More and more people want to make their home more sustainable by installing (new) insulation material. Don't forget about acoustic insulation in the process! In this article you will read everything about it.

Sustainably Insulating Your Home: Don't Confuse Thermal With Acoustic Insulation

Would you like to insulate your home (better)? An increasing number of people chooses to do so. Particularly in view of rising energy prices it is a good idea to consider this. When it comes to insulation, often the first thing people think about is thermal insulation. More and more people start making use of a heat pump. However, in making this step towards sustainable improvements, acoustic insulation is often overlooked. By combining acoustic insulation with thermal insulation you can cut a lot of costs. Apart from that, it is more efficient to do both right a away, avoiding that you need to do the insulation works twice. So, if you're planning to insulate your home thermally, don't forget about the acoustic insulation either. The tips we will provide in this article can also be applied to other buildings apart from your house.

In this article we would like to explain the following:

  • What is thermal insulation?
  • What is acoustic insulation?
  • What is the difference between thermal and acoustic insulation?
  • How can you apply these two types of insulation in the following situations?
    • Insulating roofs
    • Insulating dormer rooms
    • Cellulose insulation
    • Insulating a heating pump

Thermal (or heat) insulation is the insulation of walls, roofs, and/or rooms in order to stay warm inside or, on the contrary, to keep heat outside. This often plays a role when somebody wants to insulate his or her home. Acoustic insulation is the insulation of sound (sound insulation). This may include optimising sound, or keeping sound in or outside a room. The difference between these two types of insulation is big. The difference is that big, that the wrong type of thermal insulation may have a counterproductive effect with regards to sound insulation. Because of this, it's very likely that the sounds of the street and of traffic can be heard inside, after replacing the insulation of your roof.

The big difference between thermal insulation materials and sound insulation materials is their weight. Thermal insulation material is lightweight and fluffy, whereas acoustic insulation material is dense and heavy. Thermal insulation materials are designed to optimise the transmission of thermal energy (warmth) between the two sides of the material or construction and acoustic materials are designed to give relatively light construction more resistance against sound, most often by adding mass.

Combining thermal and acoustic insulation

We would like to give a few examples of how you can combine these two types of insulation in order to obtain the best possible end result:

  • Improving the roof's insulation
    Roof panels consist of two layers of plate material, often with foam inbetween these layers, also referred to as PIR. This material is lightweight, and as such it has ideal thermal insulation properties, but very poor acoustic ones. By adding Isomat KE, you can additionally insulate the roof panels acoustically. Isomat increases the roof's weight, ensuring vibration will be insulated. Thus, there is more resistance against soundwaves and the acoustic insulation value increases. The best approach is to first apply Isomat KE and to cover these plates with the PIR roof panels. Isomat KE can be applied using contact adhesive, and because of its weight an additional mechanical securement is appropriate, such as by means of screws or nails. We recommend using no more than two layers of Isomat. Theoretically speaking, it is reasonable to expect a reduction in the sound level of about 6 to 8 decibel (depending on the type of roof panel and Isomat). Of course, it may be the case that the panels are already installed. There is a solution to solve this problem as well. You can equip the inner side of your attic with an additional roof boarding or ceiling. A 'floating' and acoustically insulating roof boarding or ceiling can be rather easily be built using Merfoflex. Both products consist of a construction to which two layers of plasterboard can be attached. Thanks to this technique, in a way the roof is decoupled from the wall or ceiling, preventing vibration from being transmitted.
  • Insulating dormer rooms
    Since dormer rooms are often made of very lightweight plates with PIR foam inbetween, they thermally insulate well, but contain poor acoustic insulation properties. When the inside is provided with Merfoplex or a layer of Isomat KE (with a wooden plate as a finishing layer), the acoustic insulation value will significantly increase. This works the same as what we just described about insulating a roof.
  • Cellulose insulation for hollow spaces
    Cellulose insulation flakes are suitable to thermally insulate hollow spaces like a wooden storey floor, wall or ceiling. It is a material that consists of woolly cellulose flakes made from newspaper. The product is very environmental friendly. The lightweight material creates a stationairy air layer, resulting in thermal insulation. Are you planning to use cellulose insulation? Please consider the fact that you will additionally need to apply acoustic insulation material. Because of the minimal weight (and thus the limited mass) of cellulose flakes, they bearly add anything when it comes to acoustics. The material you can use to this end is Isomat KE, preferably with a weight of 14 kg/m². You will notice that after applying cellulose flakes, the middle and lower frequencies will continu to be perceivable. You can read more about this topic on our tips pages "Step-by-Step Plan for Insulating a Wooden Floor" and "Sound Insulation for Lightweight Walls".
  • Insulating a heat pump 
    Purchasing a heat pump is a sustainable alternative for heating the house. However, this brings along a few challenges, because they produce a lot more noise than often initially thought. Our tips before you install the outdoor unit of your heat pump:
    • Don't place the heat pump too close to the property boundary, avoiding nuisance to the neighbours.
    • Keep a free space around the heat pump of about one metre. In case you will later on need an enclosure this will save the cost of replacement. Additionally, there will be space left to do something about the sound problem yourself.
    • Since dormer rooms are often made of very lightweight plates with PIR foam inbetween, they thermally insulate well, but contain poor acoustic insulation properties. When the inside is provided with Merfoplex or a layer of Isomat KE (with a wooden plate as a finishing layer), the acoustic insulation value will significantly increase. This works the same as what we described above about insulating a roof.
    • Never attach the outdoor unit to a wall, and don't place it on a wooden roof either, otherwise problems with contact noise will be guaranteed.

Do you have any questions concerning this topic? Please feel free to contact us, we would love to help you.