Save Money With Insulation – Choose The Best for You

How does  Insulation Work?

Heat / cold transfer occurs through convection, radiation and conduction.   Most building codes worldwide only address radiation (R value).

Air infiltration causes loss by convection, and spray foam insulation is probably the best material for stopping this.  So if you’re using non-foam insulation, you should air seal too if possible.  (Just check what the foam is made from, and what nasties are added to make it expand and stick).

You can put in great insulation, but if there are air leaks around it, it won’t be as effective.

For radiation heat gain, radiant barriers (NASA’s space blankets) are not eco-friendly in themselves, but are effective in your attic and thus reducing your energy use.

Ultimately, all insulation is eco-friendly to some degree, in that it reduces your energy use.  However, some methods are better than others.

Insulating your home is a bit like dressing for the weather.  A wool sweater will keep you warm if the wind is not blowing and it is not raining.  On a windy, rainy day, wearing a nylon shell over your wool sweater helps keep you reasonably dry and warm.  A house is similar.  On the outside, underneath the brick or siding, there is an air barrier that does the same thing as the nylon — it keeps the wind from blowing through.  Then there is the insulation (like your sweater) and a vapour barrier, which helps keep moisture away from the house structure where it can do damage.

So, having discussed various wall insulation methods, what insulation would I choose for my home?  That would depend upon whether I was building a new home, or insulating an existing one.

I lived for many years in South Africa, an incredibly beautiful country with lots of sun.  My husband and I planned to build a small home in a semi-arid region which would be eco-friendly in terms of construction, and we’d grow our own organic vegetables, harvest the (little) rainwater and generate most of our own electrical power.  We planned a straw bale home – there are plenty of farms nearby so the raw material would be local, reasonably-priced and eco-friendly.  It’s quite difficult to find people with those skills – straw bale insulation is rather a lost art – but possible.  We’d use either sheep’s wool or Icynene spray insulation (made from castor beans) for the smaller areas and awkward corners – straw bales are large.  We’d also want to air seal before putting in the bales, to make the insulation efficient; again probably Icynene for this.  And we’d use a radiant barrier in the roof.  But most of all, we planned the house with correct orientation for the sun, with big deep verandas, and with doors and windows oriented to catch the maximum breeze.   Getting those things right, means less work for the insulation to do.  In my opinion, that’s a skill we’ve lost over the years – we rely too much on insulation and air-conditioning instead of correct siting.

Then our plans changed suddenly, and we won’t be building that home any time soon – but we still have the blueprints and the land.  It’s an idyllic concept – particularly as there are vineyards nearby, so a ready supply of wine is ensured….. hopefully one day.

Of course you have far more choice when you are building your own home.  When you live in an existing home, you need to work with what you’ve got.  One thing I will not willingly have in my home is fibreglass.  Personally, I’d use the denim insulation if it could be fitted – if not, I’d use blown-in cellulose as it can be retro-fitted easily.  If you have existing fibreglass, if it’s several years old then it won’t be functioning efficiently, so you could either get rid of it if it’s possible, and/or top it up with cellulose.  In a hot climate I’d probably look at putting a radiant barrier in the attic.

I hope this series of articles has helped with the sometimes confusing choices of wall insulation options.

Find out more about Fibreglass, or denim and wool insulation, what R-Value means, also cellulose, polystyrene and straw insulation

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