Exhaust air heat pumps – combined MVHR / ASHP systems
An exhaust air heat pump combines the functions of an air source heat pump with those of a mechanical ventilation with heat recovery system.
Key features
- Provides mechanical ventilation with heat recovery
- High coefficient of performance (CoP) due to temperature of exhaust air
- Can typically provide 4kW heating or 2kW cooling via air
- Heating or cooling is provided at a the same temperature to the whole house – limited room by room control
- Slow hot water cylinder reheat time
- No external heat pump unit required
- Not eligible for RHI (Renewable Heat Incentive)
- May need to consider additional weight
Key considerations
- Ideal mainly for a small / medium sized low energy house or Passivhaus
- The system has limited heating output and so additional electric heaters might be needed
- The system would have limited cooling output. It is not equivalent to air conditioning and would not deal with significant overheating risks
- Reheat time for hot water can be long due to the low heating capacity
- Air heating can cause lower humidity levels during winter.
- A detailed ductwork design would be needed to accommodate the ducting distribution system from the exhaust air heat pump, with larger insulated ducting compared to standard MVHR
Is it right for my project?
An exhaust air heat pump can offer a great solution in the right property, but has limitations and needs to be carefully considered. It is an innovative packaged product (just one piece of kit to provide all ventilation/heating/cooling/hot water), but needs careful thought and understanding of how these services interact with the building.
Through careful design and consideration of the limitations, exhaust air heat pumps can be a great solution. It is certainly something worth considering for smaller homes with high levels of fabric performance.
Please get in touch if you would like to discuss the suitability of an exhaust air heat pump for your project.
