Breathe a Little Easier
In July/August’s edition of the RICS Property Journal, Paul has written an article titled ‘Breathe a little easier’ as a response to an earlier article ‘Studying the links’ (November 2015, p.34), which considered the connection between indoor air quality and asthma, this will concern surveyors involved with energy-efficient buildings.
Paul Mallion explains how the German Passivhaus standard can prevent condensation and mould growth and provide excellent indoor air quality compared to more traditional designs.
The article can be found at www.rics.org (pages 38 & 39).
As a supplement to the article, here are Conker’s tips for a successful Passivhaus project:
- orient the building to the south to take advantage of solar gain and to make it easier to provide effective solar shading
- keep the building compact with an efficient form factor
- west-facing windows can be hard to shade and are most likely to cause overheating
- allow for thick wall, floor and roof insulation from the outset and do your own calculations for U values, including ties, timber studs and other repeating thermal bridges; two or more layers of overlapping insulation are more reliable than one
- plan an easily accessible plant space with sufficient room for a ventilation unit and supply and extract ducts, plus good access for replacing filters
- instead of using mastic for airtightness, use foils, tapes and compressible foam strips for sealing windows and other junctions where differential movement will occur
- blockwork is surprisingly permeable, unless plastered or parged, so avoid dry lining over masonry backgrounds
- thermal bridges must be avoided, such as steels projecting through the insulation layer
- allow for carrying out an air-leakage test before final plastering and on completion, with plumbers and electricians attending, so they can see the impact of any holes they have made
- for your first few projects, work with an experienced Passivhaus designer to guide you through the process; it will save money and time in the long run
- remember not all insulation materials are suitable for all instances, and compressible insulation is often a better fit than rigid boards even if the K value is less, as this prevents numerous small gaps that occur as the building dries out and shrinks
- drying out takes longer than normal, as there are no draughts to aid the process.
Useful Passivhaus links: