How to prevent the air conditioner from leaking outside

Whether you’re trying to save money on your utility bill or control the temperature in your home, you can insulate and seal the air in your home with these three tips. You’ll need to air-seal the “wrap” on the house, seal the ducts, and add insulation in the attic.

These are the most common air leak problems in American homes that can make a big difference for a small investment. And with high energy prices Y reports of possible blackouts expected in the US this summer, keeping air conditioning inside (and warm weather outside) is even more important. Here’s how to do all three.

Air sealing of the ‘wrapper’

First, you’ll want to start with the air sealing of the house. This will allow you to get the most improvement for the least investment. And it’s crucial that you air-seal the house before doing any insulation. Otherwise, you are wasting your time. Fibrous insulation needs an air barrier to function as intended, so it is recommended last.

When discussing air sealing the “envelope” of a home, it is important to consider how air naturally behaves in a building. The pattern of air moving in and out of your home is known as the “stack effect.” Essentially it means that hot air rises and cold air sinks. So, hot air leaves your house through the attic and cold air enters through a crawl space, unfinished basement, or other unconditioned lower part of your house.

That’s why air sealing the upper and lower levels of your home, in combination with insulation, is one of the best ways to combat air leaks.

When a window is drafty, it’s obvious to a homeowner right away, but leaks in attics or crawlspaces are often worse, but they’re usually hidden from view. And these areas are going to be the most beneficial to work against the “stacking effect”. You’ll want to air-seal window trim, doors, vents, fireplace and furnace flues, and other fixtures like pipes and wires that penetrate the “wrap” of the house.

Windows will often have gaps around the trim and under the sill. To seal them, you can use a caulking gun. Cut the top of the putty tube at a 45-degree angle. Use the pin under the gun to break the seal and put the tube into the caulking gun. Attach the caulking gun and pull the trigger as you go along the frame. The 45-degree angle allows the tip to form the bead of putty in a neat line as it is applied, but may still need some touch-ups. You can easily do this with your finger. And don’t worry, the putty rinses off easily with water.

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You can also use the caulking gun for areas like the bathroom exhaust fan, floor vents, and any other cracks. But when it comes to air sealing a fireplace, you want to make sure you use a fire-resistant putty in the areas that are most combustible to ensure fire safety. And before you air-seal a chimney, make sure the furnace is off and there’s no fire going/you’ve allowed it to cool enough.

Now, to air seal your front or back door frame, you can add a weatherstrip. These doors may have a small gap between the door and the outside that allows not only light to pass through, but also air to enter. You can choose a weather stripping kit that comes with everything you will need.

First, you’ll need to remove any existing old weather stripping from your door frame. You can then install the new weather stripping. It’s easiest to start with the left and right side of the frame first and then press fit the top. You will need to measure the side of the door frame and cut the weather stripping to fit. And when you cut it, be sure to do it from the metal side; you will get a cleaner cut.

Close the door and make sure it is locked before installing the weather stripping. If it is not locked and you place the weatherstrip too close, you could put too much stress on the lock and it could break or come off the wood.

Align the weatherstrip tightly on the side of the frame, but don’t press too hard against the door. Using a drill, put the first screw in the middle, then do the top and bottom next. Now do the same steps for the other side, and again for the top.

Now for awkward areas where there is a larger gap or wires in the way, you can seal these areas with foam can. It’s easier to just spray the foam into these openings and let it expand.

To use foam from the can, place the nozzle on top and handle with care. This will not come off your clothes or carpet.

Again, attic or basement leaks are the most important areas to address. Therefore, you can spray the foam from the can into openings around pipes and vents and into cracks in a basement and on top of interior attic walls. If you have an unfinished basement rather than a crawl space, you can use caulking or foam to air-seal the rim joist and sill plates.

Duct sealing

Moving on to the ductwork. If your ducts are leaking and are in a non-air-conditioned space (such as a crawl space, unfinished basement, basement, attic, etc.), you are literally heating or cooling the outside. So when you seal it, more of the heat/air intended for your home will get in.

Not only that, but sealing the ducts will also improve indoor air quality. If the duct is leaking, it could be bringing in dirt, dust, mold, and possibly radon from outside. Sealing the ductwork allows the duct to only draw in the air that is already in the house.

To seal the ductwork in a lower space without air conditioning, you can use a mastic sealant. Caulk is good for sealing duct joints because it is fluid and can get into hard-to-reach areas. It is also flexible because it will resist expansion and contraction due to changes in temperature.

This part is easy. Wearing a rubber glove, you can literally dip your hand into the bucket of caulk and spread it along seams, joints, and metal duct holes. Just be careful, as metal ductwork can have sharp edges.

Home renovations showing rolls of insulation

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Adding Attic Insulation

And last but not least, you’ll want to insulate your attic space. As mentioned above, if you insulate your attic before air-sealing the attic floor, you will have minimal benefit.

When talking about insulating the attic space, it’s important to keep in mind that the insulation and the air barrier must be continuous and contiguous (meaning they touch). The continuing part is that it is more effective to have 6 inches of insulation everywhere rather than 10 inches of insulation in one concentrated spot. The adjoining part is wherever the drywall is, the insulation must touch it. If you don’t touch it (for example, if the insulation is on top of the wires and not under them), the insulation won’t do anything.

Another thing to keep in mind is that you want to make sure there is no air gap between the “block” layers, which are the insulation strips.

In other words, you want the insulation to be the same depth as the joists, if you’re using batts and not loose fill (or blown) insulation, because otherwise there will be an air gap when you add the second perpendicular layer of insulation.

If the depth is lower than the joist, there will be an air gap coming from the second layer; if the depth is greater than the joist, there will still be an air gap from the joist to the second layer. Only the first layer should be the same depth, although the second perpendicular layer can be thicker.

And the first coat should be as thick as needed based on the Energy Star recommended R-Value for your geographic location. The R-value is a measure of the effectiveness of a material in preventing heat loss. The higher the R-value, the better.

Keep in mind that when insulating your attic, you should be sure to wear protective gear and cover your skin to prevent dust and fiberglass from breathing in or coming into contact with your skin.

First, you will need to clean out the joist compartment so the insulation can lay completely flat. Then put a layer of insulation in the bay and cut the length to fit snugly. Try to cut the block as perfectly as you can, but it’s okay if you mess up, as long as you fill the depth of the bay evenly with insulation.

Then add the second layer of batting perpendicularly over the joists so the wood is also insulated and not just the bay.

Energy audits and the Weatherization Assistance Program

These tips can help minimize air leaks and cold spots in your home. But if you want a deeper professional opinion before trying some of these methods, you can get a energy audit done on your home to see what specific areas your home is lacking in terms of energy efficiency.

In addition, the US Department of Energy has a Weatherization Assistance Program at the state and local levels if you qualify as low-income, over the age of 60, or are part of a family with disabilities. You can check with your local utility company for more details.

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