Home Heating Options - UPDATED
Heating is a major consideration when building a new home. Here we explore some of the options.
In a utopian world, our homes would all be so well sealed and highly insulated that they would have no need for heating systems – saving money while reducing carbon emissions. The reality is that most existing housing falls far short of these high standards, and even new-build homes in the UK still usually require some form of heating.
A fabric-first approach for a new build will minimise heating costs
Applying a fabric-first approach, orientating new homes to maximise passive solar gain and carefully considering the most suitable heating solutions will dramatically minimise the cost of heating a new-build house. But to reach the government’s net zero carbon emissions target by 2050 will require some major changes in the way we heat our homes, using low-carbon alternatives.
The government has specified that no new homes will use gas boilers or be able to connect to the gas network after 2025 and plans to introduce a Future Homes Standard in England.
No new homes in the UK will use gas boilers or be able to connect to the gas network after 2025
After its introduction, new-build properties will need to have energy-efficient insulation and be fitted with low-carbon heating systems, such as air and ground source heat pumps. Existing homes will be affected for those building an extension or making thermal upgrades.
Building Regulations will also be updated in 2022, whereby all new homes must produce 31 per cent lower carbon emissions, compared to current levels.
Domestic RHI
The Domestic Renewable Heat Incentive (Domestic RHI) is a government financial incentive to promote the use of renewable heat. People who join the scheme and stick to its rules receive payments for the amount of clean, green renewable heat it’s estimated their system produces.
A financial incentive to promote the use of renewable heat
Eligible technologies include biomass (wood-fuelled) boilers, biomass pellet stoves with integrated boilers providing space heating, ground source heat pumps, air source pumps and solar thermal panels (flat-plate or evacuated-tube only) providing hot water for your home.
On April 1, 2021 changes to Domestic RHI regulations came into force, relaxing the requirement for accreditation applications to be submitted within 12 months of the eligible heating system’s commissioning date. Participants whose heating system was commissioned on or after 1 March 2019 will now be able to apply for the Domestic RHI, until the scheme closes to new applications (midnight on 31 March 31 2022).
Applicants who commissioned their eligible heating system on or after 1 March 2019 and were previously rejected for failing to meet the 12 month rule, can re-apply for accreditation to the scheme.
Heat Pumps
Heat pumps are expected to play a key role in delivering heat for properties that are built to the Future Homes Standard, with the government planning for 600,000 installations per year by 2028.
Heat pumps have some impact on the environment as they require electricity, but the heat they extract from the ground, air, or water is constantly renewed naturally. Running costs for all heat pumps will vary depending on several factors, including the size of the house, how well it is insulated and the required room temperatures.
Air Source Heat Pumps
An air source heat pump works in a similar way to how a fridge extracts heat, only in reverse. It can extract heat from the outside air even when the temperature is as low as -15°C. This can then be used to heat radiators, underfloor heating systems, or warm air convectors and hot water in your home. Radiators will need to be bigger than those used with a conventional boiler.
The Viessmann Vitocal 100-A space-saving monobloc heat pump for outdoor installation.
The unit can be fitted to a wall, or placed on the ground, and will need plenty of space around it to get a good airflow. Unlike gas and oil boilers, heat pumps deliver heat at lower temperatures over much longer periods. During the winter they may need to be constantly on to heat your home efficiently. An air source heat pump is usually easier to install than a ground source heat pump, though efficiencies may be lower.
Ground Source Heat Pumps
Ground source heat pumps extract heat from the ground which can be used to heat radiators, underfloor or warm air heating systems and hot water. A ground source heat pump circulates a mixture of water and antifreeze around a loop of pipe buried in the garden.
(Image: Kensa Heat Pumps)
A ground source heat pump extracts low-temperature solar energy stored in the ground or water using buried pipework and compresses this energy into a higher temperature.
Heat from below the ground is absorbed into the fluid and then passes through a heat exchanger into the heat pump. The ground stays at a fairly constant temperature under the surface, so the heat pump can be used throughout the year, even in the middle of winter.
Normally the loop is laid flat or coiled in trenches about two metres deep, but if there is not enough space in your garden you can install a vertical loop down into the ground to a depth of up to 100m for a typical domestic home. The ground needs to be suitable for digging a trench or a borehole and accessible to digging machinery.
Read columnist Gerald Cole Pump and Circumstance: The 10 big ‘buts’ of heat pump home heating (TOPPING OUT September 2021)
Boilers
Boilers account for around 60 per cent of domestic energy bills, so an efficient boiler can make a big difference. Specifying the correct size for a boiler is crucial, and there are several online guides to calculate your needs. The size of boiler will directly relate to the number of radiators and hot water usage in a home.
Gas
If you have mains gas, then a gas boiler is usually the cheapest heating option. However, gas is a fossil fuel and produces carbon dioxide (CO2). Prices are continuing to rise, and are likely to remain high. Gas boilers need annual servicing to remain efficient.
Electric
Technological advances have seen electric boilers gain popularity in new UK homes, often in rural areas without an oil or gas supply. These use electricity to heat water in a wet central heating system in the same way as a gas boiler and are not the same as ‘dry’ electric storage heater systems, which store electricity during off-peak periods to radiate through heaters later.
Electric boilers are light, compact, quiet, easy to install, low maintenance and almost 100 per cent efficient, as no heat is lost via waste gases through chimneys and flues. Converting an existing heating system is likely to be costly, however, and running costs will be higher than gas alternatives. They are also susceptible to power cuts. The amount of water they can heat is limited so electric boilers are not usually suited to larger properties.
Hydrogen
Hydrogen can be produced and used without creating climate-warming emissions, smoke or pollution, but producing, storing and moving hydrogen takes energy and resources. Carbon-free hydrogen, distributed via a modified gas network to hydrogen-compatible boilers, offers a potential route to reduce CO2 emissions. The only product is water, but the technology for producing large volumes of hydrogen sustainably is currently more expensive than alternative fuels.
Most of the Viessmann Vitodens domestic boiler range is ‘H2 Ready’ meaning it can operate with a blend of 20 per cent hydrogen added to the gas grid.
Biomass
Wood-fuelled or biomass boilers burn renewable fuel of logs, pellets or chips, and are connected to the central heating and hot water system. Installation costs can be high, but if you replaced electric heating with a wood-burning system you could make significant annual savings.
The boilers themselves also tend to be larger than gas equivalents and need to be compatible with existing plumbing. Biomass boilers are often best suited to those who are not connected to mains gas with at least six cubic metres of space for covered fuel storage, close to the boiler and accessible for delivery lorries. They require maintenance, need to be fed fuel and regularly cleaned of ash.
Micro-CHP
Micro-CHP stands for micro combined heat and power. This technology generates heat and electricity simultaneously from the same energy source, in individual homes or buildings. The main output of a micro-CHP system is heat, with some electricity generation, at a typical ratio of about 6:1 for domestic appliances.
A typical domestic system will generate up to 1kW of electricity once warmed up and the amount of electricity generated over a year depends on how long the system is able to run. Any surplus electricity generated can be sold back to the grid.
Domestic micro-CHP systems are usually powered by mains gas or liquified petroleum gas (LPG), however some models are now powered by oil or bioliquids, including biodiesel. Although gas and LPG are fossil fuels rather than renewable energy sources, the technology is considered a low-carbon technology because it can be more efficient than just burning a fossil fuel for heat and getting electricity from the grid.
For the householder, there is very little difference between a micro-CHP installation and a standard boiler.
For the householder, there is very little difference between a micro-CHP installation and a standard boiler. A micro-CHP unit should be able to replace an existing boiler as it’s roughly the same size. Servicing costs and maintenance are also estimated to be similar to a standard boiler – although a specialist will be required. For more information visit renewableenergyhub.co.uk.
Underfloor Heating
Underfloor heating systems are usually either warm water (wet) systems or electric (dry), and can be fitted in new or refurbished properties, single or multiple rooms in a house.
The entire floor effectively becomes a giant radiator, providing gentle, evenly distributed background heat and virtually eliminating cold spots, with no need for radiators. Underfloor systems are not designed to provide instant heat control, and the response times to heat up and cool down are far slower.
Pipes laid out for a wet UFH system
The most common method of fitting underfloor heating is to lay flexible plastic pipework under the floor slab or fixed under a timber floor. Pipes run to a manifold and typically a house will have several circuits, which enables zoned heating areas controlled by thermostats.
Unlike radiators, underfloor heating systems emit no noise and do not need to run at high temperatures. They can be powered using renewable energy such as ground source heat pumps and solar panels, for cheap running costs, and can save 15-40 per cent over traditional heating methods.
Although it can be more expensive to install underfloor heating than standard central heating, the day-to-day running costs are more economical.
Trench Heating
Trench heating is another solution when wall space is limited and is ideal for colder spaces, such as outside walls and glass bifolds. Trenches are dug within the floor and a simple convector unit with a grille is connected to the heating system. The grilles that cover the trench come in various designs and different materials.
When used against large windows, heat emitted from the trench restricts draughts, minimising heat loss and therefore increasing efficiency. It also prevents condensation building on the windows.
The trench’s width and depth determine the size of the heating element, as well as the amount of cooler air that can be drawn in through the grilles, warmed and then naturally convected back out into the room. Greater airflow, and consequently heat, can be achieved with the installation of a fan system within the trench. Rooms are heated evenly, which eliminates draughts and cold spots and provides an even, comfortable temperature. Dust does tend to accumulate in the trenches, which will need regular cleaning.
Top Tips for Installing Wet Underfloor Heating from Richard Harvey of Wolseley Plumb & Parts
Underfloor heating is a popular choice for new homes, not only as a luxury feature but also as a green option. It is well suited to low-carbon heat pumps which use electricity rather than gas or oil. Heat pumps are very efficient as they only heat water up to around 35-40°C, but are unsuitable for conventional radiators which need an optimum operating temperature of 70-80°C. UFH is also hidden under the floor. When it comes to installation here are a few tips:
Always fit the manifold first
Fitting the pipework before the manifold can cause the pipes to get entangled while connecting it all together. It’s best practice to fit the manifold first and then route one circuit at a time from the manifold’s flow to return. It’s also recommended to mark each circuit on the manifold to make it easier to identify which circuit goes to which room or zone.
Insulate the floor appropriately
Before any pipework is laid, there should be sufficient insulation over the base of the floor. This ensures the UFH system runs effectively and minimises heat loss. In new builds, Building Regulations require 100mm of insulation and 50mm for retrofit installations.
Pressure test the UFH system
Once a system is in place, it’s vital to pressure test the system using water rather than just air. This should be completed before any flooring or screed is laid. This is the chance to check for leaks and ensures pipes reach maximum expansion. With screed, it’s important to maintain the pressure until it has been fully laid and cured to prevent any cracking later. Pressure testing can be done by following these steps:
• Pressure test at 2 bar for 10 minutes and check for leaks.
• If no problem is found, test the system at 10 bar for another 10 minutes.
• If there are no leaks after that, leave the system pressurised, but reduce the pressure to between 3 and 5 bars until the screed goes down.
• After the screed is laid, the pressure should be reduced to the working pressure which is usually between one and two bars.
Prevent leaks with antifreeze
A new build project can take weeks or even months to complete. This means that UFH pipework could be laid well before the property is ready for habitation. The pipework will be open to sub-zero temperatures, leading to the water in the pipes freezing, causing them to weaken and even split. To prevent this add antifreeze to the water. This water can be flushed out of the system later and replaced.
Minimise the number of joints
Safeguard against leaks by minimising the number of joints in the system. With long, continuous pipes, there’s little chance of leaks. Pipe-in-pipe installations can add further protection. If a joint is needed, then this should be accessible through a junction box.
Richard Harvey is Commercial Director for Plumbing and Heating at Wolseley Plumb & Parts wolseley.co.uk.
This Beginner's Guide to Home Heating Options is from the November 2021 issue of SelfBuild & Design magazine.
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