Okay, we’ve all heard the common energy savings tips such as switching our light bulbs from incandescent to compact fluorescents, weather stripping our doors and windows, buying Energy Star® appliances, and the like. Certainly these are important measures to implement…a great place to start. We encourage you all to follow them. But building science has also taught us a lot in recent years about inexpensive and proven measures that can save us money on our energy bills, increase the comfort and durability of our homes, and go a long way toward reducing our carbon footprint. These are measures that (if your home needs them) a moderately handy homeowner can undertake at minimal costs (usually well under $100.00 out-of-pocket for materials). And your energy savings could be substantial of not dramatic.
Heating and cooling energy flow from the inside of the home to outside of the home primarily by one of two methods. The first method (although we will not be concerned with this in this article) is conduction. This is heat that flows through the actual building materials by surface to surface contact of the building materials. In winter, when the furnace supplies heat to inside of the home, the drywall on the exterior walls is warmed, and that warmth is transferred through the building materials in the wall to the outside where it is swept away by the cold air. Your furnace then needs to burn fuel to replace that heat. (When you encounter the term “R-value”, this really stands for “Resistance to conductive heat flow”). The way then to stop or slow conductive heat flow is to add insulation of a high R-value. In existing homes, especially in walls or cathedral ceilings, this can be an expensive proposition, and usually should be undertaken only after the following problems have been addressed.
The second method (and the method that we will be concerned with) is convection. Convection, for the sake of this discussion, can be thought of as the heat content of the air that is exchanged between the inside and the outside of the home. It is also referred to as air infiltration. It is a very different mechanism from conductive heat loss, and has very different remedies. It will probably surprise you find out that according to the Department of Energy, air infiltration was shown to be responsible for up to 40 % of heat loss in older homes.
Finding the Problems
Interestingly, many of the larger and most costly leakage problems can be found by climbing into your attic equipped with nothing more than a flashlight and a little knowledge of what to look for: in short, any holes or air passages. The name of the game is “find the big ones first”. Historically, it was common construction practice for carpenters to have constructed a passageway called a plumbing chase from the basement through all the levels of the house and then into the attic. At the time of construction, this passageway was (and is) almost never sealed where it passes through the ceiling of the uppermost floor of the home and then into the attic. It allows very warm air (the warmer the air the more it wants to rise under pressure and flow through this hole) to escape into your attic, which is for all practical purposes the outside of the house. An open plumbing chase is akin to (and probably much worse than) leaving a window wide open all winter long. The second place to look is where the chimney of the home protrudes through the attic floor. Like plumbing chases, the chimney starts in the basement of the home and continues unobstructed into the attic. The wood framing around the masonry chimney is usually held off an inch or two on all sides from the bricks. This is done on each floor of the home, and the net result is the creation of another unobstructed path for heated air to flow under pressure into the attic. The last place to check is for any other holes through the drywall or plaster. (You will need to temporarily remove existing insulation for this step.) Remember, you are trying to stop air from flowing, so think of looking for holes in the hull of a leaky boat. These holes can include: where electrical boxes meet drywall or plaster, where electrical pipes or wires pass through the drywall or plaster, the tops of any partition walls below that don’t have top plates, around register openings, etc. You can try turning on the lights in the rooms below and then turning off the flashlight in the attic to locate some or many of the holes. Again, we’re not insulating, we’re trying to “make the boat float”.
This is a “down and dirty” method of looking for air leaks, but it works pretty well. If you want to be sure that you are getting all of the easily repairable leaks, though, it would pay to hire a certified HERS Rater or a certified BPI Building Analyst to conduct a blower door test. This test, when conducted in consort with an infrared scan, is relatively inexpensive, and should pay for itself in no time.
The Fix
If you found any large holes, such as an open chase, you’ve struck gold! Your primary tools for sealing all of the aforementioned air leaks will be expanding foam sealant (such as “Great Stuff®”) and caulk, both of which are widely available at home center stores. If you are tempted to include fiberglass insulation in your toolkit, DON’T. This stuff does not seal air leaks; it is basically the same thing that furnace filters are made of…stuff holes with it only if you care about how clean the warm air is as it flows out of your house. (As a matter of fact, if you discover places in your attic where the existing fiberglass insulation is dirty, it means that you have air leakage there.) For the large holes, you will need to fashion some sort of support for your sealant. You can use cardboard cut to size to fill the chase with cutouts for the pipes. Staple it in place and caulk around the pipes and joints. (Or you can use any other method that seems to work.) Then apply your foam sealant over the top. Just remember, the cardboard support probably won’t do much to seal the air by itself, so cover the entire assembly with the foam. Work your way down to progressively smaller holes, choosing the sealant that works best, depending on the size of the hole. Caulk will work best for smaller holes.
The heated air that was previously flowing into your attic needed to be replaced with colder outside air which was being drawn in to the home through air leaks on lower floors, adding to both high energy bills, as well as a feeling of “draftiness” throughout the entire house. Having reduced air leakage into the attic, your house will be more efficient and comfortable.
One word of caution, though. Homes need air and the inhabitants need air. There are very strict standards for the minimum amount of ventilation that a home should have; it is possible to make a house “too tight”. For older homes it is usually very difficult to get the air infiltration rate down below this level, but you should have the aforementioned HERS Rater or BPI Building Analyst check the home once air sealing measures are performed. They can certify that you are in compliance with the Baseline Air Standard.
Next time- Duct leakage: Air leakage on steroids.
Filed under: energy efficient illinois, Energy Saving Tips, Home Energy Audit, Homeowner Tools, RESNET Tagged: | BPI Building Analysis, Energy Saving Measures that Work, HERS Ratings, Home Energy Audit, Home Energy Tips, Implementing Energy Saving Measures
