Keeping things fresh with Passivhaus

GUEST BLOG: Malcolm Taylor, Product Manager at REHAU

When you’re as immersed in the fenestration world as I am, it’s easy to think that Passivhaus design and construction is all about glazing – minimising the U-Values on the windows and doors and then focusing on the sealing tapes to maximise the air tightness values.

Of course, to a large extent that is true, but what I am increasingly being reminded of by my colleagues in other parts of REHAU is that, however effective the windows and doors are in achieving air tightness in a Passivhaus building, there is always a requirement for effective ventilation.

At virtually every Passivhaus seminar or event I attend on fenestration, there are questions raised by specifiers on how to manage the issue of fresh air supply.

Of course, from REHAU’s point of view, there’s an easy answer to that because we offer our AWADUKT Thermo ground – air heat exchanger system which draws fresh air from outside and delivers tempered air into the building though a network of underground optimised polypropylene pipework.  

AWADUKT Thermo relies on laying pipework at a depth of around 1.5m and then using the natural temperature of the earth at that depth to pre-warm or pre-cool incoming air depending on the season.  In a Passivhaus building, it’s possible to achieve an impressive Coefficient of Performance of around 20, with air in the summer being cooled by up to 14°C and air in the winter being warmed by as much as 9°C.

Obviously in an air tight building, the key consideration is that the ventilation air is actually fresh and kept free from the risk of musty smells and microbial growth, and this is achieved thanks to an integrated antimicrobial silver layer on REHAU’s pipe.

UK Passivhaus Awards

At the recent Ecobuild exhibition, there were some great examples of both fenestration and ventilation solutions on show for the Passivhaus sector and there was an encouraging number of visitors expressing a real interest.

Ecobuild also of course saw the launch of this year’s UK Passivhaus Awards which REHAU are sponsoring.  They are primarily celebrating the custom/bespoke market and are open to any building with a treated floor area of up to 500m².  To enter, the building must have been completed and certified to Passivhaus/EnerPHit standard or be able to demonstrate that it has been built or retrofitted to the standard. 

The deadline for entries isn’t until 9 May so there’s plenty of time to get involved.