This guide focuses quite a lot on issues of insulation,
and is designed for people living in temperate climates with cool
winters, with temperatures reaching a few degrees below freezing.
If you live in a warmer or colder climate than this, then you should
ignore much of what is said. For really cold climates, you need
to do a lot more than is identified here. For climates with mild
winters and mild to hot summers, the issues change to being the
need to keep heat out and/or promote cool breezes in humid climates.
You will need to go somewhere else for that sort of advice.
This guide has been built up on the basis of experience of living
in the cool temperate climate cities of Dunedin, New Zealand and
Canberra, Australia. For specific advice on the needs of your home,
you need to obtain expert advice either from us or someone else
in your city.
This informal guide to energy savings around the home is intended
as a helping hand to those of you bamboozled by the competing claims
of different products. Much of what is written is based on personal
experience of trying to turn draughty, uninsulated houses into something
bearable while paying attention to the fact that as a born miser
I strenuously object to paying the power bill.
I can't speak for other cool temperate climates, but Australia
and New Zealand are afflicted by the belief that insulation is unnecessary.
Thus in New Zealand, most homes are wooden and uninsulated, with
insulation standards only coming into force in the past twenty years.
This leaves an enormous stock of older uninsulated houses. In Australia,
insulation standards are an even later arrival on the scene, and
in my current home town of Canberra buildings could go up with essentially
no insulation up until just a few years ago. This is incredible,
given than minimum overnight temperatures can reach -8 degrees C, leading
to an internal condition best described as utter misery.
At least Canberrans have the sanity to adopt central heating as
a common feature in houses, which takes the edge off the problem
until you receive your power bill. I found this out to my expense
when my first winter gas bill came in - $950 for three months of
heating. OK, so we had a newborn in the house and we were keeping
things fairly cosy, but obviously we needed to do something - and
fast.
Central heating is, however, by no means a given. In New Zealand,
central heating is as rare as hen's teeth. As a result, and as most
visitors from overseas will tell you, houses are cold and miserable.
For these houses, insulation won't save you energy, because if you
don't heat your house, what is there to save? Indeed, when I insulated
my house in New Zealand, my energy bills went up because
suddenly I could consider heating more than the space immediately
in front of my electric radiator. Beforehand, even my 16 kW multifuel
burner couldn't make the living room comfortable.
However, adding insulation will make a big difference to how cold
your house gets without heating and will vastly improve the ability
of your two bar heater to heat the living room on a frosty night!
It will also reduce problems with condensation and may even improve
your health by giving you a warmer environment. So, in summary:
insulating your house will only save you money if you use heating
- but do it anyway - it will improve your house and your life!
Roof insulation
Standard fibreglass insulation is still a good insulator, has a
good lifespan and is easy to install if you have good access to
your roof space. If you don't like handling fibreglass, or if you
prefer natural products, there are a number of perfectly acceptable
alternatives such as wool and polyester insulation that will do
the job just as well, albeit at a slight cost premium in general.
If you are on a budget or you have a difficult roof space, use macerated
paper insulation, which is cheap, effective, and can be pumped into
difficult corners.
Some people raise doubts about the effects of settling on the long
term performance of this type of insulation, but at half the cost
of other insulation types, and a good environmental profile - a
recycled product that is largely free of nasties - it's difficult
to ignore. I've used this stuff, known commercially as "Insulfluff,"
in my impossible-to-access ceiling and it does the job fairly well
and cost less than $NZ10/m2 installed, which was significantly less
than fibreglass would have cost me. In my house in Canberra, I got
R4 fibreglass blanket installed professionally for marginally over
$A5/m2 total cost, which was fantastic value - it does seem
that fibreglass insulation is cheaper in Australia than New Zealand..
Underfloor insulation
If you are building a new house, get two layers of foil draped
over your floor joists before the floor is put down. This is remarkably
cheap and effective insulation. If you are fitting insulation to
an existing house, it's worth noting that a small basement crawl
space provides a significant - if not huge - amount of insulation.
A single layer of foil under the joists - again very cheap - may
be sufficient for you. If you have a big basement like I do, or
an exposed floor, it's worth looking at significant floor insulation.
Foil-backed fibreglass blanket is the standard option, which is
effective and fairly easy to install.
Another possibility is polystyrene, which can be slotted between
the joists. Be aware that underfloor insulation may also reduce
air leakage into your house, and so also reduce the amount of water
getting into your house from the basement. These are additional
advantages that make it a really worthwhile option. When I was half
way through installing polystyrene under my floor, you could feel
the difference in temperature between the insulated and uninsulated
bits through the carpet!
Wall insulation
The easy way to do wall insulation is to install it when the house
is being built. A second line of defence is to install it if you
are relining the walls. It's important to maintain the breathing
space between the interior and exterior walls to avoid moisture
ingress, though. The insulation manufacturers are pretty good about
giving information on this, so read it! You can also get insulation
pumped into your wall cavities. This works because many wall constructions
have a breather space between the internal framing and the exterior
cladding so you can pump insulation into the gap.
However, there have been some nightmares with this sort of insulation
in the past. These have been caused by the use of insulation materials
that permit moisture to travel from the outside wall (for instance,
brick) through to the inside wall. This causes damp and mould inside
the house and is incredibly difficult to fix. However, there are
a number of products on the market that deal with this by being
hydrophobic and therefore highly resistant to moisture transfer.
I had a quote for my Canberra house at around the equivalent of
$13/m2 of floor area, giving R3 in the walls. And as soon as I can
rustle the money up, I will be doing it.
Installing Insulation
It is worthwhile being careful when installing insulation. A relatively
small gap can significantly reduce the overall insulation value.
Think of it as being like water against a dam. A few little holes
and the water will gush through and much of the value of the dam
is lost. Similarly with insulation, a few little gaps and the heat
will rush through. If you are insulating your ceiling, try to install
your insulation over the joists as well as between them - wood conducts
heat much better than insulation.
If you get insulation professionally installed, try to check it:
Although most operators will do a good job, a few less scrupulous
characters will try to get away with missing out significant areas,
or carelessly leaving lots of gaps. I have even heard stories of
insulation in new homes just being installed immediately around
the ceiling access hatch and nowhere else - so the building inspector
could reach in, feel that there was insulation there, and give it
the OK! The key fact to remember is that bad installation can seriously
reduce the value you get from your insulation.
Most houses in this part of the world have single glazed wooden
or aluminium frame windows. You have a number of options for improving
these, but beware - you will have to sift your way through a remarkably
low level of industry knowledge about the pros and cons of different
options. Unlike Europe and parts of the US, double glazing is not
a mainstream industry and product lines are not as well developed
as they could be. While I haven't met any dodgy operators, I have
found that some of the information coming from builders, installers
and even design professionals has been a little uninformed. So here
are some thoughts to consider on your way to the perfect window:
Frames
Aluminium frames may provide good air seals and thus reduce cold
draughts, but they are highly conductive and significantly increase
heat loss. An average domestic sized window, double glazed with
an aluminium frame, can have a similar heat loss to a single glazed
wooden framed window. For a small but worthwhile additional cost, you
can get aluminium frames with a "thermal break" that reduces
heat loss through the frames by nearly 50%. It's still not as good
as wood, but it's much better than just a standard frame at keeping
the cold out. A further alternative is UV stabilised PVC, which
has similar thermal properties to wood but the low maintenance advantage
of aluminium. There are now suppliers in both Australia and New
Zealand for this type of frame.
If you have wooden frames, consider the possibility of getting
double glazing put into these frames. I had that done at my house
in New Zealand, because it was 30% cheaper than replacing with double
glazed, thermally broken aluminium frames. Make sure your joiner
knows what he's doing though!
Double glazing
In the colder parts of Australia and New Zealand, double glazing
is a pretty good idea - you are unlikely to regret the decision
to install. Even if you don't make great energy savings (see earlier
comments about household heating habits), it will add to the comfort
of your home. Part of the Australasian outdoor culture ethos is
that we love our large picture windows, and believe me, there is
an enormous difference in the level of comfort when sitting next
to one of these on a frosty night if you have used double glazing.
However, I have found the level of understanding in the building
industry to be very low, so here are some guidelines to choosing
the right type of double glazing.
- The bigger the air gap the better the insulation. Try to get
double glazing with an air gap of more than 10 mm. This gets you
more insulation at essentially no cost. The difference between
6 mm and 12 mm space double glazing is about 10% in insulation
value
- Edging material. You can get metal edged double glazing units,
and insulated edge units. The insulated edge units provide significantly
better insulation, and are worth getting if you can. The difference
between the two is about 10-15% in insulation value.
- Low-e glass. This is wondrous stuff and can reduce heat loss
by 20% relative to a standard double glazing unit, but it is quite
expensive.
The last thing about double glazing is that good installation is
a must. If you can check out the experience and credentials of the
installers. A dud double glazing installation will bring you pain
for many years to come!
Cylinder insulation
Hot water installations are the one place where insulation will
always save you money. For most hot water cylinders, an insulating
cylinder wrap is an excellent investment that will pay itself off
within a year or two. Be sure to insulate at least a metre of the
hot water pipe from the cylinder. Further than that may not be economic,
but, hey, pipe insulation is cheap and it's nice being able to run
the bathroom tap and not always have to run three minutes of freezing
cold water out before it heats up. Insulating the pipe run from
the cylinder will keep the water in the pipes warmer for longer.
Shower heads
I believe there's a guideline out there that a good efficient shower
head should use less than about 7 litres per minute. It's pretty
easy to check the flow rate of your own shower with a bucket and
a watch. A new shower head will cost very little and will save you
lots of money, and will help stretch your hot water across a family
of shower-happy teenagers. So if your shower is like a tropical
storm, get a new shower head and use the money you save to fly to
the tropics and experience the real thing!
This is where I get up on my soap box and complain bitterly. If
you don't have central heating, then you will probably be using
portable heaters of some sort. However, the portable heaters on
the market are almost without exception very poorly controlled and
as a consequence are difficult to operate cost effectively. Those
heaters that have thermostats often have them mounted inside the
body of the heater at a point that is strongly affected by the temperature
of the heater itself. The net result is that the thermostat measures
the heater temperature rather than the room temperature. It's possible
to get plug in thermostats, and although these are not brilliant,
they at least provide better regulation of the room temperature,
even though most of them don't provide a temperature scale.
If you are buying a heater, be aware that radiant heaters (e.g.
electric bar heaters) are better for heating you personally in a
room that is otherwise difficult to heat. Fan heaters, oil column
heaters and convectors will provide better room heating if there
are no draughts around.
Wood and multi-fuel burners are very popular but I suspect this
may have more to do with romantic pioneer appeal than anything else.
If you are buying wood, as most of us are, it's not cheap and in
some cases it may be more expensive than electricity on a unit delivered
heat basis. Fires are lovely to have around and add to the ambience
- and, I'm told, the house value - but I personally don't want to
deal with lighting a fire on a wintry night after a day at work
and then having to wait for half an hour before I get any heat.
On the other hand, my house in New Zealand had sycamore trees growing
like weeds, so I was able to sustainably extract free firewood from
these for much of each winter. Take your choice!
I have had bad experiences with second hand electric heaters, including
having one blow up in smoke in my living room. Fortunately I was
around to prevent the rest of the house going with it, but my advice
would be to proceed with extreme care. A house fire is a high price
to pay for a cheap heater.
If you really want to save energy, look to your travelling habits
first. In New Zealand and Australia, 35-40% of the countries' total
energy use goes on transport, the majority of which is the almighty
car. Think about how much money you spend on petrol, and compare
it to your electricity bill. For most people, it's of the same order
of magnitude, but the options for reducing the this part of you
personal energy budget are far wider. Simple options are: don't
drive, drive more efficiently, or drive a smaller car. Think about
how much faster you would pay off your mortgage if you didn't have
a second car! In this area, I practice what I preach - I cycle
or bus to work and so we have only one car, and that stays at home.
I reckon I'm about $10,000 per year better off as a result, and
it's difficult to argue with that sort of logic!
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