What Are Geometrically Defined Insulation Boards?

A relatively new modification to modern Exterior Insulation Finish Systems (EIFS, or “Synthetic Stucco”) are what is called (geek alert) Geometrically Defined Insulation Boards. What exactly does that mean?

It’s a complex way of saying insulation with grooves cut into the back. The purpose of the grooves is to provide a way for water to drain out that gets behind the system. This helps to ensure that no moisture becomes trapped, causing mould or rot.

Why is this necessary? Well, it’s not if EIFS is installed by a skilled applicator, but was implemented to further assuage the fears of Architects. The problem is that even when the Architect properly specifies a system, General Contractors (and home owners) don’t always pay for true skilled applicators – and the applicators who charge less typically do so because they’re inexperienced. Less experience means higher chances of screwing up some part of an EIFS installation.

A popular argument against EIFS with drainage channels formed from cementitious adhesive (the grey streaks in the picture above) is that  the ribbons are flattened out once  the exterior insulation is pressed in place on the wall. The argument goes that if the ribbons are flattened, there is no longer any way for water to drain out if it gets behind the system. Unfortunately, there is an element of truth to the statement – I have seen insulation torn off walls as part of an inspection and observed a complete lack of drainage space because the insulation was pushed against the wall too hard.

If this was to happen, the weather-barrier that is required by EIFS manufacturers would help to protect against mould and rot problems. The majority of the time however, the vertical ribbons of adhesive stay in tact when the insulation is pressed in place (by a skilled applicator).

The Cause Of The Problem

As with all potential problems with skilled trades, it comes down to hiring the right contractor. Selecting the cheapest bid will not get you actual skilled applicators who know how install EIFS properly. This is the case with all skilled trades though, and not a problem exclusive to the EIFS industry. The problem is that every idiot GC or home owner brags when they get EIFS installed for $6 per square foot, when what they’re really doing is shooting themselves in the foot. The $6/sf “contractor” is typically an applicator who was in the industry for a couple of years and is willing to charge less because they won’t take the time to install the system properly. Whether that’s because they’re not aware of how to properly install EIFS or they just aren’t ethical people is another topic entirely. Other people hear about this then think that paying $6 per square foot for EIFS is the norm, and are shocked when something inevitably goes wrong. The few hundred or thousand dollars they save ends up costing many thousand in the long-run and in their ignorance they blame EIFS.

The purpose of the geometrically defined insulation boards is to help “idiot-proof” an EIFS installation. By creating a second layer of drainage that is difficult to clog up (in addition to the cementitious ribbons), the EIFS industry is essentially helping general contractors and home owners who are otherwise too ignorant to hire the right contractor. While the industry is aware I’m sure that someone out there is working hard to create a better idiot – it’s still a step in the right direction and will undoubtedly help a few projects.

Additional Thoughts

Notice that in the image above, the edges of the insulation board are also cut back so that there is additional means of drainage around the perimeter of the insulation boards as well as within it. Also note that this only works if the insulation boards are installed horizontally (how it’s being held in the picture) so that water can drain vertically down the cavities.

Some people have commented that cutting into the insulation reduces it’s R-value. Studies by the EIFS manufacturers have found the reduction in R-value to be negligible as less than 5% of the insulation is removed to create the channels.

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  1. w classen

     /  July 14, 2012

    ? how much dose the mesh have to overlap,can it not just join in a groove if the panales are cut to fit the mesh,with V grove.
    this I ask before I let the contractor continue,he said that detail mesh should be in all the groves,worried about build up and not a flat surface,seen some that look bad in light,but would like a flat surface,also should he double wrap the corners as in stucco.
    thanks for a reply in advance .

  2. Admin

     /  July 15, 2012

    Hi Wolfgang,
    The mesh should overlap 2.5″-4″ depending on the manufacturer specifications – you should consult with them directly. Detail mesh should be installed in V-grooves to prevent the groove from cracking. If done properly, it should not cause any visual disturbance in the wall.
    Yes, corners should be reinforced with an additional layer of mesh.

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      "Stucco" is typically what people in the Toronto area use when they're looking for EIFS (Exterior Insulation Finish Systems, or "synthetic stucco"). We use the two terms interchangeably.

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