We present you the continuation of our article « Control of heat transfer ... Which fits into the theme of the building envelope. In fact, the envelope must have a minimum thermal resistance that is provided for in the current Construction Code. Nowadays, it is possible to analyze the thermal resistance of an existing building and to know the points of heat loss as well as the points having a low heat resistance without removing the finish or piercing the walls. The device that makes these tests possible is the thermal camera (infrared thermography).
Among the range of infrared cameras, there are some models designed specifically for building experts. These cameras allow professionals to remotely check the condition of the building envelope without any contact. The analysis of the thermal images makes it possible to discover which are the places in the walls, the floors and the ceilings where the thermal resistance is weak and if there are heat losses by these same elements of the envelope.
What is thermal resistance?
On the insulating materials, we find the letter R which represents the thermal resistance of these. In other words, the R factor is the tendency of the insulation to prevent heat and cold from easily passing through it. The more efficient the insulation, the higher the R factor (thermal resistance). Each building material used in the composition of a wall has its own thermal resistance and that of a wall is the sum total of the thermal resistances of all its components. The thickness of the insulation to be added can be determined once the elements of a wall and their thermal resistances are known.
Thermal losses in the building cause discomfort to the occupants - because of cold surfaces and non-uniform temperatures - as well as high heating bills.
The causes of heat loss are among others:
- Air leakage around openings (doors and windows), electrical outlets and switches in exterior walls, around ceiling lights and at the bottom of exterior walls, and at the top of interior partitions at the junction of the attic (roof), etc .;
- In places where the quantity and quality of the insulation are not adequate: in the external walls, the insulation may be wet, wet, compacted, displaced or it may be insufficient or absent;
- Intermediate sheathing of exterior walls may be missing or damaged and the air barrier may be missing, punctured or improperly installed. This situation then causes air infiltration from the outside to the inside and, consequently, heat loss points as well as cold surfaces inside.
Tips for minimizing heat loss:
- Thermal losses at the bottom of the walls, through the floor and outside walls: The junction between the walls and floors must be sealed and / or the air barrier repaired outside, and the open seals must be sealed to the exterior cladding;
- At ceilings and along exterior walls: Seal between walls and ceilings in the attic and / or repair the air barrier as required;
- Below and around all windows: Insulate windows and seal from outside and from inside;
- Near mechanical exits: The circumference of the mechanical exits in the attic and in the outer casing must be sealed;
- Through electrical outlets: Electrical outlets must be sealed in exterior walls;
- From the attic to the internal partitions: In the attic, the junctions between the partitions and the ceiling must be sealed;
- At the various places in the walls where there are deficiencies in the envelope: You must open to see the exact cause that could be the lack of intermediate coating, a defect in the installation of the air barrier or a problem with the insulation as compacted insulation, absent or wet;
- Ceiling separating the building from the attic: The vapor barrier in the attic must be well sealed and the perimeter of the devices piercing the ceiling.
Note that the thermal image captured by the infrared camera indicates a specific location where there is a thermal loss. However, this image does not determine the exact source of the deficiency, which could be either wet, compacted, unsuitable insulation or a deficiency related to the sheathing or the air barrier, ie a problem of air infiltration. Therefore, to propose appropriate corrective work for heat losses, exploratory holes must be used to determine the exact cause of thermal losses.