A decade ago when I first got into the building industry, I was seriously overwhelmed by all of the different building materials. From the different types of engineered lumber to the hundreds of different styles and types of tiles you can put in your kitchen, it can be really challenging to sort through all of the marketing and paid brand ambassadors to figure out what really makes sense for you and your project. In this brief article, I will endeavour to try and break down with some level of clarity and without all of the technical builder jargon that confuses everyone, one of the most important building materials to think about when considering your home build or renovation project.

Spray Foam


-Also acts as a vapour control layer as well

-Very high R-value to density ratio( approx. R-6 to R-7 per inch)

-Can actually increase the structural integrity and shear values of your home


-Requires specialized skills and tools to install

-Price is typically the highest with respect to all other materials

-One of the few materials actually fabricated on site so site conditions play a big role in the final product

-Does not do much for sound or acoustic transmission

-Not as sustainable or environmentally friendly as other options

-Flammable and needs to be sprayed with an Intumescent Coating if left exposed


Mineral Wool Batts


-Higher R-value per inch than an equivalently sized fibreglass batt

-Easy to cut and install

-Made from recycled and sustainable materials

-Fire, moisture and rodent resistant

-Sound dampening


-More expensive than fibreglass

-Must wear protection when installing as inhaled mineral wool can lead to long-term health problems

-Must take more care going around pipes and wires

-Compression does affect R-value but less than fibreglass as the material is denser

Fiberglass Batts


-Cheaper than mineral wool

-Very easy to cut and install

-Readily available at most suppliers


-Compression affects R-value more than Rockwool

-Not particularly moisture-resistant

-Makes a nice home for insects and rodents

Blown Cellulose


-Very cost-effective

-Easy to fit in around pipes and wires

-Made from recycled and sustainable materials and is one of the most environmentally friendly


-Settles over time reducing R-value although not as much as blown fiberglass

-Hold moisture well which can cause mold

-Requires specialized machines to install

So which one should you use for your home build or renovation project? Unfortunately, there isn’t really a clear-cut answer and honestly, it depends on a variety of factors. Things like your overall budget, availability of qualified installers, your personal values for the performance metrics of the material and your personal proclivities with respect to the use of sustainable or environmentally friendly materials all play a role in making the right decision for you and your home. However, for the sake of this discussion let’s describe the insulation detail we recommend to all our clients and break down why we recommend it.

Based on the above list you can see pretty clearly that there are pros and cons to all of the insulation materials. When we were working together with our team and trade partners to come up with a high-performance method that we could feel confident proposing to our clients we sought to synergistically use materials to compensate for their weaknesses and maximize their strengths. Our preferred method was not created by us but once we researched it and then started putting it into practice we really couldn’t argue with the facts or the results. The method is referred to as the flash and batt method.

So what does that mean?

The flash and batt is a 2” flash of closed cell spray foam and an R-15 mineral wool batt. Let’s break that down and start with the R-value. Closed cell spray foam has an R-value of about 6-7 per inch so some quick math shows us that our whole assembly has an r value of about R-27 which is about R-5 above minimum building code or approximately 22% better than minimum code. We use a 2” flash because that is the minimum amount required to create an air seal. That means we don’t have to install a plastic vapour barrier after making less work for us and it’s hard to make a quality air seal with plastic vapour barriers. We also use mineral wool to compensate for the lack of sound-dampening qualities in the spray foam. This assembly gives us the best of everything: the additional structural integrity and high-quality air sealing from the spray foam as well as the fire, pest, moisture and sound properties from the rockwool batt all combined in a better-than-code R-value assembly. This method also allows us to reduce the amount of spray foam in the assembly keeping the cost to the consumer a little lower than a traditional full spray foam installation while reducing the use of the chemicals used in spray foam lowering the cost to the environment.

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