How to Achieve Airtightness in Your Building in Toronto?
There is growing awareness about the importance of airtightness in your building - you may have heard it talked about on your favourite home reno TV show or read about it on the internet. Airtightness in your building may not seem like a big concern - air enters and exits our buildings all the time, such as from opening doors and windows. But when approaching architecture from a building sciences approach, the airtightness of your building is an important part of building performance and longevity. Airtightness helps you more accurately control ventilation, temperature and moisture control.
Today on the blog we’re going to explain the different components that make your home or business more airtight in the building envelope, thermal and vapour layers, and insulation. We’ll also tell you a bit about air tightness testing, and what it can reveal about your building.
The Building Envelope and Airtightness in Your Building
As we talked about in our article The Importance of the Building Envelope, the building envelope is a key layer in your home’s defense against weather like wind, rain, snow, and temperature. The building envelope is made up of these parts:
And can be made out of any number of different materials. Two important parts of the building envelope that relate to the airtightness of your building are the vapour barrier and air barrier systems. We’ll be going more into depth about the vapour barrier later in this article, but an air barrier is key component in airtightness for obvious reasons - it stops or slows unwanted air flow and air leaks from the exterior to interior of your home and vice versa.
The air barrier in your home may vary - older homes had minimal air barriers and are often quite leaky, while improperly built newer homes may be so airtight that problems arise, like mold growth. If you’re renovating or retrofitting any home, old or new, paying attention to what sort of air barrier systems you employ in your building envelope will have a big effect on how airtight your home is and effect its future performance.
The airtightness of your building can often have a big impact on the energy efficiency of various appliances and on the longevity of building materials. If your home lacks airtightness, any conditioned air your furnace or A/C unit create will slowly leak from the exterior of your home; this not only makes rooms drafty and uncomfortable, but also results in an increased load on your unit, which must work more frequently to keep up with demand. It’s like trying to fill a leaky glass - you’ll always need to continue pouring more water in.
Thermal and Vapour Layers
One of the biggest problems with buildings that lack airtightness is occupant discomfort. Like we talked about in the last section, this may result in drafts, hot or cool rooms, and increased humidity. Heat moves through your building in one of three ways:
- Convection: Natural movement of air as a result of temperature differences.
- Conduction: When one thing transfers heat to another.
- Radiation: The transfer of energy by electromagnetic radiation.
Your thermal control layer will help to prevent and control these different kinds of heat transfer from occurring within your home. Some materials are better than preventing heat flow than others and need to be placed in the right location to work effectively. If you want to know more about heat, check out our article on How Can Insulation Prevent Heat Loss?
Vapour layers prevent moisture from moving through your home. Moisture is an important consideration when it comes to airtightness because water is not always a liquid - it can be a vapour as well, which allows it to travel through the air to different rooms in your building. That vapour can later condense onto another surface, becoming water again and potentially causing problems like mold growth.
Moisture can enter the home in many different ways:
- Exhaust fans from dryers and bathrooms
- Improperly sealed basements
- Leaky pipes
- Water events, like a flood or roof leak.
The ideal amount of indoor humidity is somewhere around 50% - controlling moisture in your home helps keep the humidity balanced, which is both safer for your home and more comfortable for you.
One of the biggest things you can do to affect the airtightness of your building is to ensure that you have adequate insulation installed. What is adequate differs for each home - the building sciences approach means that each part of your building envelope and the varied needs, advantages, and disadvantages of each home must be considered as a whole instead of individual component parts.
When we talk about insulation, one of the key terms used is R-Value. This refers to a material’s ability to withstand heat transfer - the higher the number, the less heat makes it through to your home. But a higher R-Value doesn’t equate to better airtightness of your building; that is something unique to each insulation material, and needs to be considered by your contractor in relation to the other component parts that are making up your building envelope.
There are two places in the home that we recommend paying attention to when it comes to insulation: the attic and the basement.
The attic is possibly the most important place in your home when it comes to making your building more airtight. The easiest analogy for this is comparing how you treat your home and your head. In the summer months, putting a hat on can help shade our face from the sun, preventing sunburn and deflecting the worst of the heat, while in the winter we wear warm wooly hats to help keep heat in and prevent chafing or frostbite. Your roof and attic behave much in the same way as your seasonal hats do - they work together to help keep your heat in during the winter months, and prevent heat infiltration in the summer months.
How this relates to airtightness is best seen in the attic, a giant room which, in most homes and businesses, is a space the size of the entire footprint of your building. This is a big space! Any problems with the airtightness of your building means that conditioned air may be escaping into the attic and out through the roof ventilation or that heated attic air may be coming down and making for an uncomfortable environment.
The same situation can be found in a basement. An uninsulated basement is unpleasant, cold, and may have moisture problems that can lead to mold growth. Insulating a basement can turn an under-utilized space into an important part of your home or business, and can help improve the efficiency of the entire home. Some types of insulation, like spray foam insulation, even help add structural stability as well as complete airtightness, making it an excellent all-in-one application.
Air Tightness Testing
The best way to assess the airtightness of your building is by having an air tightness test performed by a qualified technician. During construction, airtightness tests can be performed after the air barrier installation has been completed. But unless you have a time machine, most of us don’t have the luxury of scheduling an airtightness test during the construction of our home, which simply results in a little more time and care taken when performing the test.
An airtightness test will give you valuable information about how easy it is for air to leak through your building envelope. In an airtightness test, the first step is usually sealing all openings in your home. That includes:
- bathroom fans
- exhaust fans
- dryer vents
- HVAC system vents
- doors, windows, etc
- attic hatch
Proper sealing is the key to having an effective airtightness test of your home or business. After sealing, a ‘blower door’ (a specialized door with fans installed in it) is placed in the door of your home and switched on - the resulting changes in air pressure, flow, and air direction are then measured to give you an idea of where your home has airtightness problems. Air leakage testing will be mandatory by 2019, signaling the growing awareness and importance of this problem.
Improving Your Home’s Airtightness
If improving the airtightness of your building sounds like searching for a needle in a haystack, the good news is that it doesn’t have to be so specific - there’s no need to hunt on your hands and knees to effect an improvement in your airtightness. There are great solutions and retrofits that can be made to improve the airtightness of your building that result in a positive effect almost instantaneously. A more airtight home will result in lower heating costs, increased energy efficiency, and a more comfortable indoor environment. If you have any questions about improving the airtightness of your building, get in touch - we’d be happy to tell you more about what you can do.