Ground Source Heat Pump

ground source heat pump

Ground Source Heat Pumps – Their Cost, Their Installation and Their Efficiency

Heating accounts for a significant portion of a household’s energy demand and a ground source heat pump system can provide a cost-effective and sustainable way to warm a home. The pump uses a small amount of electricity to transfer naturally occurring heat from the adjacent ground into the house.  As the temperature just a couple of metres below the surface remains more or less constant at 11°C to 12°C, it is possible to design a very efficient heat transfer system.

How does it work?

A sealed loop of fluid-filled pipe is buried in the garden or driveway. The length required depends on the size of the home and the amount of heat required. An average system for a family dwelling will typically require pipework up to 100m long.  Vertically drilled boreholes and deeper pipes can be used in more confined spaces. Once installed, the ground is restored to its original condition and the system becomes invisible.

The ground source heat pump circulates water and antifreeze around this loop. The fluid absorbs heat from the ground before it passes through a heat exchanger.  Energy is then transferred to the heating and hot water circuits of the home. The cooled fluid flows back into the ground loop in a continuous process for as long as the heating is required. Some systems can also be designed to meet cooling needs in summer.

While there are some minor residual energy and carbon costs, hooking the pump up to a home renewable technology such as a solar panel can increase its sustainability credentials even further.

What properties are suitable?

Ground source heat pump systems are not suited to every type of property. In general, they work most efficiently in well insulated homes with a relatively even and low heat demand. They produce heat at a lower temperature than more conventional central heating so a larger area is required for heat distribution. Underfloor heating is the ideal partner, though large heat pump system radiators are available. The system also requires sufficient outside space for installation. While minimal on-going maintenance is required, there can be considerable disruption during installation, and the system tends to be more attractive for new-build or as part of a wider home improvement project.

A typical domestic ground source pump is the size of a large upright fridge freezer. To save indoor space they can be installed in an outbuilding or basement.  They just need to be as close as possible to the end of the ground loop pipe. With a typical noise level of a little over 40dB at one metre away, they are as quiet as a fridge.  That’s considerably quieter than a typical gas or oil central heating boiler.

What do they cost and how much will I save?

Costs and savings will be dependant on the size of the pump, the length and depth of loop installation, the energy efficiency of the property, the sort of heating system that is being replaced and whether any additional work is required on the wider home heating system.  A typical domestic installation costs £12,000 to £15,000, with annual running costs of £600 to £700. At current prices, the payback from a ground source heat pumps is unlikely to represent an attractive alternative to an established mains gas central heating system. However, installers claim energy savings of nearly £1,500 annually for a typical four-bedroom house when compared with standard electric heating, or around £600 when compared to oil-fired central heating. That represents a saving of nearly 5,000kg of CO2 emissions each year.  Government Renewable Heat Incentive grants are currently available for installation.

Their installation will also greatly improve your energy efficiency score on your EPC.

If you liked this article, have a look at some of our other recent posts.

Property Size and Type and its Effect on Energy Usage and Your EPC

European Directives on Building Energy Performance

Top Tips for Selling Your Home

Comparing the Energy Efficiency of Modern and Traditional Walls

Waste Water Heat Recovery Systems (WWHRS) and your EPC

Are Conservatories Energy Inefficient?

Renewable Energy Keeps Getting More Popular

If you’d like to book an EPC for your home, simply contact us by phone or email, or fill in our contact form.

 

Renewable Energy Keeps Getting More Popular

renewable energy

Renewables enjoy a rising wave of support

The UK Government monitors public attitude towards renewable energy technologies and climate change through a regular survey. The tracker was launched in March 2012 by the Department of Energy and Climate Change (DECC), now part of the Department for Business, Energy and Industrial Strategy (BEIS).

Known as the ‘Energy and Climate Change Public Attitudes Tracker’ (PAT), the main survey is carried out annually in March, with three supplementary short surveys in June, September and December. The repeat questions track the public’s views on important energy issues.  Each survey is known as a ‘Wave’ and the results of the Wave 25 survey were published recently. Wave 25 comprised 2,102 face-to-face, at-home interviews with a representative sample of UK adults. The background and detailed data are available on the UK Government website (here).

The latest survey results suggest a rising tide of public anxiety over climate change issues, with 74% of respondents saying that they were ‘very concerned’ or ‘fairly concerned’. The rise from 71% in May 2017 is a continuation of a growing trend. Perhaps due to on-going coverage in the media, a greater proportion of the public now accepts that climate change is the result of human activity rather than natural process. Just less than 50% said that they believed climate change problems were caused mainly by human activity, compared to only 10% who believed they were down solely to natural processes.

The latest Wave 25 results show overwhelming backing for renewable energy technologies, especially solar power and offshore wind farms. A comparison with the results from previous years reveals that public support for the use of renewable technologies to supply electricity, fuel, and heat has been climbing steadily.  It has now reached 85%, the highest recorded level since the tracker was set up. Only 3% were opposed.

In terms of the individual clean energy technologies, solar was given the greatest vote of confidence at 87%, with offshore wind reaching a record high of 83%. Close behind came wave and tidal power at 81%, onshore wind turbines at 76% and biomass power stations at 69%. The survey results also seem to indicate a reducing NIMBY effect, with people getting used to seeing and accepting large scale renewable projects in their own areas. 66% now say that they would be happy to have a development locally, compared to 58% in the same month of 2017.

By comparison, support for nuclear energy was largely unchanged over the year at 38%, with 22% opposed. The public’s attitude to shale gas extraction also remained essentially stable at just 18% in favour and 32% opposed.

The Wave 25 survey also included questions about perceptions of home energy efficiency.  Interviewees were asked what two things they thought use the most energy in the home. The answers included central heating (71%), large appliances (45%), and hot water (37%). When asked about home energy efficiency measures, 78% had installed double glazing, 65% loft insulation and 44% cavity wall insulation. Awareness of under floor insulation and solid wall insulation was much lower than for the other energy efficiency measures.

A question was also asked about home Energy Performance Certificates (EPCs).  63% were aware of EPCs, an increase over recent years, but only 9% claimed to know the rating of their own home.

It seems renewable energy is here to stay and will continue to play a greater role in all of our lives.

If you’d like to book an EPC, please feel free to contact us.

Like this blog post?  Please subscribe to our regular posts, here are a selection of other articles.

Property Size and Type and its Effect on Energy Usage and Your EPC

Are Conservatories Energy Inefficient?

European Directives on Building Energy Performance

Comparing the Energy Efficiency of Modern and Traditional Walls

Property Size and Type and its Effect on Energy Usage and Your EPC

EPC

Energy usage by property size and type

It’s a simple fact that large old detached houses have a lower EPC score than modern flats.

Logic suggests that, on average, larger properties will generally use more energy for heating than comparable smaller ones. However, there are many variables involved in such a calculation, not least of which will be the type of property. Flats tend to have fewer external walls and roofs than terraced houses, which in turn have fewer than semi-detached or detached houses. The larger the external surfaces, the greater the expected loss of energy. Other variables such as the age of the property, building materials and the effectiveness of energy efficiency measures that have been installed also confuse the picture.

So although there are a lot of things you can do to influence the score of your EPC, some things you can’t.

A large sample of households would be needed to make an analysis of energy need by dwelling type statistically reliable. The Government’s Home Energy Efficiency Database (HEED) provides such a data set. While not freely available to individuals, the information is available to researchers and organisations planning and monitoring progress in home energy efficiency. It includes information collected between 1995 and 2012 on some 13 million dwellings in the UK, almost half of the country’s housing stock. The data includes property age, type, tenure and energy use, and details such as glazing type, wall type, heating systems and energy efficiency measures.  All of which are fundamental to EPC calculations too.

Researchers at the Energy Institute of University College London were given access to the database to undertake a wide range of analyses, including an evaluation of average energy usage by dwelling type and number of bedrooms.  Their research is reported in the journal Energy Policy (Energy efficiency in the British housing stock: Energy demand and the Homes Energy Efficiency Database. Hamilton I.G. et al, Energy Policy 60 (2013) pp 462-480).

The researchers analysed the data to provide an overview of the statistics for gas and electricity use in 2006 by different types and sizes of dwelling. The following tables summarise their findings, giving the median value in each case (i.e. the mid value when all data are set out in increasing order of size), as they showed this to be a more representative ‘average’ than the mean. The figures for gas and Economy 7 tariff electricity are likely to be most representative of energy demand for heating.

Median energy use for different types of property

Type

Normal tariff  Electricity (kWh/yr) median

Economy 7  tariff  Electricity (kWh/yr) median

Gas (kWh/yr) median

Flat

1,967

4,309

10,242

Bungalow

2,784

4,828

16,129

Terraced house

3,038

4,845

14,983

Semi-detached house

3,310

4,765

16,571

Detached house

4,023

5,135

20,992

Median energy use for different numbers of bedrooms

Number of bedrooms

Normal tariff  Electricity (kWh/yr) median

Economy 7  tariff  Electricity (kWh/yr) median

Gas (kWh/yr) median

1

1,934

4,685

11,137

2

2,554

4,662

13,541

3

3,357

4,637

16,590

4

4,358

5,390

21,560

5+

4,890

6,171

24,246

As expected, the results confirm that detached houses and bungalows have the highest energy usage. The figures show a clear decrease in demand as the level of detachment declines, so that flats, with the highest number of party walls and ceilings, show least energy usage.  Something which EPC scores also make clear too.

The median gas demand increases on average by 22% for every additional bedroom over one in any property type. Overall electricity use also generally increases with additional bedrooms, though not as clearly and steeply as gas.

Are Conservatories Energy Inefficient?

conservatory

Do conservatories conserve energy?

How does a conservatory affect your EPC?

While undoubtedly being great for providing additional light-filled living space, the question of whether conservatories are good for energy conservation is less straightforward.   Just how much is your conservatory costing you and could it have a detrimental effect on your EPC?

A conservatory is a popular and relatively cheap way of extending a home. If it has a floor area of less than 30sqm, a door that thermally separates it from the house and it is not connected to the house heating system, a conservatory is also generally exempt from Building Regulations Part L controls, and possibly also planning permission, depending on its position and the history of extensions to the property.

However, all too often the conservatory becomes a very costly addition when on-going heating bills are considered.  The cheapest, aluminium-framed conservatories of the 1970s and 1980s and those with polycarbonate rather than glass roof panels are particularly poor in terms of energy efficiency, and there is very little retrofitting that can be done to make significant improvements.

In the right place, conservatories are great for harvesting heat from the sun, but this can mean they become too hot in the summer while being very inefficient in the short and often cloudy days of winter. A south-east facing conservatory is generally considered best, as it will collect heat from the morning sun and be less prone to overheating during the warmest part of the day.

The positive side of the winter story is that a closed and unheated conservatory may provide a slight buffer to the rest of the house against cold weather, reducing the temperature difference between the main room and the outside by a few degrees. For this to be effective, the conservatory must be thermally separated from the main part of the house with solid, draught-proof doors, or glass doors with thick curtains. Thermal mass in the conservatory will store winter heat for longer, so exposed brick walls that catch the sun and a stone floor will absorb then slowly release the energy.

The downside is that many families need the conservatory as a living space year-round, and soon discover just how inefficient they are at conserving heat.  It is simply not feasible to insulate such an extensively glazed space sufficiently, so the only energy and cost efficient way to run a conservatory is not to heat it.

While a conservatory can never be brought up to the thermal standard of even an un-insulated cavity walled room, for a family that has no option other then to use and heat the conservatory there are measures that can help a little. Modern double-glazing with ‘Four Seasons Glass’, blinds and shutters can all help to reduce the amount of wasted energy.

A more radical solution is to replace the glazed roof with solid, insulated panels. The situation in relation to planning permission and Building Regulations should be checked. Installers claim that modern panels can be up to eight times more efficient than a polycarbonate roof, and some fit ‘multifoil’ insulation which is very efficient at heat deflection in the summer while helping to protect against damp and condensation in the winter. This is said to reduce the hottest summer temperatures in the conservatory by 70% and make it 90% warmer in the winter. While such figures sound impressive, the conservatory will nevertheless still suffer a very significant loss of energy through the winter if heated.

Remember, conservatories that are not thermally separated can have a detrimental impact on your EPC score.

Hot Water Cylinder Insulation

EPC

Is your Hot Water Cylinder  insulation below standard?

An hot water cylinder heater is rather like a large kettle. It is an electric resistance loop that is inserted into a cylinder to heat stored water. Immersions are not the most efficient way of heating water in the home, but they do have the advantage of flexibility and ease of use, and they can be used on an economy night tariff electricity supply via a timer.

Homes without boilers generally rely on hot water cylinders with an immersion heater for their primary hot water supply. Many other houses with central systems have an immersion as a back up to provide hot water in case of boiler failure. 

A typical immersion heater uses 3kW of electricity an hour, and costs around £1 for two hours’ use on an average standard tariff, or perhaps a half of this on an Economy 7 tariff. This will generally provide the daily basic hot water needs for a small, one or two person household.

A large tank of expensively heated hot water will lose heat very quickly if not used immediately. Insulation is critical to energy efficiency, financial savings and minimising carbon emissions. It also makes for a more convenient system, as hot water will be instantly available without waiting for the tank to heat up again.

Modern cylinders are factory-fitted with insulation, generally in the form of a 50mm foam coating.  While this is usually sufficient, even relatively new tanks may have an out-dated coating of 38mm or less, as insulation standards have increased substantially over recent decades.  The thickness can be measured where the foam is cut away to allow the insertion of the immersion heater assembly. Any sign of copper means that there is an easy escape route for the heat.

An older hot water cylinder without foam or with a substandard layer can be insulated with a purpose-made jacket. These are widely available from DIY stores. It is worth paying a little extra for a thick jacket if there is room around the tank to accommodate it. The best cylinder jackets have a 75mm or 80mm glass fibre filling and a flame-retardant cover, and these can be bought for as little as £15. DIY fitting is straightforward, but remember not to cover the top of the immersion heater and its thermostatic cut-out.

Adding one of these jackets to an un-insulated tank can save around £80 a year on electricity bills, so the investment will pay for itself within three months. It will also reduce your annual household carbon emissions by 420kg. Using a jacket to top up a cylinder with 25mm of foam will save approximately £20 per year, with payback over nine or ten months.

It is also worth lagging the exposed hot water pipes in the immersion cupboard. These take the water from the top of the tank to the shower and taps. The sections closest to the tank can lose a lot of stored heat, and they can be very easily insulated with split foam tube that simply slips over the pipe and closes around it. This is a £20 DIY job that will save another £10 to £20 a year.

A Proactive Approach to a Passive House

EPC - Passive House

A proactive approach to a Passive House

‘Passive House’ is a standard for a cost-effective, low-energy construction concept that produces buildings with remarkable energy efficiency qualities without compromising on comfort.  

With all of the necessary information published freely on-line, it is claimed that any competent architect can design a Passive House. The standard is also relevant to non-residential buildings such as schools and offices. While it is most simply achieved with a new-build, it can also be successfully applied during a major building renovation.

Passive House buildings combine the use of energy efficient materials, a very high level of floor, window, roof and wall insulation and an airtight design. They are designed to be ‘thermal bridge free’, meaning the insulation has no cold corners or weak spots, reducing any problems with condensation. Ventilation is nevertheless essential, and an unobtrusive system supplies constant fresh air to maintain high levels of internal air quality without creating draughts. It incorporates a highly efficient heat recovery unit that captures heat for re-use in the building.

The designers ensure that the building makes such efficient use of the sun, internal heat sources such as domestic appliances and heat recovery that a conventional heating system is unnecessary, even on the coldest days of winter. This is what defines a Passive House. During the summer, passive techniques such as strategic shading help to keep the building comfortably cool.

Tests and calculations on existing Passive House dwellings are producing some impressive data. Measurements carried out on more than a hundred Passive House properties in central Europe as part of the European Union’s CEPHEUS project showed average energy savings of approximately 90% by comparison with traditional building stock, and 75% savings against new-build equivalents.

As a result, Passive Houses are environmentally friendly by definition. While some additional energy may be required initially for their materials and construction, this is insignificant by comparison with the energy savings they enable throughout the life of the building.

Similarly, the necessary financial investment in high quality materials and design required by the Passive House standard will be offset by the greatly reduced cost of installing and running heating and cooling systems. Calculations for German Passive Houses suggest that initial construction costs are now only approximately 5% higher than those of a comparable traditionally built house. Payback periods of course depend on the size and construction cost of the building, but under most circumstances the reduced running costs are likely to offset the construction costs in two to three decades, even allowing for loan repayments.

The Building Research Establishment (BRE) is one of the certifying bodies for Passive Houses, and there are fewer than a hundred of its Passivhaus buildings in the UK. The ‘Sleepy Dorset’ blog (here) tells the story of one family’s self-build Passive House since 2016 and its successful achievement of Passivhaus status. It relates how the house performed in Dorset’s coldest winter weather for many years in March 2018, and how the family awoke each morning to a comfortable 18ºC without any heating, despite outside temperatures of -6ºC and thick snow.

Ten Inexpensive Tips for Keeping Your Home Warm Next Winter

EPC

You may have installed smart heating technology, but as the winter winds whistle around the house and the cost of energy carries on rising what else can you do to keep the temperature up and the bills down?  Here are ten top tips for simple and inexpensive measures that can help to keep your home warm.

1. If you have an open fireplace that is no longer used, install a chimney balloon. They are inflated just out of sight above the fireplace, moulding to the shape of the chimney, providing excellent insulation and preventing draughts. The cost is around £20.

2. Put aluminium foil on walls behind radiators to reflect heat back into the room, especially on external walls. Tests suggest that the payback on good quality radiator reflectors is only two to three years on external walls, a better result than for kitchen foil which deteriorates and is less effective.

3. Move your furniture away from radiators to help with the free circulation of heated air into the room and the return of cooler air along the floor. Natural convection helps to ensure heat is evenly distributed, so consider the distribution of large furniture items around the room, a sort of thermal feng shui.

4. Cover floorboards and wooden floors with carpet and rugs, or at least use a flexible filler in any gaps between the boards. According to research by the National Energy Foundation, uninsulated floors can account for 10% of the heat loss from residential properties.

5. Check if your loft hatch is insulated. Even if you have top-notch loft insulation, the hatch needs similar treatment. Special loft hatches are available, or insulating board can be added to the top of existing hatches.

6. Put up thermal roller blinds or thick curtains with a thermal lining, and keep them closed during hours of darkness. A cheaper option is to add a thermal lining to existing curtains. A thick curtain might also be a useful addition to an old or draughty external door.

7. Open the curtains when the sun is out, and make the most of one greenhouse effect that is good for our environment. Even in winter when it is cold, sunlight coming into the house will warm it up.

8. Add draught-proofing products to all those less obvious nooks where draughts might find a way in. Buy old-fashioned draught excluders to protect the base of doors, they do not all have to be sausage dogs!  Think also about less obvious gaps like letterboxes, cat flaps, keyholes and extractor fans. There are products available in the DIY store to deal with all of them, and home-made alternatives generally require little specialist imagination.

9. Close up any rooms that you are not using or do not really need to use.  Keep the heating on low (never off), but ensure they are ventilated from time to time.

10. If you cannot afford double or triple glazing, or your property is listed and has restrictions, it may be possible to put up insulating film using double-sided tape that has the same effect.  It is inconvenient because you cannot get to the windows to open and close them, and it can start to peel and look tatty after a few months, but it is a good temporary measure at only a few pounds each winter.  Alternatively, secondary glazing is a cheaper, more permanent alternative.

Loft Insulation

Loft Insulation

Roof insulation

Modern houses are built with loft insulation, but older properties may be losing a quarter of their heat through the roof. Installing or topping-up insulation in a standard loft is an easy and cost-effective way of making a home more energy-efficient. 

Types of loft insulation

For an accessible loft, the most straightforward method is to lay loft rolls of mineral, glass or sheep’s wool between and over the ceiling joists to a depth of 270mm. A layer is placed between the joists then another is laid at right angles to cover them.  For topping up, the appropriate depth of loft roll is simply laid on top of the existing material.  The loft door can be insulated, but it is better to replace it with an insulated trap door.

The second method, blown installation of fire-retardant mineral wool or cellulose, is for roof spaces with difficult access. The process usually takes no more than a couple of hours.

Finally, for flat roofs, expanded polystyrene insulation boards can be attached on or beneath the roof. These can be a bit more expensive and complicated to install, and can lead to condensation problems, so installation is best left to a professional.

Storage

If the loft is used for storage and there is insufficient joist depth to accommodate the insulation, there are two solutions. The first is to infill between the joists with loft roll and then lay insulation boards and chipboard loft boards across the top. Alternatively, the level of the loft floor can be raised to accommodate two layers of loft roll, by fitting battens across the joists and nailing chipboard loft boards on top.

For either method, a gap should be left between the loft insulation and the boards to prevent condensation and compression of the loft roll, which will reduce its efficiency.

Loft conversions

The floor of an existing loft conversion can be insulated to keep the rest of the home warm, with loft roll added between pitched roof rafters and insulation boards to false ceilings, walls and dormers to keep the loft room itself cosy. A 50mm gap is needed between insulation boards and roofing felt for ventilation.

Other things to remember

For DIY, choose products with an ‘Energy Savings Trust Recommended’ logo, insulate pipes and tanks and do not install loft roll beneath the cold water tank. Remember to wear protective clothing and a mask.

If the space is used to store perishables like photographs or clothes, the roof should also be insulated to keep more heat in the loft.

An insulated loft needs to be adequately ventilated around the eaves to prevent damp. If there is an existing damp problem it is best to get professional advice.

Costs and savings

270mm of new loft insulation could yield annual savings of £225 for a detached house or £135 for a three bedroomed semi-detached. The cost would be £395 or £300 respectively. It may be possible to get grants through the Energy Company Obligation (ECO) towards the costs. Check with your energy supplier.

Keeping your walls warm

wall insulation

Escaping heat is one of the most important considerations when improving the energy efficiency of your home and your EPC score. Approximately a third of the heat loss from a brick-built home disappears through the walls, so installing wall insulation will reduce losses and save money on energy bills.

It will also make your home feel more cosy and help to prevent condensation on the walls.

How to find out if your house is suitable

The first question is whether your house has solid or cavity walls, as this determines the type of insulation that is appropriate. Pre-1930 properties generally have solid walls of a single layer of bricks. Later houses are more likely to have two layers of bricks separated by a cavity.

The width of the wall is another good indicator. Brick walls less than 270mm thick are probably solid.

Next, check whether your walls are already insulated. If your property is less than 20 years old it was probably insulated when it was built, three-quarters of houses with cavity walls are insulated. If you are not sure, an installer can drill a small hole in the outside wall to check.

Less than 5% of houses with solid walls have been insulated, despite them leaking twice as much heat as cavity walls.

What is involved?

Cavity walls are insulated by injecting foam or mineral beads into the gap through small holes drilled in the outside wall at 1m intervals. The holes are then filled to match the existing mortar.

Experienced installers can complete the straightforward process in three or four hours, depending on the size of the house.

Solid walls can be insulated externally or internally. External insulation involves fixing a layer of suitable material to the wall, then covering it with a weather-proof render or cladding. A wide range of finishes is available.

For internal insulation, boards or stud walls with a backing of mineral fibre or sheep’s fleece are fitted to the inside of the external walls of each room. Internal insulation is disruptive, requires skirting boards and electrical fittings to be removed, and a re-plaster and redecoration of the room. It will also slightly reduce the room size.

How much does it cost?

Budget £500 for cavity wall insulation in an average three-bedroom house. External solid wall insulation can cost anywhere between £8,000 and £15,000 for a three-bedroom house.  Insulating the same property internally will typically cost between £4,000 and £13,000.

How much money will I save? 

Adding cavity wall insulation to an average three-bedroomed semi-detached house could save £150 a year through reduced energy bills and will pay for itself within four or five years. Solid wall insulation in a similar sized house could save up to £300 a year, but the higher up-front cost means that the payback period may be longer.

Fitting wall insulation also adds value to a house, and it is an effective way of raising your home’s Energy Performance Certificate (EPC) energy-efficiency rating.

Installation grants may be available from the Energy Company Obligation scheme. The rules change frequently, so check with your energy supplier or the Energy Saving Trust website for the current situation.