Kya deLongchamps offers an essential introduction to retrofitting an energy-efficient heat pump in your current home and tackles presumptions.
New homes with a softly purring heat pump (HP) are steadily changing the green credentials and central heating running costs of our housing stock. However, is your older home heat pump-ready? Let’s warm up some common HP retrofit presumptions.
No, there’s no combustion. HPs at point-of-use have zero carbon emissions and use only a trace of electricity to work.
They are, in general, highly environmentally friendly option, but do contain refrigerant, properly sealed in the pump in a well-maintained unit.
HPs gather renewable solar grain stored in the earth, air, or water (termed the collector) and using a vapour compression cycle, transform that heat into energy we can use to heat our indoor air and water.
Heat is distributed around the house using forced air, conventional under-floor heating (UFH ) or water-fed radiators. We’ll refer here to air-to-water heat pumps as ASHPs.
Compared to even high efficiencies of 92% plus in conventional oil and natural gas boilers, a properly detailed, HP systems regularly produces 300% or more in terms of efficiency. For every kW unit of electricity used, three or more kW units of heat are delivered.
Termed as a Seasonal Coefficient of Performance or Scop, 300% would be Scop of 3.
This can fall to 2-2.5 in a cold winter with an air-source heat pump (ASHP), still better than conventional fossil fuel heating solutions.
If you have natural gas central heating, and a well-insulated house, the cost savings running a HP won’t be as dramatic as swapping from oil or solid fuel.
Is the Sustainable Energy Authority (SEAI) handing out grants for HPs? Hardly. For grant aid to buy and install a HP, the SEAI require a Technical Assessment using DEAP software by a registered adviser.
The adviser will provide a road map towards making your home HP ready based on a highly specific heat-loss indicator (HLI). If your favoured supplier is on the register, they still have to follow stringent protocols.
According to the SEAI, the level of insulation and air tightness of your home should contribute to a heat loss level of 2 Watts/Kelvin/m2 — in the area of a BER of B2 or better.
If you’re nowhere near a B2, then alternate improvements have to come first
There is partial (retroactive) grant aid of €200 for the Technical Assessment (from €500 to as much as €700) in addition to SEAI grant aid for a heat pump installation for eligible houses built before 2011 of €3,500.
Anyone can in theory swap out their boiler for a heat pump, but expert independent advice is crucial. Even if you don’t qualify for grant aid, you’ll have to throw some money at this.
Potentially, but this could be a journey. The technology is not cheap and the cost of air tightness and insulation prep’ work required for a successful performance with a HP can be prohibitive. In some cases the cost of the work required as determined by the Technical Advisor will make a HP unfeasible for a family in one financial jump even with grant aid.
Weigh the system cost, your budget, life stage, and financial situation.
You may be advised to start incrementally on heat-loss measures for walls, floors, and roofing using SEAI grant aid, and to replace draughty failing windows as first prudent steps.
In some cases but get independent advice. Over-sized existing radiators of the right type may be an advantage.
The water temperature running through a HP system will be lower than that expected with oil or gas-fed system, just 35-45°C so more surface area allows more heat to convect into the room (where you don’t have UFH). Dedicated low temperature radiator designs are the ideal.
Keep in mind that HP central heating is not as hot and ‘reactive’ as conventional CH — so it will stay on for longer periods.
Grant funded systems must be designed to meet 100% of the dwelling space heating demand and at least 80% of the hot water demand. Hot water requires a higher temperature than space heating, so may require some backup heating to reach adequate temperatures — SEAI. Air to air HP systems do not provide hot water.
Your heating specialist may suggest a larger hot water cylinder to increase the volume and coil capacity.
There are HP packages including a monobloc — a free-standing mains pressure water cylinder with the HP indoor components, in a crisp unit the size of an upright freezer.
These devices can be married to solar or even a secondary (bivalent) heat sources.
Your gas and oil bills will be reduced (or eliminated) but your electricity bill will obviously go up. In an A2 or A3 home with under-floor-heating and mechanical ventilation with heat recovery (MVHR), a scrap of space heating is needed for most of the year, so the bills for running a heat pump can genuinely be as low as €300pa.
The higher the heat load, and the worse your starting point (solid fuel and single glazing, electric immersion water heating), the more dramatic the energy savings will appear after a deep retrofit.
On the flipside the payback on getting the house HP-ready plus the system’s cost could prove as long as 15 years.
The majority of HP retrofits since SEAI grant aid was introduced have been ASHPs (SEAI) — serving wet rads’ and UFH. The technology is well understood by a growing number of heating engineers throughout the country.
They are compact collector/compressors that can be sited on any outside wall and above all else are the least expensive option with only a fractional difference in performance from the most costly vertical geothermal HPs which demand excavation that tear into established landscaping.
ASHPs have a fan and do produce noise while running of 45-60dB, but should not be a nuisance to you or a close neighbour (check the rating on the unit’s certification before you buy for the Quiet Mark).
If a fridge running outside your bedroom window would annoy you — don’t site the pump there.
If the house is HP ready in terms of major plumbing decisions fitting an ASHP will involve about two days from putting in concrete footings for the outdoor unit to detaching the old boiler, running cabling and water lines to setting up the system on your electrical circuit, and final commissioning.
In a larger installation, a buffer tank to prevent inefficient ‘cycling’ may be required and its position if inside the house will have been decided well in advance.
Half of properties required further works to the fabric of the house to be eligible for SEAI grant aid since the scheme launched in September 2018. Of the projects completed into the spring of 2019, the average cost of works was about €11,000 before grant aid.
A small number of geothermal heat pumps were installed and cost between €7,000 and €32,000 (SEAI).
That capital outlay that can only be nailed down by entering the process with a Technical Assessment and following up with quotes from suppliers and installers when the house is HP ready.
You must have a follow up BER assessment carried out after your HP is installed.
Anecdotal. Agents I’ve spoken to say that energy efficiency is now a more common question with their viewers.
We have as yet, no firm evidence of buyers’ reaction to better BERs and HP operated homes. Put your immediate needs and long-term cost savings first, then keep those utility bills to prove your point at sale.