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This article explains in detail how to winterize or freeze proof a building when some heat is going to be left on in the structure. The articles at this website will answer most questions about freeze protection for piping and other building plumbing and heating system components: how to winterize a building to avoid frozen pipes, and how to thaw frozen water supply & drain piping, wells, & water tanks. Our page top photo shows an old octopus furnace in a building where heat is to be left on.

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Is the building heat going to be left "on" or "off" - the answer determines the extent of freeze-proofing needed.

• If heat is to be left on in a partially winterized building see the procedure at: Winterize - Heat On (continuing below)
• If heat is to be turned off and the building completely winterized, see the procedure at: Winterize- Heat Off

How to Winterize a Building If you are Keeping Heat ON

The simple steps to winterizing a building where heat is being left on include choosing a low setting for the heating thermostat, turning off all or portions of the water supply piping, locating and correcting points of extra risk of freezing, and possibly the installation of a freeze-alarm notification system.

Thermostat Settings to Avoid Freezing

How to find the lowest "safe" temperature for setting the thermostat. In theory we simply need to keep the building just above 32 degF. But actually dropping a building interior temperature down that low is risky. Why? Because often there is some cold corner, under a sink cabinet, or in a drafty basement corner, where temperatures can fall far below the number set on the building thermostat. So we need to keep the building temperature at the thermostat high enough that the coldest spot in the building where piping may be exposed to freezing will remain warm enough. Other building corners can get a bit colder if the do not contain anything in danger of freeze damage.

If the Freeze-Safe temperature is Unknown: set the thermostat at 56-58 degF: If you have no experience with how a particular building behaves in freezing weather, it's smart to start by keeping the temperatures pretty high. It's usually "safe" to drop a thermostat to 55 degF. or even down to 50 degF (though below we also offer a few simple extra things you can do to avoid freeze-ups). But if the building is an older one with drafts and unknown freeze points, keeping the temperature a bit higher is a bit more safe. That's why some experts suggest the 56-58 deg.F. setting above.

Even hot pipes can freeze: Beware, in unusual cases even a hot water heating line can freeze-up.

A client had recurrent freeze-ups of his hot water heating baseboard piping (where the circulating water can be 180 degF !).We found a very cold drafty corner in a crawl space where freezing winter air was blowing right across an elbow in the hot water heating baseboard piping.

When the building thermostat decided that the living space was warm enough and thus turned off the heating boiler and circulator, this cold corner would freeze in very cold windy weather. The solution was simple: block the draft and insulate the corner. (Continuous operating hot water circulation as a freeze-protection method is discussed below).

How to Find the Safe Set-back Temperature for a Heating Thermostat: It's easy to do a little experimenting to find out just how low you can safely set building temperature without freezing anything if the building is occupied or if the building can be checked regularly. To start we set the thermostat down to 56 deg. F, remembering that the thermostat is only monitoring the room temperature at the precise spot where it is located. So other building locations may be warmer or colder. We watch what happens in areas of the building distant from the thermostat and possibly exposed to colder conditions.

We find the coldest point where plumbing or other freeze-protected components are located. That's the temperature that we monitor as we step the thermostat lower and lower.

• We need to actually measure temperatures around the building after outdoor temperatures have been at their low point for several hours.
  
• We can also double check that all of our plumbing fixtures are still working. It's often the case that a water line will freeze enough to reduce or stop water flow before it freezes hard enough to burst the line. So if we're checking frequently and find that suddenly our water supply has stopped, we need to immediately turn the heat up (high, to warm the building quickly) and then to proceed to locate to point at which the water pipe has frozen. As we related anecdotally above, in many buildings we can locate and correct one or two problem locations that will then let us set the building temperature lower without freeze-damage.

40 deg .F. Using this approach it may be possible to drop a building interior temperature to 40 degF. without freeze damage occurring.

How to set a thermostat below it's official minimum temperature: if your building thermostat is an older model that does not permit temperatures to be set below 50 or 55 deg .f. it may be possible to "fool" the thermostat by tilting it out of level on the wall, so that a setting of "55 degF" on the thermostat dial is really equivalent to "45 degF". A little experimenting (at a higher temperature) will show you how much to turn the thermostat on the wall to re-set its operating temperature range. See THERMOSTATS.

Why we like to keep some heat on: Even in a building with no plumbing to freeze up, it's usually better for the building to keep some heat going at this level than to allow it to reach zero or sub-zero temperatures. You may find that allowing a building to reach very cold temperatures can result in movement of building materials or cracking damage such as to flooring or even wall materials. In some locations there may also be a risk of elevated indoor humidity leading to mold contamination even if the building piping is not leaking.

Now that we've agreed to leave some heat on, it is still important to find freeze-risk points and to take some steps to avoid freeze damage by turning off water where we can, adding point heat sources, fixing drafts, etc. An experienced home inspector and some heating contractors or insulation contractors can probably point out spots where there is an extra risk of freezing pipes.

Guide to Turning off Water to a Winterized Building

Detailed step by step instructions for deciding to turn off water and when where and how to turn off building water supply can be read at  Turn Water Off ?. Details on how to find and use water shutoff valves is at WATER SHUTOFF VALVE LOCATION, USE.

Not ok to turn off water: But if the building is heated by a system that requires water, such as a steam boiler or a hot water (hydronic) heating boiler, turning off the building water supply can risk serious damage or total destruction to the heating boiler or even unsafe conditions.

That's because most heating systems that use water rely on the presence of an automatic water feed valve to assure that makeup water is sent into the heating boiler whenever its water level drops below a safe level.

Detailed step by step instructions for deciding to turn off water and when where and how to turn off building water supply can be read at  Turn Water Off ?.

Also see Water Feeder Valves, Hydronic Boiler and Low Water Cutoff Controls for more discussion of heating boiler water control valves.

What about leaving water running slowly to avoid frozen pipes. This is a last resort measure which we don't like. Not only are we wasting water, we risk flooding a septic system, or we risk freezing the building drain lines by the slow flow of water. In emergency however, such as loss of heat during a winter storm, this step could be necessary and would make sense.

Do I need to to Winterize a Water Softener or other Water Treatment Equipment?

Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

FREEZE-PROOF A BUILDING
Key Winterizing Topics
How to Winterize a Building

Winterize - Heat On Procedure
  Thermostat Settings
  Turn Water Off ?
  Winterize Water Softener & Treatment Equip.
  Find & Fix Water Pipe Freeze-Up Points
  Heat tapes, Heat, Insulation prevent Freeze-Up
  Freeze Protect Drains

Winterize- Heat Off Procedure

De-Winterized a Building
  Thawing Frozen Pipes
  Repairing Burst Leaky Pipes
  Turning on Heating
  Restoring Drains
  Turning on Water
  Water Supply/Drain Pipe Leak Types
  Restoring Water Softener & Treatment Equip

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Technical Reviewers & References

• InspectAPedia.com^® - Daniel Friedman
• Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
• "New Electric Heat Tapes Help Prevent Fires," US Consumer Product Safety Commission (CPSC) #00936
• Thanks to Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education, publications, report writing materials, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
• "Freezeproof Your House," Mike McClintock, Rodale's New Shelter, p. 30, October 1985 (approximate date)
• "How to Winterize Your Pipes," Mike McClintock, Homeowners How-To Magazine, p. 59-62, Nov-Dec 1979.

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