Garden rooms are popular and can be used throughout the year, as long as they are appropriately heated to make them comfortable.
Perfect for a variety of uses, a heated garden room can be the perfect solution to hectic family life indoors, providing a quiet and private space to create a home office away from the chaos in the main home. Likewise, for those lacking in space, a heated garden room can also be a great addition to a smaller home.
Knowing how to build a garden room can add value to a property when it comes to moving on too due to the extra square footage of living space having one provides. “A garden room should feel like an extension of your home, a room in your garden” says Chris Browne of SilverLeaf Spaces. “As it needs to be comfortable and warm all year round, heating plays a crucial role."
Here we discuss the various options for heating a garden room and which one might be the most sensible choice for your space.
Why insulation should be your first thought
Before considering what system you install to heat a garden room, it is really important to ensure it is properly insulated, as this will determine how efficient your heating system will be.
The floor, walls and roof of the garden room need to be properly insulated, with a minimum of 75mm of insulation for the floor and walls and 100mm for the roof.
"A well-insulated garden room will perform throughout the depths of winter, proving a valuable asset to extend your living space," confirms Chris Browne. Additionally, where possible, double-glazing should be installed to stop heat escaping through the windows too.
Chris is a garden room design specialist, working with creative clients on imaginative projects for over 10 years. In 2020, he launched SilverLeaf Spaces, a specialist boutique studio, dedicated to bringing architectural design to the garden room.
The options for heating a garden room
Unless you have a means to connect a separate gas or oil boiler to your garden room, or even a biomass boiler, electric heating is most likely to be the easiest and cheapest option available for heating a garden room.
Adding electric to a garden room is relatively straight forward compared to extending other types of piping – you just need a qualified electrician to lay additional cabling safely from your main home to the bottom of your garden, if not already present.
"Assuming a well-insulated space, we would very broadly recommend a 500W radiator for a small space (e.g. 2.5 x 2.5m), 1000W for a small-medium room (e.g. 4 x 3m) and 1500W for a larger space (e.g. 6 x 4m)," explains Chris Browne. "With larger spaces, it is sensible to have a couple of moderate heat sources to provide even warmth across the room."
With this in mind, here are the best choice for electric heating with some alternative fuel source heating options included too.
1. Electric panel heaters
Panel heaters are usually mounted against a wall like a radiator and incorporate an internal heating element, the air then being circulated around the room.
They are usually controlled by 24-hour timers or wi-fi remote programming, which can be more convenient, as they can be set to switch on just before use of the garden room and switch off again just after you leave.
They are relatively inexpensive and they warm up quickly. This makes them ideal for occasional use, depending on how often you actually use the garden room, and for these reasons they are usually the standard option recommended by companies installing garden rooms.
However, panel heaters are often more expensive to operate than other forms of heating. They also make the air inside the garden room very dry. It is also worth bearing in mind that panel heaters can also present a fire risk if clothes are placed on top of the heater and any objects obstructing the vents on top of or on the side of the heater will limit its efficiency.
Although panel heaters warm up quickly, it will take a while for the heated air to circulate properly around the internal space of the garden room. This is why it is a good idea to switch them on before the room is actually used.
Shop panel heaters
This heater can deliver a quick rise in temperature and features variable heat settings, a thermostat with LCD display and overheat protection. It's suitable for rooms up to 20m².
A 1kW heater with adjustable thermostat and a half wattage eco mode to ensure that the perfect amount of heating is used. Suitable for a room up to 12m².
The Futura white electric heater can be installed on any standard home building wall, or turned into a floor standing model.
2. Electric underfloor heating
Underfloor heating is also popular, as it makes the floor warm. Wet underfloor heating in the home consists of warm water pipes running through a concrete screed, but for garden rooms, which often have a timber floor, it will consist of a series of wired mats placed over an insulated underlay.
A 140W heat mat will be sufficient, laid on top of a wooden floor no more than 14 mm thick, to ensure efficient heat transmission. Above this, a floating floor should be installed on its own, that is, without the use of adhesive or flooring nails.
"Underfloor heating offers even warmth without taking up wall space. Electric or water-based systems can be installed beneath flooring, providing a comfortable environment in a discreet manner," says Kevin Moore, managing director and co-founder of My Eco Space Group. "Although initial costs may be higher, the long-term energy savings and consistent warmth make it a worthwhile investment.”
"Underfloor heating adds a gentle warmth underfoot, ideal for minimalist interiors where wall space is at a premium," adds Chris Browne.
Kevin Moore is Managing Director and Co-founder of My Eco Space Group and a Renewable energy and electrical design consultant. He leads the My Eco Space Group team on R&D with cooperation from three leading Universities for innovative design of the Impact Zone floor system designed to reduce shockwaves caused by rigorous workouts in garden gyms. Kevin is currently involved in R&D for 3D design software to improve building efficiency.
3. Portable heaters
Portable heaters can be moved around the space and they are inexpensive, especially if you choose a small portable fan heater or convection heater, which usually costs around £15.
Some air conditioning systems, while normally used for cooling a space, can also be used to heat it. These are known as ‘reverse cycle’ air conditioners and are actually a type of heat pump.
"Convector heaters warm the air quickly and are often Wi-Fi or timer-controlled for convenience," adds Chris Browne.
Oil-filled radiators, like portable electric heaters, are freestanding, and so they can be moved around. However, they do take slightly longer to heat up, because the heating element warms up the oil inside the heater. This means that a portable electric heater is probably the better option out of the two for short periods of use. For longer periods though, an oil-filled radiator provides good, even, warming.
Shop portable heaters
This silent but powerful NETTA 2500W Electric Oil-Filled Radiator with 11 fins is the perfect addition to your home or office. It will have no problem heating up medium to large-sized rooms.
Save on energy costs by only heating the space you're using. Offering powerful convection and portable heating it's compact size is great for small garden rooms.
This Dreco space heater Hyperamics 1500W advanced PTC system with a new heat funnel design to deliver heat within seconds and enhance warm air circulation for up to 200% farther reach than traditional heaters.
4. Wood burning stoves
Wood burning stoves and log burner ideas are visually attractive and thus add a sense of style to the interior of a garden room. However, log burners need to be installed by a professional heating engineer and the cost of the flue will mean an increase in the overall installation cost. They also need a constant supply of wood from a regular wood fuel supplier.
5. Solar thermal panels
Solar thermal panels installed on the roof consist of an array of water-filled tubes. When warmed by the sun, these then supply heat to radiators within the garden room. They are usually fairly expensive to install compared to other heating systems and the level of heat provided will depend on how much sunlight is available on any given day.
6. Bottle fed gas heaters
Bottle gas heaters can be used where garden rooms are not connected to mains electricity. However, the space needs proper ventilation to avoid the build up of fumes and water vapour. Bottled gas, being a fossil fuel, is not environmentally friendly.
7. Air source heat pump
“An air source heat pump is an innovative solution that can provide both heating and cooling, making it versatile for year-round comfort in your garden room," says Kevin Moore.
"By extracting heat from the outside air and transferring it indoors, air source heat pumps are energy-efficient and environmentally friendly. They can significantly reduce energy bills while ensuring a pleasant climate."
Costs of heating a garden room
The operating costs for these systems vary, depending on how well the garden room is insulated and the size of the heating system you choose:
- Portable fan heater – 17p for a 500W heater, rising to 68p for a 2kW heater
- Panel heater (electric radiator) – 19p for a 750W system, rising to 50p for a 2kW heater
- Underfloor heating – 11p for a small system covering 3 square metres of floor, rising to 56p for 15m²
- Reverse cycle air conditioner (heat pump) - 7p to 15p
- Oil-filled radiator – 9p for 400W system, rising to 56p for 2.5kW
- Solar thermal panels – no running costs, but they are often expensive to install and the amount of heat depends on the amount of sunlight, which means they will generate less heat on a cloudy day
“If a garden room is well designed and built, it won’t need much heating at all,” says Justin Murray, founder of Bio-SIP. “The key is to insulate it properly, which helps retain warmth and minimise heat loss.
"You can then harness the sun’s energy by positioning windows to the south, capturing free solar heat during the winter," recommends Justin.
To avoid overheating in summer, include roof canopies and external shutters in the design, a natural approach known as passive heating and cooling. For colder days, a small electric wall heater or underfloor heating can provide an efficient top-up.
Justin Murray is the founder of Bio-SIP, a sustainable building system made from recycled plastics and hemp. With a background in design and innovation, he is committed to low-carbon, circular construction that addresses both the housing and climate crises. Justin works with architects, developers, and local authorities to deliver modular, net-zero-ready buildings, from garden rooms to micro homes, he champions practical, scalable solutions for a greener built environment and is helping shape the future of eco-conscious construction.
With regard to environmental impact, garden rooms can help to reduce your carbon footprint, especially if they are used for home working as an isolated office space. They will require less heating than a main house, and this will reduce the environmental impact of the property’s energy use.
If they are constructed with biodiversity in mind, for example with a ‘green roof’, use sustainable materials and minimise waste, these factors will decrease the environmental impact of the space even further.
But, be sure that when picking your garden room, you've checked the rules surrounding garden room planning permission, and if you're planning on using your garden room as a bedroom, be sure to take all the extra advice into account too.
