Thermal insulation properties of windows and doors – what to pay attention to?

When renovating or building a house, owners must decide on the right windows and entrance doors. In addition to their aesthetics and functionality, it is also worth considering important parameters that affect the thermal insulation of the building. Properly selected window and door joinery not only improves thermal comfort, but also helps reduce the costs of heating and cooling the interior. In our article, we will show what to consider when buying windows and doors to achieve optimal thermal insulation and enjoy both a warm and energy-efficient home.

Why is thermal insulation of windows and doors so important?

Choosing the right windows and doors is a key factor that affects the thermal comfort in the home. Any leaks resulting from improperly selected joinery or incorrect installation or the use of poor quality products cause significant heat losses, which unfortunately translates into higher heating costs and higher energy consumption.

Heat escapes from the interior of a building most often through:

• conduction — it is related to the type of material from which the frames and profiles of windows and doors are made,
• radiation — this method of heat loss applies to windows and involves the escape of heat energy through the panes to the outside,
• leaks — cold gets inside and heat escapes outside.

Thermal insulation properties of windows — what to consider when choosing?

It is estimated that up to 30% of heat can escape through windows, which is why the right choice of window joinery and window installation method is so important to minimize losses and save on heating. Here are the most important parameters to consider:

• Heat transfer coefficient (Uw): The lower it is, the better the thermal insulation.
• Type and number of panes: It is best to opt for triple-glazed windows, equipped with several chambers (5-6). It is also worth choosing a model with special low-emission coatings, which provide additional protection against heat loss.
• Profile heat retention capacity: The value is determined by the Uf coefficient, which in energy-saving and passive windows is usually 0.8 or 0.9 W/m2K.
• Thermal energy transmittance coefficient (g): The higher it is, the more sunlight gets into the building. For energy-efficient windows, the value should be around 55%.
• Window installation type: To ensure optimal tightness and thermal insulation, it is best to opt for layered (warm) installation, which uses polyurethane foam and additional insulating layers.

External doors and thermal insulation – what to look for?

Thermal insulation properties of external doors are crucial for the energy efficiency of a building. Here are the factors to consider when buying doors:

• Heat transfer coefficient (Ud): The lower the value, the higher the thermal insulation of the door. In energy-saving passive models, the Ud coefficient is around 0.7-0.8 W/m2K.
• Material: In the production of energy-saving doors, wood, aluminum and steel are most often used together with various types of thermal insulation fillings.
• Strength and durability: Materials used to produce external doors should be resistant to weather conditions, mechanical damage and wear.
• Thickness and number of seals: Thicker models insulate heat much better (provided that high-quality filling materials are used), and the use of additional seals eliminates the risk of thermal bridges.
• Equipment with a so-called warm frame and a triple-glazed package – important when choosing doors with glazing.
• Installation method: In the case of energy-saving doors, layered assembly will also work best, in which additional insulating layers are used in the form of, among others, vapor barrier tape on the inside and vapor permeable tape on the outside.