Keeping nature at bay

Many factors contributed to problems with weathertightness. Poor design, poor project management and poor building practices played a role.

The exposure of New Zealanders to international design trends and materials has led to a wider range of housing styles, but some house designs and materials are unsuitable to specific site conditions. Some house styles and features designed for dry climate locations have been used in areas of high wind and rainfall. Features such as parapets, decks and pergolas that penetrate a dwelling’s cladding contribute to weathertightness risks, as does monolithic cladding, low-slope roofs, membrane roofs, a lack of eaves and complex junctions, especially when these are used in wet and windy conditions. House claddings do leak. That becomes an issue when the water is not dealt with effectively and affects the integrity of the house. The Canadians developed the 4Ds philosophy of weathertightness – deflection, drainage, drying and durability. In New Zealand we have adopted those principles, but we now also consider airtightness, ventilation and insulation. The ideal is to achieve all 4 Ds. Deflection devises (such as cladding and window head flashings) intercept water at a building’s exterior and deflect it away from critical junctions. Wall assemblies need to be designed and built with protected cavities to incorporate drainage to allow any water that may have penetrated the exterior cladding to drain down the back of the wall cladding and out. The amount of drying that occurs depends on the cladding type and the way it is installed and all components of a cladding and wall assembly must meet the durability requirements of the Building Code. Leaky building basics Features of a leaky building 1. Ground clearance: Inadequate cladding clearance to ground, paving or decks or insufficient fall away from building perimeter. Clearance to solid ground (concrete, asphalt, paving, decking timber) should be 150mm; clearance to soil 225mm. 2. Cracking: Look for hairline cracks in the cladding, typically found close to windows and doors or discolouration of cladding around these areas. 3. Joinery: Check for cracks along the joinery seals which can allow water ingress. 4. Penetrations: Check all penetrations in the cladding, for example around pipes, vents and meter boxes, for gaps and lack of sealant. Also check to ensure meter boxes are flashed correctly - the lack of flashing or reliance on sealant may allow water to penetrate. 5. Pergolas: Pergola frame penetrating the cladding or direct fixed through the cladding may result in water ingress. 6. Windows: Check window flashings to ensure they are correctly installed. Round, shaped or corner windows are difficult to flash, increasing the risk of water ingress. Check for staining below the window.

7. Enclosed balcony / cantilever deck:

Enclosed balconies and cantilever decks can result in a multitude of risks. (a) A lack of fall on the balustrade, (b) Handrailings attached through the plaster cladding, (c) Poorly applied waterproof membrane, (d) Insufficient drainage holes allowing water to pool after rain, (e) Lack of clearance between the cladding and the balcony floor - all are signs that water may be penetrating the building’s exterior. 8. Interior signs: These can include swollen or cracked skirting boards or architraves; mould on the inside of curtains and window liners; floor coverings showing signs of water damage; and swelling, cracking and popping of wall liners. CT

Resilient buildings

What could make a building more resilient to climate change and environmental challenges during its lifetime? There is more to this than making a structure earthquake-strong and weather-tight.

Rain on the Plains

A warming climate brings greater water-carrying capacity in the atmosphere: we can expect heavier winter snow on higher ground and more frequent rain or hail than experienced last century. Drains could be overloaded as ‘fifty year flood frequency’ becomes perhaps ‘ten year frequency’ and detaining flood water will be needed to help roadside swales cope.

In the east of NZ, climate change may mean the year’s rain falling in uneven bursts between periods of drought: rain water storage may become a part of resilience for buildings as well as farmers. Garden watering and toilet flushing are good uses for stored rainwater, reserving piped supplies fore essential uses. Water storage is also really useful in civil emergency, such as after quakes.

What’s the buzz?

Warmer temperatures and dwindling frost nights may allow mosquitoes to spread their habitat southwards, boosting demand for insect screens on windows. Longer growing seasons may favour home food production, coupled with fashionable edible decorative gardens. The resilient home needs space for raised garden beds and healthy soil left on site after construction: free from lead paint scrapings or construction debris.

Warming to the idea

Sunshine is the free heat that a resilient design incorporates by increasing north-facing glazing and reducing on the south, provided the structure has internal thermal mass to absorb heat by day and release it overnight, achieving temperature stability. External shading from mid-summer heat is important too. Insulation needs to be extensive, and be placed outside the thermal mass of the floor or sunlit walls, for it to work. Placing carpets on insulated concrete floors does not work: floors need to have attractive surfaces such as tiles, to let the energy flow in and out.

Photo-voltaic panels are most useful on building where most of the energy use is 9am to 5pm, such as schools, factories and offices; although fast developing battery technology may soon make 24 hour power storage cost effective for households. Decentralised power production increases resilience by reducing reliance on large and distant generators, linked by the national grid.

Future Living Skills

A more resource-efficient, less polluting future will call on a new life skills from building users as well as designers and constructors. We may need to know something about local food production, low-carbon transport, waste and water minimisation and community resilience. These topics feature alongside energy and eco-design in a community education programme which is freely available in Christchurch and Waimakariri. For details see www.sustainableliving.org.nz. On this website, under ‘Learn’ you will find occasional tutor-led courses and workshops, if you are ready to seek contact with others sharing this interest.

There is also good advice on including sustainability awareness in new building and renovations at:

www.ccc.govt.nz/environment/ sustainability/build-smarter

www.ecodesignadvisor.org.nz/resources

Rhys Taylor is the National Coordinator of Sustainable Living Education Trust. He lives in Canterbury.

Less waste, low carbon, great quality of life!

We do

use fun group activities, relevant web-links and accurate science

We don ’t

use guilt or fear, confusion, or free gift junk