To prevent frozen pipes, keep cold air away from them. A pipe freezes when the space around it drops below freezing — a vented crawl space, a bare rim joist, an outside wall, a garage, an attic — so the lasting fix is to air seal and insulate that space, then put insulation on the pipe. On a freezing night, do what the American Red Cross advises: keep the thermostat at the same setting day and night, never below 55°F if you go away, let the cold water drip from a faucet fed by exposed pipes, and open the kitchen and bathroom cabinet doors so warm room air reaches the plumbing. A foam sleeve on its own buys time, not safety: insulation slows heat loss, it does not add heat.
If a pipe has already frozen, look before you heat. If it has split or is leaking, or you cannot find the frozen section, shut off the main water valve and call a licensed plumber. If the pipe is whole and within reach, keep the faucet it feeds open and warm the pipe with a hair dryer, an electric heating pad or towels soaked in hot water — never an open flame — and call a plumber if it will not thaw.
Where we fit: we insulate and air seal the crawl spaces, rim joists, walls, garages and attics that pipes run through, and we insulate the pipes and ducts themselves, on residential, commercial and new construction jobs. We are not plumbers. Thawing a line, repairing a split pipe, moving a pipe out of an outside wall and replacing a valve are plumbing work, and after a burst the plumber comes first. We come in afterward to deal with the cold that froze it.
How to keep pipes from freezing tonight
When a hard freeze is in the forecast, these are the steps from the Red Cross, the Insurance Institute for Business & Home Safety (IBHS), the Insurance Information Institute, the University of Illinois researchers, New Jersey American Water, the National Fire Protection Association and the National Weather Service, in the order worth doing them.
- Hold the heat steady. The Red Cross says to keep the thermostat at the same temperature day and night, skipping the lower night setting for now; the heating bill may be higher, but a frozen and burst pipe costs far more. IBHS says at least 55°F even when no one is home. The Insurance Information Institute sets a higher bar in severe cold, a minimum of 65°F, because the inside of an outside wall where pipes run is colder than the room.
- Let faucets drip. The Red Cross says to let the cold water drip from any faucet served by exposed pipes. The University of Illinois researchers who studied burst pipes for the insurance industry add two details: hot and cold come to a fixture in separate lines, and either can freeze, so each line needs to contribute to the flow; and keep the faucet slightly open even if an ice blockage slows or stops the drip, because the open tap is what relieves the pressure.
- Open the cabinet doors under kitchen and bathroom sinks so warmer room air reaches the plumbing, and move cleaners and chemicals out of children’s reach while they are open.
- Keep the garage door closed if water lines run through the garage.
- Shut down the outdoor faucets: hoses off and drained, the inside valve closed, the outside bib left open.
- Cover vented crawl space openings temporarily during the cold snap, as IBHS advises, and uncover them afterward unless the crawl space has been built as a sealed one. Do not cover them if a gas or oil furnace, boiler or water heater sits in the crawl space: the Department of Energy’s Building America guide warns that natural draft combustion appliances are more likely to backdraft in a closed crawl space, pulling exhaust into the house. Keep a working carbon monoxide alarm, as the National Weather Service advises.
- Find the main water shutoff and make sure it turns. IBHS, the Insurance Information Institute and New Jersey American Water all say to know where it is and how to operate it; New Jersey American Water suggests testing it and tagging it for quick access.
- Use space heaters safely. The National Fire Protection Association says to keep a heater at least 3 feet from anything that can burn, including people, plug it directly into a wall outlet and never into an extension cord, and turn it off and unplug it when you leave the room or go to bed.
If the power goes out, IBHS says to open the cabinet doors so heat reaches pipes next to outside walls, and let the faucets drip.
If you will be away
Leave the heat on, set no lower than 55°F, the Red Cross says, and ask a neighbor to check the house regularly, as the Insurance Information Institute and IBHS advise, so a problem is caught early. If you will be gone longer than a week with subfreezing weather ongoing or forecast, IBHS says to consider shutting off the water by closing the main valve slowly and letting a couple of faucets on the lowest floor drain. If the house has indoor fire sprinklers, University of Illinois Extension leaves them out of the shutoff, so have a plumber confirm how they are fed before you close the main. For a house left empty for a long stretch, the Insurance Information Institute says to have the water system drained by a professional, and to tell your insurer when the home will be unoccupied for an extended period. Aquarion Water, a Connecticut water utility, warns never to shut the heat off completely unless all the pipes and toilets are drained first, and says that if you do, turn off the water heater first and drain the heating system’s pipes and radiators too. New Jersey American Water suggests a freeze alarm that calls a phone number you choose if the inside temperature drops below 45°F.
What to do if a pipe is frozen, and how to thaw it
The Red Cross says to suspect a frozen pipe when you turn on a faucet and only a trickle comes out. Likely places include outside walls and the spot where the water service enters through the foundation.
First, look for damage. If you can see water, a crack, a bulge or a split, shut off the main water valve before you do anything else, because the leak runs full force the moment the ice melts. IBHS and New Jersey American Water both say to shut off the water supply when pipes are frozen, and New Jersey American Water says not to thaw pipes without turning the main off first. Aquarion describes the other case: if there is no flow but no sign of damage, leave the faucet open while you thaw the pipe that feeds it, which is also the Red Cross’s first thawing step. When you cannot see the frozen section at all, the safer default is to shut the main and call a plumber.
To thaw a pipe you can see and reach, the Red Cross gives these steps:
- Keep the faucet open. As the ice melts, water starts to flow, and running water helps melt the rest. New York City’s Department of Environmental Protection says to open a faucet near the frozen point.
- Apply gentle heat to that section with an electric heating pad wrapped around the pipe, an electric hair dryer, a portable space heater kept away from flammable materials, or towels soaked in hot water. Stay with a space heater while it runs; the National Weather Service and New Jersey American Water both say never to leave one unattended.
- Never use an open flame. No blowtorch, kerosene or propane heater, charcoal stove or other open flame device. The city’s Department of Environmental Protection warns that a flame is not only a fire hazard but could also cause a steam explosion.
- Keep heating until full water pressure returns, then check every other faucet in the house: if one pipe froze, others may have too. If you shut the main before thawing, there is no pressure to wait for: once the section feels thawed, turn the main back on slowly with the faucet still open and check for cracks or leaks, as New Jersey American Water advises, and shut it again at the first sign of water.
- Mind the water and the electricity. University of Illinois Extension warns to be careful of electric shock in and around standing water.
Call a licensed plumber if you cannot find the frozen area, cannot reach it, or cannot thaw it, the Red Cross says. In New York City, the Department of Environmental Protection says a broken service line or pipe is the homeowner’s to have repaired by a licensed master plumber, and a meter damaged by the cold is reported to 311.
If a pipe has burst
Turn off the water first and then mop up, the Insurance Information Institute says; University of Illinois Extension adds to call a plumber and your insurance agent. Once the plumber has made the repair, wet fiberglass or cellulose insulation in the ceiling, wall or crawl space below has to come out before it is replaced, and that removal and replacement is ours. If mold has started on the insulation, joists or subfloor, a mold remediation company deals with that first, and we reinsulate once it is cleaned up and the moisture is fixed.
After it thaws: find out why it froze
Unless the heat failed or was turned down, a pipe that froze once usually froze because cold air reached it, and the same pipe is likely to freeze again in the next cold snap unless that changes. Aquarion puts it the same way: correct the problem that caused the freeze, most likely cold drafts and too little warm air around the pipe. Look at what surrounds it: an open rim joist above it, a vent or a bulkhead door nearby, an outside wall with no insulation behind it, a garage wall, a crawl space open to the wind. That is the part we fix, and a frozen pipe tells us exactly where to start looking.
Why pipes freeze, and why they burst
Water in a pipe does not freeze the moment the forecast reads 32°F. The pipe has to lose its heat to cold air around it, and how fast that happens depends on the space it runs through and how much outdoor air leaks into that space. The 1996 University of Illinois Building Research Council study on freezing and bursting pipes, prepared for the Insurance Institute for Property Loss Reduction (the forerunner of today’s Insurance Institute for Business & Home Safety), found that wind chill has a dramatic effect on uninsulated pipes and that many burst pipe losses are probably tied to wind and air leakage — unintentional leaks through the building envelope, or intentional vents in unconditioned spaces.
The same study changed how bursting is explained. The common view that growing ice simply pushes against the pipe wall “is not correct,” the researchers wrote. Once ice blocks a pipe completely, the water trapped between the blockage and a closed faucet has nowhere to go, and as more ice forms, the pressure in that trapped section can build to thousands of pounds per square inch. The rupture generally happens in a part of the pipe that has seen little ice, sometimes even inside the heated part of the house. That is why a split can turn up away from the cold spot, and why a dripping faucet helps: an open tap relieves the pressure.
The study also measured when the trouble starts: an uninsulated pipe lying on top of R-30 insulation in a vented attic, its worst case, started to freeze when it was just at or below 20°F outside, and the researchers expected occasional freezes between 20 and 32°F wherever holes in the house’s shell let cold air reach a pipe. They proposed that 20°F alert for the southern United States, but the lesson carries north: a pipe in a drafty, uninsulated spot can freeze on an ordinary cold night.
The stakes are not small. The Insurance Information Institute, working from ISO claims data, puts the average homeowners claim for water damage and freezing at $15,400 for 2019 to 2023, and calculates from 2018 to 2020 claims that each year about one in 60 insured homes has a property damage claim caused by water damage or freezing. In 2023 that category, which covers far more than frozen pipes, made up 22.6 percent of homeowners insurance losses.
Which pipes freeze: the cold spots in a house
The American Red Cross lists the pipes that freeze most often: pipes exposed to severe cold, such as outdoor hose bibs, swimming pool supply lines and sprinkler lines; water supply pipes in unheated interior areas such as basements and crawl spaces, attics, garages or kitchen cabinets; and pipes that run against exterior walls with little or no insulation. It adds one more likely spot, where the water service enters the house through the foundation. In a New York, New Jersey or Connecticut house, that list comes down to six places.
Crawl spaces
A vented crawl space is outdoor air under the floor. Where the insulation sits in the floor above it, everything below the insulation — the water lines, the drains, often the ducts — is outside the house, at whatever temperature the wind brings in through the vents. In a cold snap, IBHS tells homeowners to temporarily cover any ventilated crawl spaces. Not when a gas or oil furnace, boiler or water heater is down there; see the warning in the cold-night list above. The permanent fix runs the other way: the Department of Energy’s Building America Solution Center describes a sealed, unvented crawl space insulated at its walls as an approach that can protect floors and pipes from cold temperatures in cold climates. That is a code-defined assembly with a ground cover, air sealing and a way to condition the space, not a matter of stuffing the vents, and we close vents only as part of a crawl space built that way. The detail is in crawl space insulation and crawl space encapsulation.
Rim joists, and where the water line comes in
The rim joist, or band joist, runs around the top of the foundation and caps the ends of the floor joists. In an unfinished basement it is often bare wood with outdoor air leaking in around the sill, and it is where the water service usually comes through the wall, with the main shutoff and the first run of pipe right beside it. The Department of Energy’s Building America insulation guide for contractors tells them to stop the air leakage through the rim joist with spray foam, or with rigid foam cut to fit the cavities and sealed around the edges, and says that when insulating the entire basement is too expensive, just sealing and insulating the rim joists will save energy and improve comfort. Rim joists alone are a much smaller job than full basement walls. See basement insulation: walls, rim joists and floors.
Outside walls, and sinks on outside walls
Supply lines in an exterior wall cavity are the classic frozen kitchen or bathroom sink. The Department of Energy’s Building America Solution Center is plain about them: pipe insulation can protect pipes from freezing and cracking in winter, which can cause considerable damage in the walls of the home. Its building science guidance gives the order of layers. Air seal the wall cavity holding the pipes first, foaming the seams between the back of the cavity and the framing and sealing the holes the piping passes through, so cold air cannot flow around the pipes. Then insulate the pipes, with cavity insulation installed behind them, between the pipes and the exterior wall. What matters is where the bulk of the insulation sits: between the pipe and the outside. A pipe pressed against the sheathing with all of the insulation on the room side of it is cut off from the house’s heat and left with the cold.
In an open wall that is straightforward. In a closed wall, filling the cavity with injection foam or dense-pack also cuts the drafts; see wall insulation. Where a line sits tight against the outside sheathing with no room behind it, whether it stays or gets moved is the plumber’s call. Aquarion gives the same advice for a sink against an outside wall: insulate the wall and the exposed pipes.
Garages, and rooms over them
Water lines run along garage walls and ceilings to reach a laundry, a utility sink or the bathroom over the garage, and an attached garage is usually unheated with a big door that leaks air. The Red Cross says to keep garage doors closed if there are water supply lines in the garage. New York City’s Department of Environmental Protection adds that a water meter in an unheated garage needs extra care to stay insulated. Insulating the garage walls and ceiling, and sealing the shared wall and the rim joist between garage and house, protects those lines and the room above; see garage insulation.
Attics
A second-floor bathroom, a laundry upstairs or an ice maker line can put water pipes in the attic, which is the space the University of Illinois tests used as their worst case: an uninsulated pipe lying on top of the attic insulation, on the cold side of it. A pipe in a vented attic belongs on the house side of the insulation, insulated itself, with the attic floor air sealed so house heat reaches it rather than escaping past it. Where the pipes, ducts or equipment are spread through the attic, insulating the roofline instead brings the whole attic inside the house; see attic insulation and roof and roofline insulation.
Outdoor faucets, pool and sprinkler lines
Before the cold arrives, the Red Cross says to remove, drain and store outdoor hoses, close the inside valves supplying outdoor hose bibs, open the outside bibs to let the water drain, and keep the outside valve open so any water left in the pipe can expand without breaking it. Drain pool and sprinkler supply lines following the manufacturer’s or installer’s directions, and do not put antifreeze in them unless directed. IBHS notes that homes built before 2010 typically do not have frost-proof outdoor faucets, so in those houses the inside shutoff matters.
What the code says about pipes in cold spaces
The residential codes in Connecticut (the 2021 IRC in the 2022 State Building Code) and New York (the 2025 Residential Code of New York State) say it the same way in Section P2603.5: where the winter design temperature is 32°F or lower, a water, soil or waste pipe shall not be installed outside of a building, in exterior walls, in attics or crawl spaces, or in any other place subjected to freezing temperature unless adequate provision is made to protect it from freezing by insulation or heat or both. New Jersey’s one- and two-family dwelling subcode leaves plumbing to the state’s plumbing subcode, N.J.A.C. 5:23-3.15, which is based on the National Standard Plumbing Code. New houses are supposed to start out protected. Plenty of older ones, and plenty of additions, do not.
Fix the space, then the pipe: insulation versus pipe sleeves and heat tape
There are four ways to keep a pipe from freezing, and they work best in this order.
- Stop the cold air. The National Weather Service’s New York office at Upton says cracks and holes in outside walls and foundations near water pipes should be sealed with caulk to keep the cold air out. The Building America guide adds the crawl space version: seal all air leaks through the exterior wall, including the rim joist, and carefully seal all holes and cracks in the subfloor over the crawl space. Air leakage is what turns a cold space into a freezing one.
- Insulate the boundary of the space, not just the pipe. The crawl space walls in a sealed crawl space, the rim joists, the basement walls, the wall cavity behind the pipe, the garage, the attic floor or roofline. The Building America Solution Center says that in extremely cold climates, insulating the basement walls may be critical to keep basement temperatures above freezing, especially where there is plumbing or mechanical equipment down there. Insulation on the space keeps every pipe in it warmer at once, including the ones nobody can reach.
- Insulate the pipes themselves. The Red Cross says both hot and cold water pipes in unheated areas should be insulated. The University of Illinois research calls pipe insulation a legitimate burst protection strategy because it delays the ice blockage, and found it can protect a pipe through a cold spell of limited duration. Limited is the word to notice: a wrapped pipe in a crawl space that stays well below freezing for days can still freeze, because insulation only slows the loss of the heat the pipe already has. The same research stresses a thorough job, without gaps, covering the pipe all the way to the heated space, and warns that a poor pipe insulation job could be more hazardous than no insulation at all.
- Add heat only where the first three cannot reach. A line that genuinely cannot be brought into a warm space, such as a supply line to a detached building, is where heat tape or heat cable belongs, with the fire precautions below.
One trap catches people who insulate one thing at a time. The Department of Energy’s Building America insulation guide warns that when you insulate the ducts in an unconditioned basement or crawl space, that space will be colder, and water pipes and drains there may freeze and burst in a cold climate; it says to consider insulating the basement walls or closing and insulating the crawl space. The same guide says a basement gets colder when its ceiling is insulated, so any pipes and ducts down there need to be well insulated against freezing first. Before insulating a basement ceiling or a basement full of ducts, decide where the pipes are going to get their heat.
Heat tape and heat cable, handled carefully
The Red Cross lists UL-listed heat tape or heat cable among the products for exposed water pipes, and it is a fire risk when it is old or wrongly installed. The Consumer Product Safety Commission’s heat tape release, issued in January 1996 and still published on its site, estimated about 1,500 fires, 10 deaths and 100 injuries a year from faulty electric heat tapes, and urged replacing uncertified tape more than three years old with tape certified to the voluntary safety standards of Underwriters Laboratories, the Canadian Standards Association or the Factory Mutual Research Corporation, as the 1996 release names them. Inspect it yearly for discolored surfaces at the plug, charring, cuts and bare wires; use a three-prong outlet with ground-fault circuit interrupter protection; and never wrap heat tape over itself unless the instructions permit it. The University of Illinois report, which did not test heat tape itself, advised a high quality heating cable with heavy wire insulation and a built-in thermostat, installed to the maker’s instructions, and noted the obvious limit: heat tape and cable do nothing in a power outage.
The part that touches our work: the Commission says not to cover heat tape with insulation unless the manufacturer advises it, to use non-flammable insulation such as fiberglass if you do, and not to use foam or vinyl that could catch fire. A pipe carrying heat tape does not get a foam sleeve slid over it as a matter of course. The electrical side belongs to a licensed electrician.
Insurance, the water company and the plumber: who handles what
Standard homeowners policies cover most of the damage that results from a freeze, the Insurance Information Institute says, including pipes that freeze and burst, and it tells homeowners to check with their agent or company so they are sure what their policy covers. The conditions matter. The Institute notes that most homeowners policies carry a vacancy clause that limits or excludes coverage once a house has been unoccupied, typically for 30 to 60 days in a row, that insurers typically require proof that reasonable steps were taken to maintain a vacant home, and that failing to heat it in winter could void coverage even under a vacant home policy. One insurer’s homeowners form, as quoted in a 2013 New York court decision, excludes damage from freezing only while the dwelling is vacant, unoccupied or being constructed, and the exclusion does not apply if the owner used reasonable care to maintain heat in the building, or to shut off the water supply and drain the system. Wording differs between insurers and policy forms, so read your own before the house sits empty.
Do not count on the water company to pay for a freeze. Each utility sets its own rules, and the two whose rules we checked put protecting the pipes and the meter on the owner. New York City’s Department of Environmental Protection says homeowners are responsible for protecting their pipes and water meters from freezing; that if a meter freezes and breaks because the homeowner did not take reasonable steps to protect it, the city will repair or replace it and bill the homeowner; and that property owners are responsible for the water service line from the house to the main in the street, repairs the department notes are not covered by most home insurance policies. In Connecticut, Aquarion says property owners, not the utility, are responsible for protecting their water pipes and meters, inside or outside, and that because the homeowner is responsible for the meter and the pipes on either side of it, it charges for service calls to thaw or repair a frozen meter. If another company supplies your water, its rules decide.
Hot water pipe insulation: the energy side
A hot water line loses heat every minute the water sits in it, not just while the tap runs. That is standby loss, and it is why the first length of pipe off the water heater is the highest-value foot of insulation in the house. A Department of Energy Building America brief on insulating plumbing pipes says insulated hot and cold water pipes will let you lower the temperature on your water heater by 2 to 4°F, and that pipe insulation reduces heat loss during water circulation and keeps pipes from sweating.
Insulation on a cold water line does a different job: it keeps humid air off the cold pipe and keeps its own outer surface above the dew point, which stops the summer sweating that drips onto joists and finished ceilings below. On a recirculating hot water loop that runs continuously, the pump moves hot water around the clock, so an uninsulated loop works the water heater continuously for nothing.
The code agrees on where insulation belongs. Under Section R403.5.2 of the 2024 IECC, adopted in New Jersey and carried into New York’s 2025 energy code, service hot water piping must be insulated where it is 3/4 inch or larger inside conditioned space, anywhere outside conditioned space, from the water heater to a distribution manifold, under a slab, buried, and on the supply and return of circulating systems. The number itself sits in Table R403.5.2, which states it as a thickness rather than a resistance: not less than 1 inch of insulation across the conductivity ranges the table lists for water between 105°F and 200°F. Connecticut’s 2021 IECC covers the same piping, adds piping serving more than one dwelling unit, and states the requirement as resistance instead: not less than R-3. Section R403.4 in all three states also requires mechanical piping carrying fluid above 105°F or below 55°F to be insulated to at least R-3, which captures boiler, hydronic and chilled lines.
What thickness and which material for pipe insulation
Three products cover nearly every residential line, and the choice follows what the pipe carries and how close it sits to a flue.
- Polyethylene or neoprene foam sleeves. Pre-slit tubes sized to the pipe’s outside diameter. The Department of Energy’s Building America Solution Center describes them as flexible closed-cell polyethylene or neoprene foam, pre-cut with a lengthwise seam, sized by matching the pipe’s outside diameter to the sleeve’s inside diameter. On domestic hot and cold water lines these are the normal choice.
- Closed cell elastomeric (rubber) tube. The right product where condensation is the problem: cold water lines, chilled water lines, and the air conditioning refrigerant lines the mechanical contractor owns. Manufacturer data for AP ArmaFlex lists a thermal conductivity of 0.245 Btu·in/h·ft²·°F at 75°F mean through a 1-inch wall, near R-4 per inch, and a water vapor permeability of 0.05 perm-inch, so the closed cell structure is its own vapor retarder.
- Fiberglass pipe wrap. Rated for higher temperatures, which makes it the product for steam and hot water heating lines, for anything near a flue, and over heat tape where the tape’s maker allows insulation at all.
Clearance at a gas appliance is not optional. The Department of Energy’s weatherization installer job aid makes it a pass-or-fail item: a minimum clearance of 6 inches between pipe insulation and the water heater’s draft diverter or single-wall vent flue. That gap applies to every kind of pipe insulation. Past it, on pipe that still runs near the flue, we switch from foam to unfaced fiberglass pipe wrap at least 1 inch thick, secured with wire or aluminum foil tape. The same job aid describes the rest of a good pipe job: insulate to a minimum R-3 for at least 6 feet from the water heater on both the hot and the cold lines, size the wrap’s interior diameter to the pipe, keep it continuous with no gaps, cut pieces at 45 degrees to turn a 90-degree elbow, and do not rely on the manufactured adhesive seam seal — secure the seams with tape. For freeze protection the same rules apply with one more: the gaps at elbows, valves and wall penetrations are where a sleeved pipe still freezes, so they get covered too.
Ducts: why they lose so much, and how they get sealed
Ducts fail for the same reason pipes do: they carry heat you already paid for through attics, crawl spaces, garages and unheated basements, outside the insulated shell. ENERGY STAR says that in a typical house, about 20 to 30 percent of the air that moves through the duct system is lost due to leaks, holes and poorly connected ducts. Heat also conducts straight through the duct wall: a 2005 EPA and ENERGY STAR duct insulation fact sheet puts that conductive share at 10 to 30 percent of the energy used to heat and cool the air, lost through the duct surfaces.
The leakage is worse than the arithmetic suggests, because it is unbalanced. Supply leaks push conditioned air into the attic and depressurize the house, pulling outdoor air in elsewhere. Return leaks drag that space’s air — dusty, humid, sometimes smelling of the crawl space — into the air handler and out of the registers, which is why leaky returns produce a dust, humidity and odor problem a filter cannot fully fix. Cooling ducts also sweat: warm humid air meeting a cold duct surface condenses, which in an attic means dripping onto the ceiling below. The Department of Energy’s answer is insulation with a vapor barrier, which keeps condensation from forming on the ducts; its Building America guide says to wrap them with foil- or vinyl-faced fiberglass, vapor retarder facing out, with the facings overlapped and tightly sealed where pieces meet. It only works if every seam is sealed.
Sealing comes before insulating, always. The Department of Energy’s Building America guide says leaks and joints should be sealed with a long-lasting material such as mastic, painted onto the seams and reinforced with wire mesh tape where needed; that butyl tape, foil tape or other heat-approved tapes with the Underwriters Laboratories logo can also work on a surface cleaned of dust; and that plastic or cloth duct tape should not be used because it dries, cracks and quickly loses its bond. Its duct brief adds that studies show cloth-backed duct tape fails within months. ENERGY STAR says the same in a line: seal with mastic sealant or metal tape, and never use duct tape, as it is not long-lasting.
The code backs that up. Under Section M1601.4.1 of the 2021 IRC as Connecticut adopted it, tapes and mastics used to seal metallic and flexible air ducts must comply with UL 181B and be marked “181 B-FX” for pressure-sensitive tape or “181 B-M” for mastic. Section R403.3.4 of Connecticut’s 2021 IECC states the requirement itself: ducts, air handlers and filter boxes shall be sealed. And under Section R403.3.2 of the 2024 IECC, building framing cavities shall not be used as ductwork or plenums — a panned joist bay used as a return is a leak by design. Duct sealing is not the same as air sealing the house: one closes the distribution system, the other closes the building shell, and a house needs both; see air sealing. Aerosol systems that fog sealant through the ducts from the inside are a separate specialty offered by duct contractors; we seal by hand from the outside with mastic and UL 181 tape, before the wrap goes on.
Duct insulation R-values and what the code requires
The requirement is the same number in all three states. Supply and return ducts outside conditioned space must be insulated to not less than R-8 for ducts 3 inches in diameter and larger, and not less than R-6 for ducts smaller than 3 inches: Section R403.3.1 of the 2021 IECC that Connecticut builds to, and Section R403.3.3 of the 2024 IECC as adopted in New Jersey and in New York’s 2025 energy code. Connecticut adds a line worth quoting to any installer: the minimum values are installed R-values.
That word does a lot of work, because duct wrap is rated compressed. Owens Corning’s data sheet for its foil-faced duct wrap, assuming the standard 25 percent compression, lists a 1 1/2-inch nominal blanket at an installed R-4.2, 2-inch at R-5.6, and 3-inch nominal — 2 1/4 inches once strapped down — at R-8.3. So R-8 in an attic means a 3-inch nominal blanket. A 1 1/2-inch wrap, strapped the same way, lands at R-4.2, about half the code number, which is why the number to check on a proposal is the installed R-value from the manufacturer’s table and not the thickness on the roll. A wrap left with the flanges unstapled and the foil unsealed also gives up the vapor retarder that keeps the duct from sweating.
Closed cell spray foam on ductwork is the other way to hit the number, at R-6.9 to R-7.1 per inch, sealing and insulating in one pass. It suits ducts that are hard to wrap cleanly — crowded boots, tight crawl spaces, cramped attic runs — and will not sag the way a strapped blanket can. It costs more, and it is permanent. The code sets conditions: Section M1601.3 of the 2021 IRC as Connecticut adopted it permits spray polyurethane foam on the outside of ducts in attics and crawl spaces when its flame spread index is not greater than 25 and its smoke-developed index not greater than 450 at the installed thickness, and when it has the ignition barrier the code requires there. Elsewhere, duct coverings must meet the stricter limit of a smoke-developed index not over 50.
The better answer for pipes and ducts: bring them inside the insulated envelope
Every figure above describes the cost of pipes and ducts built in the wrong place. The Department of Energy’s building science guidance says ducts should ideally sit in conditioned space — a dropped ceiling, between floors, an insulated basement or crawl space, or an unvented attic — and the same move protects the water lines that share those spaces.
In an existing house you rarely move the pipes or the ducts. You move the boundary. Insulating the roof deck with spray foam and sealing the attic makes the attic part of the house: the ducts, the air handler and any pipes up there then sit near room temperature, and the ducts’ remaining leaks stay inside the building. The same logic runs below. The Building America Solution Center describes a sealed, unvented crawl space insulated at its interior walls as an insulated, air-sealed environment for ducts and HVAC equipment, and as an approach that can protect floors and pipes from cold temperatures in cold climates. The sequence is: seal the ducts, decide whether the space is coming inside the house, then wrap whatever stays outside it.
Old pipe insulation, and what we hand off
In an older house, the covering already on the heating pipes may contain asbestos. The EPA lists pipes covered with an asbestos blanket or tape among the places asbestos turns up in homes. Appearance does not settle it — pipe covering was made in several forms, and a jacket that looks ordinary can still contain it, so no homeowner should clear a pipe by looking at it. Do not cut it, pull it off, or slide a new sleeve over it. Have it sampled by a trained and accredited asbestos professional before anyone disturbs it, and if it is positive, removal is abatement work for a trained, accredited and, where the state requires it, licensed contractor — a separate trade we do not perform. We plan around it and flag it in writing.
The same goes for the trades around us. Thawing, repairing, rerouting or replacing water pipes and valves is the plumber’s work. Replacing a furnace, boiler, air handler or water heater, installing new duct runs, and aerosol duct sealing from the inside are the mechanical contractor’s, and heat tape circuits belong to an electrician. What we bring is spray foam, blown-in, batts, rigid board, air sealing, insulation removal and replacement, vapor barrier and encapsulation, injection foam and dense-pack, radiant barriers and duct and pipe insulation, with our own crews.
What it costs to protect pipes from freezing
Most of our projects run between $3,500 and $12,500, and freeze protection almost always sits inside one of those projects rather than beside it. The pipes get insulated while the crew is already sealing the rim joists, insulating the crawl space walls, the garage or the attic around them, which is when both are cheapest and why the two are quoted together. For scale, the average homeowners claim in the Insurance Information Institute’s water damage and freezing category, which takes in far more than frozen pipes, was $15,400 over 2019 to 2023.
Three things move the number: where the at-risk pipes and ducts actually run, how much of that space a person can physically reach, and whether the answer is a sleeve, insulation on the space, or moving the boundary so the pipes and ducts end up indoors. A price per foot quoted over the phone, before anyone has found the cold spots, is a guess. Our free estimate visit is the step that turns it into a written number.
State and utility efficiency programs in New York, New Jersey and Connecticut run insulation and air sealing incentives. Whether a given program counts rim joists, crawl space walls, pipe or duct insulation, and on what terms, changes by program and by year, so check the current rules before you count on one — see New York and New Jersey insulation rebates and Connecticut insulation rebates. The federal 25C tax credit ended for anything placed in service after 31 December 2025.
Common questions about frozen pipes and pipe insulation
At what temperature do pipes freeze in a house?
Water freezes at 32°F, but a pipe inside a house freezes when the space around it gets that cold, which depends on drafts and insulation more than on the forecast. A University of Illinois study found that an uninsulated pipe lying on top of the insulation in a vented attic started to freeze when the outdoor temperature reached about 20°F, and proposed 20°F as an alert threshold for the southern United States, while expecting some freezes between 20 and 32°F where cold air leaks reach a pipe. A pipe in a drafty crawl space or an uninsulated outside wall is at risk on any hard freeze.
Will insulating my pipes keep them from freezing?
It buys time; it does not add heat. The University of Illinois research found that pipe insulation delays the ice blockage that leads to a burst and can protect a pipe through a cold spell of limited duration. A pipe in a space that stays below freezing for days can still freeze. The lasting fix is to air seal and insulate the space the pipe runs through, whether that is a crawl space, rim joist, outside wall, garage or attic, and then insulate the pipe.
Should I let my faucets drip when it is freezing?
Yes, from any faucet fed by pipes in a cold spot. The American Red Cross says to let the cold water drip, and the University of Illinois research explains why it works: an open tap relieves the pressure that builds between an ice blockage and a closed faucet, which is what bursts a pipe. Hot and cold run in separate lines, so let both drip where both are exposed, and leave the faucet slightly open even if the drip slows or stops.
What temperature should I keep my house so the pipes don’t freeze?
Keep the thermostat at the same setting day and night during a cold snap, and never below 55°F, even when no one is home, as the American Red Cross and IBHS advise. The Insurance Information Institute sets the bar higher, a minimum of 65°F in severe cold, because the inside of an outside wall where pipes run is colder than the room. If a line runs in an outside wall, lean toward the higher number.
How do I thaw a frozen pipe?
Check the pipe first. If it has split, bulged or is leaking, or you cannot find the frozen section, shut off the main water valve before anything else and call a licensed plumber. If it is whole and within reach, open the faucet the pipe feeds, then warm the frozen section with an electric heating pad, a hair dryer, a portable space heater kept away from anything that can burn and never left unattended, or towels soaked in hot water, until full water pressure returns. Never use a blowtorch, a kerosene or propane heater, a charcoal stove or any other open flame, and be careful of electric shock around standing water. If it will not thaw, call a licensed plumber.
What should I do first if a pipe bursts?
Shut off the water at the main valve, then deal with the water, as the Insurance Information Institute advises, and call a plumber and your insurance agent. Be careful of electric shock in and around standing water. Find the main shutoff and check that it turns before winter, so you are not searching for it with water running.
Does homeowners insurance cover frozen pipes?
Usually, for a house that is lived in and heated. The Insurance Information Institute says standard homeowners policies cover most damage from a freeze, including pipes that freeze and burst. Policies can make that coverage depend on reasonable care to keep the house heated, or to shut off the water and drain the system, especially while a house is vacant. The Institute notes that most policies have a vacancy clause that limits or excludes coverage once a house sits unoccupied, typically for 30 to 60 days in a row, and warns that failing to heat a vacant home in winter could void coverage. Check your own policy with your agent before the house sits empty.
What is the best insulation for pipes in a crawl space?
A closed cell sleeve sized to the pipe and sealed at every seam and elbow, with fiberglass pipe wrap anywhere near a flue. But the pipe is the second job. The Department of Energy’s Building America Solution Center describes a sealed, insulated crawl space as an approach that can protect floors and pipes from cold temperatures in cold climates, and that work happens at the crawl space walls and rim joists, not on the pipe.
Is heat tape safe on water pipes?
It can be used safely when it is certified, installed by the maker’s instructions and inspected every year, and it is a fire hazard when it is not. The Consumer Product Safety Commission’s heat tape release, issued in January 1996 and still published, estimated about 1,500 fires, 10 deaths and 100 injuries a year from faulty heat tapes, and advised replacing uncertified tape more than three years old, using a grounded three-prong outlet with GFCI protection, and not wrapping the tape over itself. Do not cover it with foam or vinyl insulation. The circuit itself belongs to a licensed electrician.
What R-value does duct insulation need?
R-8 for supply and return ducts 3 inches in diameter and larger outside conditioned space, and R-6 for ducts under 3 inches: Section R403.3.1 of the 2021 IECC in Connecticut and Section R403.3.3 of the 2024 IECC in New Jersey and New York. It is an installed R-value, so with foil-faced duct wrap compressed the standard 25 percent it takes a 3-inch nominal blanket to reach R-8; a 1 1/2-inch blanket installs at about R-4.2.
Frozen pipe prevention in New Jersey, Connecticut, the Hudson Valley and Long Island
We follow the cold before quoting anything: where the water lines and ducts run, which of them sit in a crawl space, a garage, an attic or an outside wall, where outdoor air gets in at the rim joists, vents and penetrations, what the ducts are pulling from, and whether anything already wrapped is safe to touch. If the better answer is the crawl space walls, the rim joists or the roof deck rather than a sleeve on a pipe, that is what the scope will say. Our estimate visit is free. It is our own, not a utility or state program’s energy assessment, so if you are counting on a rebate, book the program’s visit first. Written scope, written price, no charge.
Call 914-554-2289 or use the contact form, 8am–8pm, seven days. The Home Insulators is family-owned, based in New Rochelle, NY since 2015, with a 100-plus-person in-house crew that never subcontracts. We work across all of New Jersey, all of Connecticut, New York’s Hudson Valley and Long Island; see our service area.