Underfloor Heating with Gas Boilers - Pros, Cons & Costs

Heating rooms and spaces is a basic requirement in UK homes, for which boilers are an essential component of the heating system. Traditionally, a heating system comprises boilers, radiators, and a network of pipes for transporting hot water from the boiler to the radiators. While gas boilers are commonly used in most of the UK homes, electric boilers are also in use, especially in areas where gas is not available.

In recent years, with the introduction of advanced technologies, "Underfloor Heating" (UFH) has also gained popularity, replacing conventional heating systems that traditionally use radiators. Although in theory, an Underfloor Heating System works without the use of radiators, both can be used simultaneously, especially when redesigning the heating system of an existing building. When converting a home from a conventional heating system to underfloor heating, the most common question is whether UFH can be used with a gas boiler. Simultaneously, the question arises whether one should go for it, given the upfront and ongoing costs.

In this blog, we will explore everything you need to know about installing an underfloor heating system with a gas boiler, including its pros, cons, and costs.

Under Floor Heating System (UFH) – An Overview

Under Floor Heating system, also known as Wet Underfloor Heating System, as the name suggests, is a system of heating rooms and spaces in a home that provides heat from under the floor, instead of through radiators. UFH works by circulating hot water through pipes running across the room, laid either on the floor or beneath it.

While the main part of the central heating system remains a boiler, the only difference is that radiators are replaced with a circuit of pipes, laid underneath or within the floor. Unlike the conventional radiator-based heating system, which works best at a temperature range of 60 to 75°C, a UFH can typically run successfully at a lower flow temperature, maintained at 30 to 50°C. Normally, this system comprises a mixing valve (also known as a blending valve) or an actuator (also known as a manifold). The purpose of an actuator or manifold is to control and lower the flow temperature towards the circuits of the UFH system.

Can It Be Connected with A Gas Boiler?

The simple answer to this vital question is “Yes, an underfloor heating system can be connected with a gas boiler”. However, in most cases, some modifications and adjustments would be required for this purpose.

The primary purpose of connecting a gas boiler to UFH is to heat water, which can then be used to heat a room via a circuit of pipes laid beneath the flooring. If your home already has a regular or combi boiler and you want to connect it to the underfloor heating system, it can be done. Still, you may have to make a few minor adjustments to ensure it works perfectly with the upgraded UFH system and replace the radiators.

Modification and Adjustments Required 

To make a Combi Boiler compatible with underfloor heating, the key requirement is a two-port valve. This valve allows the combi boiler to supply hot water separately to the central heating system and underfloor heating. This is critically important for the proper functioning of the entire home heating system connected to the combi boiler. In the absence of this minor modification, the boiler would overheat because both the central heating and underfloor heating would run simultaneously. In this scenario, the boiler will be overloaded.

Mixing UFH With Radiators

While underfloor heating is meant to replace radiators, both can be used simultaneously in different parts of a home, connected to the same boiler.  For this, the home needs to be divided into various zones based on the heating system to be used. In this context, ideally, the upper floors can be heated with radiators, whereas the ground or lower floors can be converted to underfloor heating. Based on a home's requirements and preferences, both systems can sometimes be used on the same floor. For example, a living room can be heated with underfloor heating, while the kitchen on the same floor may be heated with radiators.

IMPORTANT

When converting the existing heating system to underfloor heating, always consult a Gas Safe engineer or a qualified heating engineer to confirm whether the existing boiler is large enough to meet the heating requirements after conversion.

What are the Pros of Connecting Underfloor Heating to a Gas Boiler?

• This type of heating is typically ideal for living rooms and bathrooms.
• An underfloor heating system is best for even, comfortable warmth, as it radiates heat evenly from the floor up into the room.
• Since the heat is evenly distributed throughout the room, there is hardly any chance of a cold pocket.
• It saves considerable space, especially wall space, which would otherwise be taken up by radiators.
• Since the UFH system distributes heat evenly throughout the room, it is ideal for achieving the same warmth at a lower water temperature. It helps the boiler to run closer to its optimum condensing efficiency. It is a more critical factor for modern boilers. In this way, the boiler's overall efficiency is increased.
• The UFH system is also ideal for and more effective in large spaces because radiators often struggle to provide evenly distributed warmth in open-plan spaces. 
• Since there are no moving parts in the hot water circulation circuits beyond the actuators and pumps, the lifespan is far longer than that of a radiator-based heating system. In this context, it also requires less or even no regular maintenance. Some experts believe that, due to this factor, the lifespan of underfloor heating pipework may exceed 20 years.

What are the Cons of Connecting Underfloor Heating to a Gas Boiler?

• While an underfloor heating system connected to a gas boiler is typically highly efficient, it results in more carbon emissions than a system connected to an electric heat pump. 
• It may involve higher running costs, depending on the energy prices. 
• Upfront installation costs are often higher than those of a conventional radiator-based heating system.
• Converting the existing heating system to underfloor heating might be disruptive and highly expensive. Hence, the retrofitting costs may rise considerably. However, this may not always be the case with a new build property. 
• The compatibility of the existing boiler may be another drawback when converting the system to underfloor heating. It involves some fundamental engineering issues. To overcome this problem, one must hire a qualified heating engineer or a Gas Safe-registered engineer.
• It involves additional installations, such as a two-port valve or mixer, and additional controls, which may also affect the overall cost.
• An underfloor heating system takes longer to reach the desired temperature when heating. Similarly, it takes longer to cool down to the required temperature.
• Installation of an underfloor heating system is not feasible for some floor finishes, such as thick carpet or solid stone. These types of floor finishes drastically reduce heat transfer, badly affecting the overall efficiency.

What Is the Cost of Connecting Underfloor Heating to a Gas Boiler?

The actual cost of connecting UFH with a gas boiler may vary on a case-by-case basis, as it involves a variety of factors, such as system type, type of property, location, and labor cost:

1. Cost for New Build – Typically, the cost of connecting a gas boiler to an underfloor heating system ranges between £80 and £150 per m², depending on the type of floor finish. 
2. Existing Homes – The cost of connecting a gas boiler to the underfloor heating system in an existing home is somewhat higher, typically between £100 and £300, or even more, depending on the type of existing floor finish.

Conclusion 

In the UK, the underfloor heating system is gaining popularity, especially in new-build properties. For existing properties, the homeowners are often concerned about the very basic question of whether it can be connected with their existing gas boiler. Generally, there is no problem in doing so; any gas boiler, including regular and combi boilers, can be paired with the underfloor heating system, as the basic function of a boiler is to provide hot water for heating the rooms and spaces. 

Whether it ends up in a radiator or the circuit of circulation pipes, the basic function of the boiler remains the same: providing hot water. However, some alterations, modifications, and minor adjustments are essentially required to connect an existing gas boiler to the underfloor heating system. This can be achieved by hiring a qualified heating engineer, preferably a Gas Safe registered engineer.