What Insulation is Best?

This is a question we hear quite often. The short answer is that it depends. There are many different types of insulation with their own merits and drawbacks. Most of us are familiar with the pink insulation that comes in batt form. We can thank the energy crisis of the 1970s for the dominance of the pink fluffy stuff which was used for all new buildings (as the code mandated insulation). These days insulation comes in many forms and from many products so that no matter what part of your home you’d like to insulate, there are multiple ways to get the job done. There are even products like insulated sheathing that enable you to accomplish two things with one product.

I find that it’s better to discuss what the insulation will be used for rather than debate the merits and drawbacks of various insulation materials. And if you have issues with a certain product, there are always alternatives. Below are the materials I prefer for some of the most common home renovations in the GTA.

Up top - the attic

Cellulose is an excellent option when insulating your attic. It’s affordable and has the lowest embodied carbon. Made from recycled print material, you can even blow in the cellulose into your attic yourself (many home hardware stores sell machines that shred the cellulose such as this one here). As with any insulation project, make sure first to inspect the attic space for any moisture related issues and address before insulating (e.g. rot on joists).

Down low - the basement

When insulating a basement it’s very important to make sure that the renovation plan first considers water that may come in through the concrete slab (through capillary action) or the wall (via groundwater). If you are in an area that’s prone to basement flooding, consider insulating from the exterior (as that’s the most sure proof way to deal with moisture) and adding a french drain, or if you can’t dig down on the outside of your walls, a sump pump on the interior. Once moisture is dealt with properly, you can insulate as much as you like!

For basement walls, stone wool (also known as mineral wool or Rockwool) is an excellent choice. Stone wool occurs as a natural byproduct of volcanic activity and is a recycled product made with the stone dust from industrial blast furnaces. It comes in both batt form (goes between the framing) and rigid form (no need for framing).

It’s an excellent insulator if you want to avoid using petroleum products and is both fire resistant and water repellent (this is due to the inherent drying potential of the product which is also resistant to rot, mold and mildew growth). The most cost effective form of basement insulation for the interior involves adding a couple inches of rigid insulation (R8-insulating factor) and then framing with 2x4s and filling those with batt form of Rockwool (R14). Rigid insulation is always a good choice because it provides continuous insulation over the whole wall so that you don’t end up with heat loss that looks like the photo below. 

The lighter areas show the wall studs through which heat can easily flow out of the house in winter.

What about spray foam?

Many contractors prefer to use spray foam, particularly when finishing a basement or third floor cathedral ceiling. This is because some types (closed cell spray foam in particular) do a three for one job of being an air, vapour and heat barrier. It also has on average a higher insulation value per inch than cellulose, fibreglass and rockwool so you can accomplish more and save on space. You may choose not to use it because like most petroleum based products, it just sits in the landfill once it’s no longer needed. However, you may decide that it’s the best material for a job that you are undergoing - and that’s okay too! My job as an energy advisor is present you with choices so you can achieve your green renovation goals.   

What about natural insulation products?

So far we’ve focused on insulation products out there which are both readily available (which means lower cost). There are some emerging natural insulation materials such as hemp grass (which is now being manufactured in Quebec!) With most natural insulation materials, they retain moisture to some extent so should not be used in areas where moisture can pose a problem. I’d probably suggest using it for a home retrofit where insulation is being added to above grade walls from the exterior. It comes in rigid insulation form and could be used in place of any other rigid insulation. As this is a newer product (only started being manufactured in 2018) it may be hard to find in smaller quantities but once builders start using it for new homes, the costs will come down and it should become more readily available.

In short, the world is your oyster when it comes to choosing an insulation product for your home. If you don’t like what a contractor is suggesting, you can always ask for alternatives! Factors such as how the product interacts with moisture, the insulation per inch, cost and ease of installation should be considered to ensure that you choose the best product for your upgrade.