Optimizing Loft Insulation for a More Energy-Saving Roof Area: A Guide
Insulating a loft can significantly reduce your heating bills and make your home cozier. You've got two main areas to tackle - the roof and the floor level, but there are different ways to fit the insulation.
For converting your loft into a living space, you'll need to pay attention to building regulations regarding materials and fire resistance. If you're just adding storage space, you'll approach things differently.
Here's a beginner's guide to insulating a loft from Tim Pullen, a building methods and energy efficiency expert. He'll help you choose the best type of insulation, show you where to put it, and provide a practical step-by-step guide for fitting roof insulation between rafters.
Where should you insulate?
Effective modern roof insulation is a worthwhile investment. It can be fitted either between the joists (horizontal beams) or between the rafters (roof support beams). The choice depends on your intended use of the loft.
For a loft conversion, you'll always need insulation at rafter level to create a warm roof. Meanwhile, a conventional cold roof option, where insulation rolls are placed between the ceiling joists above the top floor, could be enough for storage-only lofts.
Between the rafters or over the rafters?
Placing insulation exclusively between the rafters can lead to minor condensation due to cold bridges at the positions of the rafters. Fitting a continuous layer of insulation over the rafters solves this issue, but it's only viable on new builds or renovations where the roof tiles are being stripped and relaid.
The most practical solution is to place most of the insulation between the rafters, with a smaller additional layer fixed to the underside of the rafters. Insulated plasterboard is great for this purpose.
For applications where the roof is not being completely stripped, a combination of between and under-rafter insulation, with a 50mm ventilated airspace between the upper surface of the between-rafter insulation and the traditional sarking felt, is best.
Which materials work best?
There are numerous options for insulation materials, each with different formats:
- Rigid Insulation Boards: These include polystyrene boards, mineral wood boards, and plastic foam, polyurethane-type materials.
- Semi-Rigid Insulation: These are materials like mineral wool boards with increased flexibility compared to rigid boards.
- Soft Insulation: These include familiar rolls of loft quilt that can be stuffed into voids between rafters.
- Loose-Fill Materials: These include cellulose insulation and polystyrene beads that can be blown-in.
Wool-type insulations, often sold in rolls, are the cheapest and easy to install. They're also excellent insulators. For many houses, mineral wool is often the most affordable and effective choice for insulating a loft.
Remember, when it comes to party walls in the loft space, timber studwork with mineral fibre insulation can help you achieve both heat loss reduction and noise insulation. Multifoils are another option, offering good insulation levels in a thin roll format.
Natural and eco-friendly insulation materials are increasingly popular. Sheep wool insulation is a great alternative to synthetic wools, while wood fibre insulation and hemp insulation are being used in both roll and slab format.
Don't forget, insulation doesn't have to be dry-fixed. Wool, fibers, and plastics can all be blown into position via a nozzle, which is a commonly used technique under roofs.
Happy insulating!
- Insulating a loft can help reduce heating bills and make your home warmer.
- The choices for insulation placement depend on the intended use of the loft.
- For a loft conversion, insulation at rafter level is necessary to create a warm roof.
- A conventional cold roof option may suffice for storage-only lofts.
- Placing insulation only between the rafters may cause minor condensation due to cold bridges.
- Fitting a continuous layer of insulation over the rafters solves the condensation issue, but it's only practical for new builds or renovations.
- A practical solution for insulation is to place most of it between the rafters, with a smaller additional layer fixed to the underside of the rafters.
- In applications where the roof is not being completely stripped, a combo of between and under-rafter insulation is recommended.
- When choosing insulation materials, consider rigid insulation boards, semi-rigid insulation, soft insulation, loose-fill materials, natural and eco-friendly options like sheep wool, wood fibre, and hemp insulation, as well as methods like blowing insulation into position.
