How Can I Control Drafts Cost-Effectively?

Drafts are caused by openings in the envelope of your living space that allow cold (or hot) air from the outside to leak into or out of your house.  Actually, more than one opening is required: ones that let out the conditioned air and others that let in unconditioned air.  Drafts are most pronounced in the colder months, but they rob you of energy year-round by making you heat the cold air that replaces the escaping heated air.  Moreover, cold air leaking into your house in the winter just seems to be easier to feel than hot air in the summer.

Some leakage is desirable.  In theory, if you had no leaks in your house and remained inside, you could use up all the oxygen and suffocate. So you need some fresh air circulating into your house.  Gas appliances, such as stoves and water heaters, also require a supply of air to replace the combustion-product-laden air that goes up the flue.  And, you need vents for bathroom fans, dryer outlets, and so on, to remove moist air that might cause mold.  Some of today’s new houses are so tightly constructed that controlled leaks are designed-in.

The key is to achieve a balance between needed air flow and too much air flow – or air flow in the wrong places – that wastes energy.

Where are the leaks?

As stated above, some of the leaks are necessary.  If you have a gas water heater, you will need a flue to carry away the noxious gas fumes.  Bathroom fan and dryer outlets are also required.  You can minimize the drafts caused by some of these necessary “leaks” by piping air from the outside close to the area of the leak (directly to the flame of the water heater, near the dryer intake, etc) – something that may not be practical as a retro-fit.

In addition, there are many possibilities for unwanted leaks, especially in older homes.  Here are a few to consider, and how to handle them:

• Windows – older windows may not fit in their frames as tightly as new windows; there may be chips in the glazing; top sashes might slip down, creating a narrow crack at the top.  Sometimes, even new windows in new homes have poorly-fitting sashes or gaps around the window frame.
• Exterior doors – door weatherstripping may have lost its springiness; the door sweep may be worn or missing; air may leak past the hinges, door keep, lock, or deadbolt; window glass may have a cracked or missing seal.
• Interior doors – interior doors are often cut with a substantial gap at the bottom to permit the door to swing over carpet or throw rugs.  If the door is used to separate two independently-conditioned rooms, such a gap can create drafts.
• Electrical outlets and switches – the electrical junction boxes that protect the house from the uninsulated wiring at outlets and switches are generally not insulated; they are effectively a small hole through your wall and if there is an air passage along the external siding (or top or bottom plates of the wall), you will have an air leak.
• Attic access – whether a pull-down stairway or a scuttle hole, the access into your attic often has cracks around it that leak air.
• Penetrations – these are pipes, electrical wires, vent hoses, non-insulation-contact (non-IC) light fixtures, whole-house fans, and so on.  They have to go through a wall or the ceiling, and the hole they go through is often given a finished look by a molding or escutcheon, but the hole is still not sealed against air leaks.
• Heating/cooling ducts – ducts are a huge source of leaks, especially so if the ducts run through uninsulated space.  Not only will there be leaks where the ducts enter and leave the house, but there are usually leaks in the ducts themselves, at joints and bends, that allow air to escape when pressurized, or to enter the house in the depressurized return duct.  Usually, the insulation wrap on ducts is only about R-4 at best, and does not do an effective job at sealing against leaks.  The common gray-colored “duct tape” that was used in older homes, has probably dried out, losing its effectiveness.  See our Technical Note on Air Ducts for a further discussion.
• Chimneys – these are basically a hole in your roof.  Even with a damper closed, air can transfer through the chimney.
• Baseboard moldings – these moldings are cosmetic cover ups for holes and cracks at the base of your walls, but they do not seal against air leaks.  There are generally air pathways through floor joists to unconditioned spaces, either under your house or directly to the outside through the house foundation.
• “Settling” cracks – old houses move on their foundations as they age.  This can create small air pathways to the outside.

How do I get rid of leaks?

There is no magic to finding and sealing drafts and leaks.  Professional weatherizers like NRG SVRS depressurize the interior of the house. This causes air from the outside to leak in, and the leaks can be more easily detected with a smoke pencil or even your hand.

Most leaks can be caulked if the space is smaller than ¼ inch or so.  A foaming product like “Great Stuff™” can fill larger cavities of 6 inches or more.  Great Stuff will fill the gap and insulate against heat or cold whereas caulk simply plugs the gap.

For leaky windows, the best solution is replacement windows.

Since the door gets so much use, replacing worn or defective weatherstripping on a periodic basis is recommended.  For interior doors, we recommend a removable cloth door sweep.

For electrical outlets and switches, you can purchase inexpensive foam pads – cut exactly to fit the electrical fixture –  that can be installed at each outlet and switch to minimize the draft.

GREAT STUFF^TM is a trademark of Dow Chemical Company or an affiliated company of Dow, Inc.
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Disclaimer: The information presented herein is provided for informational purposes only. Technical descriptions, specifications, details, requirements, and limitations expressed do not constitute an endorsement, approval, or acceptance of the subject matter by NRG SVRS. There are no warranties, either expressed or implied, regarding the accuracy or completeness of this information. Full reproduction is not permitted. ©,NRG SVRS, LLC.