Saving on energy costs isn’t always about buying the latest in high-efficiency heating and cooling equipment. An important building block for the cost-effective HVAC system is knowledge of how to air seal a house properly. A house that's well-sealed and properly insulated can save up to 20 percent on heating and cooling costs.
When it comes to how to air seal a house properly, every leak matters. Even small air leaks left unresolved can add up to wasted energy costs equivalent to a window-size opening left open around the clock. In otherwise well-insulated homes, air leaks are the leading cause of moisture damage. Of course, the homeowner should ensure that air leaks are sealed in tandem with the allotment of adequate ventilation.
Goal of Air Sealing
When it comes to how to air seal a house, the goal is to prevent unwanted air from both flowing into and out of the household. For example, an unsealed gap situated between the front door and that door’s frame will allow heat to undesirably escape from the home in winter and unwanted heat to enter the house in summer. When this happens, furnaces and air conditioners have to work harder to make up for either the lost or gained heat energy, depending on the season. Not only will your energy bills be higher, but overworked heating and cooling equipment will need more maintenance and will have a shorter life span. Additionally, when the gaps and cracks in a home are close to rooms that have a lot of family activity, the unwanted heat exchange will often make favorite places uncomfortable. Your goal when it comes to how to air seal a house is to reduce both energy use and physical discomfort.
Not Too Tight, Not Too Loose
Of course, it's possible to over-seal a home. When houses don't allow for fresh air intake, they become susceptible to moisture, particulates, radon, carbon monoxide (CO) and other worrisome buildups. A house should generally be sealed at a rate of .35 air changes per hour (ach), meaning that 35 percent of a household’s indoor stale air should be exchanged for fresh air every hour.
This can be achieved in one of two ways. First, the homeowner can elect to hire a professional energy auditor before sealing home. The energy auditor will take a home’s measurements and factor in the current level of air exchange in order to reach recommendations on how to air seal a house allowing for .35 ach. Or, the homeowner can first seal a home as tightly as possible and the install a mechanical ventilation system that then ventilate a house according to recommended levels. This is often considered the better, more holistic choice, as it can be user-controlled and can be set to achieve .35 ach regardless of outdoor conditions.
Finding Air Leaks
Air leaks can be found in numerous places throughout the home. Each house is built differently, and it can be advisable to complete a professional energy audit in order to identify the locations of hidden air leaks. A professional energy audit will include a blower door test, a reliable and industry-standard test that can identify rates of air exchange.
While most homeowners know how to use caulk and weatherstripping to seal gaps around window and door frames, too many completely miss bigger problem areas. Learning how to air seal a house should begin with locating and identifying the biggest holes first. This includes thoroughly checking the unconditioned spaces in your home like your attic, basement and crawl spaces. Larger and mid-sized holes will often be found around piping, where huge squares were cut away from the building material in order to make way for the cylindrical lines. Check for spaces around the furnace flue, bathtub drain hole and other similar cutaways. Only after identifying where the largest leaks are should you address the smaller, more commonly considered gaps around doors, windows and places where wires and lines penetrate the walls and ceilings.
Plugging the Holes
There are several different materials a homeowner or contractor can use to seal up leaks. Large holes should be repaired with wood and framing materials before adding insulation and spray foam. Caulk or water-based elastomeric sealant can be used to seal gaps and cracks in floor and wall joists, between window frames and elsewhere.
For more information on how to air seal a house, or to learn about other quality HVAC products and services, contact the professionals at Comfort24-7.