The Best Loft Insulation for Shallow Rafters

4 minute read

Shallow rafters are a typical feature of old buildings; a sacrifice some homeowners are willing to make in favour of preserving character over practicality. But what happens when the winter draws in and nights get longer and colder? With shallow rafters unable to accommodate adequate loft insulation to keep the building warm, these roof structures don’t make year-round comfortable living conditions. So, many builders and end users look for products that can offer the greatest level of loft insulation, without having the complication of deep roof build ups which compromise on internal head space.

U-Value Restrictions

U-Value requirements have tightened in recent years. PIR (polyisocyanurate) board or mineral wool take up a lot of room within the roof space, and although multifoils tend to be thinner, they don’t meet current standards by themselves. Therefore, it is advised to utilise a hybrid system, using a multifoil insulation alongside mineral wool.

Which Insulation Material Should I Choose?

PIR board	PIR board is reflective, has a low thermal conductivity, and holds air still. This loft insulation is specified for shallow rafters. However, to ensure an airtight fit, it needs to be cut to the size of the rafter extremely accurately. This commonly results in heat being lost through the structure.
Mineral wool	Mineral wool is a lower grade than PIR board, but it is quite fire resistant and it is significantly cheaper than more thermally efficient alternatives.
Phenolic board	Phenolic board offers the highest thermal performance over PIR board or mineral wool. However, this benefit comes with a substantial price tag to match. Therefore, it’s not everyone’s preferred material for loft insulation for shallow rafters.

Why is TLX Gold the Perfect Choice for Loft insulation With Shallow Rafters?

Our TLX Gold 2-in-1 insulating breathable membrane is a welcome addition to a roof build up, particularly in older buildings, as it is lightweight and easy to install. It comes with a breathable membrane overlap flap with integrated tape. You can join sections together with ease.

When insulating an old building, compromise is key. You want an insulation material to be as effective as possible whilst causing as little disturbance to the building as possible. This can seem an impossible task, especially when you’re grappling with building regulation requirements and the comfort factor against shallow rafters and restrictive head height. However, our TLX Gold insulating breathable membrane goes a long way to manage these challenges.

How to Meet Building Regulations

TLX Gold draped solution:

Drape TLX Gold insulating breather membrane over a 220mm deep rafter and add 160mm of PIR board in between to achieve a U-Value of 0.15.

Taut and counter-battened solution:

Secure TLX Gold insulating breather membrane over the top of a 200mm rafter with counter-battens. Then, add 160mm of PIR board in between to achieve a U-Value of 0.15.

Do you Require a Bespoke Solution?