Garden office insulation

Insulation is a key aspect of garden office design, and vital if you want to be able to use the building comfortably all year round.

We all know that insulation is essential for keeping warm in the winter, but people forget that its the insulation in our home which stop us over heating in summer!

The vast majority of garden offices sold in the UK come with insulation in the floor, roof and walls of the building, but you need to read the specification when it comes to log cabin style garden offices where the structure doesn’t always allow for the inclusion of insulation.

With SIP's garden offices the insulation is part of the structure, wrapping around the whole building

With SIP’s garden offices the insulation is part of the structure, wrapping around the whole building

Garden offices are insulated like houses

Garden offices are built using the same materials and techniques as modern housebuilding and they use the same insulating materials and performance targets.

Garden offices don’t need to comply with Building Regulations unless they contain sleeping accommodation or are very large, but many garden office suppliers use the targets for insulation set out in the Building Regulations as a guide for their buildings.

These regulations are the targets for new houses to comply with, many designers try to meet these targets or exceed them meaning their buildings perform as well as modern houses.

Comparing garden office insulation levels

When buying a garden office it is a good idea to compare several designs, reading a suppliers specification sheet can be useful when doing this.

Insulation performance is measured by its u-value, this is the rate at which heat passes through the material. Garden offices are made up of several layers of material not just the insulation and each element of the construction has its own u-value, these are combined to create the overall u-value of the section i.e. wall, floor or roof.

Most suppliers will have worked out the u-value of their structure and many will publish this on their specification sheet, allowing you to compare the performance of one supplier against another. When comparing note that the lower the u-value figure the better performing the section.

Thick insulated walls are not always better than thinner ones

As we mentioned in the previous section the way to compare the insulation values of a garden office is to compare the u-value of the floor, walls and roof. Some specifications quote the thickness of the insulation they use implying that their 150mm insulation is better than another suppliers 50mm. This is not a reliable way to compare how well the  insulation will perform.

So many different types of insulation are used in garden office construction from natural materials like sheep’s wool mats to foil backed rigid insulation’s, and they require different thicknesses to achieve the same u-value / performance, for instance 150mm of a fiberglass  might be needed to achieve the same u-vlaue as 50mm of a rigid, foil backed board like Celotex

Bear this in mind when comparing specifications and use the u-value method as your comparison tool.

Make sure the floor, walls and roof are insulated

This may seem an obvious statement, after all we have mentioned that garden offices are built like houses, but some log cabin style garden offices don’t feature insulation in all these sections because their construction doesn’t have room to accommodate it.

Many log cabin garden offices don’t have insulation in the walls, this is because this style of building is built using interlocking timbers  which form both the exterior and interior wall / finish, thus leaving no void for insulation.

The argument is that wood is a good insulator in itself, this is indeed true, but its not as good a a multi layer wall construction that includes a good level of insulation.

The design of the structure will influence they type of insulation used

Timber frame garden offices have voids in the framework which can be filled with insulation, while with structural insulated panels (SIP’s) the insulation is an integral part of the panels.

Many suppliers use house quality SIP’s whilst other suppliers create their own build-ups using rigid insulation’s such as Celotex.

There is an argument that SIP’s built garden offices are better insulated than traditional timber frame designs. With timber frames the insulation is packed between the framework this means that in the areas where there is wood there is no insulation which creates areas known as cold spots.

With SIP’s there isn’t the timber frame work so the insulation is continuous creating an envelope of insulation around the building and no cold spots!

Many types of insulation are used in garden office construction

There are lots of different insulation materials used in garden office design, and a supplier make their choice based on cost, installation speed, performance and environmental credentials.

In a sense all insulation is eco friendly because it minimizes the waste of energy, but some insulation’s are more eco friendly in their production.

Eco friendly garden office insulation

  • Sheep’s wool insulation – this is a popular choice with garden office suppliers, the fleeces are washed and made into mats which sit in the framework. There are a number of UK manufacturers of sheep’s wool insulation.
  • Recycled plastic bottle – made from our plastic drinks bottles the fibers are spun in to mats which can be fitted between the framework.
  • Hemp insulation – hemp is a plant which is easy to grow, and absorbs CO2 as it grows, it is then harvested and made into mats which can be used as insulation.

Man-made garden office insulation’s

  • Rigid insulation boards – regularly used in garden office construction because it achieves high u-values but is relatively thin meaning relatively thin walls are created. Rigid insulation comes in several types the most basic being extruded polystyrene known as XPS and expanded polystyrene known as EPS; polyurethane insulation known as PUR and polyisocyanurate known as PIR are better performing than XPS and EPS and are usually faced with foil to add reflective insulation properties, the performance of the insulation can be hampered if this foil facing is damaged. When comparing SIP’s it’s important to ask what the insulation is, some cheaper panels will have XSP or EPS insulation but SIP’s filled with PUR or PIR insulation, although more expensive will be better performing.
  • Mineral wool – this comes in two types glass mineral wool and rock wool, glass mineral wool is made from recycled glass, sand and limestone and spun to form strands which are bonded together to form a mat, rock wool is made from the recycled waste of blast furnaces. Walls insulated with mineral wool are often thicker than those insulated with rigid insulation as a deeper thickness is needed to achieve the same u-value.
  • Reflective foils – These work in a different way to mineral wool and rigid insulation’s in that they reduce radiant heat transfer. Reflective foils come in two types – foil faced bubble wrap and multi layered foils which are made up of sheets or foil and polyethylene foam. For reflective foils to work efficiently one or both the faces should face an unventilated air space. These foils are light weight and create a thin wall structure.

A well insulated will cost more now, but save you in the long run

The best insulated garden offices also tend to be the most expensive, and there are lots of more desirable features of a garden office to spend your money on, but actually the better insulated the building the less it will cost to run in the long run because it will require less energy to heat and cool the building.