The Fastwarm® Injoist 1200 x 350 x 50mm Panel offers a simple, efficient solution for installing underfloor heating pipework between traditional joists or on concrete subfloors. Designed to fit snugly between joists or battens, these panels eliminate the need for separate foil-faced insulation and spreader plates—saving both time and cost during installation.
Crafted from high-performance Expanded Polystyrene (EPS), each panel comes pre-grooved at 200mm pipe centres and is specifically designed to accommodate 16mm underfloor heating pipework. Whether you're working on timber or concrete structures, these panels deliver a secure and thermally efficient fit.
- Optimised for joist installation – Fits neatly between standard joists or battens, ideal for retrofit or new-build projects.
- Integrated groove spacing – Pre-grooved at 200mm centres to suit 16mm underfloor heating pipes.
- Panel dimensions – Each panel measures 1200mm x 350mm x 50mm for easy handling and consistent coverage.
- High-performance EPS material – Provides thermal insulation while supporting efficient heat distribution.
- All-in-one design – Removes the need for separate spreader plates and foil insulation layers.
The Fastwarm® Injoist Panel is a cost-effective, installer-friendly solution that simplifies in-joist underfloor heating setups while enhancing thermal performance and system reliability. Trusted for both domestic and commercial applications, it’s a dependable choice for delivering comfort and energy efficiency underfoot.
To install the injoist batten system you will begin by securing battens to the sides of the joist with the top of the batten 50mm below the top of the joist. This will allow the insulation to sit flush with the top of the joist.
The pipework can then be placed withing the preformed grooves within the board.
You can finish the installation of this system by installing the finished floor.
| Panel Dimensions | 1200mm x 350mm x 50mm |
|---|---|
| Panel Thickness | up to 125mm ( in 1.0mm increments ) |
| Aluminium Foil Thickness | 45 microns |
| Thermal Conductivity | 0.036 W/mK |
| Compressive Strength | 100 kPa @ 10% compression |
| Compressive Strength | 45 kPa @ 1% compression |
| Fire Classification | Euroclass F |
| Suitable Pipe Size | 15mm and 16mm |
Our May Bank Holiday Delivery Times
| Order Date | Order Time | Expected Delivery Date |
|---|---|---|
| Fri 23rd May* | Before 4:00pm | Tues 27th May |
| Fri 23rd May | After 4:00pm | Wed 28th May |
| Sat 24th May | All day | Wed 28th May |
| Sun 25th May | All day | Wed 28th May |
| Mon 26th May | All day | Wed 28th May |
| *Any pallets to be delivered on Saturday 24th May will need to be ordered before 2:30pm on Friday 23rd May. | ||
Free Delivery as Standard!
As standard we include 2 - 3 working day delivery on all orders delivered to the UK mainland. * A £5 delivery charge will be applied to all orders below £20.
Delivery cut off times
Our final delivery time for Mondays to Thursday is 4:30pm. To give us a bit more time to ensure weekend deliveries are handled and our couriers have time to collect, the final delivery time on Fridays is 4:00pm.
2-3 working day delivery
Next working day
Next working day before 10:30
Saturday Delivery
* A £5 delivery charge will be applied to all orders below £20.
Other Delivery Options
Pre 10:30am and Saturday delivery services are available on orders placed before 4:30pm. Any order placed before 4:30pm on a Friday will be delivered on the following Monday (unless its a bank holiday) so please select a Saturday service if a weekend delivery is required.
Delivery outside the UK
Delivery outside the mainland UK may be arranged by prior agreement. You will be notified of the amount of the charge for this service and will at that point have to make a decision whether you wish to proceed wth your order.
Important: Our deliveries rely on third party couriers, so, whilst we make every effort to deliver your order on the specified date and time, unfortunately there may be occasions when this will not be possible due to external influences. Due to this we strongly recommend you ensure you have received your order before any tradespeople/builders are scheduled to commence work.
Still Unsure? Talk to an expert
If you need any guidance or further information our highly experienced team are on hand to help.
Get in touch using our contact form or give us a call on 0800 023 4203 or 01268 744 479.
