As a busy home energy consultant, I perform home energy assessments on 10 to 15 houses a week. This cross section of homes consist of all shapes, sizes, ages, and construction methods. After the initial client interview to diagnose comfort issues in the home, the question I am often asked is:
Closing a vent to a bedroom or bathroom that you’re not using seems like a sensible way to increase energy efficiency. With the doors and vents shut, no heat should flow into the room, freeing the heating, ventilation, and air conditioning (HVAC) to condition the part of the home you spend the most time.
The answer is counterintuitive, and according to a study done in 2003 by Lawrence Berkley National Laboratory closing doors and air vents can increase energy use. When vents are closed, it increases pressure in the ductwork and causes more leakage to unconditioned space if the ductwork is not properly sealed, so more heated or cooled air will be lost in the crawl space or attic. Also, when the doors to the rooms are closed off, this essentially reduces the square feet of the home while the return air is pulling the same amount of cubic feet per minute (CFM); this can cause an increase in negative pressure in the conditioned area and increasing the air infiltration (air leakage) around exterior doors, under baseboards, attic accesses, and so on.
If you want to seal up rooms that you are not using, your best bet is to contact a professional energy auditor to evaluate the duct system, duct leakage, house leakage, HVAC system, insulation values that uses the “Whole House Approach” to offer a comprehensive energy package for the home.
Another energy saving measure is upgrading the old one stage 55-70 percent efficient gas furnaces to 95-98 percent efficient condensing gas furnaces which in some cases are subsidized by utility companies, not to mention the variable speed motors and condensers. Cleaning and servicing the HVAC unit cannot be overstated, do it and save money.
A newer technology for those who want to save money and isolate different zones for separate heating and cooling thresholds would be to consider installing a mini split ductless system. These units have no ductwork and are extremely efficient. They can be mounted in many different configurations and are designed to heat specific rooms or zones as opposed to a whole house. These types of systems are becoming much more popular for additions and retrofits of whole house HVAC systems.
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