How to Heat a Garden Room: Complete Guide

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Heating a garden office, summer house or log cabin allows the room to be enjoyed all year round. With so many options available, let’s take a look at the best heating solution for a comfortable temperature in any season. 

An important decision when it comes to any garden building is how you are going to keep it warm and cosy. There’s not an exact answer to this as it depends on how and when you plan to use your garden room. Living in the UK, the seasons can vary wildly, with warm summers and months of cold and frosty weather in the winter.

First, let’s consider how it will be used. For use as a garden office (or pub), a comfortable temperature is required throughout the year to ensure you can stay productive, even in the coldest of winter months. Furthermore, computer and electrical equipment should be protected from the frost to avoid damage. For this, the heating should be capable of running all-year and at a low cost. If the garden room is being used as a gym, a cooler temperature may be preferred and the heating may also only be required a few times each week. For this, a focus on quick warm-up is just as important.

Getting a heating system set-up in your garden building is straight forward, and if using an electrical heating system, does not require much planning in advance. The size of the building should be taken into account to ensure adequate performance throughout the year.  

Before you start heating a garden room

In our opinion, there is little point in trying to heat a garden room which is not built with all-year use in mind. Many base model summer houses are really designed just for the warmer months. This is going to lead to any heat being lost quickly and prove an expensive & inefficient endeavour to keep warm. Fortunately, there are many features which can be built-in or retrofitted to ensure your building is winter-ready.

Insulation

While there’s no requirement to use insulation in a garden room, it’s an easy way to lock-in warmth and reduces heating costs. For summerhouses, some manufacturers will offer insulation as an upgrade in the walls, floors and ceiling. While we recommend insulation, it can often be more cost-effective to install it yourself. 

Garden building suppliers will sell insulation kits at a premium. These are usually the same insulation which can be picked up from a local builders merchant at a lower cost. Summerhouses in particular often have thin exterior cladding and the batons already in place to put insulation in between. Installing insulation between the batons and then boarding over inside the building can reduce heat loss and allow for a house-like feel on the interior.

Log cabins are slightly different and do not always require insulation in the walls. Cabins built with thicker logs (at least 44mm) can reduce heat loss significantly on their own, even in colder weather. Where insulation should be applied in a log cabin is inside the roof and floor. Insulating the floor stops draft from underneath rising through the floorboards. Insulating the roof is key to stop heat from rising and being lost as the wood is not as thick.

There are different types of insulation available for garden buildings. PIR boards are lightweight and rigid boards which can be cut to size and placed in between batons for a high level of efficiency. Rockwool is also low cost and has great thermal properties.

Double Glazing

Windows with double glazing are increasingly offered with garden rooms, summer houses and log cabins at the time of purchase. Double glazing often looks great, especially when compared to strengthened plastic which is sometimes offered as standard. But it does have a practical purpose as well.

While most of the heat loss in a garden building will occur in the roof and walls, close to 1/5th can be lost through windows. Double glazing works as an insulator in the same way a cavity wall does, creating a poor conductor and reducing heat loss. We recommend double glazing especially for garden rooms with full pane glass doors and multiple windows.

Double glazed windows will not make a big difference where the walls and roof are not properly insulated. As most heat loss occurs through these areas, it is better to invest in insulating both of them first.

South Facing

While this is not essential, a south-facing garden building does provide the feeling of increased warmth. Positioning your building somewhere in the garden where it can get plenty of sunlight allows for it to be partly heated naturally, reducing your energy costs on a sunny day. Any large windows should be facing the sun to ensure maximum warmth. Keeping the space clear from any overhanging trees or high fence panels can also allow maximum light, particularly when the sun is lower.

Electric Heating

Using an electrical heater allows for easy installation and a huge range to choose from. While they ultimately all perform the same job, the features onboard will be different. Fan heaters will provide rapid warm-up, while oil-filled radiators will hold onto heat for a longer period once turned off. As electric heaters can be expensive to run, they are better suited for short bursts to bring the temperature up, rather than constant running.

How powerful should a heater be?

The output from electrical heaters is measured in Kilowatts (kW). A higher rating means both increased heat output and running cost. Heaters are available for as low as 0.5kW and as high as 3.5kW. For a smaller, well-insulated, garden room, a heater with 1kW power should provide enough performance to take the chill off in spring and autumn. For a medium-sized garden room or use during winter, 2kW is preferable. Many heaters have adjustable power settings, so the power can be turned down when the temperature outside is not as low.

Which electric heaters are the most efficient?

If you purchase a 1kW heater, it is going to use 1kW of energy regardless of whether it is a convector heater, oil-filled radiator or any other type. The good news is that electric heaters are near 100% efficient, they turn all their energy into heat. Choosing between the same power electrical heaters for a lower running cost is not going to make a difference if they are used for the same period of time.

It’s no secret that the cost of using an electric heater is higher when compared to gas. The unit cost of gas is lower and the reason why most of us have a gas central heating system. The average cost for a standard unit of electricity in the UK is 16.3p/kWh. We can use this to calculate the running cost of an electric heater. Using a 1kW heater for five hours per week would add around £42 to an annual electricity bill.

Convection vs radiant heat

Electrical heaters can provide both convection and radiant heat, sometimes at the same time. Convection heaters work by pulling cooler (lower) air towards them. The heated air rises upwards and then gradually falls as heat is lost. Convection heaters are great for heating large spaces quickly and ensuring heat is spread evenly over a garden room.

Radiant heaters work by radiating heat horizontally and directly towards where they are aimed, Heating objects around them. Radiant heaters reduce draft and provide a feeling of warmth to those nearby. Many find radiant heat to be more comfortable and less dry compared to convected heat. The ideal conditions are actually a combination of them both, which can be provided through electric radiators, whereas infrared heaters produce a radiant heat source.

Electric radiators

As well as in garden buildings, modern electric radiators are commonly found in homes and offices. Placed flush against the wall provides a clean look and minimises space required. The downside is that they cannot be moved around the room when needed. The placement should allow for the heat to circulate to all sides of the garden building easily.

Electric radiators produce a combination of both radiant and convection heat to ensure comfort and warmth. Heat-up is also silent and relatively quick. Many will have timers built-in, allowing for pre-heating a garden room in the morning before it is going to be used. As they are designed to be permanently installed in homes, rather than a portable solution, electric radiators can be expensive to purchase initially. Most will cost upwards of £200 with good heat output.

Oil Filled radiators

An extremely popular choice for use in garden rooms, oil-filled radiators offer a good balance of features. Oil inside is heated up and then retains its temperature. Oil-filled radiators take longer to heat up but also longer to cool down, so the electricity use will be the same. The heat given out is both a combination of radiant and convection heat. While not ideal for a rapid burst of heat, they make a great solution for running whilst inside a garden room.

Oil-filled radiators also have a quiet operation, with no mechanical parts. A downside is their size, with large thins to dissipate the heat meaning they can get in the way. Oil-filled radiators usually have wheels, allowing them to be moved and placed next to you e.g. when working from a garden office. The cost is low, but we would avoid the smaller options including the mini oil-filled radiators with less than 1kW power. Multiple heat settings are useful to provide background heat once the room has initially warmed up.

Convector Heaters

A good low-cost option, convection heaters provide a lot of flexibility and are widely used in garden buildings. Convection heaters quickly heat the air which rises and moves around the room. They do this fast and with little noise. The heat-up time is minimal and works well to quickly boost the temperature in a room. Some options are available with wall mounting fixtures. Most are now free-standing and include legs to move them around if required.

Convector heaters are widely available and can often be picked up for £40 or less. A slight downside is that they are not the smartest looking heaters, with budget options often featuring an undesirable black and white design. The air can also feel dry coming out of a convector heater. Most are slim and can be positioned out of the way next to a wall. We recommend finding a model with a thermostat and timer to pre-heat your garden room before use.

Fan Heaters

A firm favourite for heating up cold rooms, fan heaters provide instant heat without any warm-up time. This type of heater traditionally works by passing air over a heated metal element. More up-to-date versions use a PTC ceramic element which allows for exceptional heat production and safety. Fan heaters are the lowest cost heaters to initially purchase, and can be found for as little as £15.

The downside with fan heaters is that they are not suitable for running continuously. The noise from the fan can be loud and not suitable if using a garden room as an office. Also, once turned off the heat source has gone and the room can feel cold again, increasing use and driving up cost. An oil-filled radiator will hold the heat for a while longer once powered down. Fan heaters are best suited when instant warm-up is required and the room is well insulated to hold the heat.

Infrared & Halogen

Unlike convector heaters which heat the air, infrared heaters produce only radiant heat, making them great for garden rooms which are drafty or not well insulated. Objects are heated instead of air (similar to the sun) creating a feeling of warmth and not losing heat as easily. Halogen and infrared are both very similar, with infrared providing a wider range and better heat distribution. When running, infrared heaters are near-silent and warm up very quickly. This makes them a good solution for providing background heat when sitting in a summer house or log cabin.

Where infrared heaters fall short is heating the room as the heat only travels in the direction it is pointed, making them less suitable to larger garden buildings. The size can also be large and stand tall due to the size of the heating element. Infrared heaters can be mounted on walls or even the ceiling, but many will be free-standing and can be moved around with you throughout the room. The price is upwards of £40, making them mid-range in terms of heating options.

Air Conditioning

Using air conditioning may sound the opposite of trying to achieve a warm room, but most AC units are capable of delivering hot air as well. Air conditioning heat pumps provide excellent efficiency and make a great option where a garden room is used frequently. The added benefit is that the same system can be used during the summer to keep a garden room cool, maintaining the ideal temperature throughout the year.

Many office blocks are heated using air conditioning systems which removes the need for radiators. The AC unit can be mounted onto the wall of a garden room. The drawback is the high initial cost to get set-up. A professional will be required to install the system and ensuring it is safe. Once past the installation, comfort and increased efficiency can be achieved long-term.

Underfloor Heating

Previously reserved for larger and luxurious buildings, underfloor heating is now widely available and low-cost. Heating kits are available and start in the region of £80 per square metre. Using an underfloor system such as this requires the surface below it to be properly insulated to ensure any heat is not lost below ground. The decision needs to be made before laying the floor and it may affect the choice of flooring. The result feels great to walk on and often creates the impression of a warmer room.

Picking a reliable brand is important. If there’s an issue with the heater, the floor will have to be lifted up and repaired. Most kits will come with a thermostat system to allow the room to be heated on a timer. Underfloor heating keeps the walls free but the result may not be noticeable enough, particularly in the winter when the room takes a long time to heat up.

Alternative Heating

While electric heaters are easy to install, alternative heating sources may provide greater efficiency and additional benefits. If your garden room does not have electricity, options are still available to stay warm in the colder months.

Wood Burners

I’m sure you’re thinking that a wood burner inside a largely wooded construction is a bad idea, but they can be just as safe if fitted correctly. A wood burner provides a very stylish heating source which looks particularly good in log cabins. The warmth provided creates a comfortable atmosphere where you can sit and enjoy for hours and is great in the winter. Installation requires a professional fitter that is HETAS certified.

The cost of a wood burner can appear attractive, but the resulting cost can be markedly higher. Professional installation, safety features and the flue etc soon add up. The installation will also require cutting into the wood-work of your garden room. If you have access to a local supply of wood, a log burner can be efficient and sustainable. The higher initial cost can be offset over time with the running costs. Planning for a wood burner is easiest at the time of installation of a garden building.

Solar power

Technically still electricity, solar power is an option to consider if your garden room is off-grid with no connection to mains electric supply. Solar panels offer a low carbon footprint solution and practically no running costs. Installation involves a solar power kit which contains everything required to get connected. Once set-up the maintenance required is minimal. A kit will typically include the panels, cables, inverter and batteries. Space will need to be made inside the garden room to accommodate the power supply.

The downside in the UK is the little sun we get. A good quality kit will cost upwards of £500 before installation. Over the winter when energy use is going to increase, solar panels will be generating less electric. Heaters also use upwards of 500W energy which will require a high-rated solar kit and large capacity battery. We would recommend avoiding solar panels where possible due to high costs and lack of consistent supply.

Smart Heating

Recent innovations in smart home technology have created a range of smart-equipped electric heaters. To take advantage of smart technology, a constant Wi-Fi internet connection in your garden room will be required, even with the heater turned off. A smart heater can be turned on using a phone or tablet from inside your house. Ideal for frosty mornings to avoid stepping into a cold garden room.

For those with smart voice assistants, some heaters can be paired for voice-enabled activation. Asking Alexa to turn on the garden room heating is convenient and quick. Going further, heaters can be paired with smart sensors to enable automatic start when the temperature drops below a defined limit.

The range of smart heaters available is increasing all the time. Heaters without smart features can be turned into a smart heater by using a smart plug which can be turned on and off remotely. If the heater already comes on without pressing buttons when connected to power, a smart plug is a quick way to gain functionality. 

Guide: Best heaters for a garden room

Our Opinion

Overall, heating a garden office, summer house or log cabin is an important decision which should be taken early on. With the right set-up, there’s no reason a garden building cannot be used throughout the year.

Before any heating is installed, adequate insulation is essential. A poorly insulated garden building will struggle to maintain heat and cost a lot to keep heating running constantly. Double glazing is a good choice for well-insulated rooms to reduce heat loss through windows.

Our two recommended types of heaters are oil-filled radiators and fan heaters. In our opinion, the best way to heat a garden office is to use an oil-filled raditor which can provide a consistent background of both radiant and convection heat. They create a feeling of warmth and retain heat once turned off. Fan heaters are also good for garden rooms which require a fast warm-up. For use as a garden gym or pub, fan heaters can quickly increase the temperature before going in and turning the heating off.

How are you heating your garden room? Let us know in the comments below.