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Last updated: 13th November, 2023


Why Putting a Boiler Outside Is Often a Bad Idea

Why Putting a Boiler Outside Is Often a Bad Idea

Key takeaways

  • Outdoor boiler installations can face damage due to weather exposure and increased risk of rust.
  • Safety concerns and potential fire hazards become more prominent with outdoor boiler placement.
  • An outside boiler may have issues maintaining heating efficiency and face challenges with specific boiler types.

While putting a boiler outside may seem like a good idea to save space and reduce noise inside your home, it can actually lead to a number of problems and inefficiencies. Our guide explores the reasons why putting a boiler outside is often a bad idea, including increased installation and maintenance costs, reduced efficiency in cold weather, and potential safety hazards.

Installing a boiler is an important decision for every homeowner. While many people consider placing their boiler outside to save space within their home, this option may not always be the best choice. 

In this article, we will explore the reasons why putting a boiler outside can often be a bad idea.  

From potential damage due to weather exposure to concerns regarding safety and efficiency, there are various factors to consider before making such a decision.

One of the main issues with placing a boiler outside is the increased likelihood of damage due to weather conditions. Boilers, being essential components for heating and hot water, need to be protected from the elements to maintain their functionality and efficiency. 

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Placing a boiler outside also exposes it to potential rust, causing the boiler's components to corrode and diminish its effectiveness over time. Additionally, concerns arise regarding fire and safety hazards, as an outdoor boiler is more susceptible to accidents and security breaches.

Challenges with Space and Access

Outdoor Space Requirements

Positioning a boiler outside may seem like a practical solution, especially when space is at a premium within the home. However, this option brings its own set of challenges. Firstly, external boilers require a dedicated and sheltered area, typically found in a garage, outbuilding, or outhouse. This space should provide adequate protection from weather elements and be easily accessible for maintenance.

Moreover, the placement of an outdoor boiler necessitates longer pipework, which can increase heat loss and energy consumption. Furthermore, in colder conditions, the boiler will need to go into antifreeze mode more frequently, resulting in higher gas consumption and costs for homeowners.

Access Obstacles

Another challenge faced with outdoor boiler installations is the potential for accessibility issues. In cases where the boiler is located in a loft or high-up position, this could be particularly true. Gaining access to the unit for maintenance, repairs, and inspections might be a substantial inconvenience, requiring additional equipment such as ladders or scaffolding.

Additionally, outdoor installations can run into obstacles such as local planning regulations, which dictate where a boiler can be installed and may impact the homeowner's choice of location. These regulations vary by area and may require the homeowner to consult local authorities for guidance.

To sum up, although an outdoor boiler installation may seem like a space-saving solution for homeowners, it can present several challenges. Careful consideration of placement, accessibility, and local regulations should be taken into account before making a decision on whether or not to place a boiler outside.

Potential for Damage and Rust

Weather-Related Damage

One of the primary concerns with placing a boiler outdoors is the potential for weather-related damage. Winter season, in particular, can bring about adverse effects on the boiler's performance and lifespan. Freezing temperatures may lead to the pipes freezing and potentially bursting, causing significant problems.

Moreover, exposure to the elements such as rain, wind, and snow can result in a rapid deterioration of the boiler's components. The constant stress from weather can cause the casing to weaken, making it more susceptible to damage over time. For these reasons, keeping a boiler outdoors is not always advisable.

Corrosion and Rust Issues

Another detrimental issue arising from placing a boiler outdoors is the increased chance of corrosion and rust formation. A boiler system can face rust problems if oxygen enters the system and reacts with the metal and water, causing the metal to disintegrate and form rust. The combination of oxygen and water, alongside contaminants found in the water or extreme pH, can accelerate this corrosion process.

When a boiler is situated outdoors, it is naturally exposed to moisture and temperature fluctuations, leading to an increased chance of corrosion. If rust develops around the tank or connections, they can weaken, eventually causing leaks and potentially leading to the tank bursting. This issue poses a significant risk for a boiler's longevity and compromises the safety of the system.

Given the potential for weather-related damage and rust formation, it becomes clear why placing a boiler outside is often not the best choice. By keeping the boiler indoors, you can mitigate these issues and extend the lifespan of the boiler while ensuring safe and optimal performance.

Issues of Fire and Safety

When considering the placement of a boiler outside, it is essential to understand the potential fire and safety risks that may arise from doing so. In this section, we will discuss two key concerns: fire risks and carbon monoxide hazards.

Fire Risks

Locating a boiler outside presents some fire hazards that need to be addressed. For instance, the boiler room should be protected from exposure to the elements, including extreme temperature fluctuations, rain, and snow. This protection is crucial to avoid any frost build-up that may cause the boiler to operate inefficiently and dangerously. In some cases, boilers have been known to enter frost prevention mode and start running the heating system unnecessarily, wasting significant amounts of fuel and creating a potentially dangerous environment.

Moreover, when a boiler is surrounded or located near flammable materials, such as vegetation, it heightens the risk of unexpected fires. Properly maintaining the area around the boiler is, therefore, essential to ensure utmost safety and reduce fire risks.

Carbon Monoxide Hazards

Another significant safety concern is the potential for carbon monoxide (CO) poisoning. Carbon monoxide is an odourless, colourless gas that can be fatal when inhaled in large quantities. A boiler's flue is responsible for venting any combustion fumes it generates, effectively releasing those gases outside the property and preventing CO from accumulating within the living space.

However, when a boiler is placed outside, there is a risk of the flue becoming blocked due to adverse weather conditions, debris or other external factors. A blocked flue prevents the gas from being vented correctly, causing the gas to seep back into the property and potentially putting occupants' lives at risk. The NHS states that approximately 60 deaths occur each year due to carbon monoxide poisoning; hence, it is vital to ensure that boilers are installed and maintained correctly to mitigate this risk.

Heating Efficiency Challenges

Heat Losses

When a boiler is placed outside, it faces additional challenges in maintaining efficiency compared to an indoor installation. One significant issue is heat loss. As the boiler operates, it produces heat, which can be lost to the surrounding environment, particularly in colder weather. This heat loss can cause the boiler to work harder to maintain the desired temperature, leading to increased energy consumption and reduced efficiency.

Another factor contributing to heat loss is the distance between the boiler and the heated space, such as radiators or underfloor heating. The longer the pipe runs, the more opportunity there is for heat to be lost along the way, further reducing the system's overall efficiency. Insulation can help mitigate the impact of these losses, but it may not completely eliminate the issue.

Efficiency Reduction

In addition to heat losses, outdoor boilers can suffer from reduced efficiency for various reasons. For instance, they can be exposed to harsh weather conditions, like rain, snow, or frost, which can negatively impact their performance. These factors may require the boiler to use more energy to achieve the same level of heating as an indoor system, leading to lower efficiency overall.

Moreover, the tendency for combi boilers to be oversized with respect to central heating was noted from the large typical boiler thermal output sizes compared to the heat demand of the stock. An oversized boiler can cycle on and off more frequently, which can reduce its overall efficiency as well.

In summary, placing a boiler outside presents several challenges that can negatively impact heating efficiency, including heat losses and efficiency reduction due to environmental factors and potential oversizing. As such, carefully considering boiler placement and adequately addressing these challenges is crucial to ensure energy-efficient heating of a home or building.

Challenges with Specific Boiler Types

Oil Boilers

Oil boilers, though a popular choice in rural areas due to their independence from gas supply, can pose unique challenges when installed externally. Firstly, their susceptibility to freezing temperatures can lead to issues with the pipe that transports the oil, which may freeze and stop the boiler from functioning optimally. Insulating the external oil pipe can help reduce the risk of freezing, but this can also imply added expenses.

Additionally, oil boilers installed outside require proper insulation and weather protection to shield them from the elements and maintain optimal performance. While external oil boilers have been developed to tackle this issue, suitable for outdoor installation, they still may face potential threats in extreme weather conditions.

External Combi Boilers

Combi boilers, a popular type due to their compact size and their ability to provide instant hot water, can face unique challenges when they are installed outdoors. Among the primary concerns with external combi boilers would be potential water damage from precipitation.

As these appliances require electricity for their functioning, placing an external combi boiler can pose a risk element in wet conditions if it's not appropriately installed or well protected from the elements. Similarly, condensing combi boilers – which are known for their energy efficiency – may encounter issues with the condensate pipe freezing during cold weather, causing the boiler to cease operating.

In conclusion, while there are boiler types developed specifically for outdoor installation, both oil and external combi boilers have their respective challenges when installed outdoors. Adequate protection, weatherproofing, and insulation are essential measures when considering placing a boiler outside.

Servicing and Maintenance Concerns

Routine Maintenance

When a boiler is placed outside, routine maintenance can become more challenging. The boiler is exposed to various weather conditions, which may lead to quicker wear and tear on its components. Regular upkeep plays a crucial role in extending the boiler's lifespan and ensuring its efficiency. 

However, with an outdoor boiler, this might include extra tasks like clearing snow, leaves, and debris from the surrounding area and checking for signs of rust or damage on the unit's exterior.

It is essential to keep an eye on the boiler's pressure, which should ideally be between 1 and 1.5 bars. An outdoor boiler may experience fluctuating pressure due to exposure to changing temperatures and conditions. Regularly inspecting and adjusting the pressure is vital for optimal performance.

Replacement and Servicing

As a result of increased exposure to the elements, components within an outdoor boiler may need to be replaced more frequently. This could lead to higher servicing costs over time. Moreover, accessing an outdoor boiler might be more laborious for engineers, potentially leading to longer service times and higher charges.

In comparison, indoor boilers are sheltered from outside conditions and typically experience less wear and tear. Therefore, in many cases, their components may last longer and require less frequent servicing.

The process of replacing an outdoor boiler may also be more complex due to its external location. This could result in higher installation costs for a new boiler, compared to an indoor boiler.

In summary, placing a boiler outside may raise concerns regarding servicing and maintenance. These issues may lead to a reduced lifespan, increased replacement frequency, and higher costs for homeowners, ultimately making it a less suitable option in many cases.

Noise and Aesthetic Challenges

Noise Level

One common disadvantage of placing a boiler outside is the increased noise level. Outdoor boilers usually generate more noise compared to their indoor counterparts. This additional noise can be bothersome for homeowners and their neighbours, especially in quiet residential areas. The noise produced by the boiler comes from various components like the circulation pumps, fans, and burners, and could potentially disturb the peace in the surrounding environment.

Moreover, the boilers' noise might be further amplified by echoing off nearby structures or obstacles. So, while the primary goal might be to reduce indoor noise by placing the boiler outdoors, the resulting overall noise increase should be considered.

Physical Appearance

Another factor to consider when installing an outdoor boiler is its physical appearance. Outdoor boilers, especially the larger models, can have a considerable visual impact on the surrounding landscape. They often have a utilitarian design that does not always blend well with the existing aesthetic of your property. The protruding flue, pipework, and vents can also be an eyesore if they are not well-integrated with the architectural design of your home.

Furthermore, an outdoor boiler requires robust weatherproof casing to protect it from the elements. However, this might not be aesthetically pleasing and might detract from the overall appearance of the property. While the foremost priority is to ensure the boiler's functionality, homeowners should also take into account the visual impact it has on their property when making such decisions.

In conclusion, outdoor boilers come with their own set of challenges in terms of noise levels and physical appearance. It is important for homeowners to weigh these factors carefully so they make an informed decision that balances both their practical needs and personal preferences.

Legality and Regulations in the UK

The placement, installation and maintenance of boilers in the United Kingdom are governed by a set of regulations that ensure proper safety measures are observed. It is essential to understand and comply with the guidelines outlined in UK legislation to avoid risks to both residents and the environment.

Gas Safety

Gas safety is of prime importance when dealing with boiler installations. In the UK, the Gas Safe Register is the official list of engineers who can legally work on gas appliances. It is mandatory for all installations and maintenance work to be carried out by a Gas Safe registered engineer to ensure the highest levels of safety.

The Gas Safe Register validates the qualifications and competence of registered engineers, giving homeowners the confidence that they are working with a professional who is adequately trained in handling gas appliances. This includes adhering to established regulations, following best practices, and prioritising the safety of the household.

Installation Guidelines

The positioning and installation process of a boiler outside the premises require compliance with specific regulations. According to the Building Regulations for boiler installations, the flue must maintain a minimum distance of:

  • 300mm away from any window that can open, or air vents

  • 1,200mm away from a door

  • 2,000mm below a Velux-style window (dependent on boiler size)

These regulations ensure proper safe disposal of combustion gases, such as water vapour, carbon dioxide, particulates, heavy metals, and acidic gases, which are byproducts of burning gas.

Placement and installation of boilers must also consider accessibility for regular inspections, maintenance and service, ensuring that safe and efficient operation is not compromised. Proper ventilation and adherence to the manufacturer's guidelines are critical to guaranteeing the longevity and functionality of the equipment.

In summary, installing a boiler outdoors is subject to various UK regulations that focus on ensuring safety and adhering to proper guidelines. Close attention must be paid to the placement of the flue, and only a Gas Safe registered engineer should conduct installation and maintenance work. These measures minimise the associated risks, keeping both residents and their surroundings protected from potential harm.

Cost Associated with Outdoor Boilers

Installing an outdoor boiler can seem like an attractive option for homeowners looking to save space inside their homes. However, several factors can make this choice less cost-effective in the long run.

Firstly, outdoor boilers are more exposed to extreme weather conditions, which may require additional insulation or the use of antifreeze to protect the system. This not only adds to the initial installation costs but could also lead to increased energy consumption during colder months. Consequently, the energy bills might be higher than when using an indoor boiler.

Secondly, the cost of moving a boiler outside can be quite expensive. Rerouting gas connections and connecting the boiler to existing pipework can cost between £400 and £600. Additionally, if the boiler needs to be moved to a room without a gas pipe, such as a garage, the cost can further increase (£75 - £125 per metre).

When it comes to warranty and insurance, outdoor boilers may not be covered in the same manner as indoor ones. Some manufacturers might offer a lesser warranty period for outdoor installations, which may result in higher maintenance and repair costs down the line. Moreover, insurance policies might require homeowners to pay higher premiums or ensure specific protective measures are in place for outdoor boilers, which could further impact the budget.

Furthermore, outdoor boilers can be more susceptible to vandalism and theft. Consequently, homeowners might end up incurring additional expenses for security measures, such as protective enclosures or surveillance systems.

Where to Safely Install a Boiler?

When planning to install a boiler, it's important to choose a location that ensures safety, compliance with Building Regulations, and easy access for maintenance and repairs. Boilers can generally be installed in several rooms within a house, including, but not limited to, the kitchen, the garage, or even the loft. 

It's crucial to consult with a Gas Safe registered installer who can provide guidance on adherence to Building Regulations and optimal boiler placement.

One primary consideration when selecting a location for a boiler is having adequate clearances around the appliance. This ensures space for maintenance and repairs, as well as regular inspections. It's essential to find a location that minimises the risk of setbacks such as leaks or damage!

Another aspect to think about is the distance between the boiler and areas where hot water demand is highest. Having a boiler installed near the kitchen or bathroom will efficiently meet these requirements and limit inconvenience for the occupants. Moreover, avoid rooms where noise from the boiler could become a nuisance, especially in living or sleeping areas.

Compact gas combi boiler models offer a more flexible installation, allowing homeowners to safely install them within kitchen cupboards. Such boilers can also be situated in outdoor areas like the garage or external boiler spaces, but be mindful of potential issues, including exposure to weather conditions, increased energy usage or loss of heat in un-insulated locations.

In summary, boiler installation decisions should prioritise safety, Building Regulations compliance, and accessibility for maintenance and repairs. While outdoor installation may seem appealing, there are potential concerns that require careful evaluation before making a decision. Consulting with a Gas Safe registered installer will always be the best course of action for both safety and optimal performance.

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Frequently Asked Questions

Can a boiler be installed outside?

Yes, a boiler can be installed outside, as long as it complies with building regulations. There are specifically designed outdoor boilers, like the one by Worcester, for this purpose. However, do consult a Gas Safe Engineer for proper guidance.

Should a boiler be outside?

Though it is possible to place a boiler outside, there are some disadvantages to consider. In colder weather, an outdoor boiler may need to activate antifreeze mode more frequently, resulting in increased gas consumption. Additionally, there's a risk of water freezing in the pipework if the antifreeze function triggers at too low a temperature.

How long do outside boilers last?

The lifespan of an outside boiler can vary, but typically it is similar to that of an indoor one, which ranges between 10-15 years. However, external factors such as weather conditions and environmental elements might influence its longevity. Regular servicing by a professional is crucial to ensure optimal performance and lifespan.

Should a boiler be enclosed?

Enclosing a boiler is not a strict requirement, but it can offer some benefits, particularly if it's installed indoors. Enclosures can help reduce noise, enhance aesthetics, and, in some cases, provide additional insulation. If you plan to conceal your boiler, make sure there's adequate ventilation and easy access for maintenance and servicing.

Where should you not put a boiler?

It is essential not to place a boiler in enclosed, unventilated areas, such as cupboards or small rooms without proper air circulation. Avoid installing a boiler near flammable materials, inflammable surfaces, or large bodies of water. Moreover, don't position boilers at a height where it becomes difficult to access for maintenance, servicing, or in case of emergencies.

Can I cover up my boiler?

You can cover your boiler, but you must ensure that there's sufficient ventilation and clearance, as per the manufacturer's guidelines and building regulations. Avoid using flammable or combustible materials to cover your boiler, as they can be a fire hazard.

Can you install a box around a boiler?

Yes, you can build a box around a boiler, but make sure that adequate ventilation requirements are met, and there's enough clearance space for maintenance and servicing. Always follow the manufacturer's recommendations and building regulations when boxing around a boiler, and seek professional advice if you're unsure.

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Article by
Stephen Day | Co-founder
Gas Safe registered and FGAS certified engineer with over 20 years experience in the heating and cooling industry.