Pitched roofs thermal insulation below rafters

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General information

Thermal insulation of pitched roofs can be applied only to the interior side or in combination, between+below the rafters. Jointless placement of XPS below the rafters guarantees avoidance of thermal bridges. It can be installed in existing structures, as well, for posterior loft development or for energetic modernization of roof structures.

Other information

If the roof was built without thermal insulation inserted above the rafters, the most economic way for reducing the thermal bridges and improving the thermal protection is provided by a combination of thermal insulation between the rafters and fixed to the bottom plane of the roof structure; it can be used expansively in refurbishments.
What concerns the supporting structure, the XPS is self-supporting until the completion of the interior cladding; subsequently, it is squeezed between the cladding and the rafters. The tongue and groove or staggered edge finishing of the RAVATHERM XPS 300 ST panels ensure composite action of the structures, however, it is no substitute for structures designed to ensure lateral rigidity of the roof structure, e.g. wind-bracing placed between the rafters.
The thermal insulation panels are arranged bottom-to-top. From building physics aspects, highly efficient thermal insulation capable also for damp prevention can be achieved during the installation of the XPS panels.

Technical

The damp insulation layer improves also the air tightness and can be fitted between the RAVATHERM XPS plates or directly behind the interior cladding, depending on the ratio of thickness of the thermal insulation layers laid in front of and behind the foil. In the presence of vapor permeable underlay plating, the vapor barrier layer could, in general, be done without, owing to the relatively high vapor diffusion resistance and the tongue and groove edge finishing of the XPS plates, however, the vapor barrier layer is required for ensuring air tightness of the layered composition. The interior cladding can be built by using wooden panels fixed to branders or gypsum plasterboard panels fixed to lathing or a system of profiles, etc.

INSTALLATION ADVICES FOR ROOF RENEWALS

If no secondary watertight foil (i.e. underlay plating) had been built into the roof structure, such omission must be rectified. In case of posterior loft development, one should deliberate replacement or repair of the shell-plating or the lathing. If the lathing must be replaced, the new damp barrier system can be laid on top of the rafters.

The XPS plates must be installed according to a bottom-to-top arrangement with offset binding, by ensuring tight fitting of the tongue and groove edges. The elements can be fixed to the rafters by screws washers or thermal bridge free fit-tings fixed with stainless steel clips.

Following the completion of the thermal insulation, the interior cladding can be placed, by continuous laying of the air and damp tight foil.

Prior to making detailed designs, the standard checking procedures, incl. verification of the structure's flammability parameters must be completed, like in case of any other layered structure used for space delimitation.

ÉNGY, TERC code

  • Thermal insulation of pitched roof below rafters 48-007-1.2.4
    PRODUCT NAMETHICKNESSÉNGY CODE (MV)TERC CODE
    RAVATHERM XPS 300ST4048-007-054465548-007-1.2.4-0110133
    RAVATHERM XPS 300ST5048-007-054466048-007-1.2.4-0110134
    RAVATHERM XPS 300ST6048-007-054467248-007-1.2.4-0110135
    RAVATHERM XPS 300ST8048-007-054468448-007-1.2.4-0110136
    RAVATHERM XPS 300ST10048-007-054469648-007-1.2.4-0110137
    RAVATHERM XPS 300ST12048-007-438455048-007-1.2.4-0110138

Tender text

  • Pitched roof - thermal insulation above rafters- new building

    Hőszigetelés elhelyezése fa szerkezetű magastetőben szarufák fölé, vagy vasbeton
    koporsófödémben a födém felső síkjára sima felületű, csap-hornyos élképzéssel ellátott
    RAVATHERM XPS 300 ST extrudált polisztirolhab lemezzel,

    40 mm: λD=0,033 W/mK,
    XPS – EN13164 – T1 – CS(10\Y)300 – CC(2/1,5/50)130 – DS(70,90) – DLT(2)5 -WD(V)3 – WL(T)0,7 – FTCD1
    50 mm: λD=0,034 W/mK,
    XPS – EN13164 – T1 – CS(10\Y)300 – CC(2/1,5/50)130 – DS(70,90) – DLT(2)5 – WD(V)2 – WL(T)0,7 – FTCD1
    60-120 mm: λD=0,034 W/mK,
    XPS – EN13164 – T1 – CS(10\Y)300 – CC(2/1,5/50)130 – DS(70,90) – DLT(2)5 – WD(V)1 – WL(T)0,7 – FTCD1

    A szarufák felső síkján a hőszigetelés alatt statikai okok miatt szükséges palló-borítás külön tételben
    kerül kiírásra.