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How to Keep Pipes From Freezing In a Crawl Space

Frozen pipes are every homeowner’s nightmare. Not only are we without water, but to repair the leak we have to work in the cold. Circumstances like an open crawl space door can cause frozen pipes, but pipes can be protected from freezing by providing supplemental heat or insulating them against the cold. Today we will offer a few common reasons pipes freeze in a crawl space and suggest a few methods to prevent it from happening.

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Why Did the Pipes Freeze In My Crawl Space?

Pipes freeze when subfreezing air is allowed into the crawl space. In most situations, the foundation vents or crawl space access doors have been left open in cold weather, allowing unconditioned air under the home. Even when these are functioning properly, in some regions pipes will still freeze unless they are protected with insulation. In very harsh winter weather, supplemental heat is often required as well to keep the pipes above freezing.

How Do I Know If My Pipes Are Frozen?

Interestingly, identifying frozen pipes is not as easy as it may appear. The first obvious symptom is no water availability. When the ice expands inside the pipe, it blocks the passing of liquid water. For this reason, many homeowners leave a faucet running at night to prevent the forming of ice crystals. If the pipes do freeze, a lack of water will be the first indicator.

Just because a pipe freezes does not mean it will burst and cause a leak. Older plumbing materials like galvanized steel, CPVC, and copper tubing are very vulnerable to cracking and splitting when water freezes inside them. Because these materials cannot flex, they tend to burst when the expanding pressure of the ice becomes too high. Other materials however, like PEX tubing, are much more flexible and can be frozen over and over with no damage.

The most common indicators that a pipe is frozen are:

No Water to the Home

In most instances, the first indicator of a frozen pipe is no water from the fixtures. Obviously, this can be caused by other factors as well, but if the weather is abnormally cold, the chances are very good a pipe is frozen. This can be confirmed at the water meter by turning on any fixture and watching for the meter to move. If it does not move, or moves and suddenly stops, the pipes are likely frozen. 

Frost On the Pipe

The most reliable way to identify frozen pipes (especially metal pipes) is the appearance of frost on the pipe. If a pipe is frosted on the outside, it is also frozen on the inside. Depending on the type of pipe, it may thaw and return to normal without damage.

Weird Noises From the Plumbing

When pipes freeze, the ice blocks most or all liquid water from passing through the pipe. Water is supplied to homes under pressure, so when a pipe becomes blocked the pressure can actually vibrate the pipe. With metal pipes, this can result in a knocking sound as the water pressure forces the pipe to vibrate against its metal hanger.  

Smelly Odors From Drains

Although uncommon, sometimes drains in a crawl space will also freeze, allowing waste to become stuck inside the pipe and decompose. Drain pipes from fixtures should always include a trap, which remains full of water at all times to prevent sewer gasses from rising up through the drain. The trap for a first floor shower, for example, will be located in the crawlspace so if freezing is suspected, that would be a good place to look.

Spraying Water

If the other methods have failed to identify a frozen pipe, a fine mist of spray is a dead giveaway. When metal pipes burst (especially copper tubing) they do not shatter, but often form a pinhole leak. Depending on the severity of the leak, it may be difficult to see, especially in a dark crawl space. The pros will usually look for puddles on the vapor barrier and backtrack along the pipe until they locate the leak.

How Do I Prevent My Pipes From Freezing?

Fortunately, there are several ways to prevent frozen pipes in a crawl space. Any solution will involve either insulating the pipes, warming the pipes, or preventing cold air from entering the crawl space. Here we will discuss the most common methods and how they work:

Close Your Foundation Vents

Foundation vents are critical to the overall health of a home because they remove moisture. In warmer months these vents must remain open to allow fresh, dry air to circulate inside the crawl space. In winter however, the air is drier so this venting is less of a concern so the vents can be closed temporarily during unusually cold periods. The vents should be reopened however, as soon as the threat has passed.

Insulate Your Pipes

Pipe insulation is the most affordable, common way to protect pipes from freezing in a crawl space. Insulation is relatively inexpensive and does a great job of protecting pipes in all but the coldest of temperatures. Pipe insulation is very easy to install by simply sliding it over the pipe and taping it in place. The goal is to simply keep the pipes above freezing, so one layer of insulation is plenty.

Add Heat Tape or Heat Cable to the Pipes

A great way to prevent frozen pipes is to apply heat tape or cable anywhere the pipe is vulnerable. For example, a pipe located too close to a hole in the foundation will likely freeze first. Heat tape or cable is used in these areas to provide just a few degrees of heat to keep the water above freezing. Heat tape is usually peel-and-stick and applied liberally, however it does require access to electricity, so you may need an extension cord as well.

Insulate Your Crawl Space

The best, although most expensive method to prevent frozen pipes is to insulate the entire crawl space. Pipes should run parallel to the floor joists as much as possible, allowing them to be surrounded by insulation. However, pipes not located between joists can also be insulated with either open cell spray foam or standard pipe insulation. Fiberglass batts or sheet foam can also be used, but pipe insulation or closed cell expanding foam will often offer the most protection.. 

Fiberglass Batts

If using batts, it’s important to remember that the vapor barrier (the paper side) goes in first. Although it may seem backward, the vapor barrier should contact the underside of the subfloor, not the underside of the floor joists. Doing so insures that any moisture in the crawl space is repelled away from the floor and can be evaporated by the foundation vents.

Sheet Foam

Using sheet foam is more labor intensive to install, but it does a good job and is cost-effective. Due to its chemical makeup, sheet foam repels moisture without additional vapor barriers being required. Sheet foam is simply cut to the appropriate size and glued in place with construction adhesive. Depending on the thickness of the sheet, up to seven or eight layers may be required to achieve the desired R-value.

Closed Cell Expanding Spray Foam

If you want to get serious about preventing frozen pipes, consider installing spray foam into the crawl space. Known as closed cell expanding spray foam, this material will stick to virtually anything. Pipes, walls, joists, subfloors, and even masonry foundation walls can be insulated using expanding spray foam. Closed cell expanding spray foam however, is not a DIY project and will require hiring a professional to install it.

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