Kitchens across Britain could look very different over the next few years after ministers were told that gas cookers should be banned. However I am not sure how they are going to police this?
A report from the Committee on Climate Change says that developers should be forced to install low-carbon heating systems so that Britain’s legally binding emission targets can be met.
This will mean gas boiler and gas fires will need to go to. We agreed at the Paris summit that we had twelve years to come off gas.
This would mean that newly-built homes would not be able to have gas boilers or stoves fitted, stopping them being connected to the gas grid.
The committee accepted that low-carbon heating systems and extra insulation would add up to £5,000 to the cost of a new home, which would also take longer to heat up. They would have to go to Air Source Heat pumps for most homes, larger properties with a good amount of land, they could use Ground Source Heat Pumps. However these can be quite costly.
But they insist that the gas ban in new homes needs to be enforced ‘by 2025 at the latest’ to cut 14% of total UK greenhouse emissions caused by household energy use.
The Home Builders Federation condemned the proposal, arguing that it would make houses harder to sell. This is true as consumers prefer what they know...gas boilers. To overcome this hurdle we need to become educated on the alternative.
Air Source Heat Pumps are more efficient than gas boilers. For example, a new gas boiler will have an efficiency of .92%. The Air Source Heat Pump will have to have a minimum efficiency of 2.5%.
An Air Source Heat Pump (ASHP) can be an efficient means of saving money and saving carbon emissions if carefully designed for space heating of an appropriately designed building.
The first priority should be to ensure that the building is well insulated (and well managed). All new buildings should have high insulation built in and be well constructed to minimise heat loss through air leaks.
Because an ASHP is more efficient when producing a lot of warmth – as opposed to a small amount of heat – the distribution system in the building should match this: a large area of underfloor heating distributing warmth is more efficient than a small area of radiators emitting high temperatures (and causing draughts).
ASHP – Coefficient of Performance – CoP
The key to the efficiency of a heat pump is the Coefficient of Performance: the “CoP”. In spite of the first law of thermodynamics, which tells us that energy can neither be created nor destroyed, an ASHP in a good installation can transfer up to three units of heat for each unit of electricity consumed. The heat pump is not creating this energy, but merely separating a medium temperature from the external air into warmth (which can be used for heating) and cold (which can be returned to the atmosphere).
The CoP will vary with each installation, but the lower the output temperature to the heat distribution system the higher the CoP will be. If an output temperature of 60°C is needed to heat radiators the CoP is likely to fall to level of only 2.0. If the heat distribution is to a well designed underfloor heating system that works well at an output temperature of 40°C then the CoP can rise to a level of 3 in the winter (and higher in the spring and autumn).
The input temperature is also critical to the CoP of the heat pump. The higher the input temperature from the air, the lower the amount of work needed from the heat pump, the higher the CoP will be. In fact, the critical factor is the “uplift” between the source temperature and the output temperature. Therefore an ASHP is more efficient in the autumn or the spring than in the depths of winter.
Advantages of Heat Pumps
Heat pumps save money. Heat pumps are cheaper to run than direct electric heating. They are cheaper to run than oil boilers and can be cheaper than running gas boilers. Because heat pumps can be fully automated they demand much less work than biomass boilers.
Heat pumps save carbon emissions. Unlike burning oil, gas, LPG or biomass, a heat pump produces no carbon emissions on site (and no carbon emissions at all, if a renewable source of electricity is used to power them).
Heat pumps save space. There are no fuel storage requirements.
Heat pumps are safe. There is no combustion involved and no emission of potentially dangerous gases. No flues are required.
Heat pumps require less maintenance than combustion based heating systems.
Heat pumps can provide cooling in summer, as well as heating in winter.
Advantages of Air Source Heat Pumps
The chief reason for using an ASHP rather than a Ground Source Heat Pump (GSHP) is that they are cheaper and quicker to install, because you save the cost of installing a "ground loop heat exchanger" in the ground.
Disadvantages of Air Source Heat Pumps
An ASHP has no access to an interseasonal heat store in the ground - it cannot take advantage from the fact that higher temperatures are available from the ground in winter than from ambient air. It is therefore less efficient in winter and suffers from a lower coefficient of performance. It needs to spend energy (and generates noise) on a fan system to blow air across its heat exchangers. It also needs to incorporate a defrost cycle to prevent ice forming on its heat exchangers in cold conditions (when heat is most needed).
So in reality, the Home Builders Federation need to get on board and inform the consumer (potential home buyer). I think the problem is the Home Builders Federation don't really want the extra expense of fitting Air Source Heat Pumps. In rural areas where there is not mains gas supply they are still fitting Night Storage Heaters!
I think moving forward the issue is not the building of new homes, it is our existing housing stock that is the problem. There are so many existing properties that have solid brick construction. According to the English Housing Survey 2008 (https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/6703/1750754.pdf), 27% of the existing housing stock have solid walls. The focus need to be on getting these houses insulated. External wall insulation is expensive, for example for a mid terraced house the cost is upwards of £8,000.00 and even higher for an end terraced property. As a surveyor I come across so many houses that don't even have their lofts insulated, or have nominal amount of insulation. Insulation is key in reducing carbon emissions!