Does a green roof have an insulating effect?

A green roof mainly has a heat regulating effect. This is greatest in the summer months. With traditional roofing, considerable fluctuations in the indoor temperature can occur. In the summer, the building warms up because a grey roof absorbs heat from the sun. When there is a green roof, the vegetation reflects most of the direct sunlight rather than absorbing it. In addition, the moisture present in the vegetation is evaporated, which also provides additional cooling. All this ensures that the temperature in the building remains lower and so you can save on energy costs for air conditioning.

Heat regulating effect of green roof in winter

In the winter, the heat-regulating effect of a Sedum roof is less than in the summer, because a green roof retains moisture. However, a green roof with grasses or herbs contributes more to heat regulation because the substrate layer is thicker than for a Sedum roof. So you can also save on your heating bills in the winter.

Sound insulation: quieter environment indoors and outdoors

In addition to thermal insulation, a green roof also has a sound-insulating effect. The combination of substrate, plants and the embedded air in the green roof system provide good sound insulation. Sound waves are absorbed and reflected. The substrate blocks the lower frequencies, while the plants absorb the higher frequencies. Consider aircraft noise and traffic, but also the sound of heavy rain fall or a hail storm. A green roof provides more peace and quiet in your office and offers a more pleasant environment in urban areas.

Green roofs reduce sound resonance by 3 dB and provide sound insulation of up to 8 dB. This may not seem much, but for the human ear, an 10 dB reduction in noise levels is 50% quieter. The degree of sound insulation will depend on the thickness of the green roof structure. Substrate and vegetation play an important role in the degree of sound insulation. The thicker the substrate and vegetation, the better the sound insulation. In 2004, Dunnett & Kingsbury conducted research at the airport in Frankfurt, Germany. A noise reduction of 5 dB was measured after the installation of a 10 cm green roof.

Lower temperature in the area: reduction of the Urban Heat Island Effect

It is not just your office or home that benefits from the heat regulating effect of your green roof. In the summer, the temperature in the city is approximately 5-7⁰C higher than in the countryside. This is because the buildings and roads in a city absorb the warmth and then radiate it again later. This phenomenon is known as the ‘Urban Heat Island’ effect. Greenery reflects the most of the warmth which results in a lower ambient temperature. In addition, plants cool the air because the moisture they contain evaporates.  Research conducted at the Tyndall Centre for Climate Change demonstrates that we need 10% more greenery in the city to combat warming in the city and to counter the associated climate change. Since the space for greenery in cities is limited, a green roof or green facade is an ideal means of increasing the amount of greenery, and therefore for reducing the city temperature.