Foil-backed building materials appear to be economical, convenient, and popular. Some claim they are also fireproof and airtight (which is debatable at best). So why do we – and other cutting-edge builders — avoid using them?
Foil-backed building materials are supposed to be excellent insulators that prevent the transfer of heat from outside to inside your home and vice versa. They typically have a shiny, silver surface on one or both sides. This shiny surface is the hub of the problem, often leading to:- Condensation
- Mould
- Rotting timber
Foil-Induced Condensation
When there is a temperature difference between one side of a material and the other (as is the case with insulation), moisture in the air condenses. You notice this when you have a cold drink in a glass on a hot day. As the hot air touches the cold glass, moisture condenses.
Condensation is the root cause of many problems in homes including mould and timber rot.Foil-Induced Mould
The moisture that condenses on one side of foil-backed building material can drip or run onto other surfaces, causing them to become damp. This dark, damp (even wet) space provides the perfect environment for mould to grow. Sometimes it remains inside the walls and ceiling. Other times it permeates your plasterboard and starts growing on your internal walls and ceiling.
Mould can trigger many health concerns including nasal congestion, sneezing, coughing, wheezing, and respiratory infections. These can worsen over time into more serious asthma and allergic conditions.Foil-Induced Timber Rot
The moisture caused by condensation on foil-back building materials, can drip onto the timber frame of your home. This can cause the timber to rot prematurely which can compromise the structural integrity of your home. Yes, all because there is foil-backed material in the walls.
Some builders try to overcome this by using treated timber. But this just delays the inevitable. And off-gassing from the chemical treatment in the timber affects the health of those living in your home.Leaky Building Crisis
Foil-induced condensation, mould, and timber rot is so rampant in New Zealand, it’s been called the leaky building crisis. Estimates suggest it has affected more than 89,000 homes and buildings including schools. The issue is so serious it has prompted the government to amend the building code.
The Lesson
Foil backed building materials are just one of many popular products that can end up causing many unintended issues. Be sure your builder understands the building materials they are using in your home.
For more information on the best building materials to use in your home, we invite you to where we will answer your questions and show you the most efficient and affordable way to get a comfortable, energy efficient custom home you’ll love forever. Whether you’re looking to achieve certified passivhaus standards, or you simply want a house that is healthy, comfortable, and energy-efficient, we’d be glad to show you exactly how to do it the right way via our special report, The 5 Key Skills of an Energy Efficient Builder.Frequently Asked Questions
Why do quality builders avoid foil-backed building materials?
Their shiny surface, meant to insulate, often causes condensation, mould and rotting timber. Because they sit inside walls, the problems go unseen and undetected until they are expensive or even impossible to fix.
How do foil-backed materials cause condensation and mould?
When there is a temperature difference across the material, moisture in the air condenses, like a cold drink on a hot day. That moisture drips onto surrounding surfaces, creating the damp, dark conditions mould needs to grow.
Can foil-backed materials damage a home's structure?
Yes. The condensation can drip onto the timber frame and cause it to rot prematurely, compromising structural integrity. Using treated timber only delays it and adds chemical off-gassing that affects the health of those living in the home.
How widespread is the foil-backed materials problem?
It is so rampant in New Zealand it is called the leaky building crisis, estimated to affect more than 89,000 homes and buildings including schools, and serious enough to prompt the government to amend the building code.
