Kya deLongchamps warms to the economies of heat pump technology, now standard in new builds, but explores its potential as an upgrade heating system.
Heat pumps have become familiar inclusions in new builds of single one-off homes, and in the specifications for progressive developments of estates and even apartments.
We can thank 17th century Anglo-Irish genius Robert Boyle of Lismore Castle (with his canny Boyle’s Law) for at least part of their creation.
However, many consumers are still unsure of what heat pumps actually are, confusing them with a modern form of boiler or some eco-sensitive whimsy afforded only by the cosy financial upper classes.
These systems are already tried, tested and highly reliable form of primary home heating in the EU countries with brutal winters — and also in our temperate Irish climate. As I discovered, they are not confined to use in passive or near-zero carbon buildings. In the right circumstances — yes, they can be retrofitted for a more energy efficient result in an existing house.
What is a heat pump?
Using electrically powered compressor technology similar to a fridge, heat pumps recover the sustainable, free solar gain from the earth, from the air or bodies of water and via a heat exchanger, brings this free thermal energy up to a useful temperature for central heating.
The required electrical power can be multiplied into four units of heating energy for every unit of electricity used — exciting stuff and once up and running, highly economical — especially for a larger home with sufficient insulation.
There are three parts to the system: the collector, the heat pump itself (where the heat exchanger performs its magic) and a distribution system. The results in heat terms are refined by dedicated heating controls. In winter the heating may be ‘on’ fairly constantly, something familiar to anyone with under-floor-heating (UFH) — or on night-rate electricity. Radiators when used are larger, cooler but heat slowly and longer that regular radiators.
Collecting heat from the stable temperatures of the earth is called geothermal heating, and this is done via a horizontal collector made up of plastic pipes in a ‘closed loop’ set over a garden in shallow trenches one to two times the square footage the house. Water circulates through the pipes, returning to the heat pump magically warmer than when it left because it takes the heat from the earth — (generally the temperature beneath the earth’s surface here is maintained at around 9C).
Vertical geothermal collectors are bored like a well deep into the ground in a space saving spike, (often two). Water based ‘open loop’ collectors can use lakes, rivers, and wells — but this technology is more commonly applied to commercial situations and has more maintenance concerns that ground or air set ups.
Finally there is the air-to-water system which sup heat directly from the air to the heat pump, kicking up its temperature through compression, (in much the same way as a fridge) and cycling warmth to a water distribution set up (in under-floor heating), or even air-to-air in a fanned air central heating system.
With no ground or costly civic work needed for a geothermal collector, air-to-water systems are the most favoured choice when replacing a traditional central heating boiler with a heat pump. Imagine a metal appliance like a large air conditioner on a wall outside, which feeds into a heat pump the same size generally as a fridge-freezer, inside. Heat pumps do create some outdoor noise but this is generally less than that of a standard boiler (around 50db).
However, tales of disappointed expectations are not uncommon in mishandled or DIY retro-fits. Heat pumps are not boilers, and because of the way they work, they should only be installed taking into consideration the comprehensive fitness of the house and its existing distribution network.
The real potential for a heat pump.
Heat pumps can, in the best instances, serve all the heating and water needed in a house. Still, attaching a heat pump to a house not built to part L standards of the building regulations, and designed formerly around a traditional central heating system does present challenges.
The reputable suppliers that I spoke to argued passionately in favour of a realistic and holistic approach to energy efficiency when weighing up whether a heat pump would suit in a retrofit situation.
Mike Cotter, co-founder of Alternative Heating & Cooling Ltd, (AHAC) explains his chief considerations when carrying out a survey for a client. “Existing plumbing pipe-work will need to be assessed, and of course we need to look at space for the equipment and so on, but 90% of the work has to be focused on keeping the heating efficient, and altering the delivery system to suit the heat pump. Too many failed jobs are from trying to make a heat pump into a boiler. It’s a different beast.”
I asked him is choosing a pump always an energy saving adventure?
“It all depends on the running costs of the existing system, If costs are high using fossil fuels then a considerable saving can be made, the bigger the heating load (the building), the bigger the savings.”
Mike Collins is an independent energy consultant with experience in renewable technologies in Co Cork. He emphasises that the envelope of the house must be brought up to standard to get the best out of a new heat pump: “It is critical that insulation levels be increased to current building standards (if possible) for the heat pump to work as it was designed. Herein lie most of the problems where heat pumps do not work efficiently.”
What about the distribution system? UFH is the ideal because of the volume of radiating surface it offers — lots of floor space — and because the systems typically heat the water to 35-45 ºC lower that the 55 to 65C of oil or gas radiators. Without the expansive ideal of UFH, you may be able to use your existing radiators if they are nicely oversized — a common feature of heat- hungry, traditional central heating.
Mr Cotter explains: “We recommend to hold off changing any radiators until after the heat pump is installed to see how they react. Change may not be necessary.”
Air to water heat pumps produce more heat in warmer conditions and this has to be keyed into the design of your heating. Ask your supplier if your existing water tank will suffice for a heat pump system (they generally require a large tank), and if the configuration of your system will demand what is called a buffer tank to overcome inefficient ‘cycling’.
Retrofitting is not a plug n’ play project and the insulation and air tightness of the house may well need to be optimised to receive the pump. If upgrading the insulation of the building and making it sufficiently air tight is costly and problematic, and kilometres of corroded piping must be ripped out, you may (and should) be advised a heat pump is not viable for your home. Be wary of exaggerated, generic examples in potential savings.
Show me the Money
The initial investment in a heat pump-led system is significant. For new builds the pump is designed into the house from the plans forward, and the cost combined with that of the UFH. In a new build situation, it cost some €3,000 approximately more than oil and solar in an average one-off build.
When it comes to retrofits, reputable suppliers will evaluate every house on a highly individual basis. The civil works of drilling a bore (often two) for a vertical collector or laying horizontal trenches for a shallow horizontal collector, will always make geothermal more expensive. For retrofits, air to water pumps are generally promoted by suppliers based on price, performance and ease of installation.
However, air to water pumps do not currently offer quite the same high efficiencies as geothermal systems recovering heat from the ground.
An air to water system installed will come in the area of €8 to €9k for the pump and tank fitted, commissioned and all ‘made-good’ (suppliers’ figures). Geothermal, including the sensible inclusion of 200m² of UFH will cost at least €14k-€18k for a 2,500 sq ft house (SEAI).
Mike Teaghan of Ashgrove Renewables explains: “Some homes may only need to replace their existing heating system with a heat pump and that’s that. Others may find they need to do some upgrading in their insulation levels as well, for example as some people could be doing up an older cottage with original stone walls.”
Payback for geothermal will obviously take the longest to claw home, and sophisticated vertical collectors can bring recoup to 30 years. With more modestly priced systems the projection is around five to 10 years depending on your spend, but after that it’s all gravy — a valuable investment in the systematics of the property, with little maintenance and a life expectancy for the pump in the order of 15 to 20 years according to the Heat Pump
Association of Ireland (HPAI).
The magical warmth massaged from the air, earth or water may be free, but the means to transforming those degrees into thermal energy most certainly is not. The compressor requires a consistent trickle of electricity to put pressure on that coolant in the system and to defrost. The hit to your power bill is significant, an ear ringing punch of anywhere from €800 to €1,200 per year (SEAI).
Still, for every unit of electricity used to pump the heat, in theory three to four units of heat are produced. Taking the drop in your traditional fossil fuels out of the overall equation, this could put you ahead by 30% in savings and as much as 60% have been reported where heating costs were formerly sky high and the property received essential upgrades.
Mr Teahan says: “It is a bonus if we can get several years’ energy bills for the house as we can then compare what the current running cost are to what the heat pump’s projected running costs will be.
“SEAI have a cost per kWh comparison so for oil it is 7.91c per kWh, LPG 11.04c per kWh, Natural Gas 7.48c per kWh, Wood pellets would be 10.69c per kWh this is compared to a heat pump that comes in between 5.1 to 4.08c per kWh depending if you go air-to-water or geothermal.”
Is a heat pump right for you?
Imagine enjoying 20,000kWh of heating energy for €800 a year? In larger one-off new builds here, a heat pump may actually be mandated by the planning authority, as solar panels alone may not cover the Part L requirements for a sustainable energy input. (10kWh/m2/y). The heat pump must be sized for the heat requirements of the household and perfectly installed to hit its performance target.
Consultant Michael Collins says: “The heat loss from the retrofitted dwelling needs to be calculated initially using DEAP (Dwelling Energy Assessment Procedure) software. You will be carrying out a provisional BER on the dwelling off-plan, which will calculate the Total Heat Loss through the fabric of the building.
“This figure is then given to the heating system supplier who will accurately suggest the appropriate size of heat pump for that particular dwelling.”
You may be advised to include back-up water heating (an immersion for example) when using a heat pump as your primary heat source. This could be contributing some 20% to your day to day needs at certain times of the year. Your existing or new solar system can contribute passively and inexpensively to water heating or lend voltaic power to the pump, leaving the pump free to energetically heat the house. Ecologically, your carbon footprint using a well performing heat pump is low, (especially with wind energy and voltaic. However, even saving on carbon and energy, is a heat pump worth the spend? Only a full independent survey and ideally a visit to a refurbished home similar to your own t can answer the question fully.
Space heaters that whisper
Electrically powered space heater can compliment your heating system or operate as a standalone solution where insulation levels are high enough in a passive or nearly zero energy house. Independent heating units should always have detailed controls that monitor the ambient temperature to ensure they are as responsive and efficient as possible.
Merida, an elegant new range of space heaters from DeLonghi has some very impressive intelligent operating additions. One allows you to set ‘comfort mode’ detecting movement, recording habits and automatically suggesting a customised weekly setting to suit household needs.
Inbuilt sensors detect when a window is open and any sudden drop in temperature will automatically switch the heater into anti-freeze mode of 7, ideal for circulation spaces and spare rooms.
Costs €218 to €495 plus shipping. Order direct from www.cnmonline.co.uk
Heat pump basics
Heat pumps are an electrically powered solution for space heating and domestic hot water. The pump uses a compressor and coolant similar to that used in a refrigerator. Renewable solar gain stored in the earth, air or water bodies, is transformed to suitable energy via a heat exchanger.
* For every unit of electricity used for the pump, 3-4 units of thermal energy (kWh) should be returned. In practice, this may be 2-2.5 in cold weather with an air source heat pump.
* Vertical geothermal married to UFH is the most expensive capital outlay but is also the most energy-efficient option with very low running costs.
* Air to water heat pumps are the least invasive and least-costly retrofit, (not counting additional upgrades to insulation and air tightness) and won’t touch your landscaping.
* Heating controls will monitor the indoor temperature, and send heat to the floor and/or radiators as needed to bring it up or down to the temperatures set on your thermostat.
* The best performance in statistics featuring heat pumps (COPs) are generally taken from new builds where top-of-the-line vertical geothermal bores, perfectly considered buildings design, extensive UFH and superb insulations are all clicking. Beware of exaggerated claims for the performance of a retrofit system.
* There is currently no government grant support for heat pump technology itself. The Better Energy Homes Scheme does have grants for heating controls however, of up to €600. Seai.ie. Running the system on night- rate electricity will save you money.
* You must get an energy survey for your house and site. If you have efficient natural gas heating, a heat pump is probably not worth the expense to retrofit.
* The efficiently of heat pumps varies. This year for the first time, energy labelling of pumps (similar to other electrical appliances) has been introduced by the EU.
* If the radiators are of a suitable size — a retrofit of an air-to-water heat pump will involve about two days of work by two fitters working on plumbing and electrical upgrades, so make sure an energy survey is in place before changing your system.
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