Heat pumps are the most efficient way to heat an off-gas grid property. They utilise some really clever physics to convert electricity to heat at very high efficiency (anywhere from 250 to 450%). There are 2 main types of heat pump – air source and ground source, with very different benefits and costs. The bottom line is that heat pumps can really work for some homes, whilst for others they will be an expensive waste of time, so make sure you read up and make the right decision!
What type of heat pump?
Air source heat pumps are more compact and suitable for smaller urban properties, but a ground source heat pump is more efficient and will pay you more via the RHI. You can read more about the differences in this article.
Insulation a key factor
Insulation is absolutely key for a heat pump. If your property is poorly insulated, the heat pump will not be able to sufficiently heat the property. Make sure you get you loft and cavity walls insulated to the latest building regulations, or if you have an older solid wall property that you have installed solid wall insulation. More information on insulation for heat pumps can be found here.
What is the cost of a heat pump?
An average air source heat pump will set you back anywhere from £5,000 to £10,000, whilst a ground source system will be closer to £25,000. If you need to add in a wet central heating system as well, you will need to tack another £5,000 on to the price, dependant on the size of the house of course. You can read more on costing a heat pump here.
What funding is available for heat pumps?
Unfortunately you can’t use the Green Deal to get some help towards the initial cost, the reason being that the initial outlay should be recovered through the Renewable Heat Incentive (RHI) subsidy. The RHI will pay you a regular income for the system over 7 years, in some cases paying back around half of the initial costs, which means that if you can afford it up front, a heat pump can really pay back for you.
Expected returns on your installation
This will depend on what you were using before hand, but combined with the RHI the payback should be within 7 years of the initial investment.
What is the best setup?
Your heat pump should be installed in the property along with excellent insulation and ensuring there are no draughts or cold spots. You should also consider underfloor heating for your ground floor as an option instead of radiators, because underfloor heating works at a lower temperature – ideal for heat pump efficiency.
The Domestic Renewable Heat Incentive – what is it?
The Renewable Heat Incentive (RHI) is a government scheme that pays people that produce their own heating and hot water using renewable energy sources such as heat pumps or solar thermal panels.
The scheme has been launched in an effort to help the UK government meet its legal commitment to ensure 15% of the UK’s energy comes from renewable energy sources by 2020.
This scheme has been up and running in the commercial sector since November 2011, however the domestic RHI scheme kicked off in April 2014 for households in the UK. The Renewable Heat Incentive works in a similar way to the Feed-in Tariff (which is for domestic renewable electricity production); households in this case being paid based on the amount of renewable heat they produce.
There are currently 4 technologies that are eligible for the domestic renewable heat incentive
Solar heating (also known as solar thermal – only flat plate and evacuated tube solar panels are eligible)
The payments will be made quarterly for seven years and should cover a significant proportion, if not all of the initial installation costs.
Domestic Renewable Heat Incentive tariffs
Each of the renewable technologies eligible for the renewable heat incentive have different RHI rates associated with them, mainly because the cost of installing the different technologies varies considerably and the RHI payments are designed to help cover some or all of the initial install cost.
On the whole, the RHI rates have increased very slightly in line with inflation except for biomass boilers and wood pellet stoves with back boilers which have dropped considerably – the rates below are correct as of September 2018. These can change from quarter to quarter, depending on how many people claim the payments. This is known as ‘digression’. You can find current rates here.
The payments are made on a quarterly basis and last for a total of 7 years. In addition, the tariff amounts are RPI index linked, so as inflation increases over time, the tariff rates above will increase with it. The RPI increases will be applied to the rates on 1st April each year.
RHI Payments will last a total of 7 years
Much like with the feed-in tariff, once you sign up to the RHI you will be locked in at the tariff rate that you initially get – so if you installed a Ground Source Heat Pump today you would get a payment of 20.46p per kWh of renewable heat you produced for the next 7 years (although it will increase with the the RPI each year).
Since there is a finite pot of money available for the RHI payments, it is likely the current tariffs will get smaller over time (again much like the solar feed-in tariff) therefore if you are considering installing a renewable heating technology it is worth moving quickly to ensure you get the highest payment rate!
The government do a quarterly review of the RHI scheme and adjust the tariff amounts in line with the total RHI budget so as to control the costs. Therefore if you install a renewable heating system you will get (and lock in) a better rate potentially than someone who installs a renewable heating measure 2 years down the line.
RHI payments are estimated based on heat demand rather than Metered
Tariff payments will be deemed rather than metered, which means they will estimate the heat demand of the property and base the RHI payment on that. This means that it is paramount to install a heating system that is correctly sized; because if you install a more expensive, oversized biomass boiler (that creates more than you require), you will be paid the same through the RHI and potentially won’t recoup the additional unnecessary investment.
Likewise, there are ways to maximise your RHI payments!
For biomass boilers and wood pellet stoves, the RHI payment can be fairly easily calculated based on the heat demand of the property. This heat demand figure can be found right at the bottom of the Energy Performance Certificate (EPC) expressed in kWhs – so it is simply a case of multiplying £0.0674 x this number, which will give you the total annual payment.
For solar thermal, the MCS approved installer calculates the RHI payment. They will deem a figure that is the estimated contribution of the solar thermal to the home’s hot water demand, but the calculation is based on occupancy – the more people that reside in the property, the higher the payment – worth bearing in mind when you are speaking to your installer / green deal assessor.
For heat pumps (both ASHP and GSHP) the heat demand figure from the EPC is combined with the heat pumps estimated efficiency to calculate the RHI. Remember not all the heat produced by heat pumps is renewable, therefore only the part that is will receive RHI support.
The technical term for the estimated efficiency is known as the Seasonal Performance Factor (SPF) – and this tends to be somewhere between 2.5 and 4 (this is also sometimes referred to as the Coefficient of Performance or CoP). So an SPF of 3 for example, means that for every one unit (kWh) of electricity used, 3 units (kWh) of useful heat will be produced.
Therefore the RHI for heat pumps is calculated using the 2 formulas below:
1. Eligible Heat Demand = Total Annual Energy Demand x (1 – 1 / SPF)
2. Annual RHI = Eligible Heat Demand x RHI Tariff
Example calculation for Air Source Heat Pumps:
For a home with a heat demand of 25,000kWh installing an air source heat pump with a SPF of 3.5 the annual RHI payment would be:
Then multiply by RHI tariff (10.49p / kWh) = £1,873.20 per year
Only heat pumps with an SPF of 2.5 or more are considered renewable under the EU Renewable Energy Directive and only those that are considered renewable will be eligible for the RHI.
How long will my renewable heating investment take to pay back?
This is a difficult one to answer to be honest because it is so dependent on your home’s individual heat demand.
In terms of investment, you can expect to pay about £8,000 for an air source heat pump, £20,000 for a ground source heat pump, £8,000 for a biomass boiler and £4,500 for solar thermal.
If you can get an accurate view of the heat demand (from the EPC) then you should be able to calculate the annual payment from the domestic RHI, which multiplied by 7, will give you to the total payments to expect over this period.
With the investment figure and the total lifetime RHI return (comparing renewable heating to the next best alternative), you should be able to get a rough feel of the payback.
Eligibility requirements for the Domestic Renewable Heat Incentive
Renewable heating systems don’t come cheap – the domestic RHI makes these systems more affordable by offering a financial incentive based on the amount of heat they produce. However, there are quite strict eligibility criteria, so it is worth ensuring that you adhere to the rules to make sure you are entitled to the payments.
Which technologies are eligible for the domestic RHI?
As previously mentioned, the renewable heat incentive is available on installations of any of the following technologies:
Air source heat pumps (limited currently to those that heat water)
Biomass boilers
Wood pellet stoves with back boilers
Ground source heat pumps (this term also covers water source heat pumps, which are considered GSHP by RHI guidelines)
Solar thermal (only flat plate and evacuated tube solar panels are eligible)
Download the full list of eligible installations here.
Who is eligible for the domestic RHI?
The scheme covers single domestic dwellings (as soon as the heating system is providing heat to more than one property, you would need to look at the non-domestic RHI). It is open to owner-occupiers, private landlords, registered providers of social housing, third party owners of heating system and self-builders.
Note to private and social landlords: you will need to agree with the tenants that an annual servicing visit will be required to ensure the system complies with the detail set of requirements and continues to be eligible for domestic RHI payments.
New builds are not eligible for the RHI – this means the renewable heating system was installed in the home before it was inhabited for the first time.
You heating system needs to be on the Government approved list
In order to ensure eligibility for the RHI, you must make sure the renewable heating system you get installed is listed on the Governments product eligibility list (PEL) – you can download this here.
MCS accreditation is a must!
To be eligible for the scheme, the installers must adhere to the European Standard EN 45011. The Microgeneration Certification Scheme (MCS) adheres to this standard, therefore as a rule of thumb you need to ensure that the team installing your renewable heating system are MCS accredited and the kit being installed is also MCS accredited.
Equivalent schemes to MCS do exist, but don’t simply take your installers word for it that they adhere to EN 45011 – check all the relevant paperwork before getting any work done.
Getting a Green Deal Assessment is no longer required!
In early 2016, the Government changed the elegibility requirements for the RHI and one of those changes involved scrapping the need for the Green Deal Report. The EPC is still a requirement though – this needs to be dated within the last 48 months – and will be used to calculate your RHI payments.
If your EPC recommends loft and cavity wall insulation it must be installed before you apply and you’ll then need to get a new EPC that no longer recommends these measures. The reason for this is that heat pumps and solar thermal tend to produce hot water at lower temperatures than traditional gas central heating systems. This means that radiators and underfloor heating will be operating at cooler temperatures compared to regular central heating systems, therefore it is very important the house is really well insulated prior to having them installed. The insulation process should bring the heating requirements of your home right down.
I have received other grants to pay for the technology. Do I still get the domestic RHI?
DECC confirmed in 2013 that any public funding paying for the domestic renewable heating installation would be deducted from RHI payments made. In addition, where an installation was not at least in part paid for by the owner, even where the installation was funded from a private source, that installation will not be eligible for the domestic RHI. An installation which has been part-funded by the owner will be eligible.
I have already installed my renewable heating system – Can I still claim the RHI?
You must apply to join the Domestic RHI within 12 months of the commissioning date of the renewable heating system. This can be found on the MCS certificate. The team that run the admin side of the RHI at DECC offer very little wriggle room here (99 times out of 100 – zero wiggle room!) so make sure you apply within the stipulated timeframes.
Technology Specific Eligibility Requirements
Heat pumps
All heat pumps must have a Seasonal Performance Factor (SPF) greater than 2.5 to be eligible for the RHI. Heat pumps installed by legacy applicants will automatically be considered to have an SPF of 2.5, and will require a full assessment by an MCS installer to prove a higher SPF (which would lead to higher RHI payments – so may well be worth doing!)
If a heat pump is installed alongside another space heating system then a meter will need to be installed to gauge exactly how much heating is coming from the heat pump. RHI payments will be based on these meter readings rather than the estimated heat demand for the property.
Biomass boilers/wood pellet stove with back boiler
If a biomass boiler is installed alongside another space heating system then a meter will need to be installed to gauge exactly how much heating is coming from the biomass system. RHI payments will be based on these meter readings rather than the estimated heat demand for the property.
New installations of biomass boilers will need to meet strict air quality standards in relation to particulate matter and oxides of Nitrogen – as mentioned previously – legacy applications will not need to adhere to this.
If the air quality standards change in the future, you do not need to concern yourself with your installed boiler not meeting the standards.
To be eligible for the RHI, the fuel needs to be sourced from a supplier registered on the approved supplier list.
How do I apply for the domestic RHI?
The application process for the domestic Renewable heat Incentive is fairly simple, however numerous pieces of evidence (installation certificates, EPC, and photos for example) are required for the submission.
Since the RHI is funded out of a public kitty (through tax payers), it is important that the money being spent to subsidise the scheme is under the right level of scrutiny, hence the volume of evidence required.
Applying for the domestic RHI
Applications for the domestic RHI are made through the OFGEM website through the My RHI portal
However if you find the thought of carrying out this process a little too onerous, there are third party companies offering to complete this on your behalf, although obviously there is a charge for this service. The process genuinely is pretty easy though, so in our opinion certainly worth giving it a try yourself before getting this kind of company in!
The RHI is now closed to legacy applicants
If you are a new applicant (so the installation took place after the scheme launched), then you will be able to claim the RHI straight away.
Unfortunately the scheme has now closed to legacy applicants (i.e. those who installed their renewable heating system prior to the scheme going live in April 2014).
Can the set RHI levels be changed once I have applied?
The headline RHI tariff figures do change, like we have already seen for the biomass renewable heat payments, and as time goes on and the RHI budget gets used up, we expect further drops in the tariff to take place. The Government will look at the tariff levels every 3 months and adjust them accordingly – however if you are receiving the RHI – you have locked in to whichever rate was agreed at the beginning – this is the rate that you will receive for 7 years (although it will increase with RPI each year).
Is there anything else I need to know?
The government will run a “Metering and Monitoring Service Package”, which consumers can volunteer for. Data collected under this scheme will be shared by the Department of Energy & Climate Change (DECC) with the installer and consumer. Domestic RHI recipients who volunteer will receive £230 per year to have their heat pump installation monitored and £200 per year to have their biomass installation monitored.
Hybrid systems installed with a gas boiler or oil boiler will need to be metered, except solar thermal systems.
The system will need to be serviced annually in accordance with manufacturer’s instructions to ensure efficient running of the system.
Coefficient of Performance and Seasonal Performance Factor
February 28, 2014
When it comes to researching heat pumps, you will come across two terms constantly that you need to understand – Coefficient of Performance (often abbreviated to CoP) and Seasonal Performance Factor (abbreviated to SPF).
Understanding what these terms mean is absolutely key, since they reveal the efficiency of a heat pump. Obviously the more efficient the heat pump the better, since running costs will be lower, but also these values will have a direct impact on the amount you will receive via the renewable heat incentive!
The Coefficient of Performance of Heat Pumps
The Coefficient of Performance is a simple ratio of the heating provided by a heat pump to the electricity consumed.
In a heat pump, electricity is used to move heat from a cold reservoir to a hot reservoir in a very efficient way. How efficient? Where an electric heater converts 1kW of electricity into 1kW of heat, a heat pump converts that 1kW of electricity into 3 or 4 kW of heat.
It is easy to think that this is defying the laws of thermodynamics, but of course the heat from the pump is not being generated, it is simply being shipped from outside the property into the inside. The warmer the external heat source, the better, since there is less electricity required to get it up to a nice temperature.
The Coefficient of Performance therefore varies throughout the year – in the winter months, an air source heat pump will require more electricity to get the heat up to a comfortable temperature so the CoP will be relatively low (perhaps 2.5). In the summer the opposite is true; since the external temperature of the air is warm already, the heat pump doesn’t require much electricity to get the heat pump up to a nice temperature, so the CoP might be as high as 4 or more.
Now consider a Ground Source heat pump, this takes advantage of heat in the ground and uses a series of buried pipes to absorb the heat. Since the ground temperature has very little variation over the year, the CoP will likewise be relatively consistent.
Hopefully you can spot a problem with using CoP as the sole measure of heat pump efficiency – since there is massive seasonal variation we need a means of getting an average efficiency of the heat pump over a year, to be able to compare different heat pumps.
The Seasonal Performance Factor of Heat Pumps
As we have said, the temperature of the ground or air being used by the heat pump plays a key role in the system’s efficiency. The seasonal performance factor takes into account how well the pump works at both low and high temperatures, and is a far better reflector of how efficient your pump will be than the CoP.
It allows you to make calculations between different ground, air and even water source heat pumps, which is pretty fundamental since the variation in costs between the different units. For example we quote a guide price of £25,000 for a ground source heat pump, while an air source heat pump is far cheaper at just under £10,000. The SPF of a ground source heat pump could be as high as 4 over the year, while the SPF of an ASHP may be only just over the 2.5 mark. Depending on energy usage, this means that relatively quickly, opting for a GSHP could be a better decision based on energy savings.
Likewise, if you look at the calculation for the Renewable Heat Incentive – it takes into account the SPF, rewarding a heat pump that is more efficient through higher payments. You can see how to calculate the RHI here.
Good CoP, Bad CoP
As we have seen, the performance of a heat pump can vary wildly depending on a number of factors, but generally speaking ground source heat pumps can regularly be found on the market with a COP greater than 4. Air source heat pumps tend to be less efficient, and a COP over 3 is considered good. Comparing different air source heat pumps, it is worth bearing in mind that a heat pump with a higher CoP / SPF will cost more, and the same is true when comparing ground source heat pumps with one another.
Consider insulating your home before installing a heat pump!
February 13, 2014
A well insulated house is key prior to installing a heat pump
With the launch of the renewable heat incentive fast approaching, we are getting more and more interest in heat pumps.
Put simply a heat pump works by transferring heat from an (external) air or ground source into the home. There is no fuel burnt in a heat pump and therefore the efficiency losses in operating this technology are relatively small.
How does a heat pump work?
The science behind heat pumps is pretty similar regardless of whether the heat comes from the ambient air, the ground or even a water source. In the first instance a refrigerant liquid contained in the pump’s pipes is heated up by the heat source (even just be a few degrees), which causes it to evaporate and turn into a vapour.
This vapour is then fed through a compressor, which further drives up the temperature. This then travels through a heat exchanger, which transfers the heat from the refrigerant to water in the home. This heated water can then be used in the home for heating and hot water.
Water temperature versus traditional heating systems
In a traditional central heating system the water is heated when gas is burnt, which can very easily create boiling water, hence radiators can feel scalding to touch and showers can be too hot to stand under.
Conversely the majority of heat pumps currently in the marketplace are best suited for low temperature systems – so for example underfloor heating – 30-450c and radiators that operate at a maximum 550c.
In the case of ground source heat pumps, where the temperature under the ground is relatively consistent all year round, this is really no problem – the hot water can be produced to 550c even in the middle of winter at relatively high efficiency.
For an ASHP, where air temperature varies, this creates a problem. In the middle of the winter when the most heat is needed in the home, the Air Source Heat pump will have to be working very hard to get the water up to temperature – in fact, at this time of year, the Coefficient of Performance (CoP) of an ASHP in the winter can be less than 2, that means that for every one unit of electricity put in to power the heat pump you are getting 2 units of useful heat (an 85% efficient gas boiler has an equivalent CoP of 0.85, but gas is a quarter of the price).
The Key to getting the best out of a heat pump is a well-insulated house
This is a pretty simple idea, but essentially since a heat pump is going to be working at a low temperature, before you even consider installing one, you need to address the state of the insulation in the home. Basically you need to improve it so the heat loss through the walls, roof and floor is minimised, therefore the fact the home is heated to a lower temperature is no issue.
Loft insulation is a pretty easy one to get started with – ideally you are looking to install 270mm of wool insulation in the loft to get the required u-value of 0.16W/m2k. As a DIY job, this should cost you about £5.50 per m2, but getting someone in to do this could cost between £9.00 and £15.00 per m2.
Cavity wall insulation – if you home was built since 1935, chances are it will have cavity walls, which are really easy to insulate – they simply drill into the walls and inject them with insulation – this will require professional installation, but should cost approximately £8.00 per m2 of wall.
Solid walls are more problematic; homes with this type of wall construction need to be clad on the outside with insulation or have the insulation attached inside. This is a costly procedure and may cost upwards of £15,000. There is financial assistance to get this type of property insulated in the form of the ECO grant and also you can use Green Deal finance and the (early adoption cashback) to cover the costs of this.
Most new homes built since the late 90’s will already have more than adequate insulation, therefore a heat pump becomes an easy decision since these homes will retain the heat much better and be much better suited to low temperature heating systems.
Final Points to remember on heat pumps!
Below we have listed a few take home messages from this blog.
Heat pumps operate at lower temperatures – think 550c max.
Compare this with gas boilers, which create water at 850c comfortably.
During the winter an ASHP will need to use a lot of electricity to get the temperature of water up to 550c, so at this time (when heat demand is at its peak) there efficiency is far lower than that of an equivalent Ground source heat pump.
Before you consider investing in a heat pump, insulating your home is absolutely key.
Make sure an MCS approved installer carries out any heat pump installation, otherwise you won’t be eligible for the Renewable Heat Incentive.
If you are based in London and want to get a heat pump installed, we can help you through the process to ensure that you get a quality system installed by an MCS installer, as well as all the necessary documentation to get your hands on the Renewable Heat Incentive, so if you would like to know more, call us on 0208 144 0897.
Installing Underfloor Heating with Suspended Timber Floors
In our home energy surveys, we encounter some interesting properties on our travels. One property we recently Green Deal assessed, located in North London, was going through a major retrofit, including the installation of an air source heat pump with underfloor heating.
Underfloor heating we would say is a nice to have as the ability to walk on a nice warm floor even in the midst of winter is definitely a really pleasurable experience. In addition, provided you have a well-insulated property; it can be a much more efficient way of heating your property compared to using radiators. This is because the temperature the floor is heated to is much lower than trying to heat with radiators, hence less energy is required; and since heat rises a more even distribution of heat can be provided.
Now, the property in question was a Victorian semi in Primrose Hill, with solid walls and suspended timber floors throughout. Retrofitting underfloor heating and insulation on suspended floors involves a different process than if you are looking to do the same with a solid concrete floor so please bear that in mind as you read this article. The process for installing underfloor heating and insulation on a solid concrete floor can be found here.
Process of installing underfloor heating on a suspended timber floor
In this section we look the installation process for a wet underfloor heating system, although in practice you could also install an electric ‘dry’ system. We recommend going for a wet system as this is better suited to heating larger surface areas like your living room and kitchen.
Installing the insulation
1. Prior to thinking about expensive measures like renewables, you first need to insulate the envelope of the house (loft, walls and floors). In this instance it is an absolute must before starting the installing of the underfloor heating system. As mentioned the heating works at lower temperatures than conventional systems so it is imperative the heat they produce doesn’t escape, which will be the case if you get insulation.
As the photo shows, the first thing you do is fix some battens to the sides of the joists, whilst leaving enough headroom for the heating pipes and screed that will go above that.
2. Having put this in place you then install polystyrene boards like Celotex or Kingspan of variable thickness. The precise thickness of boards installed can vary from 25mm of insulation to 150mm of insulation as long as you leave a decent air gap between the boards and the ground to allow for ventilation and the prevention of damp
In the photo I made out the thickness to be 75mm, which was fixed between the joists of the whole floor area.
3. The next step is to install the heating pipes, which are then fixed to the top of the insulation boards as shown on the photo below. These underfloor coils need to be aligned close enough together to ensure there are no cold spots under the floor.
Applying a level of screed
4. This is then followed by a layer of screed (made of a combination of cement and sand), which is placed over the pipework to protect the pipes from collapsing when people stand or furniture is laid on the floor. To provide adequate protection and to ensure the floor isn’t too hot, the coils have to be buried with a decent level of screed material.
Floor Finish
5. A range of floor finishes can be applied to the screed layer including tiles, veneer or wooden boards. This entirely depends on your taste and preference. In my property example the home owner went for a veneer oak finish.
Underfloor heating with Renewables
It is also worth mentioning that underfloor heating works especially well with renewable heating solutions like air source heat pumps since they produce hot water at lower temperatures than traditional gas fired central heating systems. In addition since they are producing hot water at minimum cost once they have been installed they really do make the running of the underfloor heating system very economical.
If you have had a heat pump or solar thermal installed in the last couple of years give us a ring to see if you could benefit from the Renewable Heat Incentive which is a subsidy payment designed to help fund the installation of renewable heating solutions. Call us on 0208 144 0897 for more details.
Installing Underfloor Heating with Solid Floors
When we go out to do our Green Deal Assessments, we encounter some interesting properties on our travels. One property we recently Green Deal assessed, located in London, was going through a major refurbishment, including the installation of underfloor heating.
Underfloor heating if you have never tried it, is a real luxury; the ability to walk on a nice warm floor even in the midst of winter is definitely a most pleasurable experience! In addition, provided you have a well-insulated property; it can be a much more efficient way of heating your property compared to using radiators. This is because the temperature the floor is heated to is much lower than trying to heat with radiators, hence less energy is required and when heat rises a more even distribution of heat is achieved.
Now, the property in question was a 1975 town house in West Kensington, with cavity walls and solid floors throughout. Retrofitting underfloor heating and insulation on solid floors involves a different process than if you are looking to do the same with a suspended timber floor so please bear that in mind as you read this guide. The process for installing underfloor heating and insulation on a suspended timber floor can be found here.
Process of installing underfloor heating on a Solid Floor
In the following guide we look at installing a wet underfloor heating system, although you can install electric ‘dry’ systems.
Installing the insulation
1. Prior to laying the anything on the solid floor, you first need to insulate the envelope of the house (loft, walls and floors). This is an absolute must before starting the installing of the underfloor heating system. As mentioned they work at lower temperatures than conventional heating systems so it is imperative the heat the produce doesn’t escape, so we strongly recommend doing the insulation first, otherwise your new heating solution could essentially not work.
The first photos shows a roll of water proof membrane, which is laid out on the concrete floor. This acts as a vapour barrier that will also prevent damp from rising in the floor.
2. Having put this in place you can then install polystyrene boards like Celotex or Kingspan of variable thickness. The precise thickness of boards installed can vary from 25mm of insulation to 150mm of insulation. However on concrete floors the more insulation you put in, the more room height you sacrifice, although obviously the less heat will escape into the ground. It is vital that you don’t run the underfloor heating coils directly onto the concrete floor without first laying insulation otherwise the majority of the heat will be lost into the ground.
In the photo below I made out the thickness to be 75mm, which was added throughout the ground floor area.
3. The next step is to install the heating pipes, which are then fixed to the top of the insulation boards as shown on the photo below. These underfloor coils need to be aligned close enough together to ensure there are no cold spots under the floor.
4. This is then followed by a layer of screed (made of a combination of cement and sand), which is placed over the pipework to protect the pipes from collapsing when people stand or furniture is laid on the floor. To provide adequate protection and to ensure the floor isn’t too hot, the coils have to be buried within 65mm of screed.
5. A range of floor finishes can be applied to the screed layer including tiles, veneer or wooden boards. This entirely depends on your taste and preference. In my property example the home owner went for a carpeted finish, which meant carpet underlay went in before the carpet was rolled out.
Underfloor heating with Renewables
It is also worth mentioning that underfloor heating works especially well with renewable heating solutions like air source heat pumps or solar thermal since they produce hot water at lower temperatures than traditional gas fired central heating systems. In addition since they are producing hot water at minimum cost once they have been installed they really do make the running of the underfloor heating system very economical.
If you have had a heat pump or solar thermal installed in the last couple of years give us a ring to see if you could benefit from the Renewable Heat Premium Payment which is a cashback incentive to help fund the installation of renewable heating solutions. Call us on 0208 144 0897 or send us an email to Mailbox@TheGreenAge.co.uk
The Domestic Renewable Heat Incentive Tariffs (finally) confirmed!
July 22, 2013
After much waiting and considerable government deliberation, the feed-in-tariffs for the Renewable Heat Incentive scheme has finally been announced. This means that generating energy using alternative renewable sources such as heat pumps and solar thermal will now get you money through a similar feed-in-tariff system to those already in place for wind and solar. The scheme launches next spring.
Greg Barker, Climate Change minister says, “Investing for the long term in new renewable heat technologies will mean cleaner energy and cheaper bills. So this package of measures is a big step forward in our drive to get innovative renewable heating kit in our homes.”
“The uptake of microgeneration technologies under the Feed-In Tariffs scheme has shown that renewable technologies can move from niche to mass market in just a few years, and with the support of the domestic RHI, I hope that renewable heating technologies will see such success.”
You can take advantage of the scheme if you have had any of the technologies installed since 15 July 2009. Those applying will also need to carry out a Green Deal assessment; which assesses a property’s energy efficiency and recommends suitable energy saving measures, the Department of Energy and Climate Change (DECC) says. In order to claim the incentive, householders must also ensure that their home has a minimum 250mm of loft insulation and cavity wall insulation if appropriate.
The Renewable Heat Incentive Tariffs
The generation tariffs for each technology are as follows:
Solar thermal (evacuated tube and flate plate) – at least 19.2p/kWh*
Ground source heat pump – 18.8p/kWh
Biomass boilers and biomass pellet stoves with a back boiler – 12.2p/kWh
Air source heat pumps (air-to-water) – 7.3p/kWh
This means that for every kilowatt hour of energy you produce using your renewable system, you will get a payment as above. Of course, these technologies do have high installation costs, but there is assistance available to help with this. Until next march you can take advantage of the Renewable Heat Premium Payment, which has been running for some time now, where you can get a lump of money towards the costs of installation, dependent upon the technology in question:
Ground source heat pumps – £2,300
Biomass boiler – £2,000
Air source heat pumps – £1,300
Solar thermal – £600
You can also get a Green Deal loan to help pay for the cost of these measures, for which you will require a Green Deal Assessment (as mentioned a prerequisite of the incentive anyway). Most of these technologies, just like solar PV already, offer a great way to move yourself away from dependence on the grid, and cut your fuel bills. The payback really could be worth it, so think about booking an assessment and getting yourself ready for the scheme when it starts.
Likely Returns to expect from the Renewable Heat Incentive
In terms of returns Steve Munday, MD of SMC solar ltd said “Running the numbers for an Air Source Heat Pump I can conclude that you will get around £8,000 back on a £9,000 investment (without considering fuel cost savings).Both these figures assume that a retro-fit to an existing radiator system does not require any upgrade. So the reality is that homeowners may need to budget a little extra for upgrading their radiator system. The amount of this will only become known after detailed room-by-room heat loss assessment.
Like with the Feed-in-tariffs to incentivise solar panels, the grants will be rapidly reduced over the ensuing years deliberately to incentivise and reward early investors.This really is a ‘no-brainer’ for anyone with a moderately old oil boiler. Even owners of gas systems are eligible although the fuel cost benefit will not be so pronounced until gas prices rise, as they inevitably will. ‘The early bird will catch the worm”
So there you have, act quickly to ensure you benefit from these generous tariff payments! If you want to learn more about the renewable heat incentive please visit our dedicated page here.
Air source heat pumps convert heat energy from the air to provide heat and hot water for dwellings. They run on electricity, but are incredibly efficient (in some cases 300% or more), which means that for every one unit of electricity used, they produce 3 units of useful heat.
If you compare that to a brand new boiler which is 90% efficient (1 unit of gas produces 0.9 units of useful heat), you can quickly see why these systems are so popular. In fact, if you don’t have access to mains gas, heat pumps are definitely the way to go to fulfil your heating and hot water requirements – provided you have a well insulated home, which is discussed later.
Better still, if you decide to install an air source heat pump in your home, you can also benefit from the Renewable Heat Incentive, which pays you for each unit of hot water water you produce. In some cases, the funding will cover the cost of installing the heat pump, but it gets paid over 7 years on a quarterly basis, so you will still need to find the money upfront!
The air source heat pump needs to be located outside in the open air, and uses a fan to draw air into it. This air then flows over a heat exchanger, which contains a refrigerant liquid. An evaporator uses the latent heat from the air to heat the refrigerant liquid sufficiently until it boils and turns to a gas. This gas is then compressed by a compressor, which causes it to significantly increase in temperature. An additional heat exchanger removes the heat from the refrigerant (turning it back to a liquid), which can then be used as useful heat. There are two types of air source heat pump:
Air-to-water heat pumps
Air to water heat pumps are by far the most popular. These take heat from air outside the property and transfer this to water, which can be used for space heating or as hot water for washing within the house.
Air-to-air heat pumps
These remove latent heat from the air outside the property which is then simply fed into the home through fans. This type of heat pump cannot be used to produce hot water.
Since they include fans and compressors, air source heat pumps require electricity to operate, and bearing in mind the price of electricity is approximately 15p / kWh and gas is just 4p / kWh, on the face of it, you would expect heat pumps to be far more costly to run than gas boilers.
This is not the case though – since for every kW of electricity used to run them, they provide approximately 2.5-3.5kW of equivalent useful energy (depending on the model and the temperature of the external air). This makes running costs comparable to a traditional gas boiler.
The efficiency of air source heat pumps is measured by the Coefficient of Performance, which is simply how many units of useful energy produced from each unit of electricity are consumed to operate the system. For example, if at any moment the heat pump was producing 3kW of useful heat from each unit of electricity, the CoP would be 3.
The CoP varies throughout the year, with lower figures achieved during the colder months (meaning they are running less efficiently), since there is less ambient heat available to remove from the air. This makes comparing the efficiency of different heat pump systems very difficult, so we use what is known as the Seasonal Performance Factor to compare like for like performance of models. This is the annualised CoP, taking into account the different performance throughout the year.
Air source heat pumps don’t produce boiling water
The air source heat pump does not produce the sort of hot water temperature you would associate with a gas, LPG or oil-powered boiler. With a boiler, you would expect the hot water to be heated to about 850c, while a heat pump produces water to about 550c. Trying to increase the water temperature from a heat pump beyond this requires the compressor to work harder, meaning more electricity – this in turn reduces its efficiency or coefficient of performance.
As a result, it is very important to minimise heat loss from the property prior to installing a heat pump. This includes insulating the walls, loft and ideally the floor too. This means that even though the radiators won’t get as hot (using heat pumps), the house is still heated effectively and you are not straining the heat pump – which is expensive.
When installing a heat pump, you may be required to increase the size of some of the radiators in certain rooms too. This is simply because the heat demand will not be met with the existing-sized radiators. If this is the case, you can expect to pay about £200 – £300 for each radiator that needs to be replaced (providing the pipework running to the existing radiator can be reused).
Air source heat pumps and the Renewable Heat Incentive
Heat pumps are part of the Renewable Heat Incentive scheme recently launched by the Government. It means that, if you install a renewable heating technology, you can get paid for each unit of heat you generate. RHI payment rates depend on lots of things, but you can see detailed information here.
Occasionally, but not often, the RHI payments will be enough to cover the cost of the initial outlay of the air source heat pump. Air source heat pumps normally cost between £7,000 – £10,000.In a standard property you can expect to receive a total of about £2-5,000. RHI payments are paid quarterly over 7 years, so you will need to stump up the money up front.
Things to consider before investing in an air source heat pump
Placement of air source heat pump – An air source heat pump requires plenty of space, either to mount on an external wall or to be placed on the ground. The unit needs good air flow, and foreign objects such as boxes, containers etc need to be kept well away.
Cost of air source heat pump system vs system that is being replaced – Purchasing an air source heat pump on top of an existing heating system will prove to be an expensive option; therefore we recommend considering this when replacing an old electric or old oil-fuelled system. However an electric heater will convert 1kW of electrical energy to 1kW of heat energy and an air source heat pump will convert 1kW of electrical energy into 3.5kW (almost 4kW) of heat energy.
Insulation – The air source heat pump emits low temperatures but on a consistent basis. To maximise effectiveness, ensure that your home is suitably energy efficient by installing wall insulation (either cavity or solid wall) and draught proofing. These are low cost measures that will make a big difference to your utility bills, therefore it is worth investing in them prior to replacing your heating system with an air source heat pump.
Noise of air source heat pump – An air source heat pump does make some noise when operating, as both a fan and a compressor will be in motion. The noise is approximately 40-60 decibels (depending on the system) from a distance of one metre away. So please ensure if you invest in an air source heat pump, it is not placed directly outside your bedroom window!
We have filmed an air source heat pump in motion, (don’t say we don’t treat you) so you can see for yourself how they operate.
Efficiency of air source heat pumps – Despite air source heat pumps being able to operate at -250C, the efficiency decreases as the outside temperature drops; therefore if you live in a particularly cold place, you may well need to supplement the heat pump with an additional boiler to get the hot water you require. Try a CHP boiler if you can invest additional resources. The problem may be getting the two systems to work successfully in tandem; therefore a traditional boiler could be your only option.
Local authority regulation for air source heat pump installation
Generally there are fewer restrictions from local authorities in England and Scotland when looking to install an air source heat pump (noise being the main consideration), but please check with your council and installer before proceeding. In Wales and Northern Ireland, an air source heat pump installation requires planning permission.
Benefits
As the heat pump provides the hot water for heating, there are large savings to be made on fuel bills – typically an air source heat pump can deliver up to 3.5kW of useful energy for every 1kW of energy needed to run it.
An air source heat pump can still take heat out of the air in temperatures as low as minus 20 degrees.
By installing an air source heat pump you can reduce your carbon emissions from your homes heating by 50%.
Air source heat pumps are potential income sources, if households qualify for the government Renewable Heat Incentive (RHI) scheme. The RHI is payable on an MCS ASHP installation, carried out by an MCS Accredited Installer and the payment is backdated to include any installation installed after 15th July 2009.
Limitations
Air source heat pumps can be fairly noisy, approximately 40 – 65 decibels at a distance of 1m away (however this varies by manufacturer). Look at our video below for some first hand experience.
The equipment needs to sit outside the house, so may not be suitable if there is not sufficient space.
Air source heat pumps become less efficient at extracting heat from the air when the external temperature is low, so the amount of usable useful heat they produce is less.
Cost
An air source heat pump will cost from about £7,000 to install.
Installing heat pumps
Are you thinking about getting a heat pump? We have scoured the country for the best tradespeople, so that we can make sure we only recommend those we really trust.
If you would like us to find you a local heat pump installer, just fill in the form below and we will be in touch shortly!
Ground source heat pumps use the earth as a heat source, taking advantage of the stable temperatures in the ground to provide heat and hot water for the home.
Ground source heat pumps are not a new concept and have been around since the 19th century. This technology became very popular in Sweden in the 1970s and since then units have been sold worldwide.
In the UK, there has been a sudden surge in demand in heat pumps since the launch of the Renewable Heat Incentive, which pays homeowners for each unit of hot water produced. Although rates are no longer as high as they were, they can still cover much of the initial install costs of the systems.
How do ground source heat pumps work?
A ground source heat pump system uses heat trapped beneath the ground and boosts it to a higher temperature using a heat pump. This heat is then used to provide home heating or hot water. The heat pump performs the same role as a boiler does in a central heating system, but uses ambient heat from the ground rather than burning fuel to generate heat.
Initially, a heat transfer liquid (normally glycol) is pumped through pipes buried deep in the ground. As the liquid travels through the pipework it absorbs ambient heat from the ground and warms up, before returning back to the ground source heat pump unit. Once it returns, a heat exchanger removes the heat from the liquid and it then continues to travel round and round the pipework in a continuous cycle.
The low-grade heat is transferred through the heat exchanger, then passes through a heat pump compressor which drives the temperature up to a level that is usable for heating and hot water.
How much pipework does a GSHP require?
The length of the ground loop depends on the size of your home and the amount of heat you need – longer loops can draw more heat from the ground, but need more space to be buried in.
The pipework can either be laid horizontally or vertically. If laid horizontally, the pipework tends to be buried in trenches 2-3m deep, spread over a huge surface area to ensure the heat transfer liquid has the opportunity to increase to a sufficient temperature. If the pipework is installed vertically, boreholes get drilled in to ground (at a cost of £6,000 – £8,000 for each borehole!). These need to be drilled by professionals and will regularly exceed 100m in depth to ensure that the heat transfer liquid again has the opportunity to absorb enough heat.
There are two types of ground source heat pump, and both have a few components in common – they consist of a ground heat exchanger, a heat pump and a heat distribution system (e.g. underfloor heating or radiators).
Closed loop ground source heat pump
The majority of ground source heat pumps installed today are closed loop heat pumps. As the name suggests, no outside liquid enters the loop of pipework at any point. In this set up, a sealed loop of high density polyethylene pipe is laid either vertically or horizontally in the ground. The heat transfer fluid is in a completely closed system travelling through the pipework and returning back to heat pump.
Open loop ground source heat pump
The open-loop ground source heat pump uses ground water to pump around the system; however the number of installations of this type are decreasing, mainly because you need a source of groundwater. Also an additional associated issue with the open loop ground source heat pump is that the quality of the groundwater can actually have a detrimental effect on the system.
Ground source heat pumps require electricity
The fact that ground source heat pumps run on electricity suggests that they are expensive to run (electricity is approximately 15p / kWh while gas is just 4p / kWh). However heat pumps are in fact incredibly efficient.
In fact, ground source heat pumps are even more efficient than air source heat pumps, converting each unit of electricity (required to run the pump and compressor) into 3.5 – 4.5 units of useful heat. Compare this to a brand new energy efficient boiler, which converts each unit of gas into just 0.9 units of useful heat.
The efficiency of air source heat pumps is measured by the Coefficient of Performance (CoP), which is simply how many units of useful energy are produced from each unit of electricity consumed to operate the system. With air source heat pumps, the coefficient of performance changes throughout the year. This is because since in the winter months, the unit needs to work harder (and hence uses more electricity) to drive the temperature up to an acceptable temperature.
For ground source heat pumps the coefficient of performance is relatively consistent – this means that even in the middle of winter, when hot water and heating demand are at a maximum, the GSHP should be running equally as efficiently as it does on a red hot summer’s day. This is because the temperature underneath the ground remains relatively constant all year round – and this is one of the key advantages of GSHPs over air source heat pumps.
Heat pumps do have some impact on the environment as they require electricity to run, but the heat they extract from the ground is constantly being renewed naturally, hence they are considered a renewable heating source.
Installing a ground source heat pump
The Energy Saving Trust (EST) recommends households considering a ground source heat pump to consult a Microgeneration Certification Scheme installer and only use a properly accredited professional to complete the work. During its trial, the EST found a variety of heat pumps incorrectly installed, which therefore didn’t perform as efficiently overall as they could have. It is essential to use an MCS-approved installer to qualify for the Renewable Heat Incentive.
It is important to shop around and we always recommend getting several quotes before choosing the best option for you. Studies have shown that most suppliers tend to exaggerate the savings in energy costs this system will produce.
Renewable Heat Incentive
Heat pumps are part of the Government Renewable Heat Incentive (RHI) scheme. It means that you can get paid for every unit of renewable heat you generate. You can get a significant chunk of the cost of installation back over 7 years of payments – not to mention the savings to be made from the heat pump itself. Read more on that here.
Benefits
Ground source heat pumps can lower fuel bills, especially if you are currently using conventional electric heating (saving of £420), LPG or oil (saving of £50).
Ground source heat pumps are often classed as a ‘fit and forget’ technology because they need little maintenance, and no fuel deliveries are required, however they provide space heating and hot water 24/7.
Can reduce your carbon footprint: heat pumps can lower your home’s carbon emissions, depending on which fuel you are replacing.
Limitations
Ground source heat pumps require a reasonable amount of land outside to lay the coils underground. If this is unavailable the technology will not be suitable for your home.
If you have a vertically submerged closed loop system and there is a leak, it can be difficult to gain access to.
Cost
From £13-20,000.
Installing heat pumps
Are you thinking about getting a heat pump? We have scoured the country for the best tradespeople, so that we can make sure we only recommend those we really trust.
If you would like us to find you a local heat pump installer, just fill in the form below and we will be in touch shortly!
Water source heat pumps work on a similar principle to both air source and ground source heat pumps. Instead of taking advantage of the heat in the air or the ground, they take advantage of the relatively consistent temperatures found in a body of water.
A series of flexible pipework is submerged in a body of water, such as a lake, river or stream. A heat pump pushes working fluid through the network of piping, and this fluid absorbs the heat from the surrounding water as it goes.
This working fluid is then compressed by an electric compressor, in a similar fashion to the other types of heat pump, which raises the temperature. A heat exchanger can then be used to remove the heat entirely from this working fluid, providing you with hot water that can be used for space heating (in radiators or under floor heating). It can even be plumbed into your hot water system, where a boiler can just provide the small amount of additional heat needed to bring it up to the required temperature, so it can be used for showers and baths.
Once the heat has been removed from the working fluid via the heat exchanger, it is once again pumped back through the pipework, thereby completing a continuous cycle.
The benefits of a water source heat pump
The heat transfer rate from water is higher from the ground, making them more effective than ground source heat pumps. In addition, if using a water source heat pump with a moving body of water, the heat is constantly being replaced, as new warmer water replaces the cooler water that has had its heat extracted by the working fluid.
For every 1kW of energy required to run a water source heat pump, 4-5kW of equivalent heat energy is produced which can be used to warm your home. This makes the technology more efficient than both air and ground source heat pumps.
The supply of hot water is also pretty much constant, despite being cooler in the winter; the body of water will still possess sufficient heat to enable the water source heat pump to operate in the winter. An issue only arises if the body of water completely freezes.
Unlike ground source heat pumps, where bore holes or trenches need to be dug on your plot for the piping, the pipework for a water source heat pump is relatively simple to install; it simply needs to be situated within a body of water, which should have little impact on your plot of land.
Benefits
Installing a water source heat pump is relatively easy if there is a body of water available on your property.
Water source heat pumps have a higher Coefficient of Performance than ground source and air source heat pumps: so for every unit of electricity used to operate them, they can produce more hot water.
There is little visual impact on the property, since all the pipework in the water source heat pump system is submerged within the body of water.
Limitations
A water source heat pump is reliant on there being a body of water at your property.
Cost
Anywhere around £10k
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What funding is available for heat pumps?
