Air leakage not only leads to increased heat loss but also significantly increases the potential for condensation to occur within building elements, which may lead to insulation and structural degradation and mould growth.
As the building regulations require higher levels of insulation in attics, this in turn leads to a cooler temperature in the attic.
The following are 3 key considerations to keep in mind when planning to upgrade attic insulation.
Leaky Attic Hatches
The attic hatch is generally the single largest penetration in the ceiling of a building. It is essential not only to apply a hatch door which is certified airtight and adequately insulated, but the installation of the complete unit must be fully airtight to realise optimum performance.
Mind the Gap! Ventilation
When upgrading attic insulation in cold roofs, it is essential to ensure that eaves ventilation is not obstructed. There should be a continuous opening at eaves level of at least 10mm and a continuous opening at ridge level of at least 5 mm. Typically a space of at least 50mm should be retained between the insulation and the existing roof felt at eaves level. This ensures that any unforeseen air leakage in the attic space can be exhausted as effectively as possible. Unfortunately, it is not unusual for this critical ventilation zone to become blocked over time or even, inadvertently when attic insulation is been upgraded as illustrated on the images below.
Eaves ventilation blocked by attic insulation
Poor installation of down lights and poor application of insulation
Recessed light fittings can also lead to a significant reduction in the performance of insulation. This occurs when the insulation is moved away from the neighbouring light due to the risk of damaging both the bulb and the light. As a result, insulation performance can be dramatically reduced and air leakage into the cold attic significantly increases as shown on the images below.
There are a number of proprietary solutions available on the market to overcome this issue, such as the Optime downlight protector.
Insulating the attic is one of the most cost effective means of upgrading a buildings thermal performance. As important as it is to reduce heat loss, this should not be done without appreciating the impact of air leakage and the importance of ensuring the ventilation is retained.
To view additional information on this topic check out the full article on avoiding the pitfalls
Niall Crosson, Technical Engineer, B.TECH. MENG.SC CEPHC MIEI
Pictures and graphics provided courtesy of Ecological Building Systems Ltd.