Garden buildings such as detached garages can feel cold inside during the winter months. A low-cost heater and adequate insulation can allow for use throughout the year.
With the typically cool UK weather, buildings require heat to create a comfortable interior atmosphere during the colder months of the year. When it comes to converting a garage into a room, it’s important to consider how the structure will be heated right from the construction phase.
Common uses for converting a garage into a room include for use as a workshop, a bar or even a garden office. Most of these don’t require much physical movement and the cold can soon be noticed when spending extended periods inside. Furthermore, electrical equipment can be damaged by frost inside an unheated garage during the winter months.
To avoid temperature challenges and create a comfortable environment inside a detached garage we need to install a heat source. The structure must also be capable of holding onto the warmth so that we can run the heater efficiently and at a low cost.
Electricity costs have been rising rapidly recently, leading to it becoming more expensive to heat a garden building. Running a 2kW electrical heater for 5 hours per week could add over £100 to an annual electricity bill.
As well as producing heat, a garage heating system should also focus on keeping the warmth inside. Installing the heating system should be considered before boarding the interior walls of a garage. Planning in advance can ensure the detached garage room stays at a suitable temperature throughout all months of the year.
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Before heating a garage room
If the garage is not built to keep warmth inside, there is little point in heating the building as most of the heat will be lost quickly. The result is wasted energy and an inefficient heating solution. Modifications to the building to retain heat should be completed first before using an electric heater inside.
Insulating the garage
Insulated walls, roofs and floors are the best way to retain heat inside a building. Depending on the structure of the garage, different insulation products will be most suitable. Insulation works by slowing heat transfer from the interior to the exterior of the building, therefore keeping warmth inside for longer.
Before installing insulation, be sure to inspect the structure of the building to make sure there are no gaps. Cracks in the walls can also allow water to penetrate, potentially leading to mould issues in the future. They also reduce the efficiency of insulation by allowing warm air to escape. Any gaps around windows and doors should also be taken care of with weatherstripping so they close tightly and a draft can’t be felt between them.
Any type of garage structure can be insulated including brick garages, wooden garages and also metal garages. If the garage has a traditional large metal door, this should also be insulated as it’s potentially a large source of heat loss. Kits can be purchased online specifically for the door, or alternatively use the same products that are being used for the rest of the garage.
Insulating garage walls and ceiling
The walls of a garage are usually the largest source of heat loss. Whether they are constructed from metal or single-skinned brick, plenty of heat is still going to be lost through the walls. If the structure already has interior framing (such as a wooden or metal garage) the structure already has a cavity where insulation can fit in between.
For brick garages, a timber frame can be constructed on the interior to allow insulating material to fit in between. Plenty of choices are available for different types of insulation including roll and foil-based systems.
We recommend using rigid foam insulation boards. These are easy to work with inside a garden building as they can be cut to fit tightly inside the interior framing. Foil-backed insulation boards can be used with aluminium foil tape to create airtightness and remove the need for a separate vapour barrier. Insulation boards are very efficient at reducing heat loss, resulting in more warmth kept inside.
Insulting a garage roof can follow the same process as the walls. As heat rises, large amounts are lost throughout the roof. We can often use thicker insulation on the roof to maximise the insulating benefits. While it is possible to insulate the floor, this will be difficult if the building has already been installed. Instead, consider an underlay with insulating properties before the final garage flooring.
Guide: Insulating a shed with insulation boards
Building position
Where the structure is positioned can have a noticeable effect on how warm it feels inside. When we are trying to heat a garage in the cheapest way possible, taking advantage of the natural heat from the sun is a great idea.
We recommend positioning the garage somewhere in the garden where it can get plenty of natural sunlight. This means avoiding placing the building under large trees or anything else that may block the light on a sunny day. If the garage has lots of windows, be sure to position them in the direction of the sun.
Planning for a sunny location when constructing a garage room can allow for the sun to partly heat the building. Even during the winter, sunlight can create a feeling of warmth, leading to less running of the electric heater.
Double glazed windows
It’s not just the walls and roof where heat is lost from. Over 20 percent of the heat in a building can be lost through the windows. Double-glazing on windows can have a big impact on heat loss when the garage is already insulated.
Windows with double glazing work similar to a cavity wall, creating a poor conductor of heat to reduce heat loss through the glass. In a garage with large windows to let in plenty of light, double glazing is a smart move to cut electricity costs.
Before installing double glazing, make sure the walls and roof are well insulated first. These are much larger areas for heat loss so will often deliver a better return on investment for keeping warmth inside the garage.
Cheapest ways to heat a garage
Once a garage is insulated and able to hold onto warmth, plenty of options are available for producing heat. Electric heaters make a great choice and come in a variety of different options depending on the features required. If the garage does not have electricity installed an alternative heat source could be used such as a log burner or air conditioning.
Electric heaters
Portable electric heaters are great as they don’t take up much space and there’s a huge range to choose from. While they all perform the same job of producing heat, you may find additional features such as fast warm-up or quiet running that will narrow down the type of electric heater chosen.
Heaters are available in a wide range of power levels, with increased power producing more heat but ultimately costing more to run for the same period. Small heaters can start at 0.5kW and larger models can consume 3kW of power or more. The choice will depend on how well the garage is insulated and the time of the year in which the garage is used. While a 0.5kW heater may be fine in late summer, it won’t make a huge difference during the coldest days of the winter.
We recommend choosing a 2kW electric heater for a good blend of performance and running costs.
Electrical heater efficiency
A common question is which type of electrical heater is the most efficient. But if you purchase a 2kW heater, it will consume 2kW of electricity regardless of whether it’s an electric radiator or a fan heater. Electric heaters are nearly 100% energy efficient and turn all of the power consumed into heat. So if considering different 2kW heaters, for example, a decision between them cannot be made on running costs.
Running electrical heaters is more expensive when compared with the cost of a gas heating system. For this reason, the heater should only be run in small bursts and then turned off once the garage is up to a comfortable temperature. Running an electrical heater regularly for an extended period can add significant costs to an electricity bill.
Electrical heaters can produce both convection and radiant heat. A convection heater is great for heating large spaces quickly as it heats the air, which rises and moves around the room. Radiant heaters will radiate heat horizontally, heating objects nearby. A radiant heater can create a more comfortable atmosphere when compared with convection heaters. The best conditions are produced by a combination of both, such as with electric radiators.
Fan Heaters
Fan heaters are great at producing instant heat to warm up a garage quickly. Many of us have an old fan heater knocking around if the house heating breaks down. Fan heaters work by passing air over a heated metal element, which in turn warms up the air passing through. Modern versions use a PTC ceramic element for increased heat production and safety.
While they produce heat fast, the room can also feel cool again pretty quickly once a fan heater is turned off. The running noise can also be distracting if the garage is being used as a workshop or garden office. Fan heaters are low cost and produce plenty of heat for their small size.
Oil-filled radiators
An oil-filled radiator has many of the opposite features compared to a fan heater but still makes an excellent choice. In fact, they are one of the most popular options for heating a garden building. The heater works by warming oil inside of the radiator, which then retains heat for an extended period.
While oil-filled radiators take a long time to heat up, they also take a long period to cool down after use. This makes them great at providing background heat for an extended period. While in use they make little noise due to no mechanical parts, meaning no distractions when the heater is running.
A drawback is that some oil-filled radiators can be large. This is due to the thins that are used to dissipate heat most effectively. More expensive options will have settings such as timers and power levels.
Wood burner
If electrical heaters sound expensive to run in a detached garage, you may want to consider getting a wood burner installed. When fitted correctly, wood burners are both safe and produce a large amount of heat.
The heater could be used as a design feature as it can look extremely attractive in the right setting. Professional installation is required and regulations require safety features such as a flue being installed. Once the heater is running, it just requires access to a regular supply of wood to keep going.
Wood heaters create a comfortable atmosphere for relaxing and are great during the winter months.
Guide: Best heaters for a garden building
Summary
Heating a garage room is essential for use throughout all months of the year. Before installing heating, the building must be able to hold onto warmth inside to avoid extremely expensive running costs. Rigid foam insulation boards are ideal for a garage and are extremely efficient. Once installed, the garage can be boarded internally with a material such as plywood.
Electric heaters are the most common choice for heating a garage at a low cost. As all electric heaters are near 100% efficient, there are plenty of choices depending on the features required. Fan heaters and oil-filled radiators are some of the best options.
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