How to get in touch

Call us on 03705 601000
Email us at sales.redland@monier.com
or Click Here

Home / News / 2013 / AVOIDING CONDENSATION IN PITCHED ROOFS

AVOIDING CONDENSATION IN PITCHED ROOFS

This fact was recognised by the NHBC a couple of years ago when an increasing number of complaints regarding condensation-related damage in roofs drew attention to the problem. The organisation produced guidance in 2011 to remind builders that ventilation, at eaves and particularly at ridge level, is the recommended system for cold roofs.

The science is relatively straightforward: the rates of moisture removal that can be achieved via ventilation (convection) are far greater than can be achieved by diffusion, the method that most vapour permeable underlays rely on for their function.

The starting point is effective eaves-to-eaves ventilation. A gap is created between the insulation and underlay at the eaves so that air comes into the roof space and out the other side.

Introducing this type of low-level ventilation is a relatively straightforward process as part of a new roof construction and it can also be retrofitted to solve a recognised problem. Redland provides a number of component options to integrate this ventilation into the roof system.

While eaves-to-eaves ventilation is a good starting point it will not necessarily solve the condensation problem on its own. This is because it is dependent on wind to create the through-draft necessary to take the water vapour out of the roof space and factors such as lack of wind or building orientation can reduce the effectiveness of this method of ventilation.

Moreover, for steeply pitched roofs a through-draft from eaves to eaves may not be totally effective in removing pockets of stagnant moist air trapped in the apex.

Consequently we always recommend a combination of low and high level ventilation for cold roofs where a vapour permeable or non-breather underlay is in use. The only exception is where a well-sealed ceiling can be achieved: in this case with a vapour permeable underlay the roof can function with just high level ventilation.

The high level ventilation product, situated either at or near the ridge of the roof (perhaps in the second course of tiles down) is an effective form of passive roof ventilation in all weather conditions: it forms a stack effect, creating a draw that is not dependent on wind.

We published our own technical guidance document on this issue in 2011 and the conclusions are in accordance with both NHBC recommendations and the British Standard BS 5250.

LATEST NEWS

Redland Mini Stonewold is the perfect solution against high winds in Orkney

With prevalent high winds in excess of 130mph on the Orkney Islands, a solution was required that could withstand these elements when it came to roofing a new facility for elderly and vulnerable members of the community. The BMI Redland Mini Stonewold Slate was chosen due to its strength, robustness and appearance of natural slate.

A new faster, safer, stronger and lighter metal tile solution from BMI

Drawing on its extensive experience in lightweight metal tiles,BMI – is setting new standards with the introduction of AeroDek. A roofing solution built for the future, AeroDek is faster, safer, stronger and lighter than traditional roof coverings; while replicating the high aesthetic of clay, concrete or slate in a tile guaranteed to last for 40 years.

Band of Builders and BMI team up for community project

When building charity Band of Builders learnt of the challenges faced by plasterer Iain Dodd’s family, it was eager to do what it could to help. Band of Builders – “run by tradespeople, for tradespeople” – aims to help members of the construction industry community when times get tough: and tough describes the Dodd’s family situation.

Search the Redland website

Start typing below (4 character minimum