Mineral Wool Batts

Pros:

-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

Cons:

-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

Pros:

-Cheaper than mineral wool

-Very easy to cut and install

-Readily available at most suppliers

Cons:

-Compression affects R-value more than Rockwool

-Not particularly moisture-resistant

-Makes a nice home for insects and rodents

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 the minimum building code or approximately 22% better than the 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.

The Thermal Control Layer
Blown Cellulose
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  • Spray Foam