Technologies assessed via Appendix Q

Below is a description of the technologies currently assessed via Appendix Q

Mechanical ventilation systems

(a) Mechanical extract ventilation (MEV)

MEV is a fan driven ventilation system, which only extracts air from the dwelling. The SAP calculation is based on a throughput of 0.5 air changes per hour through the mechanical system, plus infiltration.

MEV can be either:

- centralised: air is extracted from wet rooms via ducting and expelled by means of a central fan., or
- decentralised: air is extracted by continuously-running fans in each wet room.

 

(b) Balanced whole house mechanical ventilation

Balanced ventilation provides fresh air to habitable rooms in the dwelling and extracts exhaust air from wet rooms. 

A balanced system without heat recovery extracts from wet rooms via ducting and expelled by a central fan. Air is also supplied to habitable rooms, either via ducting and a central fan or by individual supply air fans in each habitable room.

In a balanced system with heat recovery (MVHR) both the extract and supply air are provided via ducting, with a heat exchanger between the outgoing and incoming air.

 

Flue Gas Heat Recovery Systems (FGHRS)

FGHR is a system (i.e. one or more connected devices) for recovering heat from flue gases that would otherwise be wasted.  It may be passive or include powered devices such as a pump.

 

Waste Water Heat Recovery Systems (WWHRS)

WWHR is a system for recovering heat from grey water that would otherwise be wasted.  The recovered heat is transferred to the mains water, which may be fed directly into the consuming appliance and/or into the hot water generation system.

 

Hot Water Only Boilers

A Hot Water Only Boiler is a boiler that provides hot water only.  The space heating is provided by a different part of the same system or a separate system.   

 

 

Heat Pumps

a) Air Source Heat Pump (air to water)

 

A heat pump designed to transfer heat from the outside air to a water-based heating system.  The heat may be used for provision of space heating only, domestic hot water only, or both.

 

b) Ground (Brine) Source Heat Pump (water to water)

 

A heat pump designed to transfer heat from the ground to a water-based heating system.  Heat is extracted from the ground using closed loop pipes buried in the ground. A fluid of water and antifreeze (brine) is circulating in the closed loop.   The heat may be used for provision of space heating only, domestic hot water only, or both.

 

c) Exhaust Air Source Heat Pump with Whole House Mechanical Extract Ventilation – Exhaust air only (air to water)

 

A heat pump designed to transfer heat from the exhaust air to a water-based heating system.  The heat may be used for provision of space heating only, domestic hot water only, or both.

 

d) Exhaust Air Source Heat Pump with Whole House Mechanical Extract Ventilation – Exhaust air plus mixed ambient air (air to water)

 

A heat pump designed to transfer heat from a mixed air stream of exhaust air and outside air to a water-based heating system.  The heat may be used for provision of space heating only, domestic hot water only, or both.

 

 e) Exhaust Air-Source Heat Pump with Whole House Balanced Mechanical Ventilation with Heat Recovery (air to air)

 

A heat pump designed to transfer heat from the exhaust air to the outdoor (supply) air. These heat pumps may also transfer heat from the exhaust air to a water-based heating system.  The heat transferred to the water based heating system may be used for provision of space heating only, domestic hot water only, or both.