Types of Insulation

Our exploration of materials starts with a look at the most important and most under-rated of them all.  

Insulation is a warm, fluffy blanket around your home. In the cold of winter it protects you from the chill. In the ever-hotter and longer summers it protects you from the heat.  

It’s more like a reversible blanket actually…  

The job of insulation is to maintain temperature inside you home, no matter what is happening outside. That sounds pretty dull, but its important. If you can keep your home at the right temperature year round, you’ll be happier, healthier, and will use way less energy 

Using less energy means less money handed over to greedy power companies who will use it to burn more coal.  

Using less energy means you’ll need to work less for some greedy corporation just to afford to live.  

Using less energy means you become more free to pursue the life you want.  

Insulation is important. 

Batts

A few years back we demolished an old house – took it apart piece by piece to re-use the materials. As we took the roof tiles off on a frosty midwinter morning in Yass, we began to uncover these adorable microbats having a sleep.  

This is about the other type of batts though. The ones that are in pretty much every house in Australia, and are famous for being itchy and awful, shedding tiny glass fibres everywhere. They’re also infamous for being used extensively during the federal government’s insulation scheme, for better or for worse.  

Cheap builders love to use batt insulation because its cheap and easy to stuff into ceilings and walls. Whether they’ll just throw the sealed bags into the ceiling cavity or “forget” to put the batts in a wall or two is a question we won’t get into now. Its one you should remember if and when you build though… 

We want to talk here about the good types of batts. The ones that are more healthy, more sustainable, and that you can even install yourself if you’re so inclined. 

 

Batts are a pretty good type of insulation

They do a great job, they’re easy to install, simple to work with, and are really cheap. 

If you’re going to get batts installed (or do it yourself!) there are two products we’d recommend pretty much equally.  

Earthwool batts are mostly made of recycled glass, and Greenstuf batts are recycled polyester (plastic) so they’re both great on the material origin front. They both perform about the same but each has their own little foibles. Earthwool still sheds some glass fibres, but they’re much gentler than the horrible pink or yellow batts. 

Greenstuf is really good, but at the moment we’re questioning whether we want to keep using it. With evidence mounting of microplastics getting into everything (really, its horrifying) maybe creating more plastic fibres isn’t the best option. 

In the end though, the benefits of having a really well insulated home far outweigh the problems. 

Our advise is this: Use as much insulation as you can, if you go for batts pick one of these, and don’t sweat the little things.  

Cellulose

Cellulose is our next insulation material. This stuff is pretty great.

As far as the material source goes, this one ticks a lot of boxes. Its made right here in Aus from recycled paper, ground up into little chunks. The loose fluffy material is pumped into cavities like walls or ceiling spaces.

To make it fire, pest, and mold resistant, cellulose insulation is treated with Borax. This is a pretty much harmless chemical used regularly as a “natural” alternative to more toxic treatments. In the levels its used here it is very safe and of no concern at all.

Aside from being recycled and low-tox, there are a couple of other big benefits. It’s a reasonably low cost solution, and easy to install, which is good. It does have to be installed by a pro though, so you can’t DIY this one sorry.

The big plus is that you can make it as thick as you like, so you can do things like super-thick walls for insulation values way above what you’d get with standard batts. It will also fill the space you put it in so there wont be little gaps all over the place like you can get with batts.

Everything has its place in the world, and we reckon there’s a lot of uses for cellulose.

Straw Bales

Typically seen as a very fringe material used a lot in “alternative” home building, straw bales and straw panel systems are being used more for standard home building these days.  

The material itself is a great insulator and forms the bulk of the wall as well so there’s less framing to deal with. We use rice or wheat straw for building bales, which are packed tighter and drier than normal to boost their durability and insulation value. Rice straw is great too because termites don’t like eating it! 

Straw is hands down the best material for disposal at the end of it’s service life, and a close second for its origin. The straw comes from the stalks left after harvest which otherwise gets burned, so storing that carbon is a great way to use the material. At the end of the building’s long life (there are 300 year old straw bale homes in America!) you can just pull the walls down and spread the straw out to start regenerating the site. 

Four Great Features of Straw bales

Thick Walls

Thick walls are more soundproof, and feel extra secure and comforting. A good thick wall really makes you feel safe and secure, and adds a character that you cant get any other way. Looking out a window you can feel the bulk of the building around you. 

Fireproof

With 5cm of Lime render on the exterior and a massive R-value, straw bale homes are easily made into natural fire shelters. 

DIY

Building with bales is very hands on and free-form, so it works really well for a DIY building style. Even if it’s the only part of your home you build yourself, you’ll have something to show off and feel proud of forever. And it’s super easy and very forgiving. 

Community

DIY also means getting all your friends and family involved. From toddlers to oldies, everyone can have a hand in helping build. It’s such a great experience, and you’ll find loads of people willing to help so you can build a little community along with your home.

Rigid Insulation

Rigid insulation panels have a few uses, but the standard stuff is made of various forms of polystyrene foam, which is all around awful stuff, and we should all avoid using it if there’s a choice. Luckily, most of the time there is a choice!

We use rigid insulation for things like under a concrete slab, or to form a weather barrier and thermal break on the outside of framing. Panels are great for this because they can form a full skin around the building. 

It’s a little bit of a helper for extreme climates, and mostly we don’t need to worry about it here. Of course, we always want to make sure we have the best systems and materials to minimise environmental damage and energy use.

So what are the options?

Starting with the bad stuff – XPS foam boards are rot and water proof (which means they’ll never break down after disposal…) so they’re useful for under-slab and slab-edge insulation. Handy but not vital. Foam panels are sometimes used for sheathing to form that thermal break (heat can travel through your framing and the thermal break stops that). There are a few types, but on this front we have alternatives, so we’d never recommend using the stuff.

The big new player in rigid insulation is wood fibre panels. They provide a thermal break, an air and water barrier, and are made from plantation softwood. They’re imported though, so they have some carbon miles. For extreme climates, or if you want to head toward a passive standard, these are the ticket.

A great Australian made product is Durra straw panels. Insulating, sound resisting, and made form high density straw. They’re an alternative to gyprock for homes, but gyprock is pretty good anyway.

All in all, rigid insulation has its place and you should know about it, but it’s unlikely you’ll ever use it in a home in most of Australia.

Hempcrete

Hempcrete is an ancient form of infill insulation, used since early medieval times to create solid insulated wall panels. Hemp is a very fast growing woody herb which has been used for millennia for it’s long, strong fibres. 
 
The fibres were mostly used for rope and rough cloth, but these days we use the seeds and oil for their health benefits, and can turn the fibre into paper, clothes, and even bioplastic.
 
The woody part of the plant that isn’t used for fibre is very porous, and is chopped and combined with lime and water to create a slurry. This is poured into forms, and once set creates a solid, insulated wall panel.
 
Air moving slowly through the wall is filtered by the hemp, creating cleaner internal air, and over time the lime absorbs CO2, meaning this material is carbon positive. Internal clay render will also regulate internal humidity in the building, making it more comfortable and healthy.
This is really an amazing material, which has been sorely lacking from our building landscape, due to strict prohibition on cultivation. This is changing now though, and there are some big producers coming online so we should see a surge in use in the near future.