Slab-on-Grade Insulation

Commercial building slab-on-grade insulation, comfort and energy performance

Many slab-on-grade buildings in northern climates do not have adequate insulation around the foundation, especially at the slab. The lack of insulation or improper placement allows cold to be conducted into the building at floor level. In the past, a cool slab edge could be felt but not seen. Today, thermal imagers can easily see and quantify slab temperatures.

During cold weather, employees who work along the perimeter of the building quickly notice their feet and legs getting cold. They may use electric space heaters to try to offset the cold from the concrete. The typical space heater uses 1.5 kilowatts. It may or may not be turned off at the end of the day.

In extreme cases, hundreds of space heaters may be added. This affects electrical circuits and can make thermostats and heating systems ineffective. While it's easy to add electric resistance heaters, there is an operating cost factor. It costs about three to five times more to heat with electricity than with natural gas.

Commercial buildings often have an overhead heating and cooling system. A building with slab-on-grade floors and an overhead heating system may not be comfortable at floor level unless the building is well insulated, has low infiltration and the air distribution system is well designed. Warm air overhead needs to be pushed down to the floor. This is more difficult if the floor is cool.

Some buildings have perimeter hot water heating systems. This type of heating system usually offsets the lack of insulation. Nevertheless, insulation reduces heat loss to the outdoors and directs it to the occupants where it's needed and useful.

Unfortunately, adding insulation to the foundation or slab edge after the building is built is rarely cost effective. The once-in-a-30-year opportunity to get it right comes when the building is being constructed. In Northern climates it makes sense to put your money and energy into a high quality, well insulated building.

Slab Slab Slab

Copyright 2017, Building Science Corporation
These images illustrate typical approaches for slab on grade insulation. Review your local residential or commercial building code for specific details such as R-value and dimensions.


Thermal images

While the camera can represent relative thermal energy, precise temperature definition is more difficult. The IR camera takes in both emitted and reflected energy from the target and uses target emissivity, reflected apparent temperature and calculations to produce an estimated target temperature. We strive for accuracy in interpreting temperatures but do not reset the camera emissivity and reflected apparent temperature for each image.

Thermal imageThermal image

The vertical temperature scale on the right side of the image shows the highest and lowest temperatures within the image. The temperature at the cursor location is shown in the upper left box. The color palette used in these images has yellow and white as the warmest temperatures and the purple to black as the coldest temperatures.


Thermal imageDigital image

The paired thermal image and standard digital image are taken at the same time, though they have a slightly different field of view and perspective.


The information presented in these images is provided in good faith as a courtesy. MGE and its affiliates make no warranty, express or implied, regarding the accuracy, adequacy, completeness, legality, reliability or usefulness of any of the images at predicting thermal variation. MGE has not generated these images for any specific purpose and is providing this information on an "AS IS" basis. All warranties of any kind, express or implied, including but not limited to the IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED and by accepting these images you agree to use the images at your own risk.