A service gauge dropping to zero at 2:14 on a 96-degree afternoon tells you something ugly happened long before the homeowner called. The condenser didn’t suddenly “go bad.” The leak was usually building for months inside a cheap refrigerant line set, under split insulation, or at a flare connection stressed by thin copper. And here’s the part that catches even experienced installers off guard: one bad line set decision can turn a routine replacement into a bill that runs 2.3 to 3.1 times higher than the original estimate once drywall access, refrigerant loss, labor overrun, and return visits are added.
That’s the budgeting trap.
You think you’re pricing copper.
You’re really pricing risk.
A few weeks ago, I was talking with Marisol Vega, a 41-year-old property manager in Tucson, Arizona, who was replacing a failed 24,000 BTU ductless heat pump serving a renovated leasing office. The system used R-410A refrigerant, a 3/8" liquid line and 5/8" suction line, and a 35-foot exterior run that took brutal afternoon sun. Her previous installer had used a Mastercool set on another building, and the insulation jacket cracked so badly within one cooling cycle that condensation stained the stucco and forced a second crew out. She thought her next budget problem was labor. It wasn’t. It was material quality showing up later as labor.
That’s why line set replacement costs deserve their own strategy.
Below are the seven budgeting realities that matter most, from copper line set grade and insulation performance to sizing, labor time, and emergency shipping. If you’re trying to price a mini split line set, a central hvac line set, or a full air conditioning line set replacement without getting burned by callbacks, this is where you keep the numbers honest.
#1. Material Grade Changes the Real Replacement Cost — Type L Copper and ASTM B280 Matter More Than the Ticket Price
A line set for ac unit replacement is the paired refrigerant tubing that carries liquid and vapor between the indoor coil and outdoor unit. Replacement cost depends heavily on copper grade because wall thickness, purity, and dimensional consistency directly affect leak risk, flaring quality, and long-term service life.
Cheap copper looks cheap only on day one.
If the tubing varies too much in wall thickness, your flare won’t seat evenly, your bend radius gets touchy, and your leak test becomes a coin toss. I’ve seen imported AC refrigerant lines show wall variation as high as 8% to 12%, while better domestic Type L copper tubing stays much tighter, often around ±2% dimensional tolerance. That difference matters at startup, and it matters even more after a summer of thermal expansion and vibration.
Marisol learned this the hard way when she compared bids. One contractor offered a lower material figure but couldn’t verify compliance with ASTM B280. Another specified domestic copper with documented HVAC use. On paper, the gap was only $86. On a full installed job, the cheaper option would’ve been meaningless if one callback cost $240 in labor, plus refrigerant.
Why thin-wall tubing creates budget surprises
The first budget mistake is treating all copper as interchangeable. It isn’t. HVAC-rated refrigerant line copper has to handle pressure, vibration, and repeated temperature swings. When you’re running modern high-efficiency equipment, especially inverter systems, small inconsistencies in tubing quality show up faster.
What size line set do I need for a mini-split system? Most 9,000 BTU and 12,000 BTU ductless systems use 1/4" liquid by 3/8" suction. Many 18,000 BTU and 24,000 BTU systems step up to 3/8" liquid by 5/8" suction, while larger central systems commonly use 3/8" liquid by 3/4" or 7/8" suction. Always confirm against the equipment submittal because the compressor, refrigerant, and line length all matter.
Better copper doesn’t just reduce leaks. It protects your labor.
Where the low bid usually becomes the expensive bid
A replacement estimate that’s lower by $75 to $120 can disappear instantly if your crew spends an extra hour correcting a poor flare, re-bending kink-prone tubing, or chasing a slow leak. That’s why seasoned installers look beyond raw pipe cost and price the full installation outcome.
I’ve also seen this with Diversitech versus higher-tier assemblies. Their lower-R insulation can work in easier conditions, but on long outdoor runs in heat and UV, the total replacement budget should include a shorter expected service life. That’s not fear selling. That’s job costing.
And if you’re matching line quality to major equipment like Daikin, Mitsubishi Electric, or Carrier, it makes no sense to hang premium equipment on bargain tubing that becomes the weak link.
#2. Insulation Performance Drives Labor, Moisture Damage, and Energy Loss — Pre-Insulated Assemblies Budget Better
A pre-insulated ac lineset arrives with the copper already wrapped in bonded insulation sized to the tubing. Replacement costs stay more predictable because you eliminate field wrapping time, reduce installation variables, and avoid the moisture failures that often happen at seams and bends.
This is where many budgets quietly blow up.
You save a little on material, then spend it all with knives, tape, adhesive, and labor. Field wrapping typically adds 45 to 60 minutes per installation, depending on run length and bend complexity. On a truck doing four line replacements a week, that’s real payroll. And if the wrap gaps at the first elbow, it may also be a future stain repair.
Pre-insulated vs. Field-wrapped: the number nobody includes in the estimate
What is the difference between pre-insulated and field-wrapped line sets? A pre-insulated assembly uses factory-applied foam with tighter contact around the tubing and more consistent vapor control. Field wrap depends on jobsite workmanship, tape quality, weather conditions, and how carefully the installer seals every joint.
That means the labor line should never be identical.
On humid jobs, especially with attic penetrations or wall chases, underperforming insulation can create sweating on the suction line when indoor dew points rise. Once that moisture gets into drywall or trim, your “line set budget” just became a finish-repair budget. I’ve seen property managers focus on the copper price and ignore the cost of one ceiling stain claim.
Marisol was especially sensitive to this because her prior stucco damage came from failed jacket protection, not a refrigerant leak. Different symptom. Same budgeting lesson.
The insulation rating is more than a spec sheet number
A solid pre-insulated line set should use closed-cell polyethylene foam with an R-4.2 insulation rating or better. That level is strong enough to reduce condensation risk in harsh cooling loads and hot exterior chases. By comparison, some lighter assemblies sit closer to R-3.2, and that difference matters in high heat and high humidity.
This is one reason some contractors quietly standardize better materials. Mueller pre-insulated line sets stocked at Plumbing Supply And More use ASTM B280 domestic copper with a DuraGuard UV-resistant finish for professional installers and DIY mini-split buyers. If you’re pricing long exterior runs and want to compare options, it helps to review quality line sets in the same place you’re sourcing the rest of the mechanical package so your material and freight numbers stay realistic.
That’s not about paying for a label.
It’s about cutting uncertainty out of the install.
#3. Outdoor Exposure Can Double Your Replacement Frequency — UV Resistance Should Be in the Budget from the Start
Outdoor line protection is the jacket or coating that shields insulation and copper from sunlight, weather, and abrasion. In replacement budgeting, UV resistance matters because sun damage often shows up long before the copper itself fails, forcing premature rework on otherwise functional systems.
Sunlight is sneaky.
It doesn’t shut a system down in one afternoon. It slowly destroys the outer jacket until the foam cracks, separates, absorbs moisture, and leaves your ductless line set exposed. In strong sun climates, I’ve seen visibly degraded jackets in 18 to 24 months on lower-grade products. Better UV-protected assemblies can stretch useful outdoor life to 5 to 7 years before needing serious corrective attention.
Comparison: when UV failure becomes a labor problem, not just a materials problem
Here’s where budget comparisons get honest. A basic exterior run may look similar whether you price a premium coated assembly or a cheaper alternative, but the service-life difference changes the whole math. In one recurring pattern I’ve seen, JMF jacketed insulation performs adequately in protected runs but shows faster visible wear in direct sun than more heavily protected black-oxide style coverings. Once the jacket breaks down, the crew isn’t just replacing insulation. They’re often re-securing line-hide, opening penetrations, and touching up finish materials.
That’s exactly why “good enough” isn’t actually cheaper outdoors. If your replacement cycle drops from 6 years to 2 years on a sun-beaten wall, the lower upfront material number was fiction. Add one revisit, one cosmetic repair, and one refrigerant top-off, and the premium assembly becomes worth every single penny.
Marisol’s Tucson project was the perfect example. Her site didn’t need the absolute cheapest mini-split copper lines. It needed something that wouldn’t cook in desert UV and send a painter back out.
What long outdoor runs really demand
How long should refrigerant lines last on an outdoor installation? With correct sizing, secure supports, and UV-resistant insulation, many exterior runs should deliver a decade or more of service before major replacement is even discussed. When jackets crack early, it’s usually a materials or exposure-prep problem, not normal aging.
That’s why the outer protection should be budgeted as a system component, not a cosmetic extra.
When a line set gives you domestic copper, R-4.2-plus bonded insulation, and a UV shell proven to extend outdoor life by about 40%, you’re buying fewer return trips, not just tubing.
#4. Sizing Errors Inflate Cost Faster Than Most Owners Expect — Pressure Drop, Efficiency, and Charge Correction Add Up
A correctly sized hvac line set matches the equipment’s liquid and suction line requirements for tonnage, refrigerant, and total run length. Budgeting suffers when line sizes are wrong because pressure drop, oil return problems, and charge adjustments can force expensive corrective work after installation.
A wrong size doesn’t always fail instantly.
Sometimes it just performs badly enough to create nuisance complaints. Low capacity. High amp draw. Long pull-down times. And then your “replacement” becomes a diagnostic event.
What every contractor should price before ordering tubing
How do you size an ac unit line set correctly? Start with the manufacturer’s engineering data, then verify run length, lift, and fitting count. ACCA Manual S gives the right framework, but the actual equipment chart still rules because one 24,000 BTU inverter can accept a different line configuration than another.
For common residential work, these pairings show up constantly:
- 1/4" x 3/8" for many 9,000 to 12,000 BTU ductless systems 3/8" x 5/8" for many 18,000 to 24,000 BTU systems 3/8" x 3/4" for many 3-ton systems 3/8" x 7/8" for many 5-ton systems
But length changes everything. A 15-foot run and a 50-foot run don’t deserve the same assumptions.
Why “close enough” sizing usually isn’t close enough
Does copper wall thickness affect refrigerant line performance? Yes, but line diameter affects it even more in day-to-day operation. Undersized suction lines can increase pressure drop and reduce capacity, while oversized configurations can complicate oil return and manufacturer charge calculations.
Marisol’s contractor almost reused an existing run that was dimensionally convenient but not ideal for the new ductless unit. Reuse would have shaved money off the estimate. It also would have left the system with a compromise nobody could fully defend once cooling performance drifted.
That’s why replacement budgeting should include the possibility that reusing an old air conditioning line set is false economy. If the line size doesn’t match the equipment, replacement is often cheaper than troubleshooting around the mismatch for the next three summers.
#5. How to Evaluate Refrigerant Line Quality Before Your Next Installation — A Practical Decision Framework
An installation decision framework is a field checklist for judging whether a copper line set is built for long-term HVAC use or just priced to move. It protects your budget by forcing you to compare the features that actually drive leak resistance, insulation life, and labor efficiency.
Use this before you order anything.
Six criteria that separate professional line sets from budget imports
Copper origin and construction grade
Look for documented Made in USA or equivalent traceable production and Type L copper built to ASTM B280. If the seller can’t confirm HVAC-grade copper, assume wider wall variation and a higher chance of flare and bend issues.Insulation R-value and adhesion method
Ask for a real insulation value, not vague “premium foam” language. A rating around R-4.2 with bonded application is far better than loosely fitted wrap that can gap at bends and start sweating in the first humid season.UV and weather-resistance coating
Exterior runs need a jacket or coating that can survive direct sun. If protection is minimal, expect cracking, foam exposure, and a shorter replacement cycle, especially in desert, coastal, and rooftop conditions.Nitrogen charging and end-cap quality
What does nitrogen-charged mean on a pre-insulated line set? It means the tubing is factory filled with inert gas and sealed, which reduces moisture and contamination risk before installation. Unprotected tubing can arrive dirty inside, and that contamination becomes your evacuation problem later.Warranty coverage and manufacturer support
Better assemblies back the tubing and insulation separately. When you see coverage like 10 years on copper and 5 years on insulation, that tells you the manufacturer is willing to stand behind both the metal and the outer system.Refrigerant compatibility and future-proofing
Make sure the assembly is suitable for R-410A refrigerant, R-32 refrigerant, and upcoming low-GWP applications where approved. Buying only for today’s equipment can force an avoidable replacement later. 
Why this framework saves more than comparison shopping ever will
A table tells you price. A framework tells you what might fail. That’s the difference between purchasing and specifying.
And when crews start using this kind of checklist, the conversations change. They stop asking, “What’s the cheapest line set in stock?” and start asking, “Which one won’t drag us back here in August?”
#6. Clean, Dry Tubing Prevents Commissioning Headaches — Nitrogen Charging and End Caps Are Budget Protection
A nitrogen-charged refrigerant line set is factory sealed with dry inert gas to keep out moisture, oxygen, and debris before installation. Replacement budgets benefit because clean tubing shortens evacuation time, reduces contamination risk, and helps protect compressors from acid formation and oil breakdown.
This one gets overlooked all the time.
You can’t see contamination from the outside. But you’ll absolutely pay for it later if it’s there.
Comparison: sealed line sets versus questionable inventory handling
One of the more expensive “cheap material” mistakes comes from using tubing that sat uncapped, took on moisture, or wasn’t protected well in storage. I’ve seen commissioning delays tied to suspect tubing where vacuum decay wouldn’t stabilize, and the crew spent the next hour ruling out every connection before admitting the line itself may have been compromised before it ever hit the wall. Similar issues show up with lower-tier packaged options and mishandled stock, and that’s where brands with better factory sealing separate themselves.
Compared with open-ended or poorly capped assemblies, a properly sealed and dry set removes one huge variable. That matters on systems from Fujitsu wall cassettes to Lennox split systems to Bosch heat pumps, where startup procedures are already precise enough without internal contamination entering the picture. If you’re already paying for vacuum time, micron verification, and refrigerant integrity, the cleaner tubing option is worth every single penny.
Marisol’s contractor specifically rejected leftover house-stock tubing for that reason. New install. New sealed materials. Fewer unknowns.
Why moisture is so expensive when it gets into the system
Can I use the same line set for R-410A and R-32 refrigerant? In many cases, yes, if the tubing meets the required pressure and material specifications and the manufacturer approves it. But compatibility on paper doesn’t help if the inside of the line is contaminated before the refrigerant ever enters it.
Moisture in the tubing can slow evacuation, react with oil, and contribute to long-term acid issues that don’t announce themselves on day one. That’s why replacement budgeting should account for internal cleanliness, not just length and diameter. A “bargain” line that costs an extra truck hour during startup wasn’t a bargain.
#7. The Cheapest Replacement Is Usually the One That Prevents the Next Callback — Total Cost Beats Material Cost
Total replacement cost is the full installed and expected lifetime expense of a line set, including labor, refrigerant, callbacks, finish repairs, and downtime. Budgeting gets more accurate when you price the complete ownership cycle instead of comparing copper by the foot.
That’s the line item most bids hide.
They show pipe.
They don’t show pain.
What one callback really costs
If a slow leak burns off enough charge to require a revisit, you’re not just paying for one repair. You’re paying dispatch time, technician labor, travel, leak confirmation, vacuum, recharge, and reputation. On many residential replacements, one callback can land between $210 and $460 before you count customer goodwill. If drywall or exterior finish gets involved, it climbs fast.
For Marisol, the winning bid wasn’t the cheapest upfront number. It was the one that made the least trouble most likely. Her final material package cost more than the lowest quote, but she avoided another stucco repair, another tenant complaint, and another emergency service call during peak cooling season.
Where reliable sourcing helps your estimate stay honest
Contractors also forget to budget availability. Emergency replacements don’t happen on a leisurely schedule. If a line set failure takes down a rental office, server room, or occupied home in July, lead time becomes part of the install price. Freight upgrades, split sourcing, and job delays can erase your margin fast.
That’s one reason a dependable supply source matters as much as the tubing itself. If you know the product spec is consistent and the shipping window is predictable, you can quote tighter and sleep better. For a lot of contractors, that confidence matters more than shaving a few dollars off a box.
And that’s the real takeaway: the right line set doesn’t win because it’s cheap. It wins because the install stays finished.
FAQ: HVAC Line Set Replacement Costs and Budgeting
1. How do I determine the correct line set size for my mini-split or central AC system?
The correct size depends on the equipment manufacturer’s specifications, system capacity, refrigerant type, and total run length. Many 9,000 to 12,000 BTU mini-splits use 1/4" x 3/8" lines, while larger 18,000 to 24,000 BTU units often use 3/8" x 5/8". Central systems commonly step up from there.
The safe method is to start with the condenser and air handler data sheet, not a generic chart. Line length, vertical rise, and fitting count can all change acceptable sizing. A 3-ton split system might call for 3/8" liquid and 3/4" suction, while a 5-ton setup may need 7/8" suction. If you guess wrong, you can create pressure drop, poor oil return, or charging problems that make the system underperform. That’s why most experienced techs treat manufacturer tables as mandatory, with ACCA Manual S used as a planning framework rather than a substitute.
2. What is the difference between 1/4 inch and 3/8 inch liquid lines for refrigerant capacity?
A 1/4-inch liquid line is common on smaller systems because it handles lower refrigerant volume efficiently. A 3/8-inch liquid line supports larger equipment or longer runs where refrigerant flow requirements are higher. Using the wrong size can affect charging accuracy, subcooling, and overall system performance.
In the field, the difference shows up when installers try to reuse an old line set on a new system. Many 9,000 BTU and 12,000 BTU ductless units are built around 1/4" liquid lines, while 18,000 BTU and larger systems often shift to 3/8". That doesn’t mean every unit follows the same rule; inverter designs vary. A too-small liquid line can create excessive pressure drop on long runs, while a mismatched oversized line may complicate charge calculations. If you’re budgeting a replacement, include the cost of correcting mismatched tubing instead of assuming reuse will save money.
3. Why is domestic Type L copper superior to import copper for HVAC refrigerant lines?
Domestic Type L copper typically offers better wall consistency, cleaner metallurgy, and tighter manufacturing tolerances than lower-grade imported tubing. That improves flare reliability, bend quality, and long-term leak resistance. For HVAC refrigerant applications, those advantages often matter more than a small upfront material savings.
The big difference is consistency. Better HVAC tubing built to ASTM B280 is designed for refrigeration service, not general plumbing use. In practice, tighter tolerances can mean easier brazing, fewer flare leaks, and less frustration during installation. Lower-tier imports may still work, but wider wall variation can create weak points at bends and fittings, especially on systems that see vibration and repeated heating-cooling cycles. When one callback can cost hundreds of dollars, copper quality becomes a business decision, not just a supply choice. That’s why experienced installers often budget for premium tubing first and explain the reason later.
4. How does an R-4.2 insulation rating help prevent condensation compared to lighter insulation?
An insulation rating around R-4.2 gives the suction line better thermal resistance, helping it stay above the surrounding air’s dew point. That reduces surface sweating, especially in humid spaces, wall cavities, and exterior chases. Lighter insulation is more likely to allow moisture formation and eventual water damage.
Condensation problems usually start at weak points: bends, seams, and compressed sections. A solid closed-cell polyethylene foam layer with a real vapor barrier resists moisture intrusion better than thin or poorly adhered insulation. In real jobs, the difference becomes obvious in attics, closets, and hot exterior walls hvac line set where high humidity and temperature swings stress the material. If a lower-R assembly starts sweating, the repair cost can include ac unit line set Plumbing Supply And More repainting, drywall patching, or mold remediation. That’s why insulation should be budgeted as a protective component, not as packaging around the copper.
5. What does nitrogen-charged mean and why does it matter for line set installation?
Nitrogen-charged means the tubing is factory filled with dry inert gas and sealed at the ends. That keeps moisture, air, and debris out during shipping and storage. For installers, it means cleaner internal tubing, more predictable evacuation, and lower contamination risk during startup.
Dry internals matter because refrigerant systems hate moisture. Water vapor can slow vacuum pull-down, react with oil, and contribute to acid formation over time. When a line set arrives properly sealed, the installer starts with one less unknown. That becomes especially valuable on inverter systems where commissioning tolerances are tighter. It also reduces the risk of stock-yard contamination or jobsite dust entering the tubing before connections are made. In budgeting terms, nitrogen charging is one of those quiet quality features that prevents expensive startup headaches most owners never see.
6. Can I install a pre-insulated line set myself or should I hire a licensed HVAC contractor?
Physically routing and mounting a pre-insulated line set is possible for a capable DIY installer, but final connections, pressure testing, evacuation, and refrigerant commissioning are best handled by a licensed HVAC contractor. The technical risk lies less in hanging the tubing and more in achieving leak-free, contamination-free startup.
Mini-split buyers often ask this when they’re comfortable with tools and wall penetrations. The truth is the mechanical work and the refrigeration work aren’t the same thing. You might be able to run a mini split line set, use a tube cutter, and support the route correctly, but a proper install also requires a torque wrench, vacuum pump, refrigerant manifold, and leak verification. One over-tightened flare or one poor vacuum can shorten compressor life dramatically. If you do part of the job yourself, budget for a professional to complete and commission the system properly.
7. What is the difference between flare connections and sweat connections for mini-splits and split systems?
Flare connections use shaped copper ends and flare nuts to make a mechanical seal, while sweat connections are brazed joints made with heat and filler metal. Mini-splits often use flare fittings for faster installation. Traditional split systems frequently use brazed connections for durability and custom fit.
Each method has strengths. Flare systems are common on ductless equipment because they speed installation and simplify service access, but they demand clean cuts, proper deburring, and exact torque. Sweat connections can be extremely reliable when done well, especially on custom lengths and larger systems, but they take more time and require nitrogen purging during brazing to reduce oxidation. Budget-wise, flare installs may reduce labor, while brazed jobs can offer more flexibility on long or unusual runs. The right choice depends on equipment design and installer skill, not preference alone.
8. How long should refrigerant lines last in outdoor installations exposed to sun and weather?
A well-installed outdoor line set using quality copper, strong insulation, and UV-resistant ac lineset protection can often last 10 years or more. Premature failure usually comes from poor insulation jackets, direct UV damage, moisture intrusion, or mechanical abrasion rather than the copper failing first.
Climate matters a lot here. Desert sun, rooftop exposure, salt air, and freeze-thaw swings all shorten the life of weak exterior coverings. Some low-end jackets begin visibly degrading within 18 to 24 months in harsh sun, while better protected systems can remain serviceable for 5 to 7 years before insulation attention is needed and much longer before copper replacement. Good support spacing, line-hide use, and avoiding direct rubbing points also extend lifespan. If you’re budgeting replacement, ask not only how long the tubing lasts, but how long the insulation remains protective.
9. What maintenance helps extend line set lifespan and prevent leaks?
The best maintenance is visual inspection, support correction, UV protection repair, and prompt sealing of any exposed insulation before moisture gets in. Keeping the line set secure and dry prevents abrasion, sweating, and corrosion. Leak prevention starts with protecting the outer system, not just checking refrigerant pressure.
A smart inspection routine includes looking for cracked jackets, compressed insulation, loose clamps, rubbed copper, and oil stains around fittings. On mini-splits, check flare nuts for signs of seepage and verify the line isn’t vibrating against metal edges. On central systems, inspect wall penetrations and attic transitions where abrasion often starts. If exposed sections are found early, UV-resistant tape or protective covers can buy time before full replacement is needed. Ignoring damaged insulation is what turns a maintenance issue into a leak issue.
10. What is the total cost comparison between pre-insulated line sets and field-wrapped installation?
Pre-insulated line sets usually cost more upfront but often reduce total installed cost by saving labor and lowering failure risk. Field wrapping can add 45 to 60 minutes of labor and introduces more chances for gaps, poor vapor sealing, and condensation damage. The better value depends on total job cost, not material price alone.
In practical terms, pre-insulated assemblies are often the better budget choice for contractors doing repeated installs or long exterior runs. Saving even 47 minutes on wrapping, taping, and correcting insulation can offset the higher material cost quickly. Then there’s the quality side: factory-applied insulation usually fits tighter and stays more consistent through bends than hand-applied wrap. If one field-wrapped run later causes a ceiling stain or sweating inside a wall chase, the hidden cost exceeds the original savings immediately. That’s why many experienced crews standardize pre-insulated products whenever the application allows.
Conclusion
Most line set replacement budgets fail for one reason: they count materials and ignore consequences. Copper grade, insulation quality, UV resistance, internal cleanliness, and correct sizing all decide whether the install stays closed or comes back to haunt your labor sheet six months later.
Marisol’s Tucson project ended the right way because the estimate finally accounted for those realities. Better tubing. Better jacket protection. Correct sizing. No fantasy savings.
That’s the budgeting mindset worth keeping.
If you want fewer callbacks, tighter estimates, and a replacement that actually stays replaced, start pricing your hvac line set the way the field experiences it—not the way a low quote presents it.
Author Bio
Soren Ibarra is a mechanical contractor with 17 years of experience overseeing commercial HVAC and plumbing retrofits across Boise, Idaho and the surrounding Intermountain region. He holds a hydronic system balancing certification and is known for troubleshooting line-loss, commissioning issues, and replacement budgets that go sideways in extreme temperature swings.