Low carbon cooling and ventilation

Ventilation systems are highly desirable because of their role in reducing humidity; smells and CO2 build up from everyday human indoor activity. However, there is a balance to be struck between the need for fresh outdoor air, the power required to drive the systems and the need to reduce heat losses through air leakage.

A number of automatic ventilation systems are available that deliver this balance and when combined with heat recovery can recapture much of the wasted heat from exhausted outgoing air to pre-warm the incoming fresh air and save energy.

Heat pumps
Many engineers are now combining these systems with heat pumps to deliver a highly sustainable solution.

Individual room ventilators are usually installed in the wall and are fitted with a heat exchanger for the heat recovery function. They use fan power to move the treated air in and out of the room.

Centralised ventilation systems for whole buildings use ductwork built into the ceilings to move air around with grills providing air intake and extract for living rooms and bedrooms to tackle condensation and humidity. Built-in heat exchangers are capable of recovering up to 95% of the heat from outgoing air in such systems.

Heat recovery
For full blown air conditioning systems, low speed fans; efficient motors and heat recovery mean that end users can now have the increased comfort without paying the energy penalty – if the systems are properly designed and installed. The proliferation of portable units seen during British heatwaves is not a good development for the environment as this tends to be an extremely energy intensive way of cooling offices, homes and shops.

Manufacturers also offer air conditioning systems that use ‘natural’ refrigerants such as ammonia, hydrocarbons, water and CO2, however, it is important to ensure energy consumption is not compromised by the choice of refrigerant.

Issues to consider:

Is there a potential energy cost from using mechanical ventilation i.e. fan power?
What are the likely heat losses?
Is air conditioning really necessary for this building?
European F-Gas (fluorinated) Regulation is placing tougher restrictions on contractors working with refrigerants