The best outdoor boilers allow you to reclaim valuable interior room without compromising on performance, but they require careful planning.

Living spaces are shrinking faster than ever across the UK. Research shows the minimum size for new homes built since 2010 averages just 67.8 m², the smallest in the last 100 years. Current national space standards allow a minimum of 37 m² for new flats, barely enough to balance comfortable living with modern work-from-home needs. With every square metre under pressure, many homeowners are looking beyond the walls for ways to free up space indoors.

That’s where the outdoor boiler comes in. They’re compact, insulated, and designed for weather resistance. Yet moving your boiler outdoors isn’t just a matter of convenience. It must align with strict UK regulations, meet minimum efficiency standards, and follow safety and placement criteria.

Before making the switch, it’s worth understanding how these systems work, what additional protection they require, and which models are truly built for Britain’s changing climate.

Key Takeaways on Outdoor Boilers:

• Outdoor boilers are fully functional heating systems designed to operate safely and efficiently outside your home.
• They are ideal for smaller properties or off-grid heating where indoor space or noise is a concern.
• All installations must comply with Building Regulations and be carried out by a Gas Safe or OFTEC-certified engineer.
• Average installation costs range from £2,800 to £5,000, depending on the system type, fuel, and location.
• Most modern outdoor boilers achieve efficiency ratings above 90% when correctly insulated and maintained.
• Reliable operation depends on frost protection, insulated pipework, and regular servicing.

What Is an Outdoor Boiler?

An outdoor boiler, also called an external boiler or outside boiler, is a fully functional central heating unit that operates outside the main structure of your home. Rather than being tucked away in a kitchen cupboard or utility room, it sits within a weatherproof casing, often mounted on an external wall or positioned on a concrete base nearby.

Despite its location, an outdoor boiler connects directly to your home’s central heating and hot water system just like an indoor one. Insulated pipework carries hot water through the wall into your radiators and taps. Most outdoor boilers are condensing models, designed to capture and reuse heat that would otherwise be lost through exhaust gases.

This ensures they meet modern efficiency standards while maintaining strong performance, even in cold conditions.

Two main fuel types dominate the UK’s outdoor boiler market: oil and gas.

• External oil boilers are especially popular in off-grid or rural areas where mains gas is unavailable.
• External gas boilers suit homes connected to the gas grid but short on interior space.

Some manufacturers also offer LPG and biomass-fuelled outdoor systems, appealing to those seeking sustainable or flexible heating options.

The key distinction between indoor and outdoor units lies in construction. External boilers come with insulated, corrosion-resistant housings, built-in frost protection controls, and sealed electrical components to withstand rain, wind, and fluctuating temperatures. When properly installed and maintained, their lifespan is nearly identical to indoor equivalents, often 12 to 15 years, provided the casing remains intact and drainage is well designed.

In essence, an outdoor boiler is not a different technology but a different configuration of the same trusted heating system.

Can You Legally Install a Boiler Outside in the UK?

Yes, but only if the installation meets the UK’s Building Regulations, follows manufacturer specifications, and is carried out by a certified engineer. Installing a boiler outdoors is perfectly legal when done correctly, yet it comes with stricter safety and insulation requirements than indoor systems.

Under Approved Document J of the Building Regulations, all combustion appliances (including boilers) must:

• Be installed in a suitable location with proper access for servicing.
• Have adequate ventilation and flue clearance to discharge combustion gases safely.
• Be protected against frost and weather conditions that could impair performance.
• Comply with the minimum efficiency standards: 86% for gas and 85% for oil-fired boilers.

If you’re using mains gas, the work must be completed by a Gas Safe-registered engineer. For oil-fired systems, an OFTEC-certified technician is required. These certifications aren’t optional; they’re legal safeguards designed to ensure the installation meets safety, emissions, and environmental requirements.

Homeowners must also ensure that:

• Flue terminals are placed at least 300 mm from any openings into the home and directed away from windows or air vents.
• Outdoor pipework is appropriately insulated to prevent freezing.
• The boiler casing is watertight, corrosion-resistant, and securely mounted.
• There is safe drainage for condensate, with frost protection for external piping.

Failing to meet these standards can result in non-compliance notices, warranty voids, or even dangerous carbon monoxide leakage.

Homeowner checklist for outdoor boiler legality:

• Confirm the installer is Gas Safe or OFTEC registered
• Verify compliance with Approved Document J
• Ensure frost protection and insulation are in place
• Check that flue clearances meet required distances
• Notify local Building Control if planning a major relocation

With these conditions met, an external boiler can be just as compliant, safe, and efficient as any indoor system, provided it’s adequately protected against the elements.

Advantages of Installing an Outdoor Boiler

Placing your boiler outside the home brings several practical and lifestyle advantages, particularly for properties where indoor space is limited or noise is an ongoing concern. When correctly installed, external boilers deliver the same heating performance as internal systems while offering added flexibility and convenience.

1. Frees Up Valuable Indoor Space

For smaller UK homes, where the average floor area continues to fall below 70 m², every square metre counts. Relocating the boiler outdoors can free up enough room for a utility cupboard, storage area, or even a small workspace. This makes outdoor boilers especially appealing for flats, modern townhouses, and compact rural homes.

2. Quieter Operation

Even the quietest boilers produce a low hum during operation. By moving the unit outside, you eliminate this background noise. The result is a quieter kitchen, hallway, or airing cupboard, an improvement you’ll notice most during nighttime cycles or in open-plan living spaces.

3. Easier Access for Servicing

Engineers can reach outdoor boilers directly without entering your home, simplifying maintenance and annual inspections. This convenience is particularly valuable for rental properties or households where privacy or cleanliness is a concern.

4. Improved Safety and Air Quality

With the combustion process taking place outdoors, the risk of carbon monoxide exposure inside the property is greatly reduced. Flue gases are vented safely into open air, and any leaks or exhaust malfunctions occur away from living areas. This configuration can also help maintain better indoor air quality.

5. Reduced Risk of Water Damage

Internal leaks can cause expensive water damage to floors or walls. An external boiler, properly sited and drained, eliminates that risk. Many units include built-in condensate traps and external drainage systems that direct water safely away from the property.

6. Compatibility with Renewable Systems

Some homeowners choose to pair outdoor boilers with solar panels or air-source heat pumps. Since the boiler is already external, integrating hybrid systems becomes simpler and often more efficient. This setup can help lower fuel consumption and reduce overall emissions.

When professionally installed and protected from frost, an outdoor boiler performs just as efficiently as an indoor model while offering clear lifestyle and safety benefits. The trade-offs include exposure, cost, and maintenance, which are worth exploring before committing to the switch.

Disadvantages and Limitations of Outdoor Boilers

While outdoor boilers offer real space and safety benefits, there are also challenges that homeowners must weigh before choosing one. Understanding these drawbacks helps ensure the installation remains efficient, durable, and compliant over time.

1. Higher Installation Costs

Fitting a boiler outdoors can be more expensive than installing one inside. The extra cost often comes from the need for insulated pipework, frost-protection controls, and weatherproof housing. Longer pipe runs can also mean higher labour costs and materials.

2. Exposure to Weather Conditions

Even with protective casing, external boilers face more wear from rain, frost, and temperature fluctuations. Over time, this exposure can affect components such as seals, sensors, and electrical connectors. Without routine maintenance, the unit may require earlier part replacements than an indoor equivalent.

3. Heat Loss in Pipework

When hot water travels from an outdoor unit through buried or external pipes, there’s a small amount of unavoidable heat loss. Proper insulation reduces this, but older or poorly installed systems may lose up to 5–10% efficiency through unprotected pipes during cold months.

4. Limited Range of Models

Not every boiler model is suitable for outdoor installation. Most manufacturers only offer a few external versions in their product lines, typically among oil-fired or LPG models. This reduces flexibility when comparing features, output sizes, or efficiency ratings.

5. More Complex Maintenance in Harsh Climates

Although outdoor access makes servicing easier, extreme weather can complicate repairs. Heavy rain or snow can limit engineer access, and very low winter temperatures can cause frost issues even in insulated units if power to the frost protection system fails.

6. Aesthetic Considerations

Outdoor boilers can be visible from gardens or driveways. While most modern casings are compact and neutral in colour, some homeowners prefer to install a protective shelter or decorative screen to blend the unit into the exterior setting, which is an additional cost and consideration.

When properly planned, these limitations don’t outweigh the benefits, but they do require forethought. Factoring in insulation, casing quality, and professional installation ensures your outdoor boiler remains efficient and weather-resistant for many years.

Outdoor Boiler Types Explained

Outdoor boilers are built around the same core heating technology as indoor systems, but the way they’re fuelled and constructed varies by type. Understanding these differences helps homeowners choose the most efficient, cost-effective, and climate-appropriate option for their property.

Below is a quick comparison of the main outdoor boiler types available in the UK, covering their best applications, performance ranges, and distinctive features.

Boiler Type	Typical Use	Key Features	Efficiency Range
Oil-Fired External Boilers	Ideal for off-grid rural homes with no mains gas connection.	Fully weatherproof casings, built-in frost protection, and high-output models suitable for large properties.	90 – 95 %
Gas External Combi Boilers	Suited to small and medium homes with mains gas.	Compact design, quick hot-water delivery, lower running costs, compatible with smart controls.	92 – 94 %
LPG External Boilers	Common in rural areas without a direct gas supply.	Uses bottled or bulk-stored LPG, similar efficiency to gas models, and flexible siting.	90 – 93 %
Biomass or Wood-Pellet Boilers	Best for eco-focused or off-grid households.	Renewable fuel source, large storage requirements, and eligible for some green incentives.	85 – 90 %

Oil-Fired External Boilers

Oil models dominate the outdoor boiler market, offering high output and reliable performance in cold, rural settings. Brands such as Worcester Bosch, Grant, and Warmflow produce durable, weatherproof units with corrosion-resistant casings. Their efficiency often exceeds 90 %, and they operate independently of the gas grid, making them ideal for countryside homes.

Gas External Boilers

For homes connected to the gas network but short on indoor space, external gas combi boilers provide a tidy solution. They deliver both heating and hot water on demand, without the need for an internal cylinder. Units like Viessmann Vitodens or Ideal Logic Max external-kit versions maintain full condensing performance even in cold conditions, provided frost protection is active.

LPG Boilers

LPG systems mirror gas boiler design but draw fuel from an on-site tank or cylinders. They’re often used in park homes or properties far from the mains grid. Outdoor installation simplifies storage and ventilation, although LPG costs per kilowatt are typically higher than gas.

Biomass Boilers

Outdoor biomass boilers burn compressed wood pellets or logs to generate heat. While they require more space and maintenance, they appeal to homeowners seeking a renewable alternative with a lower carbon impact. A weatherproof housing keeps both the boiler and feed system protected from moisture.

Top Outdoor Boiler Models in the UK (2025)

Here are some noteworthy models of outdoor/external-ready boilers (or external variants) that homeowners in the UK should consider. These aren’t exhaustive, but represent solid options across popular fuels and outputs.

1. Worcester Bosch Greenstar Heatslave II External Oil Boiler

The Greenstar Heatslave II External remains one of the most reliable outdoor oil boilers available in the UK. Designed by Worcester Bosch, a leading domestic heating brand, it combines high efficiency with exceptional durability.

Its corrosion-resistant housing protects components from rain, frost, and UV exposure, making it ideal for exposed rural properties. The built-in frost thermostat and robust casing maintain stable performance even in sub-zero temperatures.

With outputs from 12 kW to 32 kW, it comfortably meets the needs of most medium-to-large homes while freeing up valuable indoor space.

2. Grant Vortex Pro External Oil Boiler

Grant’s Vortex Pro External range is purpose-built for outdoor installation, combining condensing efficiency with low-emission Blue Flame technology. It achieves high seasonal efficiencies and has a durable powder-coated external casing and fully sealed electronics.

Each model includes integrated frost protection, high-grade insulation, and a simplified flue connection for straightforward servicing. Available in both combi and system variants, it’s a trusted choice for off-grid homes prioritising reliability.

The quiet operation, compact footprint, and strong after-sales support through Grant UK make it a favourite among professional installers.

3. Warmflow Agentis External Combi Oil Boiler

The Warmflow Agentis External Combi brings practicality and performance together for homeowners seeking instant hot water without a separate cylinder. It offers outputs from 15 to 33 kW and includes an easy-access service door, high-density insulation, and a durable, weather-resistant casing.

The model’s patented Blue Burner technology delivers quiet, clean combustion and low NOx emissions. Designed and built in the UK, the Agentis range is known for its simple installation process and excellent long-term efficiency.

Its compact design suits both rural cottages and modern extensions that lack indoor utility space.

4. Central Boiler Classic Edge Outdoor Wood-Fuelled Boiler

For households seeking renewable heating, the Central Boiler Classic Edge provides a fully outdoor, biomass-fuelled alternative. This American-built but UK-available unit burns wood logs or pellets inside a high-efficiency stainless-steel firebox, transferring heat through water to the home’s radiators or underfloor system.

It’s housed in a heavy-gauge insulated casing designed for year-round outdoor exposure. Emissions are reduced through advanced gasification technology, and fuel costs can be considerably lower for rural properties with access to wood.

The Classic Edge is larger than oil or gas models but offers outstanding sustainability and long-term fuel savings.

Installation Costs and Key Factors

Outdoor boilers cost slightly more to install than indoor systems, primarily due to additional weatherproofing, insulation, and external groundwork. However, the long-term benefits, like quieter operation, reclaimed space, and simplified servicing, can make the extra expense worthwhile when properly planned.

Average Installation Costs

For most UK households, the total cost of fitting an outdoor boiler typically ranges between £2,800 and £5,000, depending on the type, size, and fuel source. Biomass or wood-fuelled systems can reach £8,000 or more due to larger components and storage requirements.

Boiler Type	Average Installed Cost (UK)	Notes
Gas External Combi	£2,700 – £3,800	Compact and efficient; ideal for small homes
Oil External Combi	£3,000 – £4,500	Common for rural off-grid properties
LPG External	£3,000 – £4,000	Slightly higher running costs than gas
Biomass / Wood	£6,000 – £8,500	Renewable option; higher upfront investment

Key Cost Factors

1. Distance from Property: The farther the boiler sits from the main building, the higher the cost of trenching and insulated pipework. Each additional metre of buried pipe adds to the price in materials and labour.
2. Groundwork and Base Preparation: Outdoor boilers must sit on a level, non-combustible surface such as a concrete plinth or paving slab. Preparing this area will cost you a few pounds.
3. Frost Protection and Insulation: External pipe runs need thick lagging and, in cold regions, trace heating cables to prevent freezing.
4. Flue and Ventilation: A correctly sited flue must meet clearance rules under Approved Document J. Angled or extended flue kits can add extra costs.
5. Accessibility and Property Layout: If the installation requires long pipe routes, tight access, or complex rerouting of fuel lines, labour costs may rise significantly.
6. Installer Accreditation: Hiring a Gas Safe or OFTEC engineer ensures compliance and warranty protection, and professional certification usually commands higher labour rates per day.

Example Cost Scenarios

Scenario	System Type	Approx. Total Cost (Installed)
2-bed flat with limited space – gas combi moved outside	Gas External Combi	£3,000
4-bed rural home, off-grid heating upgrade	Oil External System	£4,200
Detached eco-home using renewable fuel	Biomass Outdoor Boiler	£7,800

While upfront costs are higher, these systems often deliver equal or better efficiency than indoor boilers. The extra insulation and weatherproofing also protect long-term performance, keeping operating expenses stable over the boiler’s lifespan.

Frost Protection and Insulation Requirements

The UK’s variable climate makes frost protection one of the most critical aspects of an outdoor boiler installation. Even the most efficient external system can fail if exposed pipework or condensate lines freeze. Proper insulation, intelligent controls, and safe siting are essential to maintain steady performance throughout winter.

Why Frost Protection Matters

Outdoor boilers rely on water circulating through pipes between the unit and the home. When temperatures drop below freezing, standing water in these pipes can solidify, blocking circulation and potentially cracking components.

A frozen condensate pipe is one of the most common causes of winter breakdowns. The risk is high in northern and rural areas where overnight temperatures often fall below zero for extended periods.

Built-In Protection Systems

Most modern external boilers include automatic frost protection controls. These activate the burner or circulation pump when sensors detect low temperatures, preventing internal components from freezing. Some models also have thermostatically controlled casing heaters, which maintain a safe internal temperature without wasting energy.

For added reliability, always ensure the boiler’s power supply remains connected. Switching it off during a cold spell can turn off these protective systems.

Pipework and Lagging

Any external or underground pipes carrying heating water or condensate must be insulated with closed-cell lagging rated for outdoor use. The insulation should cover all joints, bends, and exposed valves.

For high-risk areas, such as condensate drains or long outdoor pipe runs, installers often use trace heating cables that automatically warm the pipe when frost is detected. This extra layer of protection typically costs between £200 and £400, but it can prevent costly repairs.

Safe Routing and Drainage

All outdoor pipework should be positioned with a gentle downward slope to allow water or condensate to drain freely. Standing water increases the chance of freezing, so careful routing is crucial. Condensate lines must discharge into a safe drain or soakaway, protected by frost-resistant insulation and securely clipped to prevent sagging.

Winter Maintenance Tips

• Inspect insulation every autumn for gaps, cracks, or dampness. Replace any damaged lagging immediately.
• Check the power supply to frost protection systems before the first cold snap.
• Keep the boiler casing clear of debris or snow buildup to allow air circulation around vents and flues.
• Schedule servicing before winter to confirm all sensors, thermostats, and drain lines function correctly.

Common Problems and How to Prevent Them

Even the best outdoor boilers can experience issues if exposed to harsh weather or if maintenance is neglected. Fortunately, most common problems are easy to prevent with regular checks, proper installation, and basic seasonal preparation. Below are the main issues UK homeowners encounter, along with practical steps to avoid them.

1. Frozen Condensate Pipes

One of the most frequent winter faults is a frozen condensate pipe. This small plastic drain carries condensed water away from the boiler. When temperatures fall below zero, water inside the pipe can freeze, triggering a lockout.

Prevention:

• Use 32 mm diameter piping where possible for outdoor runs.
• Insulate the entire length with weather-resistant lagging.
• Fit trace heating cables to maintain flow during cold spells.
• Ensure the pipe runs downhill with no dips or standing water.

2. Blocked or Obstructed Flue

Outdoor boilers rely on clear flue terminals to vent combustion gases safely. Debris, leaves, or even nesting birds can obstruct airflow, causing the boiler to shut down or run inefficiently.

Prevention:

• Position the flue at least 300 mm from walls, fences, or vegetation.
• Fit a flue guard if the outlet is near ground level.
• Check and clean the terminal every few months, especially before winter.

3. Water Leaks from Pipe Joints

Temperature changes cause metal and plastic pipes to expand and contract. Over time, joints and seals can loosen, leading to small leaks that reduce pressure or waste heat.

Prevention:

• Inspect all external joints and valves each autumn.
• Reseal or tighten connections showing signs of corrosion or dampness.
• Apply weatherproof joint sealant designed for heating systems.

4. Faulty Frost Thermostat

If the frost thermostat fails, the boiler’s automatic protection system may not activate during freezing weather, putting the entire system at risk.

Prevention:

• Test the thermostat during annual servicing.
• Keep the power supply switched on at all times.
• Replace sensors showing inconsistent temperature readings.

5. Casing Corrosion or Rust

Outdoor boilers are in constant contact with moisture, making casing corrosion inevitable without routine care. Rust or flaking paint can eventually expose the internal components.

Prevention:

• Wash the casing annually with mild detergent to remove dirt and salt residue.
• Touch up chipped paint using manufacturer-approved anti-corrosion coatings.
• Keep vegetation and soil at least 300 mm away from the casing to prevent damp buildup.

6. Loss of Boiler Pressure

Extended outdoor pipework or small leaks can cause pressure drops that stop the heating system from circulating water properly.

Prevention:

• Check the pressure gauge every few weeks; it should read between 1.0 and 1.5 bar when cold.
• Top up using the filling loop as directed in the manual.
• Investigate frequent drops, as they may indicate a hidden leak.

7. Electrical Moisture Damage

Condensation or rain entering through cracked seals can corrode wiring or short-circuit the control board.

Prevention:

• Inspect electrical gaskets and cable entries for cracks.
• Ensure all panels fit tightly and seal correctly.
• If moisture is detected inside the casing, have the system inspected immediately by a professional engineer.

Quick Troubleshooting Table

Problem	Likely Cause	Simple Fix
The boiler is not firing in cold weather	Frozen condensate pipe	Warm the pipe gently or fit trace heating
Repeated lockouts	Blocked flue or poor ventilation	Clear obstruction and check airflow
Sudden loss of pressure	Minor leak in pipework	Inspect joints, tighten, and repressurise
Frost light flashing	Faulty sensor or thermostat	Reset the boiler or call an engineer
Gurgling noises	Air in the system	Bleed radiators or call for service

Should You Install an Outdoor Boiler?

Installing an outdoor boiler is an excellent solution for many UK homes, but it’s not the right choice for everyone. The decision largely depends on your property layout, available space, fuel type, and tolerance for additional installation costs. Below is a guide to help you determine whether moving your heating system outdoors makes sense for your circumstances.

Ideal Scenarios for Outdoor Boilers

Outdoor boilers perform best in homes that meet one or more of the following conditions:

• Limited indoor space: If your kitchen, airing cupboard, or utility room is cramped, relocating the boiler outdoors immediately creates valuable living area.
• Rural or off-grid properties: Homes without mains gas access benefit from oil or LPG outdoor models, as they integrate easily with external fuel storage tanks.
• Detached and semi-detached homes: Houses with outdoor access on one or more sides make installation simpler and provide suitable ventilation clearance.
• Noise sensitivity: If you prefer a quieter indoor environment, external placement eliminates operational noise.
• Frequent servicing needs: Landlords or homeowners who want easy access for engineers without home disruption will appreciate the convenience of the outdoor units.

When an Outdoor Boiler May Not Be Suitable

Certain conditions make an indoor boiler more practical:

• Flats and apartments: Most lack private outdoor space for safe flue placement and maintenance access.
• Highly exposed locations: Coastal or open rural areas face salt corrosion and wind-driven rain, which can shorten the lifespan of boilers if not carefully sheltered.
• Cold northern climates: Areas that regularly experience sub-zero temperatures require advanced frost protection, increasing running costs.
• Short pipe runs are impossible: If your home’s layout demands long underground pipework, the cost and heat loss may outweigh the benefits.

Final Thoughts

Outdoor boilers have become a smart, practical option for UK homeowners who value quiet efficiency and extra indoor space. They deliver the same heating performance as indoor systems while offering cleaner air, easier servicing, and better access for maintenance. When installed to professional standards and equipped with proper frost protection, they can run reliably through even the harshest British winters.

The key to long-term success is planning and compliance. Every outdoor installation must meet Building Regulation requirements, be carried out by a Gas Safe or OFTEC-certified engineer, and include full insulation, drainage, and electrical safeguards. Taking these steps ensures both safety and maximum efficiency over the system’s lifespan.

For homes with limited space or off-grid energy supply, an outdoor boiler can transform comfort and convenience. Choosing a high-quality model with strong weatherproofing and robust controls will help protect your investment for years to come. Before committing, request a detailed quote from a qualified installer and confirm that the system meets Boiler Plus and efficiency standards.

With the proper preparation and ongoing maintenance, an outdoor boiler isn’t just a practical addition but a long-term upgrade that makes heating smarter, quieter, and better suited to the modern UK home.

FAQs on Outdoor Boilers in the UK

Can Any Boiler Be Installed Outdoors?

No. Only models specifically designed or adapted for outdoor installation can be placed outside. These units include weatherproof casings, frost protection, and waterproof electrical components. Installing an indoor-only boiler outdoors would void its warranty and breach Building Regulations.

Do Outdoor Boilers Need Extra Insulation?

Yes. All external pipework, including condensate drains, must be insulated with frost-resistant lagging. In colder regions, many installers add trace heating cables to prevent freezing. Proper insulation ensures reliable winter operation and protects efficiency.

How Often Should an Outdoor Boiler Be Serviced?

At least once a year by a Gas Safe (gas/LPG) or OFTEC (oil) registered engineer. Annual servicing keeps frost protection, seals, and casings in good condition while maintaining the manufacturer’s warranty and performance.

How Much Space Do You Need for an External Boiler?

Most outdoor boilers need at least 300 mm clearance on all sides for servicing and ventilation, plus safe flue distances from windows and boundaries. The unit should sit on a level, non-combustible base such as a paving slab or concrete pad.

Are Outdoor Boilers Safe in Freezing Weather?

Yes, when fitted with proper frost protection. Most modern units have built-in thermostats that activate the burner or pump automatically in freezing conditions. Pipe lagging, trace heating, and continuous power supply are essential for reliable operation.

Sources and References

Cities and Health Journal – COVID and the home: the emergence of new urban home life practised under pandemic-imposed restrictions

GOV.UK – Approved Document J

Worcester Bosch – Greenstar Heatslave II External overview

Grant Engineering (UK) Ltd – Vortex Pro: External

Warmflow – Agentis External Combi

Central Boiler – Classic Edge HDX