Energy efficiency retrofits can reduce your energy consumption, environmental impact and save you money. However, if not done properly, replacing windows, adding insulation and reducing air leaks can have unintended effects on your house, indoor air quality, and, your family’s safety. So before the work is started, have your house checked for pre-existing problems or conditions that could lead to problems down the road. These problems may include high humidity, water leaks, dampness, and mold. Your house may also have stale air, lingering odours, soil gas intrusion, and pollutant emissions from household products. Structural sags, cracks and deflections in the walls, floors or ceilings also represent problems that may need to be addressed first. Undertaking an energy efficiency building envelope retrofit before dealing with pre-existing problems may make the problems worse and may result in the loss of the time and money invested in the retrofit work.
Potential Issues and Solutions
Sealing air leaks can improve comfort, reduce heating costs and protect the walls, windows and attic because it cuts down on the amount of leaking into and out of your house. But, this can cause the air in the house to seem stale and odours to linger longer. Odours from previously unnoticed sources such as hobbies, pets or stored items may become more noticeable. Measuring the air leakage of the house with a blower door test before and after the retrofit work can give an idea of how much the air leakage of the house has been reduced. If the reduction is significant, it may be a good idea to add a bathroom fan, a range hood, an air exchanger or, better yet, a heat recovery ventilator. When properly designed and installed, mechanical ventilation is more energy efficient and effective than uncontrolled air leakage.
Reducing air leaks can also decrease the air needed for the safe and efficient operation of furnaces, water heaters and fireplaces. Adding powerful or numerous exhaust fans can further increase the risk that fuel-fired appliances will not properly vent combustion gases — a situation known as “backdrafting.” Providing adequate combustion air for heating appliances and sufficient make-up air to balance exhaust fans may be a necessary part of a building envelope insulation retrofit project. The safest solution is to convert fuel-fired appliances to direct-vent units or sealed-combustion units. The backdrafting risk can often be assessed by a qualified energy advisor. Mechanical contractors can be consulted regarding make-up air systems as well as direct-vent and sealed-combustion appliance options for furnaces, hot water tanks, and fireplaces.
Adding insulation to exterior walls, basement and attic can lead to moisture damage if inside and outside sources of moisture are not addressed. Outside, problems due to rain and melting snow can be reduced by ensuring that the roof properly drains water; there are adequate roof overhangs and flashings to protect the walls and window openings below; a “rainscreen” assembly is used on the exterior walls; areas around the house are sloped and eavestroughs catch and drain water away from the foundation; and, the foundation is protected from moisture.
Inside sources of moisture can be controlled by ensuring that there is adequate mechanical ventilation to remove humidity caused by showers or cooking. Installing a vapour barrier (such as a polyethylene sheet or vapour barrier paint) and, more importantly, an air barrier system to reduce air leaks, are critical parts of wall and attic insulation retrofits as they will help keep moisture out of the newly retrofitted assemblies.
An energy efficiency building envelope retrofit can reduce space heating needs to the point where the existing furnace may be oversized for the house and may not operate as efficiently. If the furnace or boiler is old enough to consider replacing as a part of the retrofit project, a qualified contractor can perform a heat loss calculation and determine the right size for the new heating equipment.
Some interior finishes and materials, especially in older houses, may contain hazardous materials, such as asbestos in insulation and siding or lead in paint and plumbing. Rodent and bird waste may also be a problem. Some equipment, such as knob and tube electrical wiring, can represent other safety hazards. When renovating, make sure care is taken to protect workers and your family from hazardous materials.
Retrofitting your home to make it more energy efficient and to reduce your heating and cooling costs is always a good idea. By recognizing and addressing the potential issues associated with any retrofit project, you will help reduce the likelihood of problems occurring after the work is done. Consult a qualified energy advisor, building professional, home inspector or contractor before you begin your energy efficiency retrofit to better understand, and plan for, pre-existing conditions and possible unintended effects of the retrofit project. Often, corrective measures can be planned that not only prevent problems but also add value to the overall project.