The roof space of a house, unless somehow converted, serves little purpose other than
to house the water tanks, the odd box and empty suitcases. If by heating the home the rising warm air was allowed to enter the roof space, it would quickly escape and be wasted. It's only sensible then that the loft is sufficiently insulated to prevent this from happening.
Considering that the loft in made up of roof timbers and ceiling joists, it is in fact a substantial timber structure that should be well maintained. Unfortunately, not many give due attention to its condition and when problems arise, they often go unseen for years, resulting in major structural problem that would be costly to put right.
Other than roof leaks, condensation in the roof space can lead to major problems if left unchecked, resulting in timber members of the roof becoming damp, which could over time cause rot or infestation. Though not an area usually associated with condensation, the roof space, given the right conditions is in fact one of the most likely areas in the home for it to exist. If you have read the articles relating to condensation, you will know that moisture in the air is more prone to condensate in a cold unventilated area such as the loft.
Thought it is not possible to completely eliminate moisture produced within the home from entering the loft area, 
every effort should be made to prevent it. An ill fitting loft hatch is the main culprit, so it would be helpful to ensure that when it is closed it does have a good seal. A draught excluder such as used to draught-proof external doors would be ideal. Another problem area could be the bathroom or shower room ceiling, where sunken ceiling light fittings have been fitted, such fittings can allow a route for a substantial amount of moisture to enter the loft space.
Despite forming a good seal between the loft and living areas, it should not be forgotten that all air contains moisture, so the loft area should always be well ventilated, either by means of soffit vents, air bricks, or vented roof tiles. In fact the regulations now state that; all new property should have a continues form of ventilation installed on both sides of the roof. Many of the older properties do not have this form of ventilating, but if the property has a cavity wall, and if the air bricks are unblocked, the air that circulates within the cavity can rise up the uncapped cavity and ventilate the roof space. However, if cavity wall insulation has been installed after the walls were constructed, then this route would be blocked and another form of ventilating would be required.
Providing ventilation to the roof space has not always been recognised, and it was common practice to push the
loft insulation into the corners of the loft where the underside of the roof would meet the ceiling. As this is now recognised as bad practice, both new and existing installations of loft installations should not extend to the end of the ceiling joists thereby blocking the gaps that would otherwise allow air to enter the roof space. Alternatively, purpose made plastic panels (eave vents) can be used. These panels fit between the ceiling joists, (beneath the insulation) and are turned up to the angle of the roof pitch, allowing the insulation to be pushed into the corner. The area that is up to the underside of the roof has channels which allow air to pass through, ensuring a permanent ventilation gap at this location.
Providing ventilation can be done in many ways, and if the construction allows it, the easiest way is by fitting round soffit vents. This is done by cutting out the appropriate diameter holes using a hole-saw and simply inserting the vents. Manufacturers of soffit vents recommended that 70mm vents should be fitted in the centre of the soffit at 200mm intervals.
Highline Plastics offer a fantastic selection of UPVC soffit vents, including soft vents designed to look wooden. Great care should be taken when fitting soffit vents. We recommend using sturdy ladders or even contacting Niftylift about their range of cherry pickers. 
