Condensation Conundrums Webinar Association of Wall & Ceiling Industries (AWCI) 24 th February 2015 Andy Russell, Proctor Group Australia Disclaimer: There are a large number of factors that need to be considered in assessing and managing condensation risk. Such factors include the local climate, building use, position, thickness and type of insulation, position and integrity of vapour barriers, and the degree and location of mechanical or passive ventilation both in the roof space and the interior. The details supplied here are based upon good practice and currently available information contained in the ABCB Condensation Handbook. However Andrew Russell, Proctor Group Australia, Dynamic Composite Technologies or the Australian Institute of Architects do not accept responsibility for losses incurred resulting from the use of any details or information contained within this presentation. Any materials mentioned are generic and do not necessarily represent materials supplied by Proctor Group Australia, Dynamic Composite Technologies or any specific manufacturer. Specific advice relating to installation or appropriate use of products should be sought from the manufacturer or supplier.
Who is Proctor Group Australia?
How will future generations look back at “industry practice”
Moisture Management by climate Wall type 1 A – Tropical B – Temperate C – Alpine
Moisture Management by climate Wall type 2 (Conditioned building) A – Tropical B – Temperate C – Alpine
Moisture Management by climate Wall type 3 A – Tropical B – Temperate C – Alpine
Moisture Management by climate But wherever I go in Australia this is what we see?
Where are the problem likely
Maybe in New Zealand but not here…. “But this is Australia. I’ve never seen it.”
it couldn’t happen here… could it ?
it couldn’t happen here… could it ?
it couldn’t happen here… could it ?
it couldn’t happen here… could it ?
it couldn’t happen here… could it ?
it couldn’t happen here… could it ? Mark Dewsbury (PhD), School of Architecture and Design, University of Tasmania
“But this is standard industry practice. That is what we’ve always done”
Denial Must be the possums …. Did you go up there with a hose pipe. Not in Australia
Anger Kevin Rudd / tree Why hasn’t huggers and all that anyone told us. energy efficiency Not in the stuff are to blame. BCA? Bloody Scotsman That is what it shows coming over here to tell us in the install guide / what we are industry handbooks. doing wrong.
Bargaining It is just happens in I build to the NCC and Tasmania, Darwin, there is nothing in New Zealand there about condensation But I used that foil If I put a powered roof with holes or the vent up there I’ll fix it foil faced blanket I’ll be long gone by the It will dry out in time it goes wrong the summer
Depression I am ruined. Why go on? This is just too hard. Better put the house in the wife’s name
Acceptance The solutions really I can fix this. aren’t that hard or expensive. If I get this right, I can make a point of difference That is all I have to do ?
What is condensation What has changed Why more problems in buildings Consequences Insulation, pliable membranes & ventilation
WHAT IS CONDENSATION ?
Building science geeks down at the pub?
Types of condensation Surface condensation Surface condensation takes place on the surface of a body when the temperature of the surface is less than the dew point temperature of the surrounding warm moist air. Interstitial condensation Interstitial condensation occurs as a result of moisture diffusing through the permeable building fabric from the high vapour pressure side to the low vapour pressure side.
Where does the moisture come from? ABCB Condensation in Buildings Handbook, 2014
Where does it end up – surface condensation OAA Mould Control Practice Guide, Ontario Association of Architects (2003)
Where does it end up - the building envelope Condensation can form under roofing that cools to the outdoor dew point. Night sky cooling makes condensation likely in many Australian locations. Sarking without insulation can collect condensate from under roofing and be allowed to either dry upon day break or drain to guttering where detailing allows. Condensation can form under sarking that cools to the outdoor dew point in ventilated and unventilated roof spaces Insulation to avoid condensation under sarking may need protection from wetting by roof condensate. Insulation on ceiling cuts heat loss but surface temperatures above become colder. Colder roof spaces require better control of air leakage through ceilings. Insulation in walls cuts heat loss but cavity temperatures become colder. Colder sub-floor spaces can raise relative humidity and increase moisture levels in timber framing. Colder sub-floor spaces may require membrane to seal ground surfaces. Condensation can form inside impermeable wraps or panels that cool to the indoor dew point.
WHAT HAS CHANGED AND WHY WE ARE SEEING MORE PROBLEMS ?
What has changed? A good builder problem • Increased air tightness • Increased insulation Industry / Cost Pressures • Reduced moisture storage capacity • More manufactured materials
What has changed? ABCB Condensation in Buildings Handbook, 2014
If we were to start all over again….? Water tight Air tight Vapour Permeable Radiant Barrier
The primary purpose of a sarking R0.9 Insulation R0.0 P’board air films etc. R0.3 Reflective air space R0.6 = R0.9 With one reflective surface facing inwards
Need more ‘bulk’ insulation R0.9 + R2.0 batts = R2.3 ? Insulation R2.0 P’board air films etc. R0.3 = R2.3 No still air space adjacent to reflective surface.
Vapour drive from inside to out
Vapour drive from inside to out
Just like on the inside of glazing
Preferable to have a cavity Insulation R2.0 P’board air films etc. R0.3 Vented Cavity R0.14 = R2.44 And you get good moisture management + Drainage + Drying + Durability
The CSIRO mentioned this back in 2001 Higher levels of insulation may introduce unforeseen problems where they are incorporated into construction styles which have previously been relatively immune to condensation. This is because insulation, whilst it keeps some surfaces warm, also keeps other surfaces cold . High levels of ceiling insulation mean that roof spaces are colder as they are not heated to the same extent from below. Incidences of condensation within pitched roof spaces with sheet metal roofs are increasing in line with the trend to higher levels of ceiling insulation .
How does water vapour move? Diffusion Air movement
Why does condensation occur in buildings ? the presence of moisture levels which are too high; the presence of temperatures in the building fabric which are too low; and uncontrolled flow of water vapour from a source to a region of cold temperature (cold condensing surface).
Permeability of different building materials Glass, Steel, Aluminium Sarking >1000MNs/g 110mm Med. Wgt. Brick 5.5MNs/g 10mm FC Sheet 1.1MNs/g 10mm Plasterboard 0.6MNs/g 90mm Insulation batts 0.5MNs/g Values from BS5250:2002
Vapour barriers, permeable sarking and beer.
Vapour diffusion and permeable materials
THE CONSEQENCES
It doesn’t always make the news....
The Consequences Visible and hidden fungus and mould growth Sick building syndrome leading to serious health problems Timber decay Corrosion Loss of structural integrity Phantom leaks Saturation of insulation and loss of insulation effectiveness Surface condensation problems
The ingredients for mould
Loss of insulation effectiveness Keep insulation dry Cammerer, J. und Achtziger,J.: Einfluß des Feuchtegehaltes auf die Wärmeleitfähigkeit von Bau- und Dämmstoffen. Bericht zu BmBau Forschungsvorhaben BI 5-800883-4, 1984.
Can one material do it all ? External Moisture Thermal Vapour Air Tightness Management Resistance Management Adapted from Habitat Congress Building America, Michigan, Building Science Consortium, 2006
Sarking types in relation to vapour diffusion Vapour Barriers (vapour diffusion retarder) • used to restrict the transmission of water vapour Vapour Permeable (breather) membrane • Intended to allow the transmission of water vapour
Where are the products being sold as breathers
Drying rates for different sarking No sarking Moisture Content of timber sample Vapour barrier Foil with holes Vapour Permeable Weeks CSR Building Knowledge Issues 5 (2014)
After 6 months Vapour Permeable Foil with holes Vapour Membrane barrier CSR Building Knowledge Issues 5 (2014)
Importance of vapour barrier integrity
WHERE TO FIND GOOD RELIABLE INFORMATION
Recommend
More recommend
