Mr Philip Daw                            HRSC0010

Written evidence submitted by Mr Philip Daw (Director, NEATAFAN Ltd)

   COOLING AND DEHUMIDIFYING A DOMESTIC UK HOUSE

Using an existing heat pump and modified ventilation system.

 

  1. In the UK summer, ambient daytime air conditions can reach 40c/ 27%RH (dew point 19c).
  2. What is often overlooked when discussing passive cooling etc. is the inability of these systems to reduce the uncomfortably high moisture content of our maritime climate.
  3. The recognised comfortable indoor condition of 25c/ 50%RH (dew point 14c) can only be achieved in practise by cooling and dehumidifying the room air with a conventional AC unit.
  4. The AC unit only recirculates the same (often stale) air with the fresh input air (if provided!) set to minimum. In addition to this, the control is via an occupant who does not set optimum conditions and lets them drift down to 20c/40%RH (dew point 6.5c).
  5. NB: The dew point is the temperature that moisture would form on surfaces when cooling one particular air condition. It is useful for the comparison of indoor and outdoor air conditions.
  6. The optimum modern new house should have (in an ideal world) external shading, a light coloured roof, high levels of insulation, an airtight envelope, a heat pump and an MVHR ventilation system.
  7. The duties of a heat pump in summer are limited to providing hot water or they are left idle, if they were fitted with a reversing valve (common practise with AC units), they could provide chilled water and cool incoming fresh air to 22-24c/55%RH. Bathing the house in healthy, filtered outdoor air at comfort conditions.
  8. The electrical energy required to do this could be a mixture of solar and the grid, putting minimal strain on existing power lines at a time when more renewable energy should be available.
  9. In addition, automatic control of the input fresh air condition will save energy over the poor control provided by using an AC remote.
  10. The government need to permit the use of heat pumps with reversing valves and encourage the building of new houses with optimum features as already mentioned.
  11. The fitting of conventional AC units to older properties should be discouraged.

 

Philip T W Daw

Director, NEATAFAN Ltd.

50 years of experience in the HVAC industry.

August 2023