By Ibrahim El-Hajj, M.Sc.Arch., CACB, MRAIC, BCQ

Manager, Building Technology

Energy Models are attacking standing walls & leaving the slabs/floors to relax in peace.

  • Is your window to wall ratio compatible with energy models?
  • Have the models properly addressed the energy efficiency of the buildings?
  • Does your modeling software identify thermal bridges and critical areas within the envelope?
  • Has your designer considered the value proposition of EIFS system?
  • Are you upgrading your window system to the current standard?
  • Argon gas
  • Warmer edge
  • Wider thermal break
  • Low-e coating & others
  • Lower U Value

The trend of today’s market is to maximize the area of the windows. This approach is valid as long as consideration to the following is taken to improve the quality, enhancing the performance of the whole window system:

  • Opacity of spandrel panels
  • Thickness of glass
  •  Glass layers (double & Triple)
  • Higher performing glass
  • Vacuuming insulated glass

Energy Models & EIFS.

I was asked for an opinion on how to reduce the thermal bridging on one of our projects in downtown.


The original drawings were called for an insulated Aluminum Panel System, which covered the poured in place concrete walls/columns as well as provided thermal protection as an exterior wall cladding system.  This proposed  system was over the budget. However,  alternative approaches were sought to meet the budget & provide cost effective solutions without affecting the thermal performance of the building envelope.

It appears that the architectural office has not given a proper consideration of an EIFS system and building science benefit. Thus the owner, requested to substitute the metal cladding system due to thermal bridging/cost consideration.

To alleviate the thermal bridging issue, the Energy Model Engineer proposed something very unique:

To split the concrete demising walls/columns through the entire building & for all the elevations

This involved:

  •  Separating the shear & load bearing walls approximately from slab to slab (recess of  800mm) and on every floor;
  •  Redesigning the rebar placements for structural stability/integrity.
  •  Allowing for a gap to accommodate the thermal bridging.
  •  Providing moisture resistive barrier with drainage provisions to the outside of the wall.
  •  Incorporating  fire resistive materials at the split area to maintain the required fire separation.
  •  Creating a junction detail at the window to wall interface.

Regardless of the efforts to split the wall, it is still connected to the structure and thermal bridging would not leave the area. With the EIFS installed would have reduced cost/time and efforts.

It appears that this decision was not made based on thorough evaluation, previous experience or past performance of similar projects, but rather based on a modeling software input. I have over a decade’s worth of experience working on several projects in downtown Toronto and the GTA, yet this is the first scenario of this sort that I’ve encountered.

A proficient architect/designer is one who incorporates a system that will provide continuous insulation, reduce the heat loss by minimizing lateral heat energy transfer along the large surfaces of wall/columns, decrease air leakage, eliminate thermal bridging & improve energy efficiency of the building overall.

By definition an EIFS is a non-load bearing exterior wall cladding that consists of water resistive barrier, thermal insulation board, reinforced base and finish coat, light and easy to install.

It is unfortunate that some Architect colleagues are not aware of the benefits on of using EIFS, especially when this system is recognized by the building industry at large:

  • EIFS is recognized by the OBC 2012.
  • EIFS is adopted by the NBC 2015.
  • National standard-development of ULC 716 family of standards.
  • Canadian Construction Material Center- CCMC, technical guide for EIFS.
  • EIFS industry and its manufacturer systems/ details.
  • Standard and specification of the installation of EIFS.
  • EIFS Quality Assurance Program. “EQI” .
  • ECC EIFS Practice Manual and Technical Bulletins.
  • Compliance with the Rainscreen principles and OAA Pro-Demnity requirements.

Over the last 45 years, the EIFS system has continued with design enhancement to address the best practice. It is a complete system which provides and includes the followings:

  • Continuous thermal protection.
  • Minimizing thermal bridging.
  • Protection of moisture sensitive.
  • Moisture management.
  • Structural protection for longer performance & durability.
  • Energy saving.
  • Cost effective solution.
  • Minimize movements, stress.
  • Reduce the dead loads & enhance the service life.
  • Decrease maintenance/repair cost.

It is critical for my Architect colleagues to analyze and investigate the implications of design decisions in the selection of systems, materials, construction details, and functional requirements related to:

  • Life cycle, durability & serviceability of the system/product.
  • Air/vapor barrier systems.
  • Rain penetration control/management system.
  • Load resistance.
  • Thermal expansion & contraction.
  • Structural design.
  • Seismic forces design.
  • Resistance to wind forces.
  • Lateral forces.
  • Thermal performance.

Returning to our original point above,

By splitting the wall, will the voices of the FLOOR speak out ?

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