When installing a balcony, insulation is often overlooked or forgotten, despite its importance. When balconies or terraces are installed over another part of the building, particularly a habitable space, the balcony is part of the building’s thermal envelope. This means that the balcony or terrace is required to meet energy efficiency targets and building regulations, which include insulation.

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Table of contents:

1. Finding the right insulation for a balcony

2. What should I use to insulate my balcony?

a) Kingspan Optim-R
b) Kingspan Kooltherm
c) SuperFoil SFUF
d) Celotex

3. How to install balcony insulation

a) Installing Kingspan Optim-R insulation
b) Installing Kingspan Kooltherm insulation
c) Installing SuperFoil SFUF insulation
d) Installing Celotex insulation

Choosing the right insulating material for a balcony

When constructing a balcony, finding insulation that fits within the construction is much more complicated than insulating a floor or wall. The balcony cannot be dug out further to allow for extra room to achieve the required U-value, unlike a floor, and similarly the insulation must be thin enough to fit below the doorway as the floor cannot be raised.

This means that the types of insulation suitable for balconies and terraces tend to be thin yet highly insulating, making more traditional products such as mineral wool less effective, and requiring more innovative solutions to ensure that the overall capacity is high, whilst thickness is minimal. Additionally, the insulation must not affect the loading capacity of the balcony, as it will be under pressure from foot traffic and potentially more.

Which products are suitable for balcony insulation?

There are a number of different insulating products that have thin yet highly insulating characteristics required for balcony insulation.

Kingspan Optim-R insulation

Kingspan has developed a specific insulation product to combat the issue of finding insulation that is effective on balconies – the Optim-R Balcony and Terrace system. The Optim-R insulation for balconies and terraces are rigid vacuum insulation panels that contain a microporous core, sealed in a thin envelope that is gas-tight. This means that the Optim-R balcony and terrace system is highly insulating whilst still being incredibly thin – starting at just 20mm. This is a market-leading, premium product for balcony insulation, and as expected with products of the highest quality, the cost is also at the higher end of the scale.

Kingspan Kooltherm insulation

Another alternative to using the Optim-R insulation for balconies and terraces is to use Kingspan Kooltherm. The Kooltherm insulation from Kingspan is available at a lower cost than the Optim-R system, but still uses the innovative and market-leading knowledge from Kingspan, so it is perfect for when a budget is constrained. The Kooltherm insulation from Kingspan is an insulation board with a phenolic foam core, which has higher insulation than more traditional insulation board cores, meaning that a thinner Kooltherm insulation board is required to achieve the same U-value as a thicker, more traditional insulation board. This makes Kingspan Kooltherm ideal for insulating balconies and terraces as it is thin at as little as 25mm, yet highly insulating.

SuperFoil SFUF insulation

SuperFoil have developed a super-thin underfloor foil insulation product called SFUF. SFUF SuperFoil insulation has been designed to be used in any place that requires thin yet high-performing insulation. The SuperFoil SFUF insulation contains multiple reflective layers of foil that reflect radiant energy into the room and is particularly useful to improve u values in tight spaces. As well as acting as a thermal insulating product, SFUF insulation also contributes to the airtightness of the building and helps to improve sound insulation, reducing impact noise. This is the optimum insulating product to use for your balcony insulation if space is at a real premium – it’s only 6mm thick.

Celotex insulation

Celotex understands the importance of ensuring your balcony insulation is thin, robust and weatherproof. Their recommendation for balcony insulation is to combine Celotex GA4000 or Celotex XR4000 insulation in between plywood sheeting when insulating a balcony. Although this is a thicker alternative than the other more specific balcony insulation products, if there is enough space to install this option it is a great cost-effective alternative, ensuring the balcony is sturdy enough to withstand a variety of traffic as well as keeping the balcony well insulated.

Installing balcony insulation

Installing Kingspan Optim-R balcony and terrace insulation

Before starting the installation process, ensure the deck is clean, dry and free from any debris.

1. The first step is to bond a vapour control layer to the deck.

2. Next, add a protection layer on top of the vapour control layer if required.

3. Now place the Optim-R panels onto the surface in a chessboard pattern, with the joints loosely butted together. With the Optim-R system, it is made to order so you’ll be provided with the correct number and sizes of insulation panels and infill panels.

4. Once the Optim-R panels have been laid, lay rigid insulation board on top.

5. Then add insulation upstands of at least 25mm thicknesses around the perimeter of the balcony.

6. Once insulation upstands have been laid, lay a waterproof membrane across the whole area.

7. Now install cover flashing around the perimeter of the area.

Your decking is now ready to be finished with the flooring material required – this can be anything from decking to paving slabs and more.

Installing Kingspan Kooltherm balcony insulation

1. Lay plywood onto the balcony deck, fixing to joists with corrosion-resistant wood screws.

2. Now add a vapour control layer, installing it according to the manufacturer’s instructions. Ensure the joins are well overlapped to prevent any water ingress.

3. Now lay the Kingspan Kooltherm insulation boards down across the VCL.

4. Next, add a second layer of plywood onto the Kooltherm insulation boards.

5. Finally apply a waterproofing membrane to the top of the plywood, and the balcony is ready for the flooring to be installed.

Installing SuperFoil SFUF balcony insulation

1. Starting at the wall edge of the balcony, ensure there is a minimum of 100mm lapping up the wall edge.

2. Roll the SFUF insulation over the joists on the deck.

3. Staple the SFUF insulation into place on the joists.

4. Butt the edges together where any edges of rolls meet and seal with foil tape.

The balcony is now ready for the decking or flooring to be installed.

Installing Celotex balcony insulation

1. First lay the first piece of plywood down – Celotex recommends using plywood that is around 18mm thick. The fixings should be long enough that they penetrate into the supporting timber by at least 38mm.

2. Now add a vapour control layer and secure it as per the manufacturer’s instructions.

3. Once the vapour control layer has been laid, the Celotex insulation board can be laid – from either the GA4000 or XR4000 range.

4. Sandwich the Celotex insulation board between plywood by adding another sheet of plywood on top of the Celotex insulation.

5. Finally add a waterproofing membrane on top of the plywood and affix it as per the manufacturer’s instructions.

The balcony is now insulated and ready for the floor finishing to be laid down.

If you still have some questions regarding balcony insulation and the best insulating products for your latest project, don’t hesitate to call the team on 01752 692206 or use the live chat and they will be more than happy to offer recommendations and product advice.

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