Thermal Insulation and What it Takes to Get There

Thermal Insulation - Our Experiences

But now to our experience with rock wool as a material for thermal insulation. While Rico is being cooked at 25 degrees Celsius on the roof of the Cabin by means of bottom heat, I have opted for the circulating air variant in the Cabin. In itself, this is a good idea, but as described above, the task assigned to me entails certain protective measures: breathing mask and long-armed protective clothing.

The Right Choice of Rock Wool

Rock wool comes in large mats of different sizes. When building exterior walls, you have several options for the thickness of the walls (2×4, 2×6, 2×10, etc.) and the spacing of the support beams from each other (16 or 24 inches). Rock wool mats are available in appropriate formats.

We used 2×6 studs for the exterior walls of our Cabin and built them 24 inches apart. Therefore, we are using insulation batts that match those dimensions exactly. In the picture above you can see this well on the middle package.

R Value

You can also see the indication R22. This is the R-value. The R-value is a unit of measurement that indicates the resistance of an insulating material to heat transfer. It indicates how well a material can store heat. The higher the R-value, the better the thermal insulation.

To calculate the R-value, the thickness of the insulation material is divided by its thermal conductivity. The thickness is measured in meters, while the thermal conductivity is expressed in watts per meter Kelvin (W/mK). The formula for calculating the R-value is:

R-value = thickness of the insulation material (in meters) / thermal conductivity of the insulation material (in W/mK)

The R-value is a recognized and commonly used key figure to evaluate the thermal insulation capacity of a material. It is used by experts and building standards to compare the efficiency of insulation materials and to evaluate the thermal insulation performance of buildings. In this sense, the R-value can be considered a reliable value to get a general overview of the thermal insulation capacity of a material.

However, the R-value has some limitations. For example, it does not take into account the influence of factors such as air movement or humidity on thermal insulation. In addition, the R-value alone cannot provide an accurate assessment of the overall thermal insulation performance of a building, as other factors such as component design, gaps or thermal bridges must also be taken into account.

Insulate Exterior Walls

Theoretically, the insulation mats fit exactly for the construction method we have chosen. However, there are now various things in such a beam gap: boxes for sockets, light switches and co, for example. Also, for reasons in some places the distances are not exactly 24 inches, but a little smaller or wider. The rock wool mats must therefore be cut to size.

To get the insulation mats into the right shape, take a large bread knife and cut slices of strudel. Sometimes thick, sometimes thin, never straight. In terms of accuracy, cutting rockwool mats into slices is like cutting slices of a loaf of oven-fresh bread. In short: it's a nerve-wracking slaughter.

Insulate Roof

The BC Building Code specifies requirements for air spaces between roof insulation and roof decking. This means that a minimum air gap of 25 mm (1 in.) is required between the top edge of the rockwool batts and the underside of the roof decking. This ventilation space helps to remove any water vapor that may be penetrating upward from the inside to the outside. Among other things, this is how we prevent condensation problems. In addition, we thus ensure a balanced temperature at the roof surface and reduce the risk of ice damming.

In order to install the correct and code compliant insulation for our roof thickness, we need to layer two layers of insulation material on top of each other. One is an R22 mat and the other is an R14 mat. The mats in sum give the insulation value necessary for our requirements and also allow the prescribed ventilation space.

However, placing mats of rock wool overhead is no walk in the park. On the one hand, gravity ensures that the mats regularly leave their traditional place again. On the other hand, the insulation mats lose enormous stability as soon as they are touched or - as mentioned above - cut into shape. Added to this is the height at which all this is done and thus the need to bring the scaffolding into action again. All this increases the tension and itching enormously, but in the end leads to a tiptop insulated roof.

Final Results

Once the mats are placed between studs and rafters, the rooms get a completely different effect. For the first time, we get a real sense of the space and the actual size. And are once again thrilled.

Is Thermal Insulation with Rockwool Worth It?

All the effort and itching was definitely worth it for us. For one thing, the temperature inside the cabin has been massively regulated. Although outside the temperatures fluctuate between 15 and 25 degrees Celsius, the temperature inside the cabin remains relatively constant. Of course, the well-insulated and coated windows also contribute to this.

On the other hand, the sound-absorbing effect is really impressive. Although the test case with the toilet is not yet possible, conversations across room boundaries have become considerably less intelligible.

Now the interior work continues with the next layer: the vapor barrier. You can already see it on one of the pictures. There will be more about this soon.