The challenge of sustainable heating was an important agenda item at a recent Peter Birtwistle Trust Almshouse Networking Event. They asked a local expert for his advice and have kindly made it available to the membership.

Our thanks to John Book of JRB Environmental Design Ltd for putting together the below notes and to Alison Evans, Executive Officer Peter Birtwistle Trust for sharing them with us.

Heating advice notes for almshouses

  1. The initial approach should always be taken as fabric first, i.e., to look at ways of improving the thermal properties of the buildings through the provision of double glazing, roof and wall insulation.
  2. Lighting should be looked at with the provision of LED lamps wherever possible.
  3. Look at the possibilities of introducing Solar PV panels for the generation of electricity, and/or wherever possible for the domestic hot water usage look at the provision of Solar Thermal panels connected into a twin coil cylinder.
  4. The heat source is the big challenge for us at the moment certainly with the drive to move away from fossil fuels, however, the following considerations should be made.
    • The initial thoughts are to try and changeover onto electrically based systems, but unless you can introduce the use of heat pumps which have a proven track record of providing 3kW of heat from 1kW of electricity, then as the cost of electricity is still currently approx., 3 times more expensive that gas, then any other electrically based systems may prove to be unaffordable to run.
    • Heat pumps take the form of 2 types, i.e., either air source heat pumps (ASHP) or ground source heat pumps (GSHP). Whilst GSHPs operate with a slightly better efficiency they are probably twice the cost to install than ASHPs simply because of the ground works required to either accommodate pipe loops or boreholes.
    • Ideally the use of heat pumps would need a 3-phase electrical supply although there are some single phase units available for domestic size ASHPs, but again the existing loading on the incoming electrical supply would have to be checked for capacity availability.
    • The only real further consideration for the use of heat pumps would be just what the existing heating system is that the present boiler is serving, as this would have been sized to provide the heat output with water supplied from the boiler at a mean temperature of 70°C, whereas heat pumps only provide a mean temperature of 50°C. This will mean that if you simply put say an ASHP onto an existing radiator system that you would have to run the system longer and lose any carbon benefits, whilst increasing running costs. Hence if heat pumps are to be looked at then the existing heating system may have also to be considered for replacement.
    • If the electrical supply is inadequate then the option may have to be to still remain with a boiler system, and where a gas supply existing then the consideration would be to look at the use of a ‘hydrogen ready’ gas boiler. New boilers are probably twice as efficient as old/existing gas boilers and hence there would be an immediate reduction in carbon generation in the order of 50%. We are currently being advised that a 20% hydrogen gas mix may become available in the next 2/3 years, through the national grid network system, and of course when this does so the already reduced carbon generation from any new/replacement gas boiler would be further significantly reduced.
    • Where gas is not available then the use of either a bio-fuel oil or a bio-LPG boiler could be considered, which would obviously show good reductions in carbon generation, albeit these costs are more expensive than conventional oil or LPG.
    • Considerations will need to be made as whether each almshouse has its own dedicated boiler system, or whether a group of almshouses is served from a common boiler plant.
    • If the almshouses are served individually then the foregoing comments would apply, if however, they are served from a common source, or whether this option may be worth looking into as an alternative, then the following other options could be considered.
    • Depending upon electrical supply capacity issues, it may be possible to consider ‘hybrid’ systems, having a mix of heat pumps and boilers with the heat pump providing enough heat to maintain a background warmth in the properties at say 15°C, with a hydrogen or biofuel boiler simply being used to raise that temperature to say 21°C when required.
    • Rather than considering direct heating from a central heat plant source to the existing heating and hot water services within each almshouse then an option would be to provide Heat Interface Units (HIU) within each almshouse, which are connected by heating flow & return pipework from the central heat source, which could still be a ‘hybrid’ system if supplies allowed.
    • Another option would be to provide to internal wall mounted water source heat pumps which would be served by an ambient water pipe loop which could be taken from any ground source available, or indeed a centralised heat pump system. This type of system is supplied from a water loop at say 30°C and then is converted internally up to normal heating boiler temperatures.
    • The use of programmable thermostat controls which can be accessed remotely would be essential to consider so that actual space temperatures and operating times may be assessed.

Summary Conclusions

Clearly whilst we all have a duty to try and reduce the carbon being generated from the heating and hot water systems, which will almost certainly require significant capital expenditure, it is also important that we should still consider making whatever heat source options are to be selected, that these are still affordable to run and maintain.

The first stage of any considerations for this would be to initially assess / survey just what the current systems comprise of along with structural assessment for thermal insulation, and of course types of lighting being used.

Note: The products/services and claims made above have not been evaluated by The Almshouse Association. Articles that recommend products/services are for information purposes only and are not endorsed by the Association. Information is provided for the general guidance of trustees and clerks, who should take their own professional advice where necessary.

posted 20 September 22