Insulating a shed or summerhouse allows for use throughout the year, even during the colder months. With the best choice of insulation, the building can stay warm when the temperature outside drops.
The humble garden building was once thought of as just another location to store tools and garden furniture. Once installed, a shed would often go untouched for years, until it was eventually time for a replacement. With many of us looking to maximise the space at our properties, turning to a shed or summerhouse is a smart way to create a room in the garden.
Converting a garden building into an additional space to enjoy is a growing trend. With many of us working from home, a summerhouse can create the perfect garden office. An old shed in the garden can be converted into a home gym, complete with weights and workout equipment. There are plenty more use cases including as a garden bar, craft room or workshop.
The biggest obstacle to using a garden building as an additional room is usually the ability to regulate temperature. While we naturally like the temperature to be consistent, the weather outside usually has other ideas. A garden shed can be freezing cold for most months of the year, and stiflingly warm in direct sunlight during the summer. Thankfully, insulation can provide the solution, providing greater control over the temperature inside.
Why does my shed or summerhouse need insulation?
With the aim to create a comfortable environment inside, we need greater control over the temperature. A consistent temperature inside avoids the need to wear a thick coat to use the building during the winter. When a garden building doesn’t use insulation, the temperature is often the same as it is in the garden.
The purpose of fitting insulation is to keep warmth inside. A timber shed or summerhouse typically features walls with a thickness of around 8-12mm. There just isn’t enough wood to have a meaningful impact on reducing heat loss. If you’re sitting inside, such as when using the shed as a garden bar, the cold temperatures are quickly felt during the evening.
Most garden buildings converted into a room feature an electric heater inside. While great for quickly warming the interior, insulation is essential to keep that additional heat in. Electric heaters feature a high wattage, which makes them expensive to run. Once they’ve provided initial heat, it’s best to only use them in small bursts.
Running a 2kW heater for 5 hours per week could add £90 to the average annual electricity bill (based on 17.2p kWh electricity cost).
If the shed or summerhouse is going to be used regularly, the insulation can begin to pay for itself straight away. Within a few years, most of the cost could be offset by reduced heating bills. Most converted garden outbuildings also leave sensitive equipment such as electrical items inside overnight. Insulation can help keep the interior temperature above freezing during the winter to prevent any damage.
Lots of choices are available when it comes to finding the best shed insulation. Finding the right solution will depend on the budget available and the results desired.
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Best foil-backed insulation for shed
Foil-backed insulation products are an extremely popular choice for garden sheds due to their ease of installation and solid thermal values. The insulating properties are sometimes achieved by lots of air bubbles wrapped inside the foil. Inside, the structure is essentially the same as bubble wrap.
The bubbles create pockets of trapped air, making it difficult for heat to transfer between each side. The outside of the insulation is covered in foil, to provide a radiant barrier that reflects heat back into the building. When air bubbles are not used, an increased number of foil layers provide density to reduce heat loss. The foil is also waterproof, providing a vapour barrier that prevents moisture from getting trapped in the walls.
Foil-backed insulation products are great value, allowing all of the shed to be insulated at a low cost. They are best suited to small sheds, as they take up minimal space on the wall, and can be applied to the floor and roof as well.
How is foil-backed insulation installed?
Installation is fairly easy and can be completed within a few hours. Before insulating any garden building, we recommend treating the walls with a wood preserver to prevent any damp issues once they are sealed under the insulation.
The insulation is rolled out against the wall, covering as much as possible with each sheet. Staples are then used to attach the insulation into position. For sheds where the cladding is not very thick, it’s best to staple at the interior framing to avoid making a hole through to the exterior.
Once all of the insulation is stapled into position, aluminium foil tape is used to cover where each piece joins. The result should be no visible gaps where the wood is exposed or pieces of insulation are joined. Using aluminium tape improves airtightness and creates a moisture barrier.
Great value and ideal for sheds
Our favourite choice of foil-backed shed insulation is from superFOIL which provides well-balanced features. The design features a 3 in 1 system to create air pockets in the middle and reflect radiant heat on the outside. Foil on both sides means heat from outside is reduced when in direct sunlight during the summer.
The 3mm thickness is easy to work with and can be cut up if required to fit the shed interior walls. The insulation is suitable for a range of purposes and is also waterproof and reduces sounds slightly. With a size of 1m x 7m, the insulation will stretch the length of most sheds, reducing the number of separate pieces required. For sustainability, the foil insulation is made from 40% recycled materials.
A premium solution for summerhouses
When it comes to foil insulation products, SuperQuilt is the most widely used and popular choice. The product is suitable for use in residential buildings and can often be found in lofts and conservatory roofs.
SuperQuilt is one of the highest performing multi-foil insulation products on the market, making it a great choice for larger garden buildings. For creating a garden office that’s used during the winter, SuperQuilt should make a solid choice. The insulation itself is like a blanket, with 19 layers of aluminium foil, creating high density, but still allowing plenty of movement.
The foil blanket can be installed inside the cavities in the shed wall, and a good quality staple gun will be required to get all of the way through and into the timber. The cost of SuperQuilt can be higher than other foil-backed insulation products, but the thermal values also provide better insulating properties.
Best Insulation boards for shed
When it comes to insulating residential properties, most builders turn to PIR (Polyisocyanurate) or XPS (extruded polystyrene) insulation boards. The rigid foam boards are extremely versatile and provide a high level of efficiency. Compared with insulation roll products, a thinner PIR board can often provide similar insulating benefits.
PIR boards provide the best thermal values and the design features foil on the exterior to reflect heat back into the property. XPS boards cost less and do not use foil on the exterior. Different thickness options are available, ranging from 10mm to over 200mm. Our favourite choice for a summerhouse is 50mm which keeps the interior warm. For a shed, 25mm is often used instead.
A drawback of insulation boards, especially PIR, is that they can be expensive. When insulating a large summerhouse, the price can quickly add up. While popular brands such as Celotex are recommended, other brands can cost considerably less and provide similar benefits.
How are insulation boards installed?
Installing insulation boards is simple once you get the hang of it. The thickness of the insulation board that can be used depends on the interior framing inside the garden building, as the board slots between. Better quality buildings often contain thicker framing, allowing for increased insulation. Be sure to measure the thickness of the framing before purchasing any insulation board.
The insulation board is cut to fit tightly in between the wooden framing. The board should sit in position without requiring anything to hold it in place. If there are gaps around the edges, expanding foam can be used to create a tight seal. As the boards are lightweight, they are also suitable for use in the ceiling.
Once all of the insulation boards are cut into position, aluminium tape is used around all of the edges. After the tape has been used, it should not be visible where the boards touch the wooden framing. The foil on PIR boards creates a vapour barrier and also improves airtightness to reduce heat loss.
CosySpace XPS Insulation boards (Amazon)
Easy to install in all garden buildings
The cosySpace XPS insulation boards are a good choice for lining the walls of a shed. Extruded polystyrene is waterproof, preventing moisture from getting trapped inside the insulation cavity. The high-density boards are lightweight, making them easy to work with and suitable for nearly all garden buildings.
The boards are just 10mm thick, making them suitable for sheds and summerhouses with thin interior framing. The anti-ageing properties protect against rot and maintain performance for years into the future. The high compression foam is able to withstand freeze and thaw cycles and also provides sound reduction properties.
Extremely efficient and ideal for a garden office
There are lots of brands available when it comes to PIR insulation boards. For a garden building, we are often looking for a good value solution. The Recticel Instafit boards are one of our favourites as they provide a low-cost solution and low thermal conductivity.
The boards are available in several different thickness options. If the building framing is thick enough, we recommend opting for the 50mm choice. The insulation is lightweight, making it easy to work with and cut during installation. The materials will not break down or degrade over time in the shed walls, keeping their insulating properties for likely longer than the shed will last.
Best insulation roll for sheds
Insulation roll comes in the form of a number of different materials including wool and fibreglass. Insulation roll is common in home building and the thick material is great at trapping heat inside. The roll is formed by the material being bound tightly together, which also protects against rot and mould getting inside.
Insulation roll would not be our first choice to insulate a shed or summerhouse. Unless you have worked with the material before, it can be challenging to get into position. The benefit of insulation roll is that some products can also provide sound insulation. Unlike rigid boards, the material is thick and dense, making it difficult for sound to penetrate through. If you plan on building a bar in the shed, insulation roll could keep your neighbours happy. Dedicated sound insulation is best for keeping the noise levels down, but some thermal insulation roll can provide reduce the sound.
How is insulation roll installed?
Insulation roll can cause skin irritation. During installation, be sure to use suitable protective equipment. Once opened, let the material expand out. The roll is packed tightly into the wood framing inside the shed or summerhouse. Thick framing is required to get all of the insulation roll inside.
Insulation slabs are ideal for use in the walls and reduces the amount of cutting required.
With the insulation in position, a vapour barrier can be installed and the interior walls can be boarded with a suitable material such as OSB.
Rockwool RWA45 Insulation Slab (Amazon)
A combination of thermal and sound insulation
Insulating a shed requires a robust insulation roll that can be used across the floors, walls and roof. Our favourite choice is Rockwool RWA45 in slabs, allowing for faster installation into walls. The high-quality resin bonded slabs are developed for thermal, acoustic and fire performance, making them a great choice for garden buildings.
A choice of thickness is available and 50mm should be suitable for most garden buildings. For structures with a thicker internal framing, a 75mm version is also available. the insulation is water repellent, protecting against moisture built up inside the shed walls. A vapour barrier should still be used on the warm side of the insulation.
Insulating a shed or summerhouse FAQ:
Fitting insulation inside a garden building can be completed as a DIY job. We recommend finding a dry weekend to carry out the work, as you’ll need some outdoor space to cut the insulation.
- Should the walls be covered once insulated?
Insulation provides great thermal benefits but isn’t the nicest wall decoration to look at. Once the insulation has been installed, the interior walls will need lining with a suitable wooden board. Be sure to consider the use of the garden building and the atmosphere you are trying to create.
Our favourite choice is Plywood which provides a hardwearing finish in a relatively thin profile. Plywood is known for its strength and is a popular choice when hanging items such as TV on the wall. OSB can also be used on the walls and costs less than Plywood. The textured pattern isn’t the nicest to look at but is fine for uses such as a garden gym.
- Does the shed or summerhouse need a vapour barrier?
A vapour barrier plays an important role inside an insulated garden building. The barrier is placed on the warm side of the insulation and stops water (from warm moist interior air) from penetrating into the insulation. This stops water & condensation from building up in the wall where it can’t escape and could lead to damp.
Foil-backed insulation products, including PIR boards, provide a vapour barrier as water cannot penetrate the foil. Using aluminium tape on the joints keeps the vapour barrier intact and improves airtightness. Insulation roll products will require a vapour barrier to be installed once the insulation is in position.
- Should I install electrics before insulation?
If you’re planning on spending lots of time in a garden building, electricity is essential. Everything from the heating to an internet connection will utilise electricity. Depending on the finish desired, a first fit may be carried out when the insulation is being installed. Holes will be cut through the insulation and interior wood lining to run the wires for the sockets. Once the wall lining is installed, the electrician will return to fit the sockets.
Electrics can still be installed after insulation. Trunking can be used to run the cabling along the wall. Any electrical work should be carried out by a qualified electrician.
Guide: How to insulate a shed
Insulating a shed or summerhouse is a great idea for use throughout the year. As we spend more time in garden buildings, insulation creates a comfortable atmosphere with increased control over the temperature. Despite the large costs upfront, the insulation can soon begin to pay for itself with reduced electricity costs to keep the outbuilding warm.
The best insulation products for a shed or summerhouse allow for easy installation and provide good value. We like insulation boards for large garden buildings where a lot of time will be spent inside. For smaller sheds, Multi-foil products also work extremely well.