SWIP — short for Stay Warm Insulation Plus — is our own branded internal wall insulation system, built for the solid-wall and period homes that can't take cavity fill. If you've been searching for “SWIP insulation” and want to know what it is, what it costs and whether it's right for your house, this guide explains it in plain terms.
What is SWIP insulation?
SWIP stands for Stay Warm Insulation Plus. It is Stay Warm Insulation's in-house internal wall insulation (IWI) system — the same well-established approach used to insulate solid walls from the inside, delivered as a complete service by our own team rather than subcontracted out.
Older homes built before about 1920 usually have solid walls with no cavity to fill, so they lose a large share of their heat straight through the masonry. SWIP tackles that by adding an insulating layer to the inside of those external walls, warming the rooms and cutting heat loss. Because it is our own system, the survey, specification and installation all sit with one accountable team — Stay Warm is PAS2030-19 certified and TrustMark registered.
The exact materials, thicknesses and build-up are not a fixed off-the-shelf recipe: they are confirmed for your property during the free survey, because the right specification depends on the wall, the room and how the house is used.
How SWIP works
In principle, internal wall insulation works the same way for every solid-wall home. An insulating layer is fixed to the inside face of your external walls and finished with a new plaster surface, ready to decorate. The result is a warmer wall surface, fewer cold spots and noticeably less heat escaping through the brickwork.
About SWIP studs
Some internal wall insulation systems are battened or framed off the wall — homeowners sometimes search for “SWIP studs” when comparing build methods. Whether a framed (studded) approach or a bonded board approach is right for your wall is exactly the kind of detail decided at survey, where the installer assesses the wall's condition and how it needs to manage moisture. We don't fix a method before we've seen the property, because the wrong build-up on a solid wall can do more harm than good.
Designed around moisture
The most important thing with any solid-wall insulation is moisture management. Solid walls behave differently from modern cavity walls, so the detailing around the insulation matters as much as the insulation itself. This is why a proper survey comes first and why the specification is tailored rather than generic.
SWIP for period and solid-wall homes
SWIP is designed for solid-wall and period properties — typically Victorian and Edwardian houses and other homes built before the 1920s. If your home has a solid wall, your two realistic routes are external or internal insulation, and SWIP is our internal option. To work out which you have, see our guide on cavity wall vs solid wall.
Internal wall insulation is often the practical choice for period homes where the outside appearance must be preserved — for example on a front elevation with attractive brickwork, or where a property is in a conservation area and external changes aren't permitted. It can also be done room by room, which suits phased budgets and lets you start with the rooms you use most.
For the full picture of how internal insulation is fitted, including the trade-offs and what to expect, read our dedicated internal wall insulation guide. If you're weighing internal against external, our EWI vs IWI comparison sets the two side by side.
What SWIP insulation costs
Because SWIP is internal wall insulation, its pricing follows the same pattern. As a rough guide, IWI typically works out at around £50–£90 per m², depending on the room, the state of the existing walls and the level of finish you want.
| Scope | Typical cost |
|---|---|
| Per square metre | £50–£90 / m² |
| A single room | £1,500–£3,500 |
| A full 3-bed house | £8,000–£15,000 |
These are indicative ranges, not a quote. The real cost depends on how many external walls you're treating, access, the condition of the walls, and the finishing details. Stay Warm provides a fixed, written price after a free survey, with no obligation — so you know exactly what you'll pay before any work begins.
Ready to find out what SWIP would cost for your home? Get a free quote and we'll arrange a free survey at a time that suits you.
SWIP insulation FAQs
What is SWIP insulation?
SWIP stands for Stay Warm Insulation Plus — it is Stay Warm Insulation’s own branded internal wall insulation (IWI) system. Like all internal wall insulation, it works by adding an insulating layer to the inside face of your external walls, so heat stays in the room instead of escaping through the masonry. It is designed and fitted by Stay Warm’s own PAS2030-19 certified, TrustMark-registered team. The exact build-up and specification are confirmed for each property during the free survey.
How much does SWIP insulation cost?
As internal wall insulation, SWIP typically works out at roughly £50–£90 per m² depending on the room, the condition of the walls and the level of finish. A single room often falls between £1,500 and £3,500, while insulating a full three-bedroom house generally ranges from about £8,000 to £15,000. Every home is different, so the only accurate figure is a fixed quote following a free survey.
Is SWIP suitable for period homes?
Yes. SWIP is specifically designed for solid-wall and period properties — the older Victorian, Edwardian and pre-1920s homes that have no cavity to fill. Because period walls need to manage moisture carefully, the specification is always tailored to the individual property at survey rather than applied as a one-size-fits-all package.
How is SWIP different from standard internal wall insulation?
SWIP is internal wall insulation — the difference is that it is Stay Warm’s own in-house system, designed, specified and installed by our own certified team rather than subcontracted. That means a single point of responsibility from survey to finished wall. The underlying principle is the same as any IWI: an insulating layer added to the inside of the wall, with the precise build-up confirmed at survey.