HVAC questions
These are the questions people actually ask about heating and cooling, grouped by topic. Every page that touches a physical action carries a safety verdict above the answer, and every regulatory claim traces to DOE, EPA, IRS or ACCA with the date it was verified.
Topics
AC not cooling
Why a system runs but the house stays warm, and which checks are safe to do yourself.
Heat not working
No heat, lukewarm air, and the difference between a control problem and a combustion problem.
Short cycling and runtime
Equipment that starts and stops too often, and what oversizing has to do with it.
Frozen coils and ice
Ice on the indoor coil or the outdoor unit — airflow starvation versus low refrigerant charge.
Water leaks and condensate
Where the water comes from, which leaks are a safe DIY fix, and which mean stop.
Noises and smells
What each sound and smell indicates — including the two that mean leave the building.
Airflow and uneven rooms
One room too hot, weak registers, and why the ducts are usually the answer.
Thermostat issues
Blank screens, wrong readings, wiring, and settings that look like equipment failure.
System types
What each kind of heating and cooling equipment is, and where it fits.
Heat pumps
How one machine both heats and cools, and what that means for your bill.
Cold-climate heat pumps
Capacity versus outdoor temperature, and why the old reputation is out of date.
Mini splits and ductless
Ductless systems, zoning, and where they beat a ducted replacement.
Furnaces and combustion
Gas and electric furnaces, AFUE, venting, and the combustion safety line.
Boilers and hydronic heat
Hot water and steam heat, radiators, and what differs from forced air.
Efficiency metrics
SEER2, EER2, HSPF2, AFUE and COP — what each measures and which generation it belongs to.
Efficiency standards by region
Federal minimums differ by region, which is why a model may not be legal to install in your state.
Refrigerants and the phasedown
R-22, R-410A, R-454B and R-32 — the regulation, and what it means for your equipment.
Sizing and load calculation
Why a Manual J load calculation — not a rule of thumb — decides equipment size.
Ductwork design and sealing
Duct sizing, static pressure, and why good equipment underperforms on bad ducts.
Indoor air quality
What your system can and cannot do about dust, allergens, and stale air.
Filters and MERV
MERV ratings, change intervals, and the airflow tradeoff nobody explains.
Humidity control
Why an oversized system leaves the house clammy, and what to do about it.
Ventilation, ERV and HRV
Bringing in outside air on purpose, and recovering the energy while you do it.
Maintenance and tune-ups
What genuinely needs doing, how often, and what a tune-up should include.
Lifespan, repair or replace
How long equipment lasts and how to decide between one more repair and a replacement.
Federal incentives
What the federal government currently offers for HVAC — and what expired.
State and utility incentives
State energy offices, utility rebates, and how to find what applies to you.
Replacement cost
What a new system costs, what drives the range, and what a bid should itemise.
Repair and operating cost
Common repair prices and what the system actually costs to run.
Hiring and reading bids
How to compare three quotes and spot the one that was done properly.
HVAC basics and definitions
What HVAC means, what the parts are called, and how the whole system fits together.
Brands and models
Who makes what, how the tiers differ, and why the installer matters more than the badge.
HVAC careers and training
Pay, schooling, apprenticeships, EPA 608 certification and state licensing for the trade.
What should you know about refrigerant?
Refrigerant circulates in a sealed loop. It is not consumed the way fuel or oil is, so a system that is low on charge has a leak. Adding refrigerant without finding and repairing that leak treats the symptom, vents the new charge over the following weeks, and costs you the same money again next season.
It is also regulated. Only Section 608 certified technicians may purchase refrigerants intended for use with stationary refrigeration and air-conditioning equipment. The restriction covers ozone-depleting substances and non-ozone-depleting substitutes — including HFCs — in cylinders, cans or drums. Wholesalers must record the purchaser's name, the date of sale and the quantity.
There is one exception that confuses people: small cans of refrigerant for vehicle air conditioning are still sold without certification. That exception is for cars and does not extend to the equipment in your house.
For new equipment, the 700 GWP limit in force since January 1, 2025 is why current systems ship with R-454B (GWP 465) or R-32 (GWP 675) rather than R-410A (GWP 2088). R-410A inventory built before 2025 can still be legally installed — EPA removed the installation deadline on May 21, 2026. The full timeline.
How is the right equipment size decided?
Nearly every persistent comfort problem traces back to equipment size, and size is decided before the first box arrives. The standard is the ACCA Manual J load calculation (ANSI/ACCA 2 Manual J - 2016), which totals the heat gain and loss of your specific house: orientation, window area and type, insulation levels, air infiltration, internal gains, and your local design temperature.
What a Manual J is not: square feet per ton, and not the old unit's tonnage. The first ignores everything that makes one house different from another. The second assumes whoever sized the old equipment got it right, and propagates their error for another fifteen years.
Oversized equipment reaches the setpoint and shuts off before it has dehumidified, so the house ends up cold and clammy at the same time. Every start is also the hardest moment in a compressor's life, so wear accelerates. And you pay for the surplus capacity twice — once to buy it and again to run it.
Ask for the completed Manual J in writing, not the claim that one was done. What it contains and how to read it.
What actually drives the cost?
We publish no national average price, and the reason matters: an average across every house, region and system type is not a number you can act on. A replacement that includes duct modification, an electrical upgrade and a permit is a different job from a straight swap, and both read as “system replacement” on a one-page proposal.
What actually drives your number:
- Equipment capacity and tier, which should come from the Manual J rather than the old nameplate.
- The ducts — whether they can move the air the new equipment needs, and what it costs if they cannot.
- Electrical work, if a circuit or panel change is required.
- Permit and inspection, usually required.
- Refrigerant — current equipment uses R-454B or R-32; remaining pre-2025 R-410A stock may price differently.
Which efficiency numbers can you actually compare?
If you are comparing efficiency figures, check which generation they belong to first. On January 1, 2023 DOE changed the test procedure and renamed three metrics: SEER became SEER2, EER became EER2, and HSPF became HSPF2. The current procedure measures at a higher external static pressure, much closer to what equipment meets once installed in a real house on real ductwork.
DOE is explicit about the consequence: “Although SEER2, HSPF2, and EER2 ratings are similar to ratings using the original metrics, they are not directly comparable. Compliance with the new standards for each model must be determined based on its measured SEER2, HSPF2, or EER2.” In practice: a SEER figure from a 2019 article cannot tell you whether a quote reading SEER2 is good, bad or identical.
That is why we publish no conversion factor. We do not publish a SEER-to-SEER2 conversion factor. DOE states that ratings on the new metrics are "not directly comparable" to ratings on the original metrics, and that compliance must be determined from the measured SEER2, EER2 or HSPF2 value. Approximate multipliers circulate widely, but they vary by equipment type and configuration, and using one to compare an old article's number against a number on today's quote is how homeowners end up believing they were offered less efficiency than they were. Compare like with like: ask for the SEER2 figure, and check it against the AHRI certificate.
The nationwide minimum for a split-system air conditioner is 13.4 SEER2, and for a split-system heat pump 14.3 SEER2 with 7.5 HSPF2. What each metric measures · minimums by region and state.
How can you verify any of this yourself?
Everything regulatory on this site traces to a primary source and carries the date it was read: DOE for efficiency standards, EPA for refrigerants and Section 608, the IRS for tax credits, and ACCA for load calculation. The sources for this page are listed at the end with the date each was consulted.
If you find a different figure elsewhere, check two things before deciding which to believe: whether the page says which generation its efficiency metric belongs to, and whether it carries a visible review date. Most of the outdated content in this category fails both tests.