▽ +09.00Technical article · Thermal insulation
Thermal insulation materials for roofs and walls: XPS, EPS and PU foam
Through Riyadh’s long summer, air conditioners run for hours against heat coming in through the roof and walls. Thermal insulation does not cool a building; it slows the heat getting in — and the material, its position and its continuity decide how well.
03minutes read
- Topic
- Thermal insulation
- Sections
- 07
- References
- 03
- Published
- Updated
- Publisher
- Prime Shield — engineering content
Where does the heat come in?
The roof takes the most sun: its outer surface gets far hotter than the air, and the heat then travels through the concrete slab into the top floors. Sun-facing walls pass heat in the same way, if to a lesser degree.
How insulation works: λ, R and U
Every material conducts heat; insulation materials do it slowly because they trap still air or gas in small cells. Thermal conductivity λ (W/m·K) describes the material; thermal resistance R = thickness ÷ λ (m²·K/W) describes a layer of it; the U-value (W/m²·K) describes the whole roof or wall, all layers and surfaces included. Doubling a layer’s thickness doubles its resistance, while gaps and thermal bridges cut the real performance. ISO 6946 is the usual calculation method.
Common insulation materials
| Material | Form | Typical position | Notes |
|---|---|---|---|
| XPS boards | Rigid, closed-cell extruded polystyrene | Inverted roofs, under floors, basement walls | Tolerates moisture and load; the usual choice above the membrane in inverted roofs |
| EPS boards | Rigid expanded-bead polystyrene | Walls, ceilings, protected positions | Lighter and less moisture-tolerant than XPS; needs a separation layer with some membranes such as PVC |
| Sprayed PU foam | Sprayed in place, closed-cell | Concrete and metal roofs, complex shapes | Continuous, joint-free; needs a top coat against UV |
| PIR / PUR boards | Rigid foam boards, usually faced | Under a membrane or behind cladding | Low conductivity per thickness; keep dry; fire classification per system |
| Foam concrete | Lightweight concrete poured to falls | Roofs, under the waterproofing | Mainly forms the falls; adds some insulation |
A general overview; the systems Prime Shield installs are on the system pages.
Matching the material to its position
- Above the membrane (inverted roof)XPS made for wet, loaded conditions, held down by ballast or tiles.
- Below the membrane (conventional roof)Boards that stay dry, with a vapour control layer where the design needs one.
- Sprayed on the roofPU foam as a continuous layer, protected by a top coat.
- WallsBoards inside the wall build-up or within the facade system, as the design details.
Specifications and the building code
The Saudi Building Code includes energy-conservation requirements for the building envelope, among them SBC 601 for non-residential buildings and SBC 602 for low-rise residential buildings. Your designer or consultant sets the values your project needs, and the material and thickness are chosen to meet them.
See the difference yourself
The thermal insulation simulator on our site lets you try different materials and thicknesses for a Riyadh roof, with an indicative engineering estimate of heat flow. Actual results depend on the design, the products and the workmanship.
Thermal and waterproofing together
On roofs, thermal insulation and waterproofing are usually installed as one system: foam-concrete falls, the waterproofing membrane, insulation boards and a protection layer or tiles. The layers work together, and the roof is flood-tested before handover.
References
Standards and guides on the subject — named to show what they cover, not to claim that any product complies.
- ISO 6946Building components: thermal resistance and thermal transmittance — calculation method.
- SBC 601Saudi energy conservation code for non-residential buildings.
- SBC 602Saudi energy conservation code for low-rise residential buildings.
General educational content; final values and requirements follow the manufacturer’s TDS and the approved project specification.
Terms in this article
Share or save this article
Technical review
Need an engineer’s view on your case?
Send drawings or photos and a short description; our engineers review the case and propose the system and the details.