Below you can find some examples of effective joisted roof solutions made with insulation layer between the joists and with insulated cross-studding. Below the standard structures you can find solutions for passive houses.

Ensure a good air gap between the insulation and the external roof structures and that the wind protection is sealed.

 

A) Insulation layer between the joists

Pitched roof 8
  • External roof structures
  • Spacer / min 50 mm air gap
  • Wind protection insulation
  • Timber joists / PAROC eXtra
  • Vapour barrier
  • Grid siding
  • Inner surface
Insulation solution with U value 
 PAROC WPS 3n (joist) 40 mm   40 mm 55 mm   40 mm 55 mm  40 mm 
 PAROC eXtra (joist) 200 mm 225 mm 250 mm  350 mm  350 mm  375 mm
 U value, W/m2K 0.15 0.14 0.12  0.10  0.09  0.09

B) Insulated cross-studding

The dimension of the joists limits the thickness of the insulation. Increase the thickness of the insulation using secondary studs internally.

 

Pitched roof 3

 

  • External roof structure
  • Spacer / min 50 mm air gap
  • PAROC WAS 25t
  • Timber joists / PAROC eXtra
  • Vapour barrier
  • Cross-studding / PAROC eXtra
  • Inner surface

 

 Insulation solution with U value

PAROC eXtra (joist)

50 mm  

50 mm

50 mm 

50 mm

50 mm 

PAROC eXtra (joist)

200 mm

225 mm

250 mm

 350 mm

375 mm

U value, W/m2K

0.13

0.12

0.11

0.09

 0.08



Passive houses

Increase the insulation thickness to meet passive house requirements by using secondary studding internally (see below). Design the inner side of the vapour barrier layer so that it provides the required air tightness. A functional air gap between the insulation and the outer roof is essential.


Pitched roof, flexible, passive house

  • Outer roof
  • Roof underlay
  • 50mm ventilation gap + spacer
  • PAROC WAS 25t or WPS 3n (d1)
  • Timber joists / PAROC eXtra (d2 + d3 + d4)
  • Vapour barrier (all joints to be taped)
  • Cross-studding + PAROC eXtra (d5)
  • Inner surface

 

Small houses 

Recommended U value 

W/m2K

0.06 - 0.09

d1

mm

30

d2 +d3+ d4

mm

375 - 600

d5

mm

50

Total insulation thickness

mm 

455 - 680

 

You can also insulate a joisted roof with blowing wool. (Note: Installation of blowing wool must be carried out by special contractors Contact Paroc for approved contractors.) The wind barrier should be tight and rigid enough to withstand the pressure from blowing wool installation. A functional air gap between the insulation and the outer roof is essential.


Joisted roofs, passive, BLT
  • Outer roof
  • Roof underlay
  • 50mm ventilation gap + spacer 
  • Wind barrier
  • I-Joists / PAROC BLT 6 or PAROC BLT 3 or BLT 9 (d1)
  • Air/ vapour barrier (all joints to be taped)
  • Cross-studding + PAROC eXtra (d2)
  • Inner facing

 

Small houses

Recommended U value 

 W/m2K

 0.06 - 0.09

 d1

mm

500 - 600

 d2

mm

50

 Total insulation thickness

mm 

550 - 650


Notes:
According to the definition of a passive house provided by the Passive House Institute, the annual heating, cooling and primary energy demand should not exceed certain values. Although good thermal insulation plays a major role in achieving the Passive House standard, it alone cannot ensure compliance. The requirements for other building components and devices can be determined by various calculations tools, such as the Passive House Planning Package (PHPP), available at www.passiv.de