Thermal Break

[Lane Stefano]

Someresearch has shown that thermal bridges can increase the whole-building conductive heat loss by more than 15%. The percentage is a function of some obvious variables: climate, building type and the location and type of the thermal bridges. The magnitude of the thermal bridging is a large factor. Some interface details increase the U value of a wall by 45%, other transition details increase the U value by only 5%. Is the building enclosure 40% curtain wall? Is there one canopy or are there fifty balconies?

The heat flow (loss) created by thermal bridges varies by the detail and the number of details. If the building design contains lots of poor or inefficient details, the contribution to overall heat loss through the envelope will be high. To improve the energy efficiency of a building, we need to improve the efficiency of the thermal envelope.

The purpose of thermal break materials and systems (thermal breaks) is to reduce the impact of thermal bridging by preventing conductive heat flow through the thermal envelope. Thermal breaks keep the heat in and push the dew point out. They break the bridge.

The thermal conductivity of a thermal break material is an important variable in determining the rate at which heat flows through that material. Heat flow also is dependent on area and temperature. Given the same boundary conditions of, temperature difference across two materials, and the same area and thickness, the material with the higher thermal conductivity will transfer heat at a higher rate.

Why is modeling necessary? Two reasons: First, heat does not flow in parallel paths when highly conductive construction materials are combined in an assembly. If it did, we could use simple math and area-weighted averaging to determine heat flow through an assembly. Second, many interface and transition details are complex and involve corners or other features that make it difficult at best to calculate heat flow.

In any connection design using a thermal break, the goal is to find the appropriate thickness/area combination that helps the wall or roof assembly meet the U value requirement based on climate zone and energy code.

While a properly designed thermal break will considerably reduce heat flow, thermal breaks are also effective at keeping connection surfaces above the dew point. This is particularly important for connection details in buildings where higher than normal relative humidity values exist (hospitals or natatoriums) or in the Southern part of the United States where humidity levels are higher.

A secondary benefit of using a thermal break is to control material surface temperatures. Thermal bridging allows heat from the interior conditioned space to flow out toward the exterior of the enclosure. When the temperature difference is large, interior material surfaces cool. To prevent the potential of condensation forming in the thermal envelope, the surface temperatures of the materials within the envelope must be kept above the dew point temperature. A risk of condensation is possible if thermal bridges that pierce the envelope are not addressed by using a thermal break.

In addition to preventing heat loss, keeping material surfaces above the dew point and having sufficient strength to maintain the integrity of a structural connection, thermal breaks should also be specified on the basis that they are resistant to burning.

Non-combustible materials do not aid combustion or add appreciable heat to a fire; however, combustible materials used in or as thermal breaks should show fire resistance compliance if they are located within a fire-resistance-rated assembly.

Is a fire rating applicable per local building code? Sufficient data should be made available to the building official to show that the required fire resistance rating is not reduced as a result of incorporating a thermal break into the building enclosure. Fire ratings of assemblies may be required per ASTM E119 or NFPA 285 testing depending on the building type and fire code.

The fire properties listed in the table above provide a better understanding of how a material will react in a real fire situation. Each of the characteristics provide different information. They do not include all of the factors required for fire-hazard or fire-risk assessment of materials, products, or assemblies under actual fire conditions. The overall hazard of the thermal break product should be assessed using a combination of tests or data that is appropriate for the end-use application.

Although it is often used to prevent thermal bridging to keep warm temperatures within a building, it can also be essential in cold storage facilities to prevent the subgrade from freezing. It can sit directly under the column base to prevent any transfer of temperature into the ground.

We also have an easy-to-follow online webinar which is ideal for architects looking to earn credits, with the course providing an overview and introduction to thermal bridging, discussing how and why it occurs, as well as how it can be prevented. By completing the webinar, you can gain one AIA HSW learning credit while learning more about thermal break solutions. It provides you with essential knowledge surrounding energy savings and information to help understand how to incorporate thermal breaks into your next project effectively to control thermal bridging issues. It also showcases and compares the difference between building details with and without thermal break solutions to highlight the importance of determining accurate values of thermal transmittance within a project.

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My Neighbours purchased a Thermally Broken system with Lowe coated double glazing. These windows were installed into a lightweight insulated wall in the typical Australian manner. One day during winter they asked why their renovation felt so cold and draughty?

We grabbed my thermal imaging camera and found that the windows seemed a lot colder than one would expect considering their performance values. We decided to remove the Architraves and have a closer look, we discovered a few problems,

To try and explain to my neighbours all of these issues we ran a simulation of the product in the wall, we set the external temperature to -18 Deg C with a solar load of 0 to highlight the air and the internal to 21 Deg C, we also set the pressure to 75 pa as this is representative of the conditions used when testing windows and doors as well as to speed up the air movement.

Fabreeka-TIM structural thermal break, or thermal insulation material (TIM), is an energy saving, load bearing thermal break used between flanged steel connections. Each Fabreeka-TIM thermal break pad has high compressive strength combined with low thermal conductivity, making it an effective solution to reduce thermal bridging through the building envelope. For further convenience, Fabreeka-TIM material is supplied in sheets or cut to size per customer drawings and/or specifications.

Fabreeka is pleased to provide our new Fabreeka-TIM Structural Thermal Break CSI 3-Part Guide Specification. The guide specification is written in Construction Specifications Institute (CSI) 3-Part Format in accordance with The CSI Construction Specifications Practice Guide, MasterFormat, SectionFormat, and PageFormat.

So that we may accurately provide you a quote, please supply us with the design connection showing dimensions of Fabreeka-TIM plate, hole size and location(s), connection plate thickness and fastener size, and also if you require washers and bushings to complete the thermal break connection. For optimal thermal break, also regarding structural steel thermal break, we recommend Fabreeka-TIM thermal break washers and bushings.

FO-V2344 and FO-V2348 are single-sided thermal break tapes, designed to reduce thermal bridging on outer and inner framing in metal buildings. Available in 1/4 inch and 1/8 inch thicknesses, the tape has excellent holding power and high-load capability.

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But an inch of Type-II EPS sheet is also R4.2, which cuts the framing loss in half, even though it cuts the loss of the R11-R15 cavity by a much lesser amount. So it's something of a thermal break for the framing, not so much for the rest.

Whether R3 ZIP-R or R6 ZIP-R is used is really a matter of your performance goals. For a 2x6 /R20 wall the R3 ZIP-R reduces wall losses by about 16% compared to ZIP without the foam, R6 ZIP by about 29%.

I'm having trouble figuring out the equation to reduce heat loss when adding foam strips to rafters. If I have an 11.875 inch 2x12 cathedral roof rafter and add a strip (not a sheet) of 1 inch polyiso over the rafter face and then drywall to finish how much does that reduce the heat loss through that rafter? How much would be reduced with a 1.5 inch strip?

I'm unable to find THERM software and confirm that it is what I'm looking for. What I did see appears to have a significant learning curve. I'm really just looking for back of napkin estimates such as what was towards the end of post #1, not a full modeling breakdown.

Yes and no. If you are layering insulation, you can just add the R-Values. If you have a surface that has different insulation levels side-by-side, you have to take the weighted average of the inverse. Which is a mouthful but it's not that complicated. To make the math easier, people use U-values, which is the inverse of R-values: U=1/R. If you have a wall with different insulation levels, the U-value of the entire wall is equal to the the sum of the U-values of the sections, weighted by their share of the area.

MS ALWAYS answer the phone and questions fast! Package was misplaced USPS said delivered but we couldn't find it so I called and MS and they sent a replacement FAST. Couldn't be happier with the V2 Kit I purchased for the NG. QUALITY ENGINEERING and prints never looked better!

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