Roof and Attic Insulation
Over 30% of your home heat is lost through the roof. Therefore, the importance of good insulation in your roof area cannot be under stated. If you have less than 200mm fibreglass insulation (or other type with equivalent thermal resistance values) between ceiling joists or rafters then you should consider upgrading.
If you are considering carrying out these works yourself make sure you understand the importance of good ventilation in the roof space and how to reduce thermal bridges.
You put a hat on your head and keep your body heat in.Thermal insulation in your roof will do the same for your house!
If you do not have insulation in your roof, up to 30% of your heat could escape, costing you money and contributing to atmospheric pollution and global warming.
If you have already insulated your roof, you may want to replace it or add another layer to improve its performance and bring it up to current Building Regulations Standards.
Insulating the 50 m² (540 ft²) attic space of a typical house costs around €400 and could save approximately €130 a year (up to 20% of your fuel bill) so it would pay for itself in about three years. Insulating a flat roof of the same size could cost about €1,000 and will pay for itself in around five years. As well as saving your money, you will be helping to reduce the emission of carbon dioxide and other environmentally- polluting substances.
Pitched roof with an attic space If you have a pitched roof with an attic space, it can be insulated in many ways. Probably the simplest is to lay quilt, such as glass fibre quilt or mineral fibre quilt in a roll between the ceiling joists and a second layer in the opposite direction over the joists.
Another method is to have shredded glass fibre, mineral fibre or cellulose fibre blown into the attic between and above ceiling joists. This method requires a professional contractor. Be careful not to compress fibreglass insulation, otherwise it will lose part of its insulating value. So if boarding is to be put down in some areas of the attic for storage, it should not compress the insulation.
After the attic is insulated at joist level, its temperature is reduced, so you must insulate the water
The water storage tank can be insulated with any semi-rigid insulating board and the pipes with closed cell neoprene, polyethylene, glass fibre and mineral fibre in pipe section form.
If you have a pitched roof with an attic space, it can be insulated in many ways. Probably the simplest is to lay quilt, such as glass fibre quilt or mineral fibre quilt in a roll between the ceiling joists and a second layer in the opposite direction over the joists.
When converting your attic into a room, insulation is placed in between the rafters. The insulation can be semi-rigid insulation boards such as expanded polystyrene board, extruded polystyrene board, glass fibre batts, mineral fibre batts, urethane foam board or phenolic foam boards. Some contractors also offer a spray-on cellulose fibre or polyurethane foam insulation system between rafters. If a first layer of insulation is placed between rafters, a second, thin layer applied to the underside of the rafters avoids thermal bridging. Glass fibre quilt and mineral fibre quilt can also be used. A vapour check should be installed on the warm side of the insulation and ventilation above.
These materials can be held in place by a plaster lining board which also provides the necessary fire protection.
Lining boards can have integral insulation backings, such as glass-fibre-backed insulated plaster and urethane-foam- backed insulated plasterboard, often lined with aluminium foil.
The type of insulation used in new flat roofs is dependent on the roof structure. On a new concrete slab, with a screed, semi-rigid insulation boards such as expanded polystyrene board, extruded polystyrene board, glass fibre batts, mineral fibre batts, urethane foam board or phenolic foam board are laid under the roof covering. In a new timber structure, glass fibre quilt and mineral fibre quilt can be laid between the joists.
If you have an existing flat roof, insulation can be increased externally with extruded polystyrene or foamed glass, or internally with an insulated lining board such as mineral fibre or polyurethane foam- backed plaster-board
Pitched roof with an attic space The majority of Irish houses have a pitched roof, which is the easiest type to insulate and with a little care and guidance can be insulated by yourself.
Attic room Attic conversions are more complicated as the roof structure has to be insulated,so the appointment of a building contractor is advised.
Flat roof The insulation of new and existing flat roofs should be carried out by a roofing contractor.
- Insulation is available from builders’ providers, DIY and hardware stores and specialist contractors.
- Buy insulation from a reputable supplier who can help you choose the most suitable insulation for your roof type. If using glass or mineral fibre wool insulation, specify a minimum thickness of 100mm between joists and 150mm across joists. To find out how much insulation you need, check the measurements between the joists, their length and the number of joist spaces in your attic.
- If installing the insulation yourself, check if special precautions should be taken when handling the material
- Before you insulate your attic, read the manufacturer’s instructions.
- Some insulation materials irritate your skin and throat, so wear a mask, rubber gloves and goggles and tuck in your clothes when handling these materials.
- Stretch a long board across two or three joists to walk and kneel on. Do not stand on the section between the joists or your foot is likely to go through the ceiling.
- Check the depth of the joists. If the insulation is going to be higher than the joists or if you are going to lay a second layer of insulation across the joists, you may need to fix timber battens to some joists to raise the boarding in the area of the attic where access will be needed, thereby avoiding compression of the insulation.
- Fill any cracks or holes in the ceiling to prevent warm, moist air rising into the attic as this causes condensation.
- Open and unroll the insulation in the attic.
- Lay insulation between joists in widths sized to fit tightly between the joists and a second layer over the joists in the opposite direction.
- If possible, fit insulation over the wallplate to abut with the wall insulation while leaving the necessary air gap around the eaves and soffits. This will help to avoid cold bridging.
- To ensure that there is adequate ventilation at the eaves, cut the ends of the insulation in a wedge shape. Alternatively buy specially shaped plastic eaves pieces to ensure that the insulation does not block the eaves ventilation.
- At the gable wall, insulation should be turned up 225mm above ceiling level.
- After you insulate the attic, its temperature will be reduced. Therefore it is essential to insulate water storage tanks and pipes to prevent them from freezing. Do not put insulation directly under the water storage tank as the warm air from below will help prevent it freezing. The tank sides and top should be insulated, as should the pipes, to prevent them freezing in the cold attic.
- Insulate the hatch by cutting a piece of insulation and sticking it onto the hatch.
- It is essential to cross-ventilate the attic space to prevent condensation by leaving a continuous air gap along the eaves at each side.
- In attic room conversions, it is essential to ventilate the roof structure between the insulation and the roofing felt with continuous air gaps along the eaves and at the ridge. Special ventilation tiles are available for ridge ventilation.
- Don’t bury electric cables under the insulation. Leave cables clear and avoid compressing. Keep plastic- insulated cables away from polystyrene insulation.
- Leave clearance for recessed lights to avoid them overheating.
- The use of combustible insulation is not recommended for attics.