My wife and I are planning to build a highly insulated property that is not served by mains gas. The property will also have solar PV panels for renewable electricity supply, solar thermal panels, MVHR and rainwater and grey water harvesting. We are now confused to how best to heat both the space and water in an efficient and eco-friendly manner. The obvious choice is an air source heating pump, but because of the high insulation and solar gains the number of times it would actually run seems to be debatable and seems hard to justify the cost of the pump. We have thought about installing a wood stove for additional heat during the coldest periods of winter, but this does not solve the problem of the best way of heating the water. Can you advise us which would be a) the most economical option to install and b) the most efficient in our circumstances.

  • Andrew Patrick

    Hello Martin

    Have you had SAP Calculations done for your design? The SAP Assessor would be able to model different types of heating and hot water systems for you, and give you information about the results. The results would show you what effect the differnent systems have on the energy performance of your overall dwelling design.

    The SAP Assessment is required for Building Regulations Approval at Design Stage and also checks other BR Criteria such as thermal fabric energy efficiency (not an issue by the sounds of it) and summer overheating risk.

    There is a range of biomass heating/hot water systems available which are as easy to control as a gas boiler, and obviously they meet your eco-friendliness criteria.

    Air and ground source heat pumps run at lower temperatures than gas boilers utilising underfloor heating and may be a good option, along with biomass secondary heating.

    The SAP Calculations would allow you to assess all the options and would contribute to your decision. A proactive SAP Assessor will research potential products for you if you need that kind of help. There may be innovative solutions which can be identidied.

    If you have been using an architect they may have a SAP Assessor in house or an associate they use.

    As you may have guessed by now, I am a SAP Assessor and would be happy to help, if you would like to contact me at

    If you need some help please contact me and I can let you have a quote once I have seen your drawings.

    In any event good luck with your project.

    Kind regards

    Andrew Patrick OCDEA

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