New Green Building Guide to Combat Thermal Bridging 11

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Tuesday, September 30th, 2014
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A new report aims to help engineers and architects tackle the challenges of mitigating thermal bridging to reduce energy consumption in buildings.

Research and monitoring of buildings is increasingly showing the importance of reducing thermal bridging in new construction and mitigating the impact in existing buildings

Thermal bridges are localized areas of high heat flow through walls, roofs and other insulated building envelope components. Thermal bridging is caused by highly conductive elements that penetrate the separation between the interior and exterior planes of a building, allowing heat flow to bypass the insulating layer and reducing its insulation effectiveness.

The thermal bridge may go through a wall and its insulation, through the space between the glass and steel of a curtainwall or simply through a leaky roof.

The impact, however, can be significant to whole building energy use, the risk of condensation on cold surfaces, and occupant comfort.

Green codes such as the USGBC’s LEED standard award high points for buildings that utlise natural light rather than artificial light and enable sunlight penetration through curtainwall, clerestories and large windows. But more glass can often lead to more opportunities for thermal bridging and other penetrations of a building envelope.

The traditional approach of building codes to reducing space heating loads in buildings was to introduce progressively higher levels of thermal insulation and more stringent glazing performance requirements. This was because, in the past, the effects were assumed to be negligible.

However, we now know that the additional heat flow due to major thermal bridges can add up to be a significant portion of the heat flow through opaque envelope assemblies. Studies have shown that the contribution of details that are typically disregarded can result in the underestimation of 20 per cent to 70 per cent of the total heat flow through walls.

The cost of adding extra insulation, not just additional materials but also potentially reduced useable floor space, is not justified if no substantial energy savings are realized in practice.

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The primary aim of the guide is to raise awareness of the impact of and methods to mitigate thermal bridging. It provides four key outcomes:

  • Catalogues the thermal performance of common building envelope assemblies and interface details
  • Provides data driven guidance to enable engineers to more easily and comprehensively consider thermal bridging in building codes and bylaws, design and whole building energy simulations
  • Examines the costs associated with improving the thermal performance of opaque building envelope assemblies and interface details, and forecasts the energy impact for several building types and climates
  • Evaluates the cost effectiveness of improving the building envelope through more thermally efficient assemblies, interface details and varying insulation levels

The report was produced by international engineering firm Morrison Hershfield developed in collaboration with co-sponsors and industry partners BC Hydro Power Smart, the Canadian Wood Council, Fortis BC, FPInnovations, and the Homeowner Protection Office.

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Discussions
11
  1. David Kuhnert

    Hi , Great info on stick frame Building , how about sum up to date info on ICF CONSTRUCTION .Regards David Kuhnert

  2. Luca Oggianu

    Glass is a major contributor to energy efficient buildings.

  3. Steve Withers

    Hi Justin
    If you are serious about doing articles on energy efficiency in construction , Why don't you do an article on Eco- ICF Building and Esky Deck –
    the revolutionary insulated suspended flooring system which alleviates the need for costly form workers.

    the Benefits of ICF construction over stick frames or Brick
    Category class 1 cyclonic can easily be achieved
    180/180/180 fire rating
    7.5 star plus insulation rating easily achieved
    high sound insulation
    High seismic rating easily achieved
    Plus, Plus, Plus…..

    Why would you build in anything else ?

  4. mike nagle

    external insulation and finishing systems (eifs) have been around for decades. like many systems out here its simply not recognised and not understood .. up to 30% more efficient than batts between studs . bca puts it into lightweight construction group.

  5. Andrew John

    As Mike Nagle states, external insulation and finish systems dominate the landscape as these systems are the most thermally efficient solutions for the building envelope. Thermal bridging is no longer a consideration when monolithic insulative cladding systems are applied to either frame/masonry/tilt. These systems have been in use around the world for more than four decades. From a global perspective, the age of "cold face" (non-insulative) claddings such as fibre cement, has long since passed. Also in New Zealand, wall types that feature a typical stud/batt/stud configuration, no longer attract the R value of the batts alone. In effect what has been recognised is that the studs (@ approx R0.5) are in effect thermal bridges at 450 centres.

  6. Andrew John

    In the photograph, note the fixings associated with the application of a RockWool (fire rated, insulative, monolithic) panel system to masonry/tilt – no thermal bridging there, as these anchors are entirely plastic – just pre-drill and hammer!

  7. Frank Baker

    In addition to ICFs, Structural Insulated Panels SIPs are superior, by far, in reducing thermal bridging to stick framing. When ICFs and SIPs combined are very difficult to beat in real world performance.

  8. George Modrovic

    That is what we have been doing for the past twelve (12) years. The next big discovery for construction professionals and general public are the effects of RADIANT heat.
    60-80% heat gained in summer, or lost in winter is through radiant heat. It is radiant heat which heats up conventional building materials, brick, wood, stone, steel…, and transferring ambient, many times severe weather conditions, to the inside of a building via conductivity. If that heat is reflected and never enters the product, then R-Value (conductivity heat transfer) is no longer a factor, as R-Value is the time it takes for heat to pass through a product once it has entered the product.

  9. SCOTTY

    Where is the report?

  10. John Patterson

    Yes thermal bridging with Styrofoam ridged board is a very good idea. I have a 1920 s house no studs solid brick an block , cold walls when you live in upstate NY, my wife and I just installed 3/4 in aluminum faced Styrofoam board . She primed it with primer paint than paint the board to match the wall. You cannot tell it is there. I found by using a liquid nail adhesive that it held the rigid board. Using my thermal camera there is at least a 5 degree difference where the board was installed and the cold plastered wall. We did not install over all the rooms just 2 bed rooms. .