As we embark on the journey of innovation, it's crucial to reflect on the origins of today's popular facade products and applications, delving into their initial use cases and intended purposes. This week, let's delve deeper into rainscreens... and explore beyond 👇 👇 👇

More and more building codes are now requiring continuous insulation outboard of the sheathing. This is good. In addition to this, we know that putting insulation outboard of the sheathing and using a rainscreen approach (drained and back-ventilated wall type) is the best way to build exterior walls. While Europe has adopted this approach heavily since the 1980s, it is still a relatively new phenomenon in the United States. There are significant challenges and considerations surrounding the implementation of the rainscreen cladding. Let's briefly look at some. 

For centuries, the Norwegians used the "open-jointed barn technique" building drained and back-ventilated claddings. They have done it intuitively without any science behind it, and now we have science to prove why this is the best way to build.

Here are some advantages of using drained and back-ventilated (rainscreen) cladding approach:

1. Better water and air protection of the envelope (by moving the water away from the structure).

2. Better thermal performance (by moving the heat or the cold further away from the structure. Insulation also performs better outboard of the sheathing where it can dry out).

3. Moving the dewpoint outside of the wall cavity (reducing mold issues and improving interior air quality)

4. Allowing the moisture to escape (through ventilation)

5. Better Acoustical Performance (more sound is deflected by cladding and exterior insulation)

6. More cladding choices (we can put almost anything on the cladding now)

7. Longevity of the cladding (100s of years if properly designed)

I believe that there should be no question that this method of building (even for residential projects) is the way to go. Let's move away from plywood with non-permeable air/water barrier stapled to it and cladding nailed on top of all this. This is unsustainable and frankly irresponsible.

The current industry buzzword is the carbon impact. We are being asked about EPDs and our embodied carbon (I don't know much about this yet - still learning). We constantly battle to squeeze the extra sustainability out of the lifecycle of products. While the idea of this is good and opens a larger conversation about sustainability, we should not get tunnel vision on just the products. The design and execution play a crucial role in sustainability. Because who cares what products are being used if they have to be replaced in 5-10 years due to poor cladding design or poor execution? I can think of a huge stadium in my city that had to be completely re-clad due to a variety of issues that could have been avoided.

Even if we agree, properly designed rain screen is the way to go, and here comes the challenge: The rainscreen claddings are suspended away from the wall and need to be structurally supported, as well as withstand its own dead loads, wind loads, seismic loads, snow loads, inter story drift, and accommodate the live loads of the building (think deflection joints). The rainscreen system needs to also:

Are you overwhelmed yet?

The structural supports have traditionally been wood and metal. The wood is not the best for fire and longevity in the wet area. The metals are really strong structurally but also transfer quite a bit of thermal energy into the building, reducing the effective R-value of the cavity insulation.

In recent years, there have been developments to use fibreglass materials as structural supports to reduce thermal bridging. Fiberglass is less thermally conductive than metal but also presents the following concerns:

We also see the preference for stainless steel members that are less thermally conductive than regular steel and aluminum, while still offering good structural properties. This is a good approach but does cost more than steel and aluminum.

We can see that one product is not and end-all solution.

So, as facade designers and professionals, we have a lot to manage. The construction tolerances are getting worse and the project documentation is getting less accurate, shifting more and more responsibility on installers and suppliers. We need to be better educated than ever and lead the discussion on sustainability by offering good design and good solutions to the market.

Ilja Aljoskin (PMP®, LEED AP BD+C)
LUHA Facade Solutions | Founder/President
+1(651) 802-4649
[email protected]