Three Alternative Solutions dependant on roof pitch and span
Cold roofs with traditional underlays and well-sealed ceilings
The ventilation requirements for cold roofs with traditional underlays (vapour impermeable underlays - high resistance) and 'well-sealed' ceilings are the same as without 'well-sealed ceilings'. The 'well-sealed ceiling' reduces the heat loss by convection through the ceiling and provides an energy efficient solution. The heat loss due to low speed air currents over the cold side of the insulation caused by ventilation of the loft space is negligible.
The eaves to ridge ventilation specified in this detail can be used on all roof pitches over 15 degrees and on any size of building.
Where the pitch of the roof is less than 15 degrees the eaves ventilation must be increased to 25,000 mm2 / m.
Where the pitch of the roof is greater than 15 degrees but less than 35 degrees eave to eave ventilation as specified above can be used.
