Types of heat loss in a home

Heating Trends, last updated on December 4, 2022

Have you decided to build or renovate a house and you've come across the concept of heat loss and thermal insulation? Let's go over the types of heat loss and why thermal insulation is so important.


Types of heat loss in a home

Whether you live in a house or an apartment, you want the space where you and your family spend time to be cozy and comfortable. One of the important elements of every residential building is the facade, that is, the insulation system as part of the facade. In addition to having a protective role, insulation systems play a huge role in reducing heat losses and save money.

Heating insufficiently insulated spaces requires a larger amount of energy, which leads to an increase in the cost of using and maintaining the space, but also to greater environmental pollution. By improving the thermal insulation characteristics of the building, it is possible to reduce the total heat loss of the building by over 50%.

Thermal insulation is important in construction, because it prevents heat loss in winter, cold perimeter structures, damage caused by condensation (moisture) and overheating of the space in summer.

The consequences of insufficient thermal insulation are excessive use of energy, structural damage and uncomfortable and possibly unhealthy housing.

Types of heat loss in a home

Technically, heat is lost through the thermal process of conduction, radiation, convection, air infiltration and evaporation. Heat loss in buildings occurs via concrete slabs, thermal bridges, floors, walls, doors, windows and roof. Of course, heat loss also occurs when a window or a door is opened because of the exchange between indoor and outdoor air.

Illustration of percent of heat loss through floor, roof, walls and windows

Windows and doors can account for up to 15 percent of total house heat loss, even more if they are made of wood and in a bad shape with lots of cracks allowing heat to escape. Floor accounts for 15%, roof for 25% and walls for 35% of the total house heat loss.

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Practical example of a heat loss

There's a lot of science behind the mechanisms of heat transfer, but it's easy to understand the basic principles with a practical example.

If we take a living room window as an example, we can observe that it's cold to the touch because it's conducting heat away from the living room. Because the heat passes from a hotter to a colder body, the inside surface of the window glass will be cold, while the outside surface will be warm.

Radiation is driven by the emissivity of the surface, it's area and the difference in temperature of the surface and the surrounding air. In our example, because of it's large surface, the window makes a great thermal conductor to pass the heat away.

Convection also plays an important role in heat loss. If it's a nice and sunny day outside, the heat is lost through a window by convection at a somewhat slow rate because the thin layer of air wrapped around the surface of the glass acts as a barrier and lowers the difference in temperature between the glass surface and the surrounding air.

But on windy days, the heat passing through the window surface will be whisked away more quickly, thus speeding up the thermal energy transfer process and making heat loss faster. Since the window is not getting colder more quickly, more energy needs to be produced on the inside to compensate for the losses on the other side.

Air infiltration occurs when the warm air inside the house is let to escape freely through cracks on windows, doors or through cracks in the attic, and also by opening windows and doors to let some fresh air in.

Evaporation can sometimes occur on the surface of the building, on the roof or within the building which will produce a cooling effect. Through the process of evaporation the heat gets lost through the conversion of water to gas.

Although we've used a window for our example, the same heat loss happens with doors, and walls. That's where insulation steps in.

Thermal insulation to prevent heat loss

Heat passes from a hotter to a colder body. In the case of your home, this means that in winter, parts of the emitted heat go to the outside space, and in the summer the opposite process takes place, the outside heat is transferred to the inside space.

This occurs naturally because of the thermal equilibrium principle which demands that all objects in contact with one another come to the same temperature. When the temperatures balance out, heat stops flowing.

We can't stop heat loss entirely, but there are measures we can take to slow it down. In order to reduce heat losses, it is necessary to insulate the living space with thermal insulation.

Thermal insulation reduces the transfer of thermal energy between objects of different temperature which are in thermal contact.

Thermal wall insulation

Better thermal insulation is achieved by installing materials with low thermal conductivity, i.e. high thermal resistance. The thermal resistance of the material increases with respect to the thickness of the material.

A good knowledge of the thermal properties of building materials is one of the prerequisites for designing energy-efficient buildings. Heat losses through the building element depend on the element's composition, orientation and thermal conductivity coefficient.