It’s warm, light and dry
In practical applications, a very beneficial effect of installing over-the-rafter thermal insulation is the significant reduction, if not complete elimination, of thermal bridges in the roof structure. Thermal bridges compromise the roof structure and the overall energy use of a building.
The primary advantage of over-the-rafter thermal insulation systems comes from an obvious fact: other roof thermal insulation arrangements include inherent thermal leaks, known as cold or thermal bridges. Thermal bridges take the outdoor temperature and act as heat sinks for the indoor heat, absorbing a lot of the energy we put into a building and drawing it outside.
Thermal bridges require additional thermal insulation. More often than not, they need solutions to prevent the hazardous process of diffusive indoor condensation. An over-the-rafter thermal insulation arrangement provides a uniform thermal barrier on the outside of the roof framing, fully bypassing the issue of thermal bridges. All structural parts of the roof are located inside the thermal insulation envelope, preventing the hazardous problems highlighted above.
It's ergonomic and aesthetic
There are two primary advantages of over-the-rafter thermal insulation in the department of aesthetics and ergonomic performance. First, over-the-rafter thermal insulation exposes and helps to manage the naturally beautiful roof framing timber inside the building. This opens up a world of creative indoor finishes, from the classically rustic to extremely avant-garde designs.
Second, the room under the roof framing becomes larger, and there is more clear height indoors. This facilitates a greater range of installation possibilities, e.g. shelving, lamps, shower cubicles, or book racks in a neat and pleasing mezzanine, right under the roof.
It’s fast, easy and safe
No matter who says it: master roofers and apprentices alike agree that over-the-rafter thermal insulation makes roofing work much easier and faster.
The mechanical properties of the polyurethane core in the thermal insulation sandwich panels eliminates many risks of damaging the material, a frequent cause of failure of roofing sheets and membranes. Other advantages of polyurethane-core sandwich panels include dust-free processing, the availability of various panel thicknesses (40 to 120 mm), low weight over a large surface area (1.2 x 2.4 m) and safe handling over the wooden members of the framing. This further enhances the advantages of installing an over-the-rafter thermal insulation system.
This is how the trend is looking
At present, environmental concerns can still seem rather abstract and futuristic, but nothing could be more misleading. It will not be long before regular building design engineering permanently features modern solutions based on sustainable growth, green certificates, and multi-criterion building assessment methods.
When this happens, an elementary life cycle assessment analysis will show that the polyurethane-core over-the-rafter thermal insulation on pitched roofs is 20% cheaper than mineral-wool thermal insulation solutions. It is expected that the value of fixed property will soon be heavily dependent on how “green” its integrated construction materials are (not to mention their energy ratings).
Considering the multi-criterion analyses, we also need to understand that poorer ratings (which mean higher costs) will also relate to the materials, for which the environmental costs of production, application and use will be high, with the first-choice construction materials featuring a relatively low content of natural fossil materials.
Here polyurethane-based thermal insulation proves its advantage over other materials. Unlike the latter, manufacturing the base components of polyurethane has no need for scarce fossil materials, such as crude oil, as biologically renewable plant-derived resources can be used (like corn, flax, sunflower, soy, palm, castor and fish oils, or refuse from agricultural processing, which include corn cobs, straw, waste oils, animal fat, etc.). Soon, when people think about polyurethane production, they will think of the “heady” smell of extensive fields of rapeseed or flax, or exotic palm tree farms, rather than acrid industrial fumes.
“That ain’t gonna last, mister!”
Sandwich panels with a rigid polyurethane core, like THERMANO, are a state-of-the-art thermal insulating material featuring extreme service life and durability. The mechanical properties make it difficult to strain or deform, while its low water absorbability protects it from water and the corrosion it may cause during incidental or permanent exposure. The chemical composition makes it impervious to most types of biological attack and degradation, as well as many aggressive chemicals.
The most renowned thermal insulation testing centre, Forschungsinstitut für Wärmeschutz e.V. (FIW) in Munich, Germany, tested 28 and 33 year old PUR samples taken from existing buildings for:
- Thermal conductivity
- Compressive strength
- Moisture content
- Dimensional deviations and sandwich panel integrity
The final test results states: FIW confirmed that the PU foam “(...) shows no material (or worth mentioning) damage or defects”. Furthermore, “(...) after 33 years of use, the PUR thermal insulation panels remain fully functional and continue to demonstrate all the declared specifications and performance”. What this means is that if someone thermally insulates a roof well with THERMANO sandwich panels, then their grandchildren will be able to remove the panels after decades of operation and reuse them without new project costs and with all the original thermal insulation performance retained. This is unlike anything else seen in thermal insulation systems so far.
Krzysztof Milczarek, Engineer