Garage conversions
When looking to extend or improve an existing property, garage conversions are a popular choice for creating a new habitable space.
U-value Calculator
Start your U-value calculationTurning an uninsulated garage into a comfortable area means complying with national building regulations in terms of thermal performance and, where applicable, acoustic performance. For garage conversions, PIR insulation and glass mineral wool insulation products can help to achieve both.
Depending on the specific product chosen, these types of insulation for garage conversions can provide a number of benefits, including:
- Lower U-values.
- Long-term energy savings.
- Improved acoustic performance.
- Excellent fire ratings.
- Lightweight, easy to handle.
- Fast and easy cutting and installation.
- Minimal impact on internal room space.
Deciding on a garage conversion
A garage is almost always outside the thermal envelope of an existing property. That is, the heating system of the house does not extend into the garage, and the garage structure itself is uninsulated. As a result, it has never had to meet any regulatory requirements for energy efficiency.
Once the need for planning permission has been established and, if necessary, obtained, thoughts turn to complying with national building regulations. Whatever type of living accommodation the conversion will create, how the existing garage connects to the house impacts on the amount of work required to make the project a success.
Is it a single storey structure attached to the side of the house? Or is it an integral garage, with the living accommodation wrapping around the back and over the top? Which parts of the structure need to be treated with insulation depends on this relationship.
The conversion process
Starting with the floor, all garages have a concrete slab that needs to be insulated before installing a screed or a chipboard covering. A vapour control layer, and maybe a damp proof membrane, will also likely be required as part of the build-up.
The difference in height between the garage and house floor levels is usually the determining factor of how much insulation can be accommodated to meet or exceed the required U-value. A thermally efficient, rigid foam insulation like Celotex PIR boards can achieve the required thermal performance in the available floor depth, while acting as a sound base for the floor covering and finish.
Insulating the garage walls and roof
Because they did not have to be insulated when first built, garage walls are usually solid - either 100mm (4-inches) or 225mm (9-inches) thick, depending on the design of the property.
There are many options for insulating solid walls, some of which may be more suitable than others depending on the age and condition of the walls. Internal wall insulation (IWI) is the most likely solution, but external wall insulation (EWI) could be considered in the right circumstances.
Thermal insulation options also depend on the amount of space available. With their rigidity and lower lambda value, PIR boards offer different wall insulation solutions with minimal thickness. Alternatively, glass mineral wool batts or rolls can be fitted between timber or metal studs forming an independent stud wall inside the existing external wall.
In terms of the roof, an integral garage often has a heated space above it. There is no need to consider thermal insulation in the ceiling, though acoustic insulation may need to be fitted for sound insulation purposes.
For a garage with its own pitched roof, the type of insulation depends on how the loft space will be used. Loft insulation laid at ceiling level is the most likely route to take. In the rare event that a pitched roof is substantial enough to accommodate further living space then it may be converted accordingly.
Acoustic insulation requirements
Where the conversion of the garage space into habitable accommodation requires internal partition walls, those walls may be subject to the requirements of building regulations that deal with noise. An appropriate acoustic insulation should be installed to meet those requirements.
The building detail is for illustrative purposes only. It does not constitute advice and should not be relied upon.
Insulation products
| Product Name | Thickness Range | Sizes | Lambda |
|---|---|---|---|
| Celotex GA4000 | 50-100mm | Width 1200mm, Length 2400mm | 0.022 |
| Celotex TB4000 | 20-40mm | Width 1200mm, Length 2400mm | 0.022 |
| Celotex XR4000 | 110-200mm | Width 1200mm, Length 2400mm | 0.022 |