Heat pumps for large old homes

This week came the disappointing news that the government is abandoning plans to require all new homes to be carbon neutral from 2016. This makes it even more critical that we look hard at our existing housing stock to see what can be done to improve it. And I love to pick that low hanging fruit – the kind of project that can equate to saving the equivalent to the output of dozens of new homes. Very often though the potential to save money and fossil fuel on these properties is overlooked because they are seen as hard to treat and this is equated with “won’t be worth it” or just plain “won’t work”. But if you want to develop your business and get some prestigious projects under your belt, these kinds of properties should be on your prospecting list, and what’s more there’s no need to wait until a major refurbishment drives change; done right these projects can pay and offer benefits to owners and custodians even when the emitters are old and there won’t be double glazing.

Two recent award-winning projects we have completed show the value of this kind of approach. First up is Plas Newydd – a huge grade 1 listed National Trust mansion. It was clear from the start that ripping out the ornate, cast iron Victorian radiators was not going to be an option. The same sort of considerations were at play with grade 2 star listed Soulton Hall – a historic manor house and hotel. But this kind of building has a huge financial and practical incentives to seek alternatives to fossil and solid fuels and moreover have assets and mindsets that make them ideal candidates:

  • Cost. Plas Newydd was burning thousands of pounds worth of oil a week. And with fossil fuels – or indeed solid fuels like biomass - you are at the mercy of the markets if this cost escalates. Reducing these costs and reducing exposure to market fluctuations is a front-of mind-issue for the owners and managers of these properties because the numbers are so large - Soulton Hall now saves £10k a year on its heating costs for example.
  • Large properties run on oil, gas or biomass mean large stores of fuel with an associated fire risk. Getting rid (or even reducing the size) of this store is a weight of worry removed for owners. The ongoing maintenance involved with biomass in particular can be a hassle, particularly as owners become more elderly.
  • Large properties often have large grounds and even access to water for the most efficient water and ground source systems, perhaps - as at Soulton Hall and Plas Newydd – even allowing them to use solar energy to offset their electricity usage
  • The owners and custodians of these properties think in the long term both in terms of the economics and the sustainability; they tend to have a mindset that allows them to understand the value of capital investment that saves in the long term and preserves their property and environment for the future. The owners of Soulton Hall, for example, have aspirations to make the whole estate as energy self-sufficient as possible.
  • Reducing reliance on oil, gas and biomass also gets rid of the associated management of deliveries, which can be a consideration for semi-commercial properties.

So how do you get a heat pump system to work effectively when you have leaky old radiators and no insulation to speak of? When you can’t even zone the system properly because you can’t install modern thermostats and cut outs? You can’t run a heat pump system hot to mimic a boiler without ruining the efficiency and longevity of the system – so how on earth does it all work? Surely this is a recipe for disaster the like of which we haven’t seen since the first few years of heat pumps becoming popular in this country? Put like this it does sound like a crazy idea and you can see why you might never think of approaching a client in that situation.

The short answer is that we run the heat pumps for a longer period of time and at low temperatures, but we make sure the source is good enough to ensure a good COP. Really high performing ground loops (moisture retentive soil helps here and with extra length added to compensate if required) or water source make this a whole lot easier. But as previously mentioned, space and access to water often come with large properties. The COP of a heat pump is not only to do with the SPF of the emitter circuit:it also has a lot to do with the source temperature. Because it is such an important part of the calculation we always provide installers with support to work on these calculations to ensure that the needs of the property will be met on such a project.

For clients this means that they have to become accustomed to different heating patterns and understand that they won’t have rapid response times, but need to keep the heating on for longer at lower temperatures. Whereas I have often said that in the UK climate it is not necessary to run a continuous heating pattern with new build or retrofit homes where the emitters are updated, this is not the case where you are stuck with a legacy system. This is in many ways a benefit to owners of these large properties who will enjoy greater stability in their comfort. Moreover, for properties such as Plas Newydd, which contain numerous objects of value, consistently controlling the humidity of the building to preserve them is also vitally important and best served with this kind of heating pattern. And, most importantly, even with a continuous pattern, properties like this can save hugely on fuel costs and carbon. Another thing to consider is that bivalent systems are often appropriate for these properties – a heat pump sized for 50% of peak load will usually supply 80% of the property’s needs at lower up front cost, and offer a bit more flexibility with response times if temperatures drop suddenly.

So if you have clients in your area who might have themselves have dismissed the idea, it might just be worth re-evaluating to see if there is anything you might be able to do. A quick first approach is to take the litres of oil used per annum and divide it by 250 to get a kW size for the heat pump to see if the project might have some legs.