Unveiling Hidden Stories in Existing Buildings With Thermal Imagery

Exploring three applications for identifying thermal weak spots, reducing demo costs, and measuring window performance.

Megan Brown using the thermal camera
March 12, 2024
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If a picture is worth a thousand words, is a picture that shows what the eye cannot see worth even more? Documenting the built environment through the lens of a thermal camera offers a lot of value to building owners and design teams. We find thermal imagery to be both fascinating and highly informative. Kind of like a “How It’s Made” documentary… (you just never know when you will need to make your own aluminum foil).

Today we are sharing 3 uses of thermal imagery in renovations and some examples from a recent project.  

Thermal imagery measures the infrared radiated temperature of an object’s surface. It aids in visualizing patterns of heat loss through assemblies or thermal bridging, highlighting insulation deficiencies, air infiltration and even the presence of moisture under certain conditions. This tool, along with our observations and analysis of original drawings, help inform our recommendations for improving the envelope of existing buildings.

Our work at Finegold Alexander leads us through many existing buildings. While each building has a unique set of challenges, they commonly experience the same energy culprits: excessive air infiltration and insufficient insulation or thermal bridging. The following examples are three specific ways that thermal imagery can help target these key energy issues.


There are a myriad of construction methods and designs in existing buildings, but there are also common problem areas that can be highlighted in a thermal analysis. It is beneficial to specifically capture unique details, changes in materials, changes in geometry, or uncommon assemblies in a building. They might not be an obvious problem to the naked eye, but these are typically the trickier areas to air seal or maintain continuous insulation.

The picture-perfect example of this is a connection point between two different materials in the following existing building. Constructed in two different eras, this existing library has a ‘newer’ wing from the 1980’s which abuts an older foundation wall from the late 1800’s (the original stone foundation). Part of the original foundation is now enclosed within the 1980’s wing and the stone was left exposed on the interior for a unique glimpse into historic construction. The junction point between old and new, however, is a definite weak spot. Thermal imagery illustrates the cold air infiltration at this joint, highlighting the need for air sealing and making the case for exterior insulation.


Renovations of existing buildings are critical to reducing global energy consumption, and they can be very costly. Building envelope upgrades must be considered in tandem with mechanical equipment selection and energy reduction estimates. In the case that large-scale envelope work is not feasible on a project, a thermal imagery investigation can assist in highlighting the most critical areas of focus. Targeted renovations can reduce demo scope and costs for owners while assigning resources where they will be most useful.

A common example is missing stud cavity insulation. In the project below, the cavities that are lacking sufficient insulation are instantly obvious in a thermal picture. If the project scope only encompasses fixing the missing insulation, the cost estimate is straightforward and the impact on the rest of the room is limited. No stud finder needed! (Note: thermal cameras cannot see through grandfather clocks, unfortunately.)


Windows are another costly investment in energy retrofit projects. Typically, a window frame is the lowest performer of thermal resistance in a wall assembly, even in new construction. It can be a challenge to find the budget for window replacement in a renovation project. To help make the case for replacing windows, adding storm windows, or simply air sealing around existing frames, the existing window performance can be measured with thermal imagery. Modeling and estimating window performance in simulation software is useful and widely used, but we still find a lot of value in measuring actual performance in real-life situations.

In the following project example, the ΔT (or difference in temperature) from the surrounding walls to the existing window frame was significant. These images were taken on a cold winter day before sunrise. This project had a mix of aluminum frame windows and historic wood windows. Even with some existing exterior storm windows, we found that the interior temperature of the wood frames was nearly the same as the outdoor temperatures that day. The existing aluminum windows were much better but still measured over 20°F colder than the ambient room temperature. These low surface temperatures inside the building could lead to moisture accumulation or cold drafts for occupants near the windows. Measuring the performance at windows all around the building helped guide our recommendations for tiered renovation options depending on budget.

Withall our existing building work, we never know what will show up in a thermal imagery shoot, but there are always interesting clues about the current conditions and breadcrumbs for how we can focus our efforts for improvement. Ina sense, thermal imagery is a master storyteller. It tells a heart wrenching story about loss (heat), bridging differences (also with heat, aka thermal bridge), and the hope of a better future (with reduced EUI’s).