MVHR (Code 4 home)

The Code 4 uses a mechanical system for ventilation and heat recovery.  The system specified in this project is Nuaire's MRXBOX90.  This is an all in one heat recovery solution for ventilation, space heating and summer free cooling. The concept is to provide optimised, balanced (supply and extract) mechanical ventilation with heat recovery. 

This is a whole house ventilation system incorporating extract and supply ducts and a heat exchanger to transfer heat. The unit is stored in the roof space while allowances have been made for enough space in the floors and walls for the ducting. The layout of the homes have been considered with this in mind. The MVHR unit used in the Code 4 home is the Nuaire MRXBOX90. This unit is SAP Appendix Q compliant.


The system will quietly and efficiently provide the dwelling with warmth when required, and fresh, filtered air all year round. 

Among other features, it is 95% efficient with DC motors using 50% less energy than traditional fans. Two self adjusting fans provide constant fresh air. The supply and extract filters remove up to 95% of dust from the atmosphere. To recover heat from the extract air an aluminium heat exchanger block is used. This heat exchanger can recover over 70% of the normally wasted heat.

Further information


Open the Code 4 MVHR doc (12.16KB) or see more information on the Nuaire website (new window).


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Fact 24

Almost 150 MtCO2 could be saved if all dwellings inthe UK were zero-carbon.
Source: Energy Saving Trust 2008