One of the most common deficiencies we find in modern properties is a lack of insulation and ventilation in the roof space and the defects that come with it.
The use of attic spaces has changed over the years and current Building Regulations expect lofts to be a fully insulate and well-ventilated space rather than a storage room or somewhere to hide the train set.
Below is a rough guide to how to get the most of your attic space
To get the most energy efficiency, reduce the amount of warm air in the loft and to comply with current standards, the recommendation is 270mm of a Fibreglass insulation material (or its equivalent). This should be laid across and between ceiling joists and over the trap hatch. Eaves should be kept free to allow a degree of ventilation, especially if the property has exposed rafter feet or soffit grill vents
The trouble with boarding the loft
Many of us will have boarded part or all of the loft in one home or another to store anything from suitcases and Christmas decorations to a lifetime worth of stored items. While better than clogging the corridors, boarding in the loft can compress insulation material. This reduces its effectiveness and can put pressure on ceilings, leading to cracking. If boarding is necessary, then the recommendation is to use suspended boarding to allow insulation to work effectively. Modern rafters can only take around 25kg per square metre, so don’t store heavy items.
Modern attics have a breathable membrane to the underside of the tiles and battens, which provides secondary weathering from wind driven rain and allows the roof to breath. When warm air is trapped in the loft for a prolonged period, condensation to the rafters can eventually cause timber decay. It also softens loft boarding which can make it unsafe to walk on or store items. Most modern houses have a bitumen underfelt which doesn’t allow the roof to breath. It is impractical to replace as the whole roof covering needs lifting in order to do so. We recommend tile vents to opposing elevations to allow cross ventilation. Gable end air bricks are good on detached houses. Soffit grills can work well as long as they’re not blocked and are on more than one elevation
- Make sure mechanical extractor fans vent externally and don’t discharge directly into the loft
- Too large a gap in the eaves allows a point of ingress for mice, birds and wasps. Nests of the latter two can block eaves and soffit grill ventilation. Eaves grills can help prevent animal ingress
- If no holes are cut into the bitumen underfelt behind retrospective tile vents, then they will not work effectively
- Foil backed insulation to the rafters can keep warm air in the attic