How to seal plumbing and electrical penetrations

If you have been following along for the last few weeks chances are you may have already addressed the penetrations that we will talk about this week. Plumbing penetrations, vent fans, chimneys and other major penetrations may be obvious leaks or they may create leaks in other parts of the home and you don’t realize where the source is.

There are two types of leaks direct and indirect.

Direct leaks are leaks that occur directly at the wall penetration. An example of this may be a dryer vent or door.

An Indirect Leak is one in which the leak occurs at one location and the air exits at another. In this situation the air flows through holes and spaces in the wall cavity. An example would be a leak that occurs where a plumbing drain line enters the home but exits at an outlet.

Indirect leaks are one of the most common and problematic because you don’t know where the entry point is. To eliminate this you must seal all openings to the home.

Plumbing and Electrical:

In newer homes most of these penetrations will already be sealed due to code. However some may have been missed and there are a lot of older homes so we will visit how to correct them.

Electrical are the easiest. Using some fire caulk or silicone caulk depending on the situation you just have to locate the holes and put in some caulk. Fire caulk is required by code in new construction where wires or pipes penetrate floors and ceilings. If you have a larger hole you can use foam to seal it but in most cases electrical holes will not be much larger than 3/4”. Most of your penetrations are going to be in the crawlspace, basement or ceiling. Very few will be on exterior walls.

Plumbing penetrations may require a variety of fixes. If the hole is small, like with supply lines, you can caulk but if they are larger will need to use foam or rigid foam board to cover the gap. Foam will usually be fine around drain lines and vent pipes. You may find a large hole under your tub though. In this case you can use rigid foam board to cover the hole and use an adhesive or spray foam to affix it.

Vents and Fans:

If you have vent fans in your bathroom you are likely to have a large leak at this point. Often times the drywall will be cut larger than the fan box. This can be sealed using either spray foam or caulk depending on the size. Hopefully most will only need caulk but if yours needs spray foam (larger than ½”) then be careful because the spray foam may bend the fan housing if the metal is then.

Once you have the ceiling sealed you may need to look at the vent. Newer models will have a damper at the unit so that it closes and creates a seal from the outside when not in use. If yours doesn’t have this or if you still feel a leak you can install a damper in the vent at the end. This is rather easy if you can access the line as it exits the home. The dampers are rather inexpensive but they can help with this pesky leak.

Dryer vents and most other exhaust fans can also have the same problem and you can typically install a damper in them also to help out. If you do this make sure that it is not against building code or manufacturer recommendations.

Seal up your fireplace

Chimneys can be a major point of leakage in a home when the fireplace is not in use. In these situations you can do two things to help reduce this costly necessity. You can install air tight doors to prevent the chimney from drawing air out of the home or you can use a chimney pillow. The pillow is the less expensive fix and relatively easy to install. The pillow is inserted into your chimney and is inflated to seal up the opening. This prevents air from moving through the chimney when not in use. When you want to use the fireplace just pull the cord and remove the pillow.