Quick answer: not every internal stud wall needs insulation, and there is no single insulation product that is automatically right for every partition. The choice depends on why you are filling the cavity: reducing sound transfer, separating areas with different temperatures, or following a tested fire or acoustic wall system.
Choose the insulation as part of the complete wall build-up. Do not put a product between the studs simply because it physically fits the gap.
Why put insulation in an internal stud wall?
For a normal room-dividing partition, the most common reason to fill the cavity is to improve acoustic comfort. An empty framed cavity can allow sound to pass through the wall more easily, while a suitable acoustic insulation product can form part of a better-performing wall build-up.
In other situations, insulation may be required because the wall separates spaces with different thermal conditions or because the chosen tested wall system specifies a particular cavity product.
The important distinction is that insulation is one component. The plasterboard type and layers, stud section and centres, cavity depth, fixings, joints and other details can all affect the finished performance.
What insulation should go between timber studs?
For acoustic timber partitions, manufacturers commonly specify mineral-wool products intended for partition-wall use. Products designed for this job are made to fit within the stud cavity and contribute to the tested or declared acoustic build-up.
ROCKWOOL’s timber stud wall guidance, for example, recommends choosing fit-for-purpose insulation for the cavity and fitting it accurately rather than leaving significant gaps. British Gypsum tested timber partition systems likewise specify particular insulation products where the tested wall requires them.
That is a better basis for choosing than simply selecting any roll or rigid board labelled “insulation”.
Can I use loft insulation in a stud wall?
Do not assume a loft roll is the correct partition-wall product just because it is mineral wool and will fit between timber studs. Loft products are primarily sold for loft applications; partition-wall systems may call for a product with different density, acoustic characteristics or tested-system documentation.
Check what the wall is intended to achieve and use a product suitable for that application.
Can I use PIR board between stud-wall timbers?
Rigid PIR can be useful in appropriate thermal constructions, but it is not a universal replacement for acoustic partition insulation. If the purpose of an internal partition is sound reduction, choose the wall build-up for acoustic performance rather than assuming a rigid thermal board gives the same result.
Where a wall has a defined thermal requirement, follow the design and the insulation manufacturer’s guidance for that construction.
Does acoustic plasterboard mean I do not need cavity insulation?
No single product should be treated as a complete soundproofing solution. Acoustic plasterboard can form part of an acoustic wall, but the performance comes from the complete assembly.
British Gypsum publishes timber stud systems where the board type, number of layers, stud section and spacing, insulation and fixing details are all specified together. Changing one component means you should not simply assume the published system performance still applies.
Does insulation make a stud wall fire rated?
No. Putting insulation in a cavity does not by itself create a fire-rated wall. Fire performance belongs to a tested or specified wall system.
If a wall requires a particular fire resistance, follow the relevant tested construction including the exact board layers, studs, centres, insulation where specified, fixings and joint treatment. Do not build a fire specification by combining products that individually mention fire performance.
How much stud-wall insulation do I need?
Start with the area of the cavity that actually needs filling: wall length × wall height, then account for doorways, windows and other openings. That gives an area estimate, but it still does not tell you which product or thickness the wall requires.
Measure the actual cavity depth and stud layout as well. Insulation should fit the intended cavity properly without relying on large gaps or an improvised build-up.
This is another reason we do not provide a one-size-fits-all stud-wall calculator: two walls with the same overall area can have different openings, cavity depths, board systems and performance requirements.
Why there is no generic insulation product in our Stud Wall Project collection
You will not see us put a loft roll or general PIR board into the project collection simply to make the list look complete. That would imply it is our default recommendation for an internal partition when the correct product depends on what the wall needs to do.
Our Build a Stud Wall project collection currently focuses on the components we can confidently present for the job: CLS framing, plasterboard, door linings and fixings. For insulation, choose a product that matches the required wall system rather than forcing a convenient substitute.
Plan the insulation before boarding
Decide on the cavity product before closing the wall so the framing depth, services and board system all work together. Fit insulation neatly to the required area and avoid leaving avoidable gaps around the cavity.
For the complete framing sequence, read How to Build an Internal Stud Wall with CLS Timber. For stud layout, see Stud Wall Spacing – 400mm vs 600mm Centres.
If you are unsure what wall build-up you need, give Wern-Wood a call and we can discuss the products and options we stock. Where a specific acoustic, fire, thermal or structural performance is required, follow the relevant design or tested manufacturer system.
General guidance only. Product suitability and wall performance depend on the complete construction and the relevant manufacturer or project specification.
